Patent Application
20070278947
Embodiment Modes of the present invention will be explained below with reference to the accompanying drawings. However, it is to be easily understood that the present invention is not limited to the explanation below, and various changes and modifications will be apparent to those skilled in the art without any departure from the spirit and scope of the present invention. Therefore, it is to be understood that the present invention is not limited to the defined content of the Embodiment Modes explained below.
In the present embodiment mode, a manufacturing method for a thin film light-emitting element of the present invention will be explained using
In
The substrate 110 is used as a base for a light-emitting element. For the substrate 110, for example, glass, quartz, plastic, or the like can be used. It is to be noted that if the substrate 110 functions as a base during a manufacturing process of a light-emitting element, other materials can be used in addition to these, and a material that can withstand the temperature of a heat treatment process that will be described later should be used.
For the first electrode 101 and the second electrode 106, a metal, an alloy, a conductive compound, or a mixture of any of these can be used. It is to be noted that, for obtaining surface emission of light, either one of the first electrode 101 or the second electrode 106 must be a transparent electrode or both of them must be transparent electrodes. For a transparent electrode, for example, electrodes of indium tin oxide (ITO), indium tin oxide containing silicon or silicon oxide (ITSO), indium zinc oxide (IZO), indium oxide containing tungsten oxide and zinc oxide (IWZO), and the like can be given. These conductive metal oxide films are formed using sputtering. For example, an IZO film can be formed by sputtering using indium oxide to which zinc oxide is added for a target of from 1 wt % to 20 wt % of zinc oxide. In addition, an IWZO film can be formed by sputtering using indium oxide to which tungsten oxide is added for a target of from 0.5 wt % to 5 wt % and zinc oxide is added for a target of from 0.1 wt % to 1 wt %. In addition to these, for a metal electrode, aluminum, silver, gold, platinum, nickel, tungsten, titanium, chromium, molybdenum, iron, cobalt, copper, palladium, or a nitride of one or a plurality of any of these metallic materials, for example, titanium nitride, or the like can be used. Furthermore, when a metallic electrode is used for the electrode that is transparent, even if the material is one which has low transmittance for visible light, by film formation at a thickness in the range of about 1 nm to 50 nm, preferably, of about 5 nm to 20 nm, the metallic electrode can be used as the transparent electrode. It is to be noted that, in addition to manufacturing of the electrode using sputtering, the electrode can be manufactured using vacuum deposition, CVD, or a sol-gel process.
The first electrode 103 is a layer containing a material acting as a luminescent center. For an element acting as a luminescent center, copper, silver, gold, manganese, terbium, europium, thulium, cerium, praseodymium, samarium, erbium, aluminum, chlorine, fluorine, or the like can be used; for a material containing an element acting as a luminescent center, a single one of these elements or a compound containing one or a plurality of any of these elements can be used. For a compound containing one or a plurality of any of these elements, copper sulfide, copper chloride, copper fluoride, copper sulfate, silver sulfide, silver chloride, silver fluoride, manganese sulfide, manganese chloride, manganese fluoride, manganese sulfate, manganese carbonate, manganese oxide, terbium chloride, terbium fluoride, europium oxide, europium chloride, europium fluoride, thulium oxide, thulium fluoride, praseodymium chloride, praseodymium fluoride, samarium oxide, samarium chloride, samarium fluoride, cerium oxide, cerium chloride, cerium fluoride, erbium oxide, erbium chloride, erbium fluoride, aluminum sulfide, aluminum chloride, or the like can be used. A thin film including a simple substance or compound of one or a plurality of these elements acting as luminescent centers is formed by a vacuum vapor deposition method, such as resistive evaporation, electron beam vapor deposition (EB vapor deposition), or the like; a sputtering method; a metal organic CVD method; a low-pressure hydride-transport CVD method; an atomic layer epitaxy method (ALE); or the like. Although there are no particular limitations on the thickness of the film, a film thickness in the range of 1 nm to 100 nm is preferable.
The second layer 104 is a layer that contains a host material. For the host material, a sulfide, an oxide, or a nitride can be used. For the sulfide, for example, zinc sulfide, cadmium sulfide, calcium sulfide, yttrium sulfide, gallium sulfide, strontium sulfide, barium sulfide, or the like can be used. In addition, for the oxide, for example, zinc oxide, yttrium oxide, or the like can be used. Furthermore, for the nitride, for example, aluminum nitride, gallium nitride, indium nitride, or the like can be used. Moreover, zinc selenide, zinc telluride, or the like may be used, or a compound of three elements, such as barium aluminum sulfide, calcium gallium sulfide, strontium gallium sulfide, barium gallium sulfide, or the like, may be used. A thin film using one or more of these kinds of host materials can be formed using a vacuum vapor deposition method, such as resistive heating evaporation, electron beam vapor deposition (EB vapor deposition), or the like; a sputtering method; a metal organic CVD method; a low-pressure hydride-transport CVD method; an atomic layer epitaxy method (ALE); or the like. Although there are no particular limitations on the thickness of the film, a film thickness in the range of 10 nm to 1000 nm is preferable.
It is to be noted that, in the host material, a material to which one or a plurality of elements acting as luminescent centers is added can be used. For example, ZnS to which Cu and Cl are added (ZnS:Cu,Cl), ZnS to which Mn is added (ZnS:Mn), or the like can be used.
Although there are no particular limitations on the first insulating layer 102 and the second insulating layer 105, it is preferable that dielectric strength voltage be high and film quality be high, and, moreover, it is preferable that the dielectric constant be high. For example, either a mixed film of any of the following or a film of two or more stacked films of any of the following can be used: yttrium oxide, titanium oxide, aluminum oxide, hafnium oxide, tantalum oxide, silicon oxide, barium titanate, strontium titanate, lead titanate, silicon nitride, and zirconium oxide. An insulating film of one or more of these can be formed by sputtering, vapor deposition, CVD, or the like. Although there are no particular limitations on the thickness of the film, a film thickness in the range of 10 nm to 1000 nm is preferable. When driving is to be performed by low voltage driving, a film thickness of 500 nm or less is preferable, and a film thickness of 100 nm or less is even more preferable.
Next, heat treatment of the thin film element 100 is performed. This heat treatment can be performed in vacuum or under atmospheric pressure, or it may be performed under an N2 atmosphere or under an Ar atmosphere. It is to be noted that a heat treatment temperature of from 500° C. to 1200° C. is preferable. By performance of this heat treatment process, an element acting as a luminescent center contained in a layer containing a material acting as a luminescent center is dispersed throughout a layer containing a material acting as a host material, whereby a light-emitting layer is formed. It is to be noted that by control of temperature and time conditions, a light-emitting layer can be manufactured to which an element acting as a luminescent center of a different density distribution is added. In addition, when a host material to which an element acting as a luminescent center is added is used, a light-emitting element that has a plurality of luminescent colors can be manufactured; when each of the luminescent colors has a complementary color relationship, white light can be obtained.
In the manufacturing method of a light-emitting element of the present embodiment mode, by performance of heat treatment on a thin film element, a plurality of elements acting as luminescent centers can be easily added to a host material. As a result, a low-cost light-emitting element that emits light at a plurality of light emission wavelength peaks can be manufactured.
It is to be noted that the present embodiment mode can be combined with other embodiment modes as appropriate.
In the present embodiment mode, a thin film light-emitting element of the present invention will be described using
In
For the substrate 210, the first electrode 201 and second electrode 207, and the first insulating layer 202 and second insulating layer 206, the materials described in Embodiment Mode 1 can be used.
The first layer 203 and the third layer 205 are layers containing materials that act as luminescent centers, and the materials described in Embodiment Mode 1 can be used. It is to be noted that a material acting as a luminescent center that contains the same element acting as a luminescent center can be used, or, alternatively, a material acting as a luminescent center that contains a different element acting as a luminescent center can be used. When a material acting as a luminescent center that contains a different element acting as a luminescent center is used, a light-emitting element that emits light at a plurality of light emission wavelength peaks can be obtained.
The second layer 204 is a layer containing a host material, and the host materials described in Embodiment Mode 1 can be used. It is to be noted that, in the host material making up the second layer 204, a host material to which one or a plurality of elements acting as luminescent centers are added can be used.
Next, heat treatment is performed on the thin film element 200, and an element acting as a luminescent center contained in a layer containing a material acting as a luminescent center is diffused throughout the layer containing a host material. By diffusion of an element acting as a luminescent center from the first layer 203 and diffusion of an element acting as a luminescent center from the third layer 205, a light-emitting element that emits light with a plurality of light emission wavelength peaks can be obtained. It is to be noted that, by control of temperature and time conditions, a layer to which is added an element acting as a luminescent center of a concentration differing from the concentration of the element acting as a luminescent center contained in the second layer 204 can be manufactured. In addition, when a host material to which an element acting as a luminescent center is used is added, a light-emitting element with a plurality of luminescent colors can be obtained; when each of the luminescent colors has a complementary color relationship, white light can be obtained.
The light-emitting element of the present embodiment mode is a light-emitting element in which a plurality of elements acting as luminescent centers are added to a host material and the light-emitting element that emits light with a plurality of light emission wavelength peaks.
It is to be noted that the present embodiment mode can be combined with other embodiment modes accordingly.
In the present embodiment mode, a thin film light-emitting element of the present invention will be explained using
In
For the substrate 310, the first electrode 301 and second electrode 309, and the first insulating layer 302 and second insulating layer 308, the materials described in Embodiment Mode 1 can be used.
The first layer 303, the third layer 305, and the fifth layer 307 are layers containing materials acting as luminescent centers, and the materials described in Embodiment Mode 1 can be used. It is to be noted that a material acting as a luminescent center that contains the same element acting as a luminescent center may be used, or, alternatively, a material acting as a luminescent center that contains a different element acting as a luminescent center may be used. When a different element acting as a luminescent center is used, a light-emitting element that emits light with a plurality of light emission wavelength peaks can be obtained.
The second layer 304 and the fourth layer 306 are layers that each contain a host material, and the host materials described in Embodiment Mode 1 can be used. It is to be noted that the same host materials may be used, or, alternatively, different host materials may be used. When different host materials are used, even when the same element acting as a luminescent center is added, because the locations of the emission wavelength peaks are different, a light-emitting element with a plurality of emission wavelength peaks can be obtained.
Next, heat treatment is performed on the thin film element 300, and an element acting as a luminescent center contained in a layer containing a material acting as a luminescent center is diffused throughout the layer containing a host material. By diffusion of an element acting as a luminescent center from the first layer 303 and diffusion of an element acting as a luminescent center from the third layer 305, emission of light from a layer containing the host material of the second layer 304 can be obtained. In addition, by diffusion of an element acting as a luminescent center from the third layer 305 and diffusion of an element acting as a luminescent center from the fifth layer 307, emission of light from a layer containing the host material of the fourth layer 306 can be obtained. By obtainment of the emission of light from a plurality of layers containing host materials, a light-emitting element that emits light with a plurality of light emission wavelength peaks can be obtained. It is to be noted that, by control of temperature and time conditions, a layer to which is added an element acting as a luminescent center of a concentration differing from the concentration of the element acting as a luminescent center contained in the second layer or that of the element acting as a luminescent center contained in the fourth layer can be manufactured. In addition, when a host material to which an element acting as a luminescent center is added is used, because an even greater number of a plurality of elements acting as luminescent centers is included, a light-emitting element that emits light covering all wavelengths of the visible light region of the electromagnetic spectrum can be obtained.
The light-emitting element of the present embodiment mode is a light-emitting element in which a plurality of elements acting as luminescent centers are added to a plurality of host materials and a light-emitting element that emits light with a plurality of light emission wavelength peaks.
It is to be noted that the present embodiment mode can be combined with other embodiment modes accordingly.
In the present embodiment mode, one aspect of a light-emitting device will be explained with reference to
In this light-emitting device, a signal for displaying images is applied to each of the first electrode 416 extending in one direction of the substrate 410 and the second electrode 418 extending in a direction that intersects with the direction in which the first electrode 416 extends, whereby emission of light or non-emission of light for a light-emitting element is selected. That is, the light-emitting device is a passive matrix display device in which pixel driving is performed by a signal received exclusively from an external circuit. For this kind of display device, because the structure is simple, even if the area is enlarged, the display device can be easily manufactured.
In the above, if aluminum, titanium, tantalum, or the like is used for the first electrode 416 and indium oxide, indium tin oxide (ITO), indium zinc oxide (IZO), or zinc oxide is used for the second electrode 418, the display device can be set as one in which the display 414 is formed on a counter substrate 412 side. In this case, with a thin oxide film formed over the surface of the first electrode 416 to form a barrier layer, by a carrier blocking effect, luminous efficiency can be increased. If indium oxide, indium tin oxide (ITO), indium zinc oxide (IZO), or zinc oxide is used for the first electrode 416 and aluminum, titanium, tantalum, or the like is used for the second electrode 418, the display device can be set as one in which the display 414 is formed on the substrate 410 side. In addition, if the first electrode 416 and the second electrode 418 are both formed as transparent electrodes, the display device can be set as one with double-sided display.
It is to be noted that the counter substrate 412 may be provided according to necessity; by provision of the counter substrate 412 to match the arrangement of the display 414, the counter substrate 412 can be set as a protector. Even if this counter substrate 412 is not made of a tabular-shaped hardwood, a resin film or an applied resin material can be substituted in for the counter substrate 412. The first electrode 416 and the second electrode 418 are drawn out into the vicinity of the edge of the substrate 410, and a terminal connecting to an external circuit is formed. That is, the first electrode 416 and the second electrode 418 form contact with flexible wiring substrates 420 and 422 in the edge of the substrate 410. For the external circuit, in addition to a controller circuit that controls an image signal, a power supply circuit, a tuner circuit, and the like are included.
Cross-sectional views taken along A-B and along C-D in
In
In addition, an alternative structure of the display 414 is shown in
The display device of the present embodiment mode is one in which a light-emitting element emits light at low voltage, whereby boosting circuits and the like become unnecessary, and the structure of the device can be simplified.
In the present embodiment mode, by a transistor, an active light-emitting device controlling the driving of a light-emitting element manufactured using the present invention in a pixel portion will be explained using
It is to be noted that a lead wiring 608 is a wiring used for transmitting a signal input to the source-side driver circuit 601 and the gate-side driver circuit 603 and receives video signals, clock signals, start signals, reset signals, and the like from an FPC (Flexible Printed Circuit) 609 acting as an external input terminal. It is to be noted that, here, only the FPC is shown, but a printed wiring board (PWB) may be attached to this FPC. The light-emitting device of the present specification includes not only the light-emitting device itself but also a condition in which the FPC or the PWB is attached to the light-emitting device.
Next, a cross-sectional structure will be explained using
It is to be noted that the source-side driver circuit 601 is formed of a CMOS circuit that is formed of a combination of an n-channel TFT 623 and a p-channel TFT 624. In addition, for the TFTs forming a driver circuit, the TFTs may be formed as publicly known CMOS circuits, PMOS circuits, or NMOS circuits. Furthermore, in the present embodiment mode, a driver integrated type in which a driver circuit is formed over a substrate is shown, but it is not absolutely necessary that the driver circuit be formed in this way, and the driver circuit may be formed, not over the substrate but externally. It is to be noted that there are no particular limitations on the structure of the TFT. A staggered TFT may be used, or an inverse-staggered TFT may be used. In addition, there are no particular limitations on the crystallinity of a semiconductor film used in the TFT. An amorphous semiconductor film may be used, or a crystalline semiconductor film may be used. Furthermore, there are no particular limitations on the semiconductor materials; an inorganic compound may be used, or an organic compound may be used.
In addition, the pixel portion 602 is formed of a plurality of pixels each including a switching TFT 611, a current controlling TFT 612, and a first electrode 613 electrically connected to a drain of the current controlling TFT 612. It is to be noted that an insulator 614 covering an edge of the first electrode 613 is formed. Here, the insulator 614 is formed using a positive-type photosensitive acrylic resin film.
Furthermore, in order to obtain favorable coverage, a curved surface with curvature is made to be formed over the upper edge or below the lower edge of the insulator 614. For example, when a positive-type photosensitive acrylic is used for the material of the insulator 614, it is preferable that only the upper edge of the insulator 614 be made to have a curved surface having a radius of curvature (from 0.2 μm to 0.3 μm). In addition, for the insulator 614, either a negative-type that becomes insoluble in etchant by radiation of light or a positive-type that becomes soluble in etchant by radiation of light can be used.
An EL layer 616 and a second electrode 617 are each formed over the first electrode 613. At least one of the first electrode 613 and the second electrode 617 has a light-transmitting property, and light can be emitted from the EL layer 616 and drawn to external.
The EL layer 616 includes a light-emitting layer described in Embodiment Modes 1 through 3.
It is to be noted that, for a method for forming the first electrode 613, the EL layer 616, and the second electrode 617, a variety of methods can be used. Specifically, a vacuum vapor deposition method, such as a resistive heating evaporation method, an electron beam vapor deposition (EB vapor deposition) method, or the like; a physical vapor deposition (PVD) method such as a sputtering method or the like; a chemical vapor deposition (CVD) method such as a metal organic CVD method, a low-pressure hydride-transport CVD method, or the like; an atomic layer epitaxy (ALE) method; or the like can be used. Alternatively, an inkjet method, a spin coating method, or the like can be used. Furthermore, every electrode or every layer may each be formed using a different formation method.
Additionally, by affixing of the sealing substrate 604 to the element substrate 610 using the sealant 605, a light-emitting element 618 comes to have a structure in which it is included in the space 607 enclosed by the element substrate 610, the sealing substrate 604, and the sealant 605. It is to be noted that, in the space 607, a filler is filled in, and in addition to the space 607 being filled in with an inert gas (such as nitrogen, argon, or the like), there are cases where the space 607 is filled in with the sealant 605.
It is to be noted that using an epoxy-based resin in the sealant 605 is preferable. In addition, it is preferable that these materials be materials that permeate as little moisture and oxygen as possible. Furthermore, for materials used in the sealing substrate 604, in addition to a glass substrate or a quartz substrate, a plastic substrate made from any of the following can also be used: FRP (Fiberglass-Reinforced Plastics), PVF (polyvinyl fluoride), Mylar (registered trademark), polyester, acrylic, or the like.
As described above, a light-emitting device including a light-emitting element manufactured using the present invention accordingly can be obtained.
The light-emitting device described in the present embodiment mode has the light-emitting element described in Embodiment Modes 1 through 3 and can operate at low driving voltage. For this reason, a light-emitting device in which power consumption is reduced can be obtained.
In addition, the light-emitting device of the present embodiment mode is one in which manufacturing costs for the light-emitting device can be reduced because a driver circuit with a high dielectric strength voltage is unnecessary. In addition, reduction in weight of the light-emitting device and miniaturization of a driver circuit portion can be done.
In the present embodiment mode, an electronic device included in part of the light-emitting device of Embodiment Modes 4 and 5 will be explained. The electronic device described in the present embodiment mode includes the light-emitting element described in Embodiment Modes 1 through 3. By a light-emitting element with high luminance being included, an electronic device with high luminance can be obtained.
For electronic devices manufactured by application of the present invention, a camera such as a video camera, a digital camera, or the like; a goggle-type display; a navigation system; an audio reproducing system (for example, a car audio system, an audio component system, or the like); a computer; a game machine; a handheld terminal (for example, a portable computer, a cellular telephone, a portable game machine, an electronic book reader, or the like); an image reproducing device provided with a recording medium (specifically, a device that can play storage media such as a DVD (Digital Versatile Disc) and the like and that includes a display device that can display the images); and the like can be given. Some specific examples thereof are shown in
In
The computer of
The cellular phone of
The camera of
As described above, the scope and field of application of the light-emitting device of the present invention are extremely wide, and it is possible to apply the light-emitting device to electronic devices of any field. Use of the light-emitting device of the present invention allows an electronic device with a highly reliable display with low power consumption to be provided.
In addition, the light-emitting device employing the present invention can be used for a lighting system. An example of a light-emitting device employing the present invention which can be used for a lighting system will be explained using
By use of the light-emitting device of the present invention as a backlight for a liquid crystal display device, a backlight with a high luminance and a long life can be obtained, and the quality of the display device is improved. In addition, for the light-emitting device of the present invention, because the light-emitting device emits light by surface light emission and a shift to a large area can be achieved, a shift to a large area for the backlight can be achieved as well, and a shift to a large area for the liquid crystal display device can also be achieved. Furthermore, because the light-emitting element is thin, a liquid crystal display device in which the backlight has been thinned can be provided.
In addition, because the light-emitting device to which the present invention is employed is one in which light can be emitted at high luminance, the light-emitting device can be used for a headlight of a car, bicycle, ship, or the like.
The lighting system to which the light-emitting device of the present invention is applied is not limited to the examples shown in
This application is based on Japanese Patent Application serial No. 2006-155473 filed in Japan Patent Office on Jun. 2, 2006, the contents of which are hereby incorporated by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-155473 | Jun 2006 | JP | national |
