Patent Application
20160299454
1. Field of the Invention
The present invention relates to a light emitter that includes an organic electroluminescent device and to an image formation system and an exposure unit in which such a light emitter is used.
2. Description of the Related Art
Printers with laser scanners, which are printers based on the technology of electrophotography, have gained widespread use. Common laser beam printers have a scanner with which light emitted from a laser source is scanned over a photosensitive element to make this element exposed to the light. This laser scanner, because of its structure, cannot be easily reduced in size.
Meanwhile, researchers have been studying laser beam printers that use an elongated light source for exposure (an elongated exposure light source) including an array of light-emitting devices to make a photosensitive element exposed. Allowing for the use of a smaller light source unit, this approach is effective in miniaturizing printers. Organic electroluminescent (EL) devices in particular, which are low power consumption light-emitting devices that can be densely arranged, can be used in light emitters for light source units of printers.
Organic EL devices have a pair of electrodes and an organic layer between the electrodes. Carriers injected from the pair of electrodes recombine in the organic layer, producing excitons. When the excitons return to the ground state, light is emitted.
Organic EL devices are promising light-emitting devices, but as known, they have their excellent properties affected when exposed to moisture. This means that the light-emitting properties of an organic EL device can be maintained by protecting the device from the entry of moisture during production and after completion.
Japanese Patent Laid-Open No. 2010-280066 describes the use of an organic EL device as an exposure section of an image formation system. This organic EL device has a substrate and an organic layer formed using a coating technique. There are walls on the substrate to prevent the coating liquid, in which an organic compound is dissolved, from flowing beyond the edge of the substrate. The device further has an upper electrode, which is continuous and stretches over the walls.
As a consequence of having an upper electrode stretching over the walls, however, this organic EL device may suffer from defects in the upper electrode or a thin-film seal optionally provided on the upper electrode if there is any contaminant on the walls. Such defects in a seal or the upper electrode provide pathways for moisture to penetrate, thereby causing the properties of the organic EL device to be affected.
An aspect of the invention provides a highly reliable light emitter. This light emitter has projections and an upper electrode spaced from each other, and this structure limits the formation of ways in for moisture or other contaminants to reach the organic EL devices in the light emitter.
To be more specific, an aspect of the invention is a light emitter that includes an elongated substrate and a plurality of emission elements on the substrate. The emission elements include a first electrode, an organic layer, and a second electrode in this order from the substrate side. The organic layer stretches over one of the emission elements and a next one in the longitudinal direction of the substrate. The light emitter further has a plurality of projections on the substrate. Each of the projections is adjacent to each of the emission elements in the transverse direction of the substrate. The emission elements are located between one of the projections and another. The projections are higher than the second electrode with respect to the principal surface of the substrate. The projections and the second electrode are spaced from each other.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
An aspect of the invention is a light emitter that includes a substrate and a plurality of emission elements on the substrate.
The emission elements include a first electrode, an organic layer, and a second electrode in this order from the substrate side.
The organic layer stretches over one of the emission elements and a next one in the longitudinal direction of the substrate.
The light emitter further has a plurality of projections on the substrate. The projections are adjacent to the emission elements, on a one-by-one basis, in the transverse direction of the substrate.
The emission elements are located between one of the projections and another.
The projections are higher than the second electrode with respect to the principal surface of the substrate.
The projections and the second electrode are spaced from each other. The projections protect the organic EL devices from external contact.
The light emitter according to an aspect of the invention has projections higher than the second electrode with respect to the principal surface of the substrate. This means that the projections are taller than the second electrode. This structure ensures that the projections come into contact with external components first, preceding the second electrode, thereby making the projections more likely to catch contaminants than the second electrode is. These projections and the second electrode, or the organic EL devices, are spaced from each other. Even if any contaminant on the projections forms pathways for moisture to penetrate, this structure limits the formation of pathways through which the moisture could reach the organic EL devices.
An example of a situation where the projections catch a contaminant is when the projections come into contact with a mask for deposition, for example.
The substrate has two different directions: first and second directions. The substrate is described as elongated when its length in the first direction is greater than its length in the second direction. The first and second directions may be perpendicular to each other. The first and second directions of an elongated substrate may be referred to as longitudinal and transverse directions, respectively.
An elongated substrate may bend if the substrate is held only at its longitudinal ends. In an aspect of the invention, the projections provided in the light emitter can be used to hold the substrate in addition to the longitudinal ends of the substrate.
The reduced bending of the substrate, as a result, allows the user to form the organic layer with good characteristics, even by vapor deposition for example.
The projections according to an aspect of the invention can be made from inorganic or resin materials. Inorganic projections can be obtained by working silicon oxide or silicon nitride using dry etching, photolithography, or similar. Resin projections can be obtained by curing a photosensitive resin, such as a photoresist.
The height of the projections in relation to the top of the substrate can be 1 μm or more, preferably 2 μm or more and 10 μm or less.
Although the projections 5 in
In this embodiment, the data line 8, the organic layer 6, and the scanning circuit 11 are arranged in this order in the transverse direction of the substrate. In other words, the organic layer is located between the data line and the scanning circuit. This arrangement, in which the organic layer 6 is located between the two components and therefore is away from the transverse ends of the substrate, effectively prevents the entry of external moisture. The data line and other wire lines, or collectively the wiring, may be all along one side of the substrate.
The light emitter 20 further has source/drain electrodes 19 and metal wiring 21 on the interlayer dielectric 14. The source/drain electrodes are electrically coupled to the channel 15 and the gate electrode 17 of the TFTs 18 via holes created in the interlayer dielectric 14. The metal wiring 21 provides the power line 10 and the data line 8.
On the interlayer dielectric 14, on which there exist the source/drain electrodes 19 and the metal wiring 21, the light emitter 20 has a passivator 22 made of silicon oxide, silicon nitride, or any other inorganic insulator as a protection for the metal wiring.
A first electrode 25 of an organic EL device 28 is located on the interlayer dielectric 14, coupled to a source/drain electrode 19. The first electrode may also be referred to as the lower electrode. The first electrode is covered with a pixel separator 23 at its ends to prevent short circuits between the first electrode and a second electrode 27. An organic layer 26 is located between the first electrode 25 and the second electrode 27. The pixel separator 23 has an opening 24, in which the organic layer 26 is in contact with the first electrode 25. The second electrode 27 is spaced from the projections 5. The second electrode may also be referred to as the upper electrode.
There is also a seal 29 made of an inorganic material, covering the second electrode and the projections.
The substrate can be, for example, a glass substrate or a silicon substrate. A flexible substrate can also be used. Even if a flexible substrate is used, the projections allow the user to perform vapor deposition without contact of organic EL devices with the masks for deposition.
The undercoat and the interlayer dielectric are layers of inorganic insulators, such as silicon oxide and silicon nitride.
At least one of the first and second electrodes is transparent or translucent. The term translucent means that the material has a transmittance of 50% or more. The other electrode may be a reflective electrode.
Transparent electrodes can be made from materials such as indium tin oxide and indium zinc oxide. Translucent electrodes can be layers of materials such as aluminum and silver having an appropriate thickness, e.g., 20 nm or more and 30 nm or less. Translucent electrodes can be made from materials highly reflective to the visible spectrum. Besides pure aluminum and silver, such electrodes can also be made from their alloys or be multilayer structures containing these metals, preferably an Ag—Mg alloy or multilayer structure if silver is used.
The pixel separator is a layer that prevents short circuits between the first and second electrodes. The organic layer interposed between the first and second electrodes are not thick enough to prevent these electrodes from short-circuiting. Thus, the pixel separator is provided.
The opening in the pixel separator defines the plane where the first electrode and the organic layer come into contact. In other words, emission regions are defined by the pixel separator.
The pixel separator can be made from organic or inorganic materials, preferably inorganic materials. Examples of materials for organic pixel separators include resins such as polyimide. Examples of materials for inorganic pixel separators include silicon oxide and silicon nitride.
The organic layer includes an emission layer. Although the organic layer in
The seal is a layer of an inorganic material. Specific examples of materials include silicon oxide, silicon nitride, silicon oxynitride, and aluminum oxides. Silicon oxide, silicon nitride, silicon oxynitride can be formed into a layer by sputtering or CVD, and aluminum oxides can be formed into a layer by ALD (atomic layer deposition). A water permeability of 10−6 g/m2·day or less provides sufficient tightness to the seal. The thickness of the seal is not limited. A thickness of 2 μm or more ensures sufficient tightness.
The light emitter may have a second seal such as a glass cap over a seal 29 with a desired thickness as a tentative sealing structure.
The seal 29 extends over the entire surface of the substrate. The bonding pad 12 is exposed in a separate operation and then is connected to the outside.
In
An example of a light emitter that uses the arrangement pattern illustrated in
The light emitter can also be a linear emitter in which emission elements are arranged in an array of 2 rows and 2506 columns as illustrated in
Alternatively, the emission elements may zigzag in a staggered pattern along the direction of columns as in
Projection pitch 37−Projection width 38−Second electrode width 36≧105 μm (1)
The projection pitch 37 is the sum of the projection width, the total width of the spaces, and the second electrode width. Formula (1) means that the total transverse length of the spaces that exist between one projection and the other, which is located across the organic layer, is 105 μm or more. Such a design ensures the second electrode and the projections remain spaced during the process of vapor deposition including deposition mask patterning.
As a result, the second electrode and the projections are spaced reliably in actual production, where positional variations can occur because of inaccurate alignment of substrates and masks.
Given the fact that most contaminants are particles with diameters smaller than 1 μm, the distance between a projection and the second electrode in the transverse direction of the substrate can be 2 μm or more.
The projections 5 may have any shape for the purpose of the protection of the emission elements 4. Strip-shaped projections, preferably non-segmented ones, have the ability to serve as a seamless protector.
The projections may have any longitudinal length. The projections may be longer than the emission elements in the longitudinal direction of the substrate, preferably longer than the organic layer, more preferably than the second electrode covering the organic layer. This ensures that any flaws due to rubbing or similar are substantially confined to the outside of the second electrode, limiting the formation of pathways that moisture can reach the organic EL devices through.
The following describes the production of an organic light emitter according to an aspect of the invention. The production of an organic light emitter according to an aspect of the invention includes at least the following production processes:
(A) providing a pixel separator, which defines emission regions, on a first electrode;
(B) providing projections on the pixel separator;
(C) forming an organic layer on the first electrode;
(D) covering the organic layer with a second electrode; and
(E) providing a seal to cover the second electrode.
In this aspect of the invention, the second electrode and the projections are spaced from each other, preferably satisfying the relationship below.
Projection pitch 37−Projection width 38−Second electrode width 36≧105 μm (1)
This limits the formation of ways in for moisture that occurs in the course of producing the light emitter when the substrate comes into contact with a patterning mask and catches any contaminant on the projections during vacuum deposition. As a result, a highly reliable organic light emitter is obtained.
This section describes a first production method.
An undercoat 13 as a layer of an inorganic insulator, such as silicon oxide or silicon nitride, is formed on a substrate 3, for example a glass substrate, using CVD or similar.
TFTs 18 including a channel 15, a gate dielectric 16, and a gate electrode 17 are formed on the undercoat 13 in the same way as in the known production of TFTs.
An interlayer dielectric 14 as a layer of an inorganic insulator, such as silicon oxide or silicon nitride, is formed on the undercoat 13 with the TFTs 18 thereon using CVD or similar.
The interlayer dielectric 14 is perforated with holes using photolithography and dry etching to expose the electrodes of the TFTs 18. Components including source/drain electrodes 19 and metal wiring 21 are then formed. The source/drain electrodes 19 are coupled to the TFTs 18 via the holes.
A passivator 22 as a layer of an inorganic insulator, such as silicon oxide or silicon nitride, is formed on the interlayer dielectric 14 with the source/drain electrodes 19, the metal wiring 21, and other components thereon using CVD or similar.
The passivator 22 is perforated with holes using photolithography and dry etching to expose the source/drain electrodes 19. A first electrode 25 is then formed and coupled to the source/drain electrodes 19 via the holes.
After the first electrode 25 has been formed, a pixel separator 23 as a layer of an inorganic insulator, such as silicon oxide or silicon nitride, is formed using CVD or similar.
The pixel separator 23 is patterned using photolithography and dry etching to create openings 24 that define emission regions.
The pixel separator 23 is coated with a photosensitive resin material, such as polyacrylate or polyimide, using spin coating or similar. The coating of the photosensitive resin material is photolithographically patterned to form projections 5. This coating for the formation of the projections 5 according to an aspect of the invention needs to be thick enough that the projections 5 will protrude in the direction perpendicular to the surface of the substrate in relation to the second electrode 27 (described hereinafter). Resin materials can be formed into a thick film with relative ease.
An organic layer 26 is formed to cover the exposed area, in the opening 24 created in the pixel separator 23, of the first electrode 25 through vapor deposition using a mask. The organic layer 26 has an emission layer that contains a light-emitting material, and may optionally have other layers such as a hole transport layer and an electron transport layer. Superposing the substrate 1 and the mask on one another as illustrated in
A second electrode 27 is formed on the organic layer 26 and the pixel separator 23. The second electrode 27 is a metal film, such as one made from aluminum, silver, or magnesium or an alloy of these metals, formed through sputtering or vapor deposition using a mask. The organic layer 26 is covered with the second electrode 27. In this way, organic EL devices 28 that include the first electrode 25, the organic layer 26, and the second electrode 27 are formed.
Light emitters produced in this embodiment may have the bottom emission structure, in which light is taken out from the substrate side, or the top emission structure, in which light is taken out from the opposite side. When the organic EL devices 28 are bottom emission devices, the first electrode 25 is made from a transparent electrode material, such as ITO, and the second electrode 27 from a reflective electrode material, such as aluminum. When the organic EL devices 28 are top emission devices, the first electrode 25 is made from a reflective electrode material, and the second electrode 27 is made from a transparent electrode material.
A seal 29 as a layer of silicon nitride, silicon oxide, or similar is formed on the entire surface using sputtering, CVD, or similar. When the organic EL devices are bottom emission devices, the seal 29 does not need to be permeable to light. When the organic EL devices are top emission devices, the seal 29 needs to be permeable to light because the light the organic EL devices 28 generate is taken out on the seal 29 side.
When manufacturing elongated exposure light sources in which organic EL devices are arranged in a row, a possible way to reduce the cost is batch production of multiple exposure light sources on a single mother glass. For example, it is possible to produce 138 elongated exposure light sources (219 mm×4.7 mm) in a batch on a second-generation mother glass (460 mm×365 mm) if an array of 69 rows and 2 columns is used. The inventors, however, have found through research that batch production of multiple elongated exposure light sources on a large mother glass substrate suffers from the following disadvantage at the formation of the organic layer 26 and the second electrode 27.
As illustrated in
When a substrate and a mask for deposition with different amounts of flexure are placed over one another, the substrate first touches the mask at its center and then in its outer areas as illustrated in
The light emitter according to an aspect of the invention can be produced without contact between its substrate and a mask because the projections serve as spacers. For this purpose, and given the fact that most of contaminants typically found in clean rooms for the manufacture of semiconductor devices or similar are particles with diameters of 1 μm or less, the height of the projections can be 1.0 μm or more, preferably 2.0 μm or more and 10 μm or less. This limits the contact between the emission elements and the mask and reduces the occurrence of dark spots.
It should be understood that although
This section presents another method for the production of the organic light emitter, only describing differences from the first production method.
A pixel separator 23 as a layer of an organic insulator, such as polyimide or polyacrylate, is formed on the passivator 22 on which the first electrode 25 has been formed. These hygroscopic resins may be dehydrated through a thorough baking in vacuum beforehand if they are used in the organic layer 26.
It is possible to produce multiple elongated light emitters 20 (219 mm×4.7 mm) in a batch on a second-generation mother glass substrate (460 mm×365 mm). For example, a dense array of 69 rows and 2 columns formed in the middle of the mother glass substrate like the arrangement illustrated in
The light emitter according to an aspect of the invention has multiple projections 5 that protrude in the direction perpendicular to the surface of the substrate in relation to the second electrode 27 and are arranged in the longitudinal direction of lines of emission elements. When the mother glass substrate and a mask for deposition are placed over one another, the mask is supported by the projections in contact with them, whereas the pixel separator, the organic layer, and the second electrode are spaced from the mask.
The projections can have any height greater than that of the upper electrode. The height of the projection can be 1.0 μm or more, preferably 2 μm or more and 10 μm or less. This is based on the fact that contaminants found in clean rooms are 1 μm or smaller in size and is to ensure that when a mask for deposition approaches the substrate with such contaminants on the substrate, the mask does not come into contact with the substrate.
The light emitter according to an aspect of the invention has projections, and these projections come into contact with the mask first. Contaminants are caught by the projections, with only limited adhesion to the light emitter. As a result, the occurrence of dark spots due to contaminants is reduced.
Contact of a mask for deposition and the projections may cause transfer of deposits on the mask to the projections. Deposits transferred to the projections can serve as starting points for cracks to grow in the seal 29 formed on the second electrode 27. A cracked seal is no longer as effective in shielding the organic EL devices 28 from the ambient atmosphere including moisture and oxygen as it has been. The use of fewer projections can be a solution to this.
Light emitters according to this embodiment can be implemented even with relatively few projections and, therefore, can be relatively free from cracking in the seal starting from projections.
In all other respects, this embodiment is equivalent to the first embodiment. The efficient arrangement of projections in the light emitters according to this embodiment reduces the number of points of contact with external components, limiting the adhesion of contaminants. This embodiment, furthermore, provides an efficient way of manufacturing light emitters in which four columns of light emitters can be produced on a single substrate.
This embodiment is equivalent to the foregoing one except for the arrangement of the projections the light emitters have.
In this embodiment, the arrangement and total number of projections are the same across the four columns of light emitters on the mother glass substrate.
The efficient arrangement of projections in the light emitters according to this embodiment reduces the number of points of contact with external components, limiting the adhesion of contaminants. This embodiment, furthermore, provides an efficient way of manufacturing light emitters in which four columns of light emitters can be produced on a single substrate. Even in a four-column batch production of light emitters, further reduction of the adhesion of contaminants is possible.
This embodiment is different from the foregoing ones in that the projections are not dot-shaped at least in part. Specific examples of the shapes such projections can have in their cross-sections parallel to the substrate include circular, oval, and strip-like shapes.
The use of strip-shaped projections leads to further reduction in the number of projections and limitation of the adhesion of contaminants.
In this aspect of the invention, the number of light emitters that can be produced on a single glass substrate increases with decreasing width of each elongated substrate. The width of each elongated substrate can be 10 mm or less, or more specifically 1 mm or more and 10 mm or less.
The seal is not essential for light emitters according to an aspect of the invention.
An image formation system according to an aspect of the invention has a photosensitive element, a charging section configured to charge the surface of this photosensitive element, an exposure section configured to expose the photosensitive element to light to form an electrostatic latent image, and a developer section configured to apply a developer solution to the photosensitive element to develop the electrostatic latent image formed on the surface of the photosensitive element. The exposure section of the image formation system includes an organic light emitter according to an aspect of the invention.
Organic light emitters according to an aspect of the invention can also be used as a component of exposure units configured to expose photosensitive elements to light. An example of an exposure unit that has an organic light emitter according to an aspect of the invention is one in which the organic light-emitting devices as a component of the organic light emitter according to an aspect of the invention are arranged in rows along a predetermined direction.
The image formation system 40 in
In
In
The pattern of the emission segments (42α and 42β) constituting the exposure light source in
Organic light emitters according to an aspect of the invention therefore offer an extended and stable display of images with good quality.
The following describes certain aspects of the invention by providing some examples. It should be understood that the process from undercoating to the formation of a pixel separator performed in the production of organic light emitters in Examples is included in an aspect of the invention, as long as it falls within the range of typical processes in the manufacture of semiconductor devices.
In the following description of Examples, some arrangements of emission elements are mentioned but non-limiting factors, such as the size of substrates, is not.
A light emitter was produced in accordance with the process illustrated in
An undercoat 13 as a layer of an inorganic insulator (silicon nitride) was formed on a glass substrate 10 using CVD. TFTs 18 including a channel 15, a gate dielectric 16, and a gate electrode 17 were formed on the undercoat 13 in the same way as in the known production of TFTs. An interlayer dielectric 14 as a layer of an inorganic insulator (silicon oxide) was formed on the undercoat 13 with the TFTs 18 thereon using CVD. The interlayer dielectric 14 was perforated with holes using photolithography and dry etching to expose the electrodes of the TFTs 18. Components including source/drain electrodes 19 and metal wiring 21 were then formed. The source/drain electrodes 19 were coupled to the TFTs 18 via the holes. A passivator 22 as a layer of an inorganic insulator (silicon oxide) was formed on the interlayer dielectric 14 with the source/drain electrodes 19, the metal wiring 21, and other components thereon using CVD. The passivator 22 was perforated with holes using photolithography and dry etching to expose the source/drain electrodes 19. A first electrode 25 was then formed using indium tin oxide (ITO), and coupled to the source/drain electrodes 19 via the holes. A pixel separator 23 as a 200-nm-thick layer of an inorganic insulator (silicon nitride) was formed on the first electrode 25 using CVD. The pixel separator 23 was patterned using photolithography and dry etching to create openings 24 that defined emission regions measuring 40 μm by 40 μm.
The total number of emission elements on the substrate was 500, and they were arranged in a row (n=1, m=500). The substrate was dehydrated through a backing at approximately 250° C. before the formation of an organic layer (described hereinafter).
A 2-μm-thick coating of a photosensitive resin material (polyimide) was formed on the pixel separator 23 using spin coating and photolithographically patterned to leave projections 5. The 2-μm-thick coating was patterned in the longitudinal direction 2 of the substrate 1 in such a manner that the width in top view would be 10 μm, that the transverse distance from the middle line of the row of emission elements would be 360 μm, and that the projection pitch would be 720 μm, leaving projections 5 on the substrate 1. Their length was shorter than that covered by the emission elements. In this way, two non-segmented 2-μm-tall and 10-μm-wide projections were formed, with one on one side and one on the other side across the organic layer. The first electrode, a component of emission elements, was therefore positioned between one projection and the other.
An organic layer 26 was formed through vapor deposition using a mask to cover the exposed area, in the opening 24 created in the pixel separator 23, of the first electrode 25. During this process, the mask was in complete contact so that the organic layer 26 would be formed within a predetermined area. The organic layer was composed of a hole injection layer, a hole transport layer, an electron blocking layer, an emission layer, a hole blocking layer, an electron transport layer, and an electron injection layer deposited in this order. All materials in the individual layers were known and commercially available. The emission layer was configured to emit light in red in order to match the wavelengths of light that the photosensitive material reacts to.
A second electrode 27 was formed to cover the organic layer 26. The second electrode 27 was a 200-μm-thick film of aluminum and was formed within a predetermined area through vacuum deposition using a mask. The transverse width of the second electrode was 600 μm, and its middle line was aligned with the middle line of the row of emission elements. As a result, the second electrode 27 was spaced from the projections 5 by at least 2 μm.
A seal 29 as a 2-μm-thick layer of silicon nitride was formed on the entire surface using CVD. In this example, the pixel separator 23 and the seal 29 were in contact with each other.
A bonding pad 22 was exposed through photolithography and dry etching and connected to an external circuit. In this way, an organic light emitter 20 was obtained.
A light emitter was produced as in Example 1 except that the pixel separator was formed from an organic insulator.
A change was made to the formation of a pixel separator on a glass substrate (1-1;
The procedure in Example 2 was repeated, except in the formation of projections on a pixel separator (1-2;
A light emitter was produced in the same way as in Example 2, except in the formation of projections on a pixel separator (1-2;
A light emitter was produced in the same way as in Example 2, except in the formation of projections on a pixel separator (1-2;
A light emitter was produced in the same way as in Example 2, except in the formation of projections on a pixel separator (1-2;
A light emitter was produced in the same way as in Example 2, except in the formation of a pixel separator on a glass substrate (1-1;
A change was made to the formation of a pixel separator on a glass substrate (
The organic light emitter obtained in this example was in the top emission structure, a structure in which light is taken out from the sealed side. Except for these, the same procedure as in Example 2 was repeated to produce a light emitter.
A light emitter was produced in the same way as in Example 8, except that the substrate in Example 8 was changed to a silicon substrate. The organic light emitter obtained in this example, too, was in the top emission structure, a structure in which light is taken out from the sealed side.
The procedure in Example 1 was repeated, except in the formation of projections on a pixel separator (
The procedures in Examples 1 and 2, respectively, were repeated except that no projections were formed.
In this comparative example, the light emitter had projections but not spaced from the second electrode.
In the formation of projections on a pixel separator (1-2;
The production of a light emitter under these conditions was tried five times, but in all attempts, the second electrode 27 overlapped the projections 5.
In this comparative example, too, the light emitter had projections but in contact with the second electrode.
An organic light emitter was produced in the same way as in Comparative Example 3, except that the organic layer 26 was covered with the second electrode 27.
In this reference example, the relationship among the projection pitch, the projection width, and the second electrode width did not satisfy formula (1). In the formation of projections on a pixel separator (1-2;
Failure to satisfy formula (1) caused the projections and the second electrode to overlap in some cases.
The production of a light emitter under the above conditions was attempted five times, but in three attempts, the second electrode 27 overlapped the projections 5. In the production of light emitters, satisfying formula (1) can be a solution to this.
The organic light emitters produced in Examples and Comparative Examples were studied as follows. The light emitters in Examples 1 to 10 were produced five times each, and in all of these light emitters, the second electrode and the projections were spaced from each other.
Light Emission after Mounting
The light emitters in Examples 1 to 10 were cut out from a mother glass and mounted in a predetermined casing. The projections 5, formed as a protector, protected the emission regions, and any damage associated with the mounting operation was confined to the projections 5, not involving the second electrode 27. Since the projections 5 and the second electrode 27 were spaced from each other, the emission elements were not reached by damaging gases, such as moisture and oxygen, penetrating through seal defects that occurred near the projections.
The emission elements were also protected from similar damage caused by contaminants that adhered to the projections during production. The projections 5 defended the finished light emitters from fatal flaws, making the light emitters reliable for extended periods.
The devices produced in Comparative Examples 1 and 2 were not as reliable. These devices experienced defects that caused flaws that grew to reach the emission elements.
The light emitters were stored at 85° C. and 85% RH. The light emitters in Examples 1 to 10 successfully emitted light even after 1000 hours of storage.
The light emitters in Comparative Examples 1 and 2 had seal defects at the edge of the organic layer and the upper electrode caused by contaminants transferred from a mask to the substrate during film formation, and these defects had increased the area of non-emission regions. In Comparative Example 3, three emitters in which the second electrode overlapped the projections 5 allowed moisture to seep thereinto through seal defects caused by contaminants on the projections. The moisture permeated the structure between the second electrode 27 and the substrate and reached the emission elements, leading to poor light emission. In Comparative Example 4, all emitters allowed moisture to seep thereinto through seal defects caused by contaminants on the projections 5. The moisture permeated the structure between the second electrode 27 and the substrate and reached the emission elements, leading to poor light emission. In Reference Example 1, moisture seeped through seal defects caused by contaminants on the projections 5. The moisture penetrated the organic layer 26 and reached the emission elements, leading to poor light emission.
The light emitters produced in Examples, in which the organic layer 26 was covered with the second electrode 27 to reduce damage to the emission elements associated with the penetration of moisture and oxygen, were found to be reliable.
An aspect of the invention provides a highly reliable light emitter. This light emitter has projections and an upper electrode spaced from each other, and this structure limits the formation of ways in for moisture or other contaminants to reach the organic EL devices in the light emitter.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2015-079478, filed Apr. 8, 2015, and Japanese Patent Application No. 2015-106772, filed May 26, 2015, which are hereby incorporated by reference herein in their entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-079478 | Apr 2015 | JP | national |
| 2015-106772 | May 2015 | JP | national |
