JP4047015B2 - Light emitting element, light emitting device, electric appliance - Google Patents

Description

[0001]
[Field of the Invention]
The present invention relates to a light emitting device using an organic light emitting element having an anode, a cathode, and a film containing an organic compound that emits light by applying an electric field (hereinafter referred to as “organic compound film”). In particular, the present invention relates to a light-emitting device using an organic light-emitting element in which an organic compound film contains a low-molecular compound that can be vacuum-deposited, has a lower driving voltage than the conventional one, and has a long element lifetime, and a method for manufacturing the same. Note that the light emitting device in this specification refers to an image display device or a light emitting device using an organic light emitting element as a light emitting element. In addition, connectors with organic light-emitting elements such as anisotropic conductive film (FPC: Flexible Printed Circuit) or TAB (Tape Automated Bonding) tape or TCP (Tape Carrier Package) attached, printed on the end of TAB tape or TCP It is assumed that the light emitting device includes all modules provided with a wiring board or modules in which an IC (integrated circuit) is directly mounted on an organic light emitting element by a COG (Chip On Glass) method.
[0002]
[Prior art]
An organic light emitting element is an element that emits light when an electric field is applied. The light emission mechanism is based on molecular excitation by applying a voltage across the organic compound film between the electrodes, recombining electrons injected from the cathode and holes injected from the anode at the emission center in the organic compound film. It is said that when a molecular exciton returns to the ground state, it emits energy and emits light.
[0003]
Note that the type of molecular exciton formed by the organic compound can be a singlet excited state or a triplet excited state. However, in this specification, both excited states contribute to light emission. .
[0004]
In such an organic light emitting device, the organic compound film is usually formed as a thin film having a thickness of less than 1 μm. In addition, since the organic light emitting element is a self-luminous element in which the organic compound film itself emits light, a backlight as used in a conventional liquid crystal display is not necessary. Therefore, it is a great advantage that the organic light emitting device can be manufactured to be extremely thin and light.
[0005]
For example, in an organic compound film of about 100 to 200 nm, the time from carrier injection to recombination is about several tens of nanoseconds considering the carrier mobility of the organic compound film. Even if the process from light emission to light emission is included, light emission occurs in the order of microseconds or less. Therefore, one of the features is that the response speed is very fast.
[0006]
Furthermore, since the organic light emitting element is a carrier injection type light emitting element, it can be driven with a direct current voltage, and noise hardly occurs. Regarding the driving voltage, the thickness of the organic compound film is first made to be a uniform ultra-thin film of about 100 nm, and electrode materials that reduce the carrier injection barrier for the organic compound film are selected, and further a heterostructure (two-layer structure) 100cd / m at 5.5V by introducing ² (Reference 1: CW Tang and SA Van Slyke, “Organic electroluminescent diodes”, Applied Physics Letters, vol. 51, No. 12, 913-915 (1987)).
[0007]
Due to these thin, lightweight, high-speed response, and direct current low voltage driving characteristics, organic light-emitting devices are attracting attention as next-generation flat panel display devices. Further, since it is a self-luminous type and has a wide viewing angle, the visibility is relatively good, and it is considered effective as an element used for a display screen of a portable device.
[0008]
By the way, in the configuration of the organic light-emitting device shown in Document 1, first, as a method for reducing the carrier injection barrier, a low-work function and relatively stable Mg: Ag alloy is used for the cathode, and electron injection is performed. Increases sex. This makes it possible to inject a large amount of carriers into the organic compound film.
[0009]
Furthermore, as an organic compound film, a hole transport layer made of a diamine compound and tris (8-quinolinolato) aluminum (hereinafter referred to as “Alq”). _Three The recombination efficiency of carriers is drastically improved by applying a single heterostructure in which an electron transporting light emitting layer composed of “)” is stacked. This is explained as follows.
[0010]
For example, Alq _Three In the case of organic light-emitting devices with only a single layer, Alq _Three Therefore, most of the electrons injected from the cathode reach the anode without recombining with holes, and the efficiency of light emission is extremely poor. That is, a material that can transport both electrons and holes in a balanced manner (hereinafter referred to as “bipolar material”) is used in order to efficiently emit light (or drive at a low voltage) in a single layer organic light emitting device. Need, Alq _Three Does not meet that requirement.
[0011]
However, if a single heterostructure as in Document 1 is applied, electrons injected from the cathode are blocked at the interface between the hole transport layer and the electron transporting light emitting layer and confined in the electron transporting light emitting layer. Therefore, carrier recombination is efficiently performed in the electron-transporting light-emitting layer, leading to efficient light emission.
[0012]
If the concept of such a carrier blocking function is developed, it becomes possible to control the carrier recombination region. As an example, by inserting a layer capable of blocking holes (hole blocking layer) between the hole transport layer and the electron transport layer, the holes are confined in the hole transport layer, and There is a report that succeeded in making one emit light. (Reference 2: Yasunori KIJIMA, Nobutoshi ASAI and Shin-ichiro TAMURA, “A Blue Organic Light Emitting Diode”, Japanese Journal of Applied Physics, Vol. 38, 5274-5277 (1999)).
[0013]
In addition, the organic light-emitting device in Document 1 can be said to be an idea of functional separation in which hole transport is performed by a hole transport layer, and electron transport and light emission are performed by an electron transport light-emitting layer. This concept of functional separation has further evolved into a double heterostructure (three-layer structure) in which a light emitting layer is sandwiched between a hole transport layer and an electron transport layer (Reference 3: Chihaya ADACHI, Shizuo TOKITO, Tetsuo). TSUTSUI and Shogo SAITO, "Electroluminescence in Organic Films with Three-Layered Structure", Japanese Journal of Applied Physics, Vol. 27, No. 2, L269-L271 (1988)).
[0014]
The advantage of such functional separation is that it is no longer necessary to have various functions (such as light-emitting properties, carrier transportability, and carrier injection properties from electrodes) at the same time due to the functional separation. Etc. (for example, it becomes unnecessary to search for a bipolar material forcibly). That is, a high light emission efficiency can be easily achieved by combining materials having good light emission characteristics and materials having excellent carrier transportability.
[0015]
Because of these advantages, the concept of the laminated structure (carrier blocking function or function separation) itself described in Document 1 has been widely used up to now.
[0016]
[Problems to be solved by the invention]
However, since the laminated structure as described above is a junction between different kinds of materials, an energy barrier always occurs at the interface. If an energy barrier exists, the movement of carriers at the interface is hindered, which raises the following two problems.
[0017]
The first is that it becomes an obstacle to further reducing the drive voltage. In fact, in the current organic light-emitting device, the driving voltage is superior to the device with a single layer structure using a conjugated polymer, and the top data in power efficiency (unit: [lm / W]) (however, singlet) (Reference 4: Tetsuo Tsutsui, Journal of the Japan Society of Applied Physics, Organic Molecules and Bioelectronics, Vol. 11, No. 1, P. 8) (2000)).
[0018]
Note that the conjugated polymer described in Document 4 is a bipolar material, and the carrier recombination efficiency can achieve a level equivalent to that of the laminated structure. Therefore, if the recombination efficiency of carriers can be made equal without using a laminated structure, such as by using a bipolar material, a single layer structure with fewer interfaces actually shows a lower drive voltage. Yes.
[0019]
For example, at the interface with the electrode, there is a method of inserting a material that relaxes the energy barrier and increasing the carrier injection property to reduce the driving voltage (Reference 5: Takeo Wakimoto, Yoshinori Fukuda, Kenichi Nagayama, Akira Yokoi). , Hitoshi Nakada, and Masami Tsuchida, "Organic EL Cells Using Alkaline Metal Compounds as Electron Injection Materials", IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 44, NO. 8, 1245-1248 (1997)). In Reference 5, Li as an electron injection layer ₂ By using O, the drive voltage has been successfully reduced.
[0020]
However, the carrier mobility between organic materials (for example, between the hole transport layer and the light-emitting layer, hereinafter referred to as “organic interface”) is still an unsolved field, and has a low monolayer structure. This is an important point for catching up with the driving voltage.
[0021]
Furthermore, as another problem caused by the energy barrier, the influence on the device lifetime of the organic light emitting device can be considered. That is, the movement of carriers is hindered and the brightness is reduced due to the accumulation of charges.
[0022]
Although no clear theory has been established regarding this degradation mechanism, the luminance can be reduced by inserting a hole injection layer between the anode and the hole transport layer, and using rectangular wave ac drive instead of dc drive. (Ref. 6: SA VanSlyke, CH Chen, and CW Tang, "Organic electroluminescent devices with improved stability", Applied Physics Letters, Vol. 69, No. 15, 2160-2162 (1996) )). This can be said to be experimental support that the reduction in luminance could be suppressed by eliminating charge accumulation by inserting the hole injection layer and ac driving.
[0023]
From the above, the laminated structure has the advantage that the carrier recombination efficiency can be easily increased, and the material selection range can be widened from the viewpoint of functional separation, while the carrier structure can be increased by creating many organic interfaces. It can be said that the movement is hindered and the driving voltage and the luminance are lowered.
[0024]
Therefore, in the present invention, by fabricating an element having a concept different from that of a conventionally used stacked structure, the energy barrier existing in the organic compound film is relaxed to improve carrier mobility, and at the same time, Similar to the functional separation, it is an object to develop the functions of various materials (hereinafter referred to as “functional expression”). Accordingly, an object of the present invention is to provide an organic light emitting device having a lower driving voltage and a longer device life than the conventional one.
[0025]
It is another object of the present invention to provide a light-emitting device that has a lower driving voltage and a longer lifetime by using such an organic light-emitting element. Furthermore, it is an object of the present invention to provide an electric appliance that uses the light-emitting device to produce an electric appliance that has lower power consumption than the conventional one and that can be maintained for a long time.
[0026]
[Means for Solving the Problems]
Regarding the relaxation of the energy barrier in the laminated structure, it is noticeable in the technique of inserting the carrier injection layer as shown in Document 5. An explanation using an energy band diagram is shown in FIG. 1 by taking the hole injection layer as an example.
[0027]
In FIG. 1A, the anode 101 and the hole transport layer 102 are directly joined, but in this case, the energy barrier 104 between the anode 101 and the hole transport layer 102 is large. However, a material having a HOMO level located between the ionization potential of the anode and the highest occupied molecular orbital (hereinafter referred to as “HOMO”) level of the hole transport layer is inserted as the hole injection layer 103. As a result, the energy barrier can be designed stepwise (FIG. 1 (b)).
[0028]
By designing a step-like energy barrier as shown in FIG. 1B, the carrier injection property from the electrode can be improved, and the drive voltage can be lowered to some extent. However, the problem is that by increasing the number of layers, the number of organic interfaces increases conversely. This is considered to be the reason why the single layer structure holds the top data of the driving voltage and power efficiency as shown in Document 4.
[0029]
In other words, by overcoming this point, while taking advantage of the laminated structure (a variety of materials can be combined and no complicated molecular design is required), the driving voltage and power efficiency of the single layer structure can be achieved. I can catch up.
[0030]
Therefore, the present inventors have devised a method for reducing the energy barrier in the organic compound film by substantially eliminating the interface in the organic compound film in the organic compound film containing two or more kinds of vacuum-depositable organic compounds.
[0031]
That is, the organic compound film can block the hole injecting compound that receives holes from the anode, the hole transporting compound, the electron transporting compound, the electron injecting compound that receives electrons from the cathode, the movement of holes or electrons. In the case of containing at least two compounds that can be vacuum-deposited, selected from the group of blocking compounds, by providing a region where the at least two compounds are mixed (hereinafter referred to as “mixed region”), This is a technique for eliminating the interface in the upper organic compound film. Hereinafter, this method is referred to as mixed bonding.
[0032]
In this case, the hole injecting compound, the electron injecting compound, the hole transporting compound, and the electron transporting compound may have a function of exhibiting light emission.
[0033]
The mixed region is preferably formed at a position away from the anode and the cathode. One reason is to relax the barrier by setting the interface in the organic compound film as a mixed region while retaining the regions capable of expressing each function such as carrier injection, carrier transport, and light emission.
[0034]
In particular, when the mixed region has a light emitting function, it is necessary to keep the mixed region away from the electrode and away from the electrode in order to prevent quenching by the electrode (hereinafter referred to as “quenching”). In that case, it is preferable to separate the mixed region from the electrode by 20 nm or more in consideration of diffusion of molecular excitons. As for the degree of the separation distance, the most efficient distance may be selected in consideration of the carrier balance.
[0035]
By the way, when such a mixed junction is formed, a method of doping a guest into the mixed region is also conceivable. In the mixed region, since the carrier movement is considered to be lubrication, it is preferable to use a light-emitting compound that emits light as a guest.
[0036]
By performing the mixed bonding as described above, an organic light-emitting element capable of exhibiting a function without showing a clear laminated structure (that is, without a clear organic interface) can be manufactured.
[0037]
In the organic compound film containing the first organic compound and the second organic compound different from the first organic compound, the first organic compound and the second organic compound are A method of providing a region where the concentration of the first organic compound and the concentration of the second organic compound are changed (hereinafter referred to as “concentration change region”) is also suitable for the present invention. It is. In other words, it can be said that this is a concept of giving a density change to the mixed region. Further, it is more preferable that the density change in the density change region is continuous. Hereinafter, these methods are referred to as “continuous bonding”.
[0038]
A conceptual diagram of a conventional laminated structure and continuous bonding according to the present invention is shown in FIG. FIG. 2A shows a conventional laminated structure (single heterostructure). That is, it has an organic compound film 203a composed of the first organic compound 201 and the second organic compound 202, and is formed of a laminated structure (or a layer formed from the first organic compound layer 201a and the second organic compound layer 202a). A clear organic interface). In this case, it can be seen that there is no region where the concentration of the first organic compound 201 and the concentration of the second organic compound 202 gradually change, and the regions are discontinuous (that is, the concentration is 0 at the organic interface). % To 100%, or 100% to 0%).
[0039]
However, in the case of the present invention (FIG. 2B), the concentration of the first organic compound 201 and the concentration of the second organic compound 202 are gradually changed in the organic compound film 203b (that is, the concentration change region). 204b) exists, so there is no clear organic interface. However, since there is a region where the first organic compound can express the function (first functional region 201b) and a region where the second organic compound can express the function (second functional region 202b), the function of each material is expressed. it can. FIG. 2 (b) particularly shows a continuous junction in which the concentration change is continuous.
[0040]
By performing the continuous bonding as described above, an organic light-emitting element capable of exhibiting a function without showing a clear laminated structure (that is, without a clear organic interface) can be manufactured.
[0041]
By the way, the first organic compound and the second organic compound included in the concentration change region are different from the viewpoint of the concept of the present invention (that is, the functions of various materials are expressed without using a laminated structure). It preferably has a function.
[0042]
Therefore, the first organic compound and the second organic compound have a hole injecting property that receives holes from the anode, a hole mobility that is higher than an electron mobility, and a hole mobility that is higher than the hole mobility. The electron mobility has a higher electron mobility, the electron injection property for receiving electrons from the cathode, the blocking property that can block the movement of holes or electrons, the light emission property that emits light, and the property selected from the group Cases having different properties are included in the present invention.
[0043]
In particular, the first organic compound has a hole transporting property, the second organic compound has an electron transporting property, and the concentration of the first organic compound decreases with respect to the direction from the anode to the cathode, and the second organic compound. A technique in which a continuous junction is formed so that the concentration of s is increased is a preferable technique from the viewpoint of carrier balance.
[0044]
In addition, if the second organic compound contained in the concentration change region is light-emitting and the first organic compound is hole-transporting, the first organic compound has a function of the direction from the anode to the cathode. It is preferable to form a concentration change region in which the concentration decreases and the concentration of the second organic compound increases (in the concentration change region, the hole transporting material has a high concentration on the anode side).
[0045]
Conversely, if the first organic compound contained in the concentration change region is light-emitting and the second organic compound is electron-transporting, the first organic compound is in the direction from the anode to the cathode. It is preferable to form a concentration change region in which the concentration decreases and the concentration of the second organic compound increases (in the concentration change region, the electron transporting material is concentrated at the cathode side).
[0046]
As the first organic compound, an aromatic diamine compound having a high hole transporting property is preferable, and 4,4′-bis [N- (3-methylphenyl) -N-phenylamino] -biphenyl (hereinafter, “ TPD ”), 4,4′-bis [N- (1-naphthyl) -N-phenylamino] -biphenyl (hereinafter referred to as“ α-NPD ”), 4,4 ′, 4 ″ -Tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine (hereinafter referred to as “MTDATA”) and the like are mainly used. The second organic compound is preferably a metal complex containing a benzoquinoline skeleton having a high electron transporting property, an oxadiazole derivative, a triazole derivative, or a phenanthroline derivative, and Alq _Three In addition, bis (10-hydroxybenzo [h] -quinolinato) beryllium (hereinafter referred to as “BeBq ₂ ), 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (hereinafter referred to as “PBD”), 1,3-bis [5 -(P-tert-butylphenyl) -1,3,4-oxadiazol-2-yl] benzene (hereinafter referred to as “OXD-7”), 3- (4-tert-butylphenyl) -4- Phenyl-5- (4-biphenylyl) -1,2,4-triazole (hereinafter referred to as “TAZ”), 3- (4-tert-butylphenyl) -4- (4-ethylphenyl) -5- ( 4-biphenylyl) -1,2,4-triazole (hereinafter referred to as “Et-TAZ”) and the like are mainly used.
[0047]
Further, when performing the continuous bonding as described above, a method of adding the function of the guest by adding a third organic compound as a guest in the concentration change region is conceivable. From the viewpoint of function expression, it is preferable to use a light-emitting compound exhibiting light emission as a guest. This is because the first organic compound and the second organic compound that form the concentration change region have carrier transporting property or blocking property, and a luminescent compound is added to the concentration change region, thereby regenerating the carrier. This is because it is considered that the coupling rate is increased and the luminous efficiency is increased.
[0048]
The conceptual diagram is shown in FIG. In FIG. 3A, an organic compound film 303 containing a first organic compound and a second organic compound is provided on the substrate 301 between the anode 302 and the cathode 304, and the concentration changing region 305 emits light. A light emitting compound 306 was added to form a light emitting region.
[0049]
As the light-emitting compound, a metal complex including a quinoline skeleton that stably emits light, a metal complex including a benzoxazole skeleton, or a metal complex including a benzothiazole skeleton is preferable. _Three , BeBq ₂ In addition, tris (4-methyl-8-quinolinolato) aluminum (hereinafter “Almq”) _Three Etc.) are mainly used.
[0050]
In recent years, from the viewpoint of luminous efficiency, organic light-emitting elements that can convert energy emitted when returning from a triplet excited state to a ground state (hereinafter referred to as “triplet excited energy”) into light emission are high in that. It attracts attention because of its luminous efficiency (Reference 7: DF O'Brien, MA Baldo, ME Thompson and SR Forrest, "Improved energy transfer in electrophosphorescent devices", Applied Physics Letters, vol. 74, No. 3, 442-444 ( 1999)) (Reference 8: Tetsuo TSUTSUI, Moon-Jae YANG, Masayuki YAHIRO, Kenji NAKAMURA, Teruichi WATANABE, Taishi TSUJI, Yoshinori FUKUDA, Takeo WAKIMOTO and Satoshi MIYAGUCHI, "High Quantum Efficiency in Organic Light-Emitting Devices with Iridium-Complex as a Triplet Emissive Center ", Japanese Journal of Applied Physics, Vol. 38, L1502-L1504 (1999)).
[0051]
Document 7 uses a metal complex having platinum as the central metal, and Document 8 uses a metal complex having iridium as the central metal. Organic light-emitting elements that can convert these triplet excitation energy into light emission (hereinafter referred to as “triplet light-emitting elements”) can achieve higher luminance emission and higher emission efficiency than conventional ones.
[0052]
However, according to the report example of Reference 8, the initial luminance is 500 cd / m. ² When set to, the luminance half-life is about 170 hours, which causes a problem in the element lifetime. Therefore, by applying the present invention to a triplet light-emitting element, it is possible to realize a very high-performance light-emitting element in which the lifetime of the element is long in addition to high luminance light emission and high light emission efficiency by light emission from a triplet excited state. .
[0053]
Therefore, a case where a material capable of converting triplet excitation energy into light emission is selected as the third organic compound that is a guest and added to the concentration change region is also included in the present invention.
[0054]
What is considered as the third organic compound is not necessarily limited to the light-emitting compound that emits light. In particular, when the first organic compound or the second organic compound emits light, as the third organic compound, the highest occupied molecular orbital compared to the first organic compound and the second organic compound. It is preferable to use a compound (that is, a compound capable of blocking carriers and molecular excitons) having a large energy difference (hereinafter referred to as “excitation energy level”) between the vacant molecular orbitals and the lowest unoccupied molecular orbitals. By this method, it is possible to increase the recombination rate of carriers and increase the light emission efficiency in the concentration changing region formed by the first organic compound and the second organic compound.
[0055]
The conceptual diagram is shown in FIG. In FIG. 3 (b), an organic compound film 303 containing a first organic compound and a second organic compound is provided on the substrate 301 between the anode 302 and the cathode 304, and carriers and Compound 307 capable of blocking molecular excitons was added.
[0056]
Note that in FIG. 3B, a light emitting region in which a light emitting compound 306 that emits light is further added to the concentration changing region 305 is also provided. That is, it is a form combined with a method using a light-emitting compound that emits light as the third organic compound (FIG. 3A). Here, since the compound 307 capable of blocking carriers and molecular excitons is on the cathode side of the luminescent compound 306 exhibiting light emission, the compound 307 capable of blocking carriers and molecular excitons should be of a hole blocking property. That's fine.
[0057]
The compound capable of blocking carriers and molecular excitons is preferably a phenanthroline derivative, oxadiazole derivative, or triazole derivative having a large excitation energy level. In addition to PBD, OXD-7, TAZ, Et-TAZ, bathophenanthroline, bathocuproin Etc. are mainly used.
[0058]
By the way, it is considered that elemental analysis by SIMS is an important technique when the concentration change region as described above is specified. In particular, when the concentration change is continuous, it is considered that a significant difference appears as compared with the conventional laminated structure, as can be seen from the conceptual diagram shown in FIG.
[0059]
Therefore, among the elements constituting the first organic compound or the second organic compound, a region in which the detected amount of the element that can be detected by SIMS continuously changes in the direction from the anode to the cathode. The light emitting device having the above is included in the present invention.
[0060]
Moreover, when a metal complex is used as the first organic compound or the second organic compound, a continuous concentration change can be detected by detecting a metal element. As a metal element contained in a metal complex often used as an organic light-emitting device, aluminum, zinc, beryllium and the like are mainly used.
[0061]
Furthermore, when the third organic compound is added as a guest to the concentration change region, the detection region of the third organic compound that can be detected by SIMS is a region that includes both the first organic compound and the second organic compound. A light-emitting device that is (that is, a density change region) is also included in the present invention.
[0062]
In addition, a metal complex may be used as a compound serving as a guest, particularly a light-emitting compound that emits light. Therefore, the third organic compound is a metal complex having a metal element, and the detection region of the metal element that can be detected by SIMS is a region including both the first organic compound and the second organic compound (that is, the concentration). The light emitting device which is the change region is also included in the present invention.
[0063]
As the metal element contained in the metal complex used as the light emitting compound, aluminum, zinc, beryllium, or the like is mainly used. Further, when the third organic compound is a light-emitting compound that emits light from a triplet excited state, iridium and platinum can be detected because iridium and platinum are mainly used as metal complexes.
[0064]
By implementing the present invention as described above, it is possible to provide a light emitting device having a driving voltage lower than that of a conventional device and having a long lifetime. Furthermore, by producing an electric appliance using the light emitting device, it is possible to provide an electric appliance that consumes less power than the conventional one and is kept long.
[0065]
DETAILED DESCRIPTION OF THE INVENTION
Below, the form at the time of implementing this invention is described. Note that an organic light-emitting element only needs to have at least one of an anode and a cathode transparent in order to extract light emission, but in this embodiment, the element structure is such that a transparent anode is formed on a substrate and light is extracted from the anode. Describe. Actually, a structure for extracting light from the cathode and a structure for extracting light from the side opposite to the substrate are also applicable to the present invention.
[0066]
In carrying out the present invention, a manufacturing process for forming a mixed region or a concentration changing region is important. The inventor of the present invention has devised a process of forming a mixed region or a concentration changing region using a vacuum deposition process in an organic compound film containing a low molecular compound that can be vacuum deposited. Therefore, here, a method for manufacturing a light-emitting device using the organic light-emitting element disclosed in the present invention will be described.
[0067]
Multi-chamber method (in-line method) to prevent contamination of each material when stacking hole transport materials, light-emitting layer materials, electron transport materials, etc. by vacuum deposition in conventional processes, especially mass production processes The vapor deposition apparatus is used. The top view is shown in FIG.
[0068]
The example shown in FIG. 4 is a conceptual diagram of a vapor deposition apparatus for forming a three-layer structure (double heterostructure) of a hole transport layer, a light emitting layer, and an electron transport layer. First, a substrate having an anode (ITO or the like) is carried into the carry-in chamber, and the anode surface is first cleaned by irradiating ultraviolet rays in a vacuum atmosphere in the ultraviolet irradiation chamber. In particular, when the anode is an oxide such as ITO, an oxidation treatment is performed in the pretreatment chamber. Furthermore, in order to form each layer of the laminated structure, the hole transport layer is formed in the vapor deposition chamber 401, the light emitting layer (three colors of red, green, and blue in FIG. 4) is formed in the vapor deposition chambers 402 to 404, and the electrons are formed in the vapor deposition chamber 405. A transport layer is formed, and a cathode is deposited in the deposition chamber 406. Finally, sealing is performed in the sealing chamber, and the organic light emitting device is obtained by taking out from the carry-out chamber.
[0069]
A feature of such an in-line type vapor deposition apparatus is that vapor deposition of each layer is performed in different vapor deposition chambers 401 to 406. Therefore, each of the vapor deposition chambers 401 to 406 is usually provided with one vapor deposition source 411 to 416 (however, in the vapor deposition chambers 402 to 404, when a light emitting layer is formed by doping a dye, co-vapor deposition is performed. Two deposition sources may be required to form a layer). That is, the device configuration is such that the material of each layer hardly mixes with each other.
[0070]
On the other hand, the conceptual diagram of the vapor deposition apparatus which produces the organic light emitting element of this invention is shown in FIG. FIG. 5A is a top view of the single chamber system in which one vacuum chamber 510 is provided as a deposition chamber and a plurality of deposition sources are provided in the vacuum chamber. A material having various functions such as a hole injecting compound, a hole transporting compound, an electron transporting compound, an electron injecting compound, a blocking compound, a light emitting compound, and a constituent material of a cathode, respectively Stored separately in the source.
[0071]
In a vapor deposition apparatus having such a vapor deposition chamber, first, a substrate having an anode (ITO or the like) is carried into a carry-in chamber, and when the anode is an oxide such as ITO, an oxidation treatment is performed in the pretreatment chamber. (Although not shown in FIG. 5 (a), an ultraviolet irradiation chamber can be installed to clean the anode surface). Further, all materials for forming the organic compound film are deposited in the vacuum chamber 510. The cathode may be formed in the vacuum chamber 510, or a vapor deposition chamber may be provided separately to form the cathode there. In short, the organic compound film may be formed in one vacuum chamber 510. Finally, sealing is performed in the sealing chamber, and the organic light emitting device is obtained by taking out from the carry-out chamber.
[0072]
A procedure for manufacturing the organic light-emitting element of the present invention using such a single chamber deposition apparatus will be described with reference to FIG. 5B (a cross-sectional view of the vacuum chamber 510). In FIG. 5B, for simplification of the drawing, a vacuum chamber 510 having two vapor deposition sources (an organic compound vapor deposition source a518 and an organic compound vapor deposition source b519) is used, and a first organic compound 516 and a second organic compound are used. A process of forming a mixed region or a density change region composed of 517 will be described.
[0073]
First, the substrate 501 having the anode 502 is carried into the vacuum chamber 510 and fixed by the fixing table 511 (usually, the substrate is rotated during vapor deposition). Next, the vacuum chamber 510 is depressurized (10 ^-Four Then, the container a512 is heated to evaporate the first organic compound 516, and after reaching a predetermined deposition rate (unit: nm / s), the shutter a514 is opened and deposition is started.
[0074]
Thereafter, the shutter a514 is closed, and the heating of the container a512 is finished to prevent the first organic compound 516 from evaporating. At this time, the atmosphere in which the first organic compound exists is present in the vacuum chamber 510. 503 has occurred. Further, the second organic compound 517 is evaporated by heating the container b513 and opening the shutter b515 while maintaining this state (the state shown in FIG. 5B). By this procedure, it is possible to form the organic compound film 504 having a mixed region or a concentration change region.
[0075]
Specific shapes of the organic compound deposition source a518 and the organic compound deposition source b519 are shown in FIG. As the shape of the vapor deposition source, there are a type using a cell and a type using a conductive heating element. FIG. 24 shows a type using a conductive heating element. That is, the container a512 and the container b513 are electrically conductive heating elements, the container a512 containing the first organic compound 516 is sandwiched between the electrode a2401 and the container b513 containing the second organic compound 516 is sandwiched between the electrode b2402 and energized. By doing so, the container a512 and the container b513 are heated and deposited.
[0076]
By the way, as a specific method for utilizing the atmosphere in which the previously deposited organic compound exists, there is a method of paying attention to the pressure in the vacuum chamber as shown in the conceptual diagram in FIG. That is, when a certain organic compound is evaporated, the pressure in the vacuum chamber rises compared to the initial reduced pressure state before starting the vapor deposition, but the next time before the initial reduced pressure state can be recovered while operating the vacuum pump. By evaporating the organic compound, a mixed region or a concentration changing region is formed.
[0077]
From FIG. 6 (a), it can be seen that when the organic compound film is formed in one vacuum chamber, the atmosphere in which the previously deposited organic compound exists can be used by setting the interval or the like short.
[0078]
Using this method, even if you want to form a clear laminated structure on the way, you can wait until the pressure in the vacuum chamber returns below the initial reduced pressure state, and then deposit the next organic compound, so the application range Is wide.
[0079]
FIG. 6 (b) shows copper phthalocyanine (hereinafter referred to as “CuPc”), MTDATA, α-NPD, Alq. _Three Is a pressure change in the vacuum chamber when the vapor deposition is sequentially performed in one vacuum chamber.
[0080]
In FIG. 6 (b), the heating start (closed circle in the figure) represents the period from the start of current flow to the conductive heating element until the organic compound starts to evaporate, and the deposition rate control period (in the figure) (Open Triangle) indicates the period from when the organic compound starts to evaporate until the shutter is opened, and the deposition period (open square in the figure) indicates the period during which the shutter is opened to deposit the vapor. (Cross in the figure) represents a period until the next organic compound starts to be heated. The plot is recorded every 10 seconds.
[0081]
Incidentally, in addition to the procedure for forming the mixed region or concentration changing region described above, after the formation of the organic compound film and the cathode, 10 ^-Four It is desirable to perform heat treatment under reduced pressure below Pascal. By adding this process, it is easy to induce diffusion between organic molecules and form a concentration change region, particularly a continuous concentration change region. The temperature of the heat treatment may be any temperature that does not cause glass transition or volume change, but is preferably about 60 ° C to 100 ° C.
[0082]
By the manufacturing method as described above, the mixed region or the concentration changing region disclosed in the present invention can be formed.
[0083]
【Example】
[Example 1]
In this example, an example in which the organic light-emitting device disclosed in the present invention is manufactured in a vapor deposition chamber in which two organic compound vapor deposition sources are installed in one vacuum chamber is shown.
[0084]
First, indium tin oxide (hereinafter referred to as “ITO”) is formed to a thickness of about 100 nm by sputtering to prepare a glass substrate on which an anode is formed. The glass substrate having the anode is carried into a vacuum chamber.
[0085]
Next, as disclosed in the present invention, TPD is deposited in one vacuum chamber, and then Alq. _Three Was evaporated to form an organic compound film having a total film thickness of about 100 nm. Finally, an Mg: Ag alloy was deposited as a cathode to about 150 nm.
[0086]
FIG. 7 shows a cross-sectional TEM photograph of the organic light-emitting device fabricated as described above. As shown in FIG. 7, TPD and Alq are included in the organic compound film. _Three There is no clear organic interface formed, which suggests that a mixed region or a concentration changing region is formed unlike the conventional laminated structure as shown in FIG.
[0087]
FIG. 8 shows element characteristics of the organic light-emitting element manufactured in this example. The IV characteristic has a shape peculiar to a rectifying element such as an organic light emitting element. The emission spectrum is Alq _Three Is consistent with the emission spectrum of TPD. _Three It can be seen that each function of luminescence (and electron transport property) is expressed.
[0088]
[Example 2]
In this example, an example in which the organic light-emitting element disclosed in the present invention is manufactured in a deposition chamber in which a plurality of organic compound deposition sources are installed in one vacuum chamber is shown. Here, a triplet light-emitting element using an iridium complex as a light-emitting compound was manufactured.
[0089]
In many cases, a triplet light emitting element using an iridium complex is formed by forming a multilayer structure. This is due in part to the fact that host materials having a large excitation energy that can excite the iridium complex are limited and that functional separation is necessary. Another factor is the need for a blocking layer to prevent diffusion of molecular excitons because the diffusion length of triplet molecular excitons is much longer than that of singlet molecular excitons. .
[0090]
The basic structure of the triplet light emitting device is shown in FIG. 9 (Reference 9: MA Baldo, S. Lamansky, PE Burrows, ME Thompson, and SR Forrest, "Very high-efficiency green organic light-emitting devices based on electrophosphorescence", Applied Physics Letters, vol. 75, No. 1, 4-6 (1999)). In Reference 9, tris (2-phenylpyridine) iridium (hereinafter referred to as “Ir (ppy)”) that emits light from a triplet excited state. _Three 4,4'-N, N'-dicarbazole-biphenyl (hereinafter referred to as "CBP") is used as a host against the above, and bathocuproin (hereinafter referred to as "BCP") as a blocking layer. And a multi-layer structure (four-layer structure in Reference 9) is formed.
[0091]
Here, as a preliminary experiment, as disclosed in the present invention, α-NPD is sequentially deposited in one vacuum chamber, and 10 wt% Ir (ppy) _Three The cross section of the device fabricated by co-evaporation of CBP and BCP was observed by TEM. The element structure and the film thickness calculated from the film thickness monitor (quartz crystal resonator) are shown in FIG. Moreover, the cross-sectional TEM photograph is shown in FIG.
[0092]
FIG. 11 suggests that there is no clear organic interface in the organic compound film, and that a mixed region or a concentration change region is formed unlike the conventional multilayer structure as shown in FIG. From this fact, as shown in FIG. 10 (b), the region 1001, in which α-NPD can express the function, Ir (ppy) _Three Although there is a region 1002 where CBP can express a function and a region 1003 where BCP can express a function, it is considered that there is no clear organic interface in the broken line part of FIG.
[0093]
Although it was suggested that there was no clear organic interface, an element as shown in FIG. 12 (a) was fabricated in order to confirm whether each material actually exhibited a function and led to light emission. The manufacturing method is shown below.
[0094]
First, indium tin oxide (hereinafter referred to as “ITO”) is formed by sputtering to a thickness of about 100 nm to prepare a glass substrate on which an anode is formed. The glass substrate having the anode is carried into a vacuum chamber.
[0095]
Next, as disclosed in the present invention, α-NPD was sequentially deposited in one vacuum chamber, and then 7 wt% Ir (ppy) _Three And CBP are co-evaporated, BCP is evaporated, and electron transportability is further imparted to the cathode side by Alq. _Three Was evaporated to form an organic compound film having a total film thickness of about 110 nm. Finally, about 400 nm of Yb was deposited as a cathode.
[0096]
FIG. 13 shows element characteristics of the organic light-emitting element manufactured in this example. The IV characteristic has a shape peculiar to a rectifying element such as an organic light emitting element. The emission spectrum is Ir (ppy) _Three Α-NPD hole transport property, Alq _Three Electron transport properties, BCP blocking properties, CBP host material performance, and Ir (ppy) _Three It can be seen that each function of triplet light emission is expressed.
[0097]
From this fact, as shown in FIG. 12 (b), the region 1201 in which α-NPD can express the function, Ir (ppy) _Three And region 1202 where CBP can express function, region 1203 where BCP can express function, Alq _Three It is suggested that there is no clear organic interface in the broken line part of FIG.
[0098]
[Example 3]
In this example, a light-emitting device including the organic light-emitting element disclosed in the present invention will be described. FIG. 14 is a cross-sectional view of an active matrix light emitting device using the organic light emitting element of the present invention. Note that although a thin film transistor (hereinafter referred to as “TFT”) is used here as an active element, a MOS transistor may be used.
[0099]
Further, although a top gate TFT (specifically, a planar TFT) is exemplified as the TFT, a bottom gate TFT (typically an inverted staggered TFT) can also be used.
[0100]
In FIG. 14, reference numeral 1401 denotes a substrate. Here, a substrate that transmits visible light is used. Specifically, a glass substrate, a quartz substrate, a crystallized glass substrate, or a plastic substrate (including a plastic film) may be used. Note that the substrate 1401 includes an insulating film provided on a surface thereof.
[0101]
A pixel portion 1411 and a driver circuit 1412 are provided over the substrate 1401. First, the pixel portion 1411 will be described.
[0102]
The pixel portion 1411 is an area for displaying an image. There are multiple pixels on the substrate, and each pixel has a TFT (hereinafter referred to as “current control TFT”) 1402 for controlling the current flowing in the organic light emitting element, a pixel electrode (anode) 1403, and an organic compound film 1404 and cathode 1405 are provided. Although only the current control TFT is shown in FIG. 14, a TFT (hereinafter referred to as “switching TFT”) for controlling the voltage applied to the gate of the current control TFT is provided.
[0103]
As the current control TFT 1402, a p-channel TFT is preferably used here. Although an n-channel TFT can be used, when a current control TFT is connected to the anode of the organic light emitting element as shown in FIG. 14, the p-channel TFT can reduce power consumption. However, the switching TFT may be an n-channel TFT or a p-channel TFT.
[0104]
In addition, a pixel electrode 1403 is electrically connected to the drain of the current control TFT 1402. In this embodiment, since a conductive material having a work function of 4.5 to 5.5 eV is used as the material of the pixel electrode 1403, the pixel electrode 1403 functions as an anode of the organic light emitting element. As the pixel electrode 1403, typically, indium oxide, tin oxide, zinc oxide, or a compound thereof (ITO or the like) may be used. An organic compound film 1404 is provided on the pixel electrode 1403.
[0105]
Further, a cathode 1405 is provided on the organic compound film 1404. As a material for the cathode 1405, it is desirable to use a conductive material having a work function of 2.5 to 3.5 eV. As the cathode 1405, a conductive film containing an alkali metal element or alkalinity metal element, a conductive film containing aluminum, or a stack of aluminum or silver over the conductive film may be used.
[0106]
A layer including the pixel electrode 1403, the organic compound film 1404, and the cathode 1405 is covered with a protective film 1406. The protective film 1406 is provided to protect the organic light emitting element from oxygen and water. As a material for the protective film 1406, silicon nitride, silicon nitride oxide, aluminum oxide, tantalum oxide, or carbon (specifically, diamond-like carbon) is used.
[0107]
Next, the drive circuit 1412 will be described. The driver circuit 1412 is an area for controlling the timing of signals (gate signals and data signals) transmitted to the pixel portion 1411, and is provided with a shift register, a buffer, a latch, an analog switch (transfer gate), or a level shifter. FIG. 14 shows a CMOS circuit composed of an n-channel TFT 1407 and a p-channel TFT 1408 as a basic unit of these circuits.
[0108]
The circuit configuration of the shift register, buffer, latch, analog switch (transfer gate) or level shifter may be a known one. In FIG. 14, the pixel portion 1411 and the driver circuit 1412 are provided over the same substrate, but an IC or LSI can be electrically connected without providing the driver circuit 1412.
[0109]
In FIG. 14, the pixel electrode (anode) 1403 is electrically connected to the current control TFT 1402, but a structure in which the cathode is connected to the current control TFT can also be adopted. In that case, the pixel electrode may be formed using a material similar to that of the cathode 1405 and the cathode may be formed using a material similar to that of the pixel electrode (anode) 1403. In that case, the current control TFT is preferably an n-channel TFT.
[0110]
Incidentally, although the light emitting device shown in FIG. 14 is manufactured in the process of forming the wiring 1409 after the pixel electrode 1403 is formed, in this case, the pixel electrode 1403 may cause surface roughness. . Since the organic light-emitting element is a current-driven element, the characteristics may be deteriorated due to the surface roughness of the pixel electrode 1403.
[0111]
Therefore, as shown in FIG. 15, a light emitting device in which the pixel electrode 1503 is formed after the wiring 1509 is formed is also conceivable. In this case, it is considered that the current injection property from the pixel electrode 1503 is improved as compared with the structure of FIG.
[0112]
14 and 15, each pixel provided in the pixel portion 1411 or 1511 is separated by a positive taper bank-like structure 1410 or 1510. By making this bank-like structure into, for example, a reverse taper type structure, it is possible to adopt a structure in which the bank-like structure does not contact the pixel electrode. An example is shown in FIG.
[0113]
In FIG. 16, a wiring and separation unit 1610 that also serves as a separation unit using wiring is provided. As shown in FIG. 16, the shape of the wiring and isolation portion 1610 (structure with eaves) is formed by laminating a metal constituting the wiring and a material (for example, a metal nitride) having a lower etch rate than the metal. Can be formed. With this shape, a short circuit between the pixel electrode 1603 and the wiring and the cathode 1605 can be prevented. In FIG. 16, unlike a normal active matrix light-emitting device, the cathode 1605 on the pixel has a stripe shape (similar to a passive matrix cathode).
[0114]
Here, an appearance of the active matrix light-emitting device shown in FIG. 15 is shown in FIG. 17A shows a top view, and FIG. 17B shows a cross-sectional view of FIG. 17A taken along PP ′. Also, the reference numerals in FIG.
[0115]
In FIG. 17A, reference numeral 1701 denotes a pixel portion, 1702 denotes a gate signal side driving circuit, and 1703 denotes a data signal side driving circuit. A signal transmitted to the gate signal side drive circuit 1702 and the data signal side drive circuit 1703 is input from a TAB (Tape Automated Bonding) tape 1705 through the input wiring 1704. Although not shown, instead of the TAB tape 1705, a TCP (Tape Carrier Package) in which an IC (integrated circuit) is provided on the TAB tape may be connected.
[0116]
At this time, reference numeral 1706 denotes a cover material provided above the organic light-emitting element shown in FIG. 15, and is bonded by a sealing material 1707 made of resin. Any material may be used for the cover material 1706 as long as it does not transmit oxygen and water. In the present embodiment, as shown in FIG. 17B, the cover material 1706 includes a plastic material 1706a, and carbon films (specifically diamond-like carbon films) 1706b provided on the front and back surfaces of the plastic material 1706a. It consists of 1706c.
[0117]
Further, as shown in FIG. 17B, the sealing material 1707 is covered with a sealing material 1708 made of a resin so that the organic light emitting element is completely enclosed in the sealed space 1709. The sealed space 1709 may be filled with an inert gas (typically nitrogen gas or a rare gas), a resin, or an inert liquid (for example, liquid fluorinated carbon typified by perfluoroalkane). It is also effective to provide a hygroscopic agent or oxygen scavenger.
[0118]
Further, a polarizing plate may be provided on the display surface (the surface on which an image is observed) of the light emitting device shown in this embodiment. This polarizing plate has an effect of suppressing reflection of light incident from the outside and preventing an observer from being reflected on the display surface. Generally, a circularly polarizing plate is used. However, in order to prevent light emitted from the organic compound layer from being reflected by the polarizing plate and returning to the inside, it is preferable to adjust the refractive index so that the structure has less internal reflection.
[0119]
Note that any of the organic light-emitting elements disclosed in the present invention may be used as the organic light-emitting element included in the light-emitting device of this example.
[0120]
[Example 4]
In this example, a passive matrix light-emitting device is illustrated as an example of a light-emitting device including the organic light-emitting element disclosed in the present invention. FIG. 18A shows a top view, and FIG. 18B shows a cross-sectional view of FIG. 18A taken along PP ′.
[0121]
In FIG. 18A, reference numeral 1801 denotes a substrate, and here a plastic material is used. Plastic materials include polyimide, polyamide, acrylic resin, epoxy resin, PES (polyether sulfone), PC (polycarbonate), PET (polyethylene terephthalate) or PEN (polyether nitrile) in the form of a plate or film Can be used.
[0122]
Reference numeral 1802 denotes a scanning line (anode) made of an oxide conductive film. In this embodiment, an oxide conductive film obtained by adding gallium oxide to zinc oxide is used. Reference numeral 1803 denotes a data line (cathode) made of a metal film. In this embodiment, a bismuth film is used. Reference numeral 1804 denotes a bank made of acrylic resin, which functions as a partition for dividing the data line 1803. Both the scanning lines 1802 and the data lines 1803 are formed in a plurality of stripes, and are provided so as to be orthogonal to each other. Although not shown in FIG. 18A, an organic compound layer is sandwiched between the scanning line 1802 and the data line 1803, and the intersection 1805 is a pixel.
[0123]
The scanning line 1802 and the data line 1803 are connected to an external drive circuit via the TAB tape 1807. Reference numeral 1808 represents a wiring group formed by aggregating the scanning lines 1802, and 1809 represents a wiring group formed by a set of connection wirings 1806 connected to the data line 1803. Further, although not shown, instead of the TAB tape 1807, a TCP having an IC provided on the TAB tape may be connected.
[0124]
In FIG. 18B, reference numeral 1810 denotes a sealing material, and 1811 denotes a cover material bonded to the plastic material 1801 by the sealing material 1810. As the sealing material 1810, a photo-curing resin may be used, and a material with low degassing and low hygroscopicity is desirable. The cover material is preferably the same material as the substrate 1801, and glass (including quartz glass) or plastic can be used. Here, a plastic material is used.
[0125]
Next, an enlarged view of the structure of the pixel region is shown in FIG. Reference numeral 1813 denotes an organic compound layer. As shown in FIG. 18C, the bank 1804 has a shape in which the lower layer is narrower than the upper layer, and the data line 1803 can be physically divided. Further, the pixel portion 1814 surrounded by the sealing material 1810 has a structure in which the organic compound layer is prevented from being deteriorated by being blocked from the outside air by a sealing material 1815 made of resin.
[0126]
The light-emitting device of the present invention having the above structure can be manufactured by a very simple process because the pixel portion 1814 is formed of the scanning line 1802, the data line 1803, the bank 1804, and the organic compound layer 1813. .
[0127]
Further, a polarizing plate may be provided on the display surface (the surface on which an image is observed) of the light emitting device shown in this embodiment. This polarizing plate has an effect of suppressing reflection of light incident from the outside and preventing an observer from being reflected on the display surface. Generally, a circularly polarizing plate is used. However, in order to prevent light emitted from the organic compound layer from being reflected by the polarizing plate and returning to the inside, it is preferable to adjust the refractive index so that the structure has less internal reflection.
[0128]
Note that any of the organic light-emitting elements disclosed in the present invention may be used as the organic light-emitting element included in the light-emitting device of this example.
[0129]
[Example 5]
In this embodiment, an example in which a light-emitting device shown in Embodiment 4 is modularized by providing a printed wiring board will be described.
[0130]
In the module shown in FIG. 19A, a TAB tape 1904 is attached to a substrate 1901 (here, including a pixel portion 1902, wirings 1903a and 1903b), and a printed wiring board 1905 is attached via the TAB tape 1904. Yes.
[0131]
Here, a functional block diagram of the printed wiring board 1905 is shown in FIG. Inside the printed wiring board 1905, at least ICs functioning as I / O ports (input or output units) 1906, 1909, a data signal side drive circuit 1907, and a gate signal side circuit 1908 are provided.
[0132]
In this specification, a module having a configuration in which a TAB tape is attached to a substrate having a pixel portion formed on the substrate surface and a printed wiring plate having a function as a drive circuit is attached via the TAB tape is described in this specification. In particular, it will be called a drive circuit external module.
[0133]
Note that any of the organic light-emitting elements disclosed in the present invention may be used as the organic light-emitting element included in the light-emitting device of this example.
[0134]
[Example 6]
In this embodiment, an example in which a printed wiring board is provided in the light emitting device shown in Embodiment 3 or Embodiment 4 to form a module is shown.
[0135]
The module shown in FIG. 20 (a) has a TAB tape 2005 attached to a substrate 2001 (including a pixel portion 2002, a data signal side drive circuit 2003, a gate signal side drive circuit 2004, and wirings 2003a and 2004a). A printed wiring board 2006 is attached via a TAB tape 2005. A functional block diagram of the printed wiring board 2006 is shown in FIG.
[0136]
As shown in FIG. 20 (b), at least an I / O port 2007, 2010 and an IC functioning as a control unit 2008 are provided inside the printed wiring board 2006. Although the memory unit 2009 is provided here, it is not always necessary. The control unit 2008 is a part having functions for controlling drive circuit control, video data correction, and the like.
[0137]
A module having a configuration in which a printed wiring board having a function as a controller is attached to a substrate on which an organic light emitting element is formed is specifically referred to as a controller external module in this specification.
[0138]
Note that any of the organic light-emitting elements disclosed in the present invention may be used as the organic light-emitting element included in the light-emitting device of this example.
[0139]
[Example 7]
In this embodiment, an example of a light-emitting device in which a triplet light-emitting element as shown in Embodiment 2 is driven by digital time gray scale display is shown. The light emitting device of this embodiment is very useful because it can achieve high luminous efficiency by utilizing light emission from a triplet excited state and at the same time can obtain a uniform image by digital time gradation display.
[0140]
As a structure of the organic light emitting element, in addition to the constituent material of the organic compound film described in Example 2, CuPc which is a hole injecting compound is sequentially deposited after α-NPD as disclosed in the present invention. Vapor deposited on the anode. Thereafter, an organic compound film was formed by the method shown in Example 2.
[0141]
FIG. 21A shows a circuit configuration of a pixel using an organic light emitting element. Tr represents a transistor, and Cs represents a storage capacitor. In the circuit configuration in FIG. 21A, the source line is connected to the source side of the transistor Tr1, and the gate line is connected to the gate of the transistor Tr1. The power supply line is connected to the storage capacitor Cs and the source side of the transistor Tr2. Since the anode of the organic light emitting element of the present invention is connected to the drain side of the transistor Tr2, the opposite side of the transistor Tr2 across the organic light emitting element is a cathode.
[0142]
In this circuit, when a gate line is selected, a current flows from the source line to Tr1, and a voltage corresponding to the signal is accumulated in Cs. And the voltage between the gate and source of Tr2 (V _gs The current controlled by) flows in Tr2 and the organic light emitting element.
[0143]
After Tr1 is selected, Tr1 is turned off and the Cs voltage (V _gs ) Is held. Therefore, V _gs It is possible to continue the current as much as depending on the current.
[0144]
FIG. 21B shows a chart for driving such a circuit by digital time gray scale display. That is, one frame is divided into a plurality of subframes. In FIG. 21B, a 6-bit gradation is used to divide one frame into six subframes (SF1 to SF6). TA is the write time. In this case, the ratio of each sub-frame light emission period is 32: 16: 8: 4: 2: 1 as shown in the figure.
[0145]
FIG. 21 (c) shows an outline of the TFT substrate drive circuit in this embodiment. In the substrate configuration in FIG. 21 (c), a power supply line and a cathode as shown in FIG. 21 (a) are connected to a pixel portion in which the organic light emitting device of the present invention is used as each pixel. The shift register is connected to the pixel portion in the order of shift register → latch 1 → latch 2 → pixel portion. A digital signal is input to the latch 1, and image data can be sent to the pixel portion by a latch pulse input to the latch 2.
[0146]
The gate driver and the source driver are provided on the same substrate. In this embodiment, since the pixel circuit and the driver are designed to be digitally driven, a uniform image can be obtained without being affected by variations in TFT characteristics.
[0147]
[Example 8]
The light-emitting device of the present invention described in the above embodiment has an advantage of low power consumption and long life. Therefore, an electric appliance in which the light-emitting device is included as a display unit or the like is an electric appliance that can operate with lower power consumption than the conventional one and that can be maintained for a long time. In particular, an electric appliance such as a portable device that uses a battery as a power source is extremely useful because low power consumption is directly linked to convenience (battery is unlikely to run out).
[0148]
Further, since the light-emitting device is a self-luminous type, a backlight like a liquid crystal display device is not necessary, and the thickness of the organic compound layer is less than 1 μm, so that it can be thin and light. Therefore, an electric appliance in which the light emitting device is included as a display unit or the like is an electric appliance that is thinner and lighter than conventional ones. This is also extremely useful because it is directly connected to convenience (lightness and compactness when carrying), especially with respect to electric appliances such as portable devices. Furthermore, in general electrical appliances, there is no doubt that being thin (not bulky) is also useful from the viewpoint of transportation (capable of mass transportation) and installation (securement of space such as rooms).
[0149]
Note that since the light-emitting device is a self-luminous type, the light-emitting device is superior in visibility in a bright place as compared with a liquid crystal display device and has a wide viewing angle. Therefore, an electric appliance having the light-emitting device as a display portion has a great merit in terms of easy viewing.
[0150]
That is, the electric appliance using the light emitting device of the present invention is extremely useful because it has the advantages of low power consumption and long life in addition to the advantages of the conventional organic light emitting device such as thin and light weight and high visibility.
[0151]
In this embodiment, an electric appliance including the light emitting device of the present invention as a display portion is illustrated. Specific examples thereof are shown in FIGS. In addition, any of the elements disclosed in the present invention may be used as the organic light-emitting element included in the electric appliance of this example. Moreover, any form of FIGS. 14-21 may be used for the form of the light-emitting device contained in the electric appliance of a present Example.
[0152]
FIG. 22A shows a display using an organic light emitting element, which includes a housing 2201a, a support base 2202a, and a display portion 2203a. By manufacturing a display using the light-emitting device of the present invention as the display portion 2203a, a display that is thin, lightweight, and long can be realized. Therefore, transportation becomes simple, space saving during installation is possible, and the service life is also long.
[0153]
FIG. 22B shows a video camera, which includes a main body 2201b, a display unit 2202b, an audio input unit 2203b, operation switches 2204b, a battery 2205b, and an image receiving unit 2206b. By manufacturing a video camera using the light-emitting device of the present invention as the display portion 2202b, a lightweight video camera with low power consumption can be realized. Therefore, the consumption of the battery is reduced and the carrying becomes easy.
[0154]
FIG. 22C shows a digital camera, which includes a main body 2201c, a display portion 2202c, an eyepiece portion 2203c, and an operation switch 2204c. By manufacturing a digital camera using the light-emitting device of the present invention as the display portion 2202c, a lightweight digital camera with low power consumption can be realized. Therefore, the consumption of the battery is reduced and the carrying becomes easy.
[0155]
FIG. 22D shows an image reproducing device provided with a recording medium, which includes a main body 2201d, a recording medium (CD, LD, DVD, etc.) 2202d, operation switches 2203d, a display unit (A) 2204d, and a display unit (B) 2205d. including. The display portion (A) 2204d mainly displays image information, and the display portion (B) 2205d mainly displays character information. By producing the image reproducing device using the light emitting device of the present invention as the display unit (A) 2204d and the display unit (B) 2205d, the image reproducing device that is low in power consumption and lightweight and is kept long. realizable. Note that the image reproducing device provided with the recording medium includes a CD reproducing device, a game machine, and the like.
[0156]
FIG. 22E shows a portable (mobile) computer, which includes a main body 2201e, a display portion 2202e, an image receiving portion 2203e, an operation switch 2204e, and a memory slot 2205e. By manufacturing a portable computer using the light-emitting device of the present invention as the display portion 2202e, a thin and light portable computer with low power consumption can be realized. Therefore, the consumption of the battery is reduced and the carrying becomes easy. The portable computer can record information on a recording medium in which flash memory or nonvolatile memory is integrated, and can reproduce the information.
[0157]
FIG. 22F shows a personal computer, which includes a main body 2201f, a housing 2202f, a display portion 2203f, and a keyboard 2204f. By manufacturing a personal computer using the light-emitting device of the present invention as the display portion 2203f, a thin and lightweight personal computer with low power consumption can be realized. In particular, when a portable application such as a notebook computer is required, it is a great advantage in terms of battery consumption and lightness.
[0158]
In addition, the electric appliances often display information distributed through an electronic communication line such as the Internet or wireless communication such as radio waves, and in particular, opportunities for displaying moving image information are increasing. The response speed of the organic light emitting device is very fast, and it is suitable for such moving image display.
[0159]
Next, FIG. 23A shows a mobile phone, which includes a main body 2301a, an audio output unit 2302a, an audio input unit 2303a, a display unit 2304a, an operation switch 2305a, and an antenna 2306a. By manufacturing a mobile phone using the light-emitting device of the present invention as the display portion 2304a, a thin and lightweight mobile phone with low power consumption can be realized. Therefore, the battery consumption is reduced, the carrying becomes easier and the body can be made compact.
[0160]
FIG. 23B shows an acoustic device (specifically, an on-vehicle audio), which includes a main body 2301b, a display portion 2302b, and operation switches 2303b and 2304b. By manufacturing an acoustic device using the light-emitting device of the present invention as the display portion 2302b, a lightweight acoustic device with low power consumption can be realized. In the present embodiment, in-vehicle audio is shown as an example, but it may be used for home audio.
[0161]
In addition, in the electric appliances as shown in FIGS. 22 to 23, the light emission luminance is modulated according to the brightness of the use environment by further incorporating a light sensor and providing means for detecting the brightness of the use environment. It is effective to have such a function. The user can recognize the image or the character information without any problem if the brightness of 100 to 150 can be secured in the contrast ratio as compared with the brightness of the usage environment. That is, when the usage environment is bright, it is possible to increase the brightness of the image for easy viewing, and when the usage environment is dark, the brightness of the image can be suppressed to reduce power consumption.
[0162]
Various electric appliances using the light-emitting device of the present invention as a light source can be said to be very useful because they can operate with low power consumption and can be thin and light. Typically, an electrical appliance including the light-emitting device of the present invention as a light source such as a backlight or a front light of a liquid crystal display device or a light source of a lighting device can achieve low power consumption and be thin and lightweight.
[0163]
Therefore, even when the display units of the electric appliances shown in FIGS. 22 to 23 shown in this embodiment are all liquid crystal displays, the electric appliances using the light emitting device of the present invention as a backlight or a front light of the liquid crystal display. By producing a thin, lightweight electric appliance with low power consumption can be achieved.
[0164]
【The invention's effect】
By implementing the present invention, a light-emitting device with low power consumption and excellent lifetime can be obtained. Furthermore, by using such a light-emitting device for a light source or a display portion, it is possible to obtain an electric appliance that is bright and consumes little power and is kept long.
[Brief description of the drawings]
FIG. 1 shows the role of a hole injection layer.
FIG. 2 is a diagram showing a configuration of an organic light emitting element.
FIG. 3 is a diagram showing a configuration of an organic light emitting element.
FIG. 4 shows a vapor deposition apparatus.
FIG. 5 shows a vapor deposition apparatus.
FIG. 6 is a diagram showing a degree of vacuum during vapor deposition.
FIG. 7 is a cross-sectional TEM photograph of an organic compound film.
FIG. 8 is a graph showing characteristics of an organic light emitting element.
FIG. 9 is a view showing a structure of a conventional organic light emitting element.
10 is a diagram showing a configuration of an organic compound film in FIG. 11. FIG.
FIG. 11 is a cross-sectional TEM photograph of an organic compound film.
FIG. 12 shows a structure of an organic light emitting element.
FIG. 13 is a graph showing characteristics of an organic light emitting element.
FIG 14 illustrates a cross-sectional structure of a light-emitting device.
FIG 15 illustrates a cross-sectional structure of a light-emitting device.
FIG 16 illustrates a cross-sectional structure of a light-emitting device.
FIGS. 17A and 17B illustrate a top structure and a cross-sectional structure of a light-emitting device. FIGS.
18A and 18B are a top view and a cross-sectional structure of a light-emitting device.
FIG 19 illustrates a structure of a light-emitting device.
FIG 20 illustrates a structure of a light-emitting device.
FIG 21 illustrates a structure of a light-emitting device.
FIG. 22 is a diagram showing a specific example of an electric appliance.
FIG. 23 is a diagram showing a specific example of an electric appliance.
FIG. 24 is a diagram showing a specific example of a vapor deposition source.

Claims (4)

Between the electrodes,
A first region comprising a first organic compound that is hole transporting;
A second region comprising a second organic compound that is electron-transporting;
Have
Between the first region and the second region,
The concentration of the first organic compound decreases from the first region toward the second region, and the concentration of the second organic compound decreases from the second region toward the first region. A third region in which the first organic compound and the second organic compound are mixed so as to decrease;
The first organic compound or the second organic compound Ri organic compound der emit light,
The third region, the first organic compound and the than the second organic compound, blocking the best energy difference between the occupied molecular orbital and the lowest unoccupied molecular orbital large active, the carrier and molecular excitons emitting element characterized in including that the third organic compound. The first organic compound is an aromatic diamine compound;
The second organic compound is a metal complex containing a benzoquinoline skeleton, an oxadiazole derivative, according to claim 1, characterized in that a triazole derivative, tris (8-quinolinolato) aluminum, and one compound selected from a phenanthroline derivative The light emitting element as described in. A light emitting device comprising the light emitting element according to claim 1 in a pixel portion. An electric appliance comprising the light emitting device according to claim 3 as a display unit.

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