JP2009259573A - Organic el device - Google Patents

Abstract

An organic EL device having a more uniform emission wavelength in a light emitting region is provided.
A substrate portion 21 having a uniform refractive index, a partition wall 27 formed on the substrate portion 21 to partition a light emitting region A, an anode layer 45 and a cathode layer 47 formed on the substrate portion 21; A light emitting layer 46 disposed between the anode layer 45 and the cathode layer 47, and a through hole 42 </ b> A is formed inside the outer peripheral edge of the light emitting region A on the upper surface of the substrate portion 21.
[Selection] Figure 2

Description

  The present invention relates to an organic EL device used as, for example, a line head of an image forming apparatus.

A line printer (image forming apparatus) is known as a printer using an electronic transfer method. In this line printer, devices such as a charger, a line-shaped printer head (line head), a developing device, and a transfer device are arranged close to each other on the peripheral surface of a photosensitive drum serving as an exposed portion. That is, an electrostatic latent image is formed on the peripheral surface of the photosensitive drum charged by the charger by selective light emission operation of a light emitting element provided in the printer head, and this latent image is developed. The toner image is developed with toner supplied from the device, and the toner image is transferred onto the paper by the transfer device.
By the way, in recent years, as a light emitting element of such a printer head, an EL element (electroluminescence element), in particular, an organic EL device having a light emitting element as an organic EL element capable of producing a light emitting point with high accuracy is used as a printer head. Has been proposed.

In such an organic EL device, a light emitting region is partitioned by a partition formed on a substrate, and a light emitting layer is applied in an opening of the partition. Here, in the light emitting layer, the outer peripheral edge portion that is in contact with the inner side surface of the partition wall may be located above the central portion. For this reason, as for a light emitting layer, an outer peripheral part becomes thick compared with a center part. When the thickness unevenness occurs in the light emitting layer, the light emitting efficiency in the light emitting region and the emission extraction efficiency vary, and the life of the light emitting layer is shortened.
Therefore, it has been proposed to form a recess in the central portion of the light emitting region so that the thickness of the inner peripheral portion is equal to the thickness of the central portion even if the inner peripheral portion is located above the central portion (for example, Patent Documents 1 and 2).
JP 2005-294205 A JP 2005-322469 A

However, also in the conventional organic EL device described above, it is desired to make the emission wavelength in the light emitting region more uniform.
The present invention has been made in view of the above-described conventional problems, and an object thereof is to provide an organic EL device in which the emission wavelength in the light emitting region is made more uniform.

  The present invention employs the following configuration in order to solve the above problems. That is, an organic EL device according to the present invention includes a substrate portion, a partition wall formed on the substrate portion to partition a light emitting region, an anode layer and a cathode layer formed on the light emitting region on the substrate portion, A light emitting layer disposed between the anode layer and the cathode layer, and a reflective layer disposed above the light emitting layer, the substrate unit having a uniform refractive index at least in the light emitting region; It has the recessed part formed inside the outer periphery of the said light emission area | region in an upper surface, It is characterized by the above-mentioned.

  In this invention, by forming a recess in the substrate portion having a uniform refractive index in the light emitting region, the thickness of the light emitting layer can be made uniform to make the light emitting efficiency uniform, and interference occurs in the light transmitted through the substrate portion. The extraction efficiency of the emitted light can be made uniform. Thereby, the light emission intensity in the light emitting region is made uniform. That is, light is generated in the light emitting layer by applying a voltage between the anode layer and the cathode layer. Here, since the concave portion is formed in the central portion of the light emitting region, the film thickness of the light emitting layer is uniform even if the position of the peripheral portion in the light emitting layer is higher than the position of the central portion. For this reason, the luminous efficiency in the light emitting region is made uniform. And the component which goes to the upper layer among the light which generate | occur | produced in the light emitting layer is reflected toward a board | substrate part in a reflection layer. At this time, since the substrate portion has a uniform refractive index in the light emitting region, the light transmitted through the outer peripheral portion of the recess does not interfere when passing through the substrate portion, and the spectral change of the light transmitted through the outer peripheral portion is suppressed. Is done. For this reason, the spectrum in the light emitting region is made uniform. Therefore, the light emission efficiency and the extraction efficiency in the light emission region are made uniform, the light emission intensity is made uniform, and the life of the organic EL device can be extended.

In the organic EL device of the present invention, the substrate unit includes a substrate body and a recess forming layer formed on the substrate body and having a refractive index equivalent to that of the substrate body. It may be formed in the formation layer.
In this invention, the thickness of the light emitting layer is made uniform by laminating a concave portion forming layer having a refractive index equivalent to that of the substrate main body and having a concave portion formed in a portion corresponding to the central portion of the light emitting region. Plan

In the organic EL device of the present invention, the substrate portion may be formed of a substrate body, and the concave portion may be formed on an upper surface of the substrate body.
In the present invention, the thickness of the light emitting layer is made uniform by forming a recess in the upper surface of the substrate body.

Further, the organic EL device of the present invention includes a substrate portion, a partition wall formed on the substrate portion to partition a light emitting region, an anode layer and a cathode layer formed on the light emitting region on the substrate portion, A light emitting layer disposed between the anode layer and the cathode layer; and a reflective layer disposed below the light emitting layer, wherein the substrate portion is formed on the inner side of the outer peripheral edge of the light emitting region on the upper surface. It is characterized by having a concave part.
In the present invention, as described above, the light emission efficiency and the extraction efficiency in the light emitting region are made uniform, the light emission intensity is made uniform, and the life of the organic EL device can be extended. Here, the component which goes to the lower layer among the light generated in the light emitting layer is reflected toward the upper layer in the reflection layer.

[First Embodiment]
Hereinafter, a first embodiment of an organic EL device according to the present invention will be described with reference to the drawings. In each drawing used in the following description, the scale is appropriately changed to make each member a recognizable size. Here, FIG. 1 is a schematic plan view showing an organic EL device, and FIG. 2 is a cross-sectional view showing an element substrate.

[Organic EL device]
The organic EL device 1 according to the present invention is used as a line head of an exposure head in an optical printer. As shown in FIG. 1, a plurality of light emitting areas A are arranged in a line on a substantially rectangular element substrate 2 in plan view. It has a configuration. Note that the light emitting regions A may have other configurations, for example, formed in two rows in a staggered manner. The plurality of light emitting areas A are substantially circular in a plan view, and the organic EL element 11 is provided.
In addition, the element substrate 2 controls the TFT elements 12 that drive the organic EL elements 11, power supply lines 13 and 14 that supply power to the organic EL elements 11, the scanning lines 15, and the driving of the TFT elements 12. Drive control circuit 16 is formed.

Next, a detailed configuration of the light emitting region A of the element substrate 2 will be described with reference to FIG.
As shown in FIG. 2, the element substrate 2 includes a substrate portion 21, a base film 22, a gate insulating film 23, first to third interlayer insulating films 24 to 26, and a partition wall 27 stacked on the substrate portion 21. I have. The element substrate 2 includes a semiconductor layer 31 formed on the base film 22, a gate electrode 32 formed on the gate insulating film 23, and a source electrode 33 and a drain formed on the first interlayer insulating film 24. The electrode 34 and the organic EL element 11 formed on the third interlayer insulating film 26 are provided. In this specification, the partition wall 27 side is an upward direction when viewed from the substrate portion 21.

The substrate unit 21 includes a substrate body 41 and a recess forming layer 42 stacked on the substrate body 41.
The substrate body 41 is made of a light-transmitting material such as glass, for example, and has a uniform refractive index as a whole.
The recess forming layer 42 is made of SiO ₂ having a refractive index equivalent to that of the substrate body 41, and has a thickness of 0.7 μm, for example. And in the recessed part formation layer 42, the through-hole (recessed part) 42A which makes the shape similar to the outer periphery shape of the light emission area A by planar view is formed inside the outer periphery of the light emission area A. As shown in FIG. The diameter of the through hole 42A is, for example, 100 μm. Therefore, a concave portion that opens upward in accordance with the shape of the through hole 42 </ b> A is formed inside the outer peripheral edge of the light emitting region A in the substrate portion 21.

The base film 22 is formed of a light transmissive material such as SiN, for example.
The gate insulating film 23 is made of a light-transmitting material such as SiO ₂ and covers the semiconductor layer 31 formed on the base film 22.
The first interlayer insulating film 24 is made of a light-transmitting material such as SiO ₂ and covers the gate electrode 32 formed on the gate insulating film 23.
The second interlayer insulating film 25 is made of a translucent resin material such as acrylic.
The third interlayer insulating film 26 is formed of a light transmissive material such as SiN, for example.

The partition wall 27 has a configuration in which an inorganic bank 43 and an organic bank 44 are laminated in order from the third interlayer insulating film 26. The partition wall 27 divides each of the plurality of light emitting regions A, and has a substantially circular through hole 27A formed corresponding to the light emitting region A in a plan view. The through hole 27A is concentric with the through hole 42A formed in the recess forming layer 42, and has a diameter of, for example, 150 μm.
The inorganic bank 43 is formed of a light-transmitting material such as SiO ₂ and covers an anode layer 45 (to be described later) that is formed on the third interlayer insulating film 26 and constitutes the organic EL element 11. The organic bank 44 is formed of a resin material such as acrylic and is formed on the inorganic bank 43.

The semiconductor layer 31 has a channel region and a source region and a drain region formed by implanting impurity ions. The channel region is disposed to face the gate electrode 32 with the gate insulating film 23 interposed therebetween. The source region is connected to the source electrode 33 through a contact hole that penetrates the gate insulating film 23 and the first interlayer insulating film 24. The drain region is connected to the drain electrode 34 through a contact hole that penetrates the gate insulating film 23 and the first interlayer insulating film 24.
The gate electrode 32 constitutes a part of the scanning line 15. The source electrode 33 is connected to the power supply line 14. The drain electrode 34 is connected to the drain of the TFT element 12. The TFT element 12 is formed by the semiconductor layer 31, the gate electrode 32, the source electrode 33 and the drain electrode 34. The TFT element 12 is configured to supply power to the anode layer 45 via the power supply line 13 in accordance with the scanning signal supplied from the drive control circuit 16 via the scanning line 15.

The organic EL element 11 includes an anode layer 45, a light emitting layer 46, and a cathode layer 47 that are sequentially stacked from the substrate unit 21 side.
The anode layer 45 is formed of a light-transmitting conductive material such as ITO (Indium Tin Oxide), for example, and the drain electrode 34 via the contact hole H formed in the second and third interlayer insulating films 25 and 26. It is connected to the. The anode layer 45 is exposed in the opening region of the partition wall 27 through the through hole 27 </ b> A formed in the partition wall 27.

The light emitting layer 46 is formed on the anode layer 45 exposed in the opening region by the through hole 27 </ b> A of the partition wall 27. The light emitting layer 46 is formed by applying the constituent material of the light emitting layer 46 using a wet method such as a droplet discharge method or a spin coat method, and drying it. Here, in the light emitting layer 46, the difference in height in the stacking direction between the peripheral portion and the central portion of the light emitting region A is, for example, 40 nm.
Note that other functional layers such as a hole injection layer, a hole transport layer, and an electron transport layer may be disposed between the light emitting layer 46 and the anode layer 45 and between the light emitting layer 46 and the cathode layer 47. Good.

The cathode layer 47 has a structure in which a LiF (lithium fluoride) film and an Al (aluminum) film are stacked in this order from the light emitting layer 46 side, and is formed on the partition wall 27. The cathode layer 47 is connected to the power line 14 and serves as a common electrode over the entire light emitting region A. Here, the Al film constituting the cathode layer 47 functions as a reflective layer that reflects the light generated in the light emitting layer 46 toward the anode layer 45. In other words, the organic EL device 1 has a bottom emission structure in which the cathode layer 47 that functions as a reflective layer is disposed farther from the substrate portion 21 than the light emitting layer 46.
The cathode layer 47 is formed of an inorganic compound such as a silicon compound such as silicon oxide, silicon nitride, or silicon nitride oxide, and prevents the cathode layer 47 from corroding in the manufacturing process. A cathode layer protective film (not shown) is provided.

In the organic EL device 1 having such a configuration, when a voltage is applied between the anode layer 45 and the cathode layer 47, holes move from the anode layer 45 toward the cathode layer 47, and electrons move from the cathode layer 47 to the anode layer. Move towards 45. The light emitting layer 46 emits light by recombination of holes and electrons. At this time, since the film thickness between the peripheral portion and the central portion of the light emitting region A is equal in the light emitting layer 46, the light emission intensity in the light emitting region A is made uniform.
Then, the generated light is emitted from the lower surface of the substrate body 41 as a component toward the cathode layer 47 is reflected toward the substrate body 41 in the cathode layer 47. At this time, when the generated light is transmitted through the substrate portion 21, the recess forming layer 42 has a refractive index equivalent to that of the substrate main body 41, so that almost no reflection occurs at the interface between the recess forming layer 42 and the substrate main body 41. For this reason, the change in the spectrum is suppressed between the peripheral portion and the central portion of the light emitting region A, and light having a uniform intensity is emitted.

  Here, FIG. 3 shows the relationship between the position in the light emitting region and the light emission intensity when the concave portion is formed in the substrate portion 21 and when the concave portion is not formed. As shown in FIG. 3, it can be understood that the light emission intensity of the light emitting layer 46 is made uniform by forming the concave portion in the substrate portion 21.

[Exposure head]
The organic EL device 1 described above is provided in an exposure head 50 as shown in FIG. 4, for example. Here, FIG. 4 is a schematic block diagram showing the exposure head 50.
The exposure head 50 includes a housing 51 and an optical member 53 disposed between the housing 51 supported and fixed to the housing 51 and the photosensitive drum 52. The housing 51 has an opening formed on the photosensitive drum 52 side, and the organic EL device 1 is fixed so that light from the organic EL is emitted toward the opening.

[Image forming apparatus]
Further, the above-described exposure head 50 is used in an optical printer 60 as shown in FIG. 5, for example. Here, FIG. 5 is a schematic configuration diagram showing the optical printer.
The optical printer 60 includes an exposure head 50, a photosensitive drum 52, a corona charger 61, a developing roller 62, a transfer roller 63, a cleaning device 64, and a transfer medium 65 such as paper.

The photosensitive drum 52 is configured to rotate clockwise as shown in FIG. 5, and the exposure light is irradiated from the exposure head 50 when the photosensitive drum 52 reaches a position facing the emission surface of the exposure head 50. It has become. That is, the photosensitive drum 52 is configured such that line scanning is sequentially performed by the exposure head 50 every time the circumferential surface reaches a predetermined position by rotation.
The corona charger 61 is disposed upstream of the predetermined position in the rotation direction of the photosensitive drum 52 and is configured to uniformly charge the peripheral surface of the photosensitive drum 52.

The developing roller 62 is disposed downstream of the predetermined position in the rotation direction of the photosensitive drum 52. The developing roller 62 applies a toner as a developer to the electrostatic latent image formed on the photosensitive drum 52 so that a visible image ( Toner image).
The transfer roller 63 is disposed downstream of the developing roller 62 in the rotation direction of the photosensitive drum 52, and is configured to transfer a visible image formed on the photosensitive drum 52 to a transfer medium.
The cleaning device 64 is disposed between the transfer roller 63 and the corona charger 61 in the rotation direction of the photosensitive drum 52, and remains on the surface of the photosensitive drum 52 after the transfer of the visible image to the transfer medium 65. The toner is removed.

  As described above, according to the organic EL device 1 in the present embodiment, the light emitting layer 46 is formed by laminating the concave portion forming layer 42 having the same refractive index and having the through hole 42 </ b> A formed on the substrate body 41. The thickness of the light is made uniform, and the light emission intensity is made uniform. Further, since reflection at the interface between the recess forming layer 42 and the substrate main body 41 is prevented, interference of light transmitted through the substrate portion 21 is suppressed, and the spectrum of the emitted light is made uniform. Therefore, the lifetime of the organic EL device 1 can be extended.

[Second Embodiment]
Next, a second embodiment of the organic EL device according to the present invention will be described with reference to the drawings. In the present embodiment, since the direction of extraction of light generated in the light emitting layer is different from that in the first embodiment described above, this point will be mainly described, and the same reference numerals are given to the components described in the above embodiment. A description thereof will be omitted. Here, FIG. 6 is a cross-sectional view showing the organic EL device.

In the organic EL device 100 according to the present embodiment, as shown in FIG. 6, the anode layer 102 of the element substrate 101 is formed of a conductive material having reflection characteristics such as Al. Therefore, the anode layer 102 has a function as a reflective layer. That is, the organic EL device 100 has a top emission structure in which the anode layer 102 functioning as a reflective layer is disposed closer to the substrate unit 21 than the light emitting layer 46.
The cathode layer 103 is formed of a light-transmitting conductive material such as ITO.
Also in the organic EL device 100 having such a configuration, since the film thickness between the peripheral portion and the central portion of the light emitting region A is equal in the light emitting layer 46, the light emission intensity in the light emitting region A is made uniform. The
Further, the generated light is emitted from the upper surface of the cathode layer 103 as a component directed to the anode layer 102 is reflected toward the cathode layer 103 in the anode layer 102.

  As described above, also in the organic EL device 100 according to the present embodiment, the same operations and effects as those of the first embodiment described above are exhibited.

In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.
For example, the planar shape of the light emitting region is not limited to a circle and may be other shapes. Similarly, the planar shape of the recess is not limited to a circular shape concentric with the light emitting region, and may be another shape.
In addition, the amount of protrusion to the inside of the outer periphery of the recess with respect to the opening of the light emitting region may be appropriately changed as long as the thickness of the light emitting layer can be made uniform.

In the first embodiment, the concave portion is formed in the substrate portion by laminating the concave portion forming layer in which the through hole is formed on the flat plate substrate main body, but the substrate main body is not provided with the concave portion forming layer. It is good also as a structure which forms a recessed part in the upper surface of this.
In the second embodiment, the concave portion only needs to be formed below the anode layer functioning as the reflective layer, and may be formed, for example, in the second interlayer insulating film. In addition, since the light generated in the light emitting layer does not pass through the substrate portion, the refractive index of the substrate body and the recessed portion forming layer need not be the same, and the recessed portion forming layer is not provided on the upper surface of the substrate body as described above. It is good also as a structure which forms a recessed part.

In the first embodiment, the cathode layer also functions as a reflective layer, but a reflective layer may be separately provided above the cathode layer. Similarly, in the second embodiment, the anode layer also functions as a reflective layer, but a reflective layer may be separately provided below the anode layer.
The organic EL device constitutes a line head in the optical printer, but is not limited to the line head and may be used in a display device. Electronic devices including an organic EL device are not limited to line heads, but include cellular phones, PDAs (Personal Digital Assistants), personal computers, notebook personal computers, workstations, digital still cameras, in-vehicle monitors, Car navigation system, head-up display, digital video camera, television receiver, viewfinder type or monitor direct-view type video tape recorder, pager, electronic organizer, calculator, electronic book or projector, word processor, video phone, POS terminal, touch panel It may be another electronic device such as a device including a lighting device or a lighting device.

1 is a schematic plan view showing an organic EL device according to a first embodiment of the present invention. It is sectional drawing which shows an element substrate. It is a graph which shows the emitted light intensity in a light emission area | region. It is a perspective view which shows the line head module which can apply this invention. It is a schematic block diagram which shows an optical printer provided with a line head module. It is sectional drawing which shows the organic electroluminescent apparatus in 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,100 Organic EL device, 27 Partition, 27A Through-hole (opening), 31 Substrate part, 41 Substrate body, 42 Recess formation layer, 45 Anode layer, 46 Light emitting layer, 47 Cathode layer (reflection layer), 102 Anode layer (Reflective layer), 103 cathode layer, A light emitting region

Claims (4)

A substrate section;
A partition wall formed on the substrate portion and defining a light emitting region;
An anode layer and a cathode layer formed in the light emitting region on the substrate part;
A light emitting layer disposed between the anode layer and the cathode layer;
A reflective layer disposed above the light emitting layer,
2. The organic EL device according to claim 1, wherein the substrate portion has a uniform refractive index at least in the light emitting region, and has a recess formed on an upper surface of the outer peripheral edge of the light emitting region. The substrate portion includes a substrate body, and a recess forming layer that is laminated on the substrate body and has a refractive index equivalent to that of the substrate body,
The organic EL device according to claim 1, wherein the recess is formed in the recess forming layer. The substrate portion is formed of a substrate body;
The organic EL device according to claim 1, wherein the recess is formed on an upper surface of the substrate body. A substrate section;
A partition wall formed on the substrate portion and defining a light emitting region;
An anode layer and a cathode layer formed in the light emitting region on the substrate part;
A light emitting layer disposed between the anode layer and the cathode layer;
A reflective layer disposed below the light emitting layer, and
The organic EL device according to claim 1, wherein the substrate portion has a concave portion formed on an inner side of an outer peripheral edge of the light emitting region on the upper surface.

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