JP2008235419A - Organic electroluminescent device and manufacturing method therefor, and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic electroluminescent device capable of maintaining white balance, even if a light-emitting element deteriorates due to change with the passage of time, to provide a manufacturing method of the organic electroluminescent device, and to provide electronic equipment. <P>SOLUTION: In respective light-emitting elements 3R, 3G, 3B, a blue light-emitting layer 70B is formed with an optimum film thickness where a luminous life becomes the longest, and a red light-emitting element 70R and a green luminous layer 70G are formed thinner than the optimum film thickness where the luminous lifetime becomes the largest. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an organic electroluminescence device, a method for manufacturing an organic electroluminescence device, and an electronic apparatus.

  In recent years, with the diversification of information devices, there is an increasing need for electro-optical devices that consume less power and are lighter. As one of such electro-optical devices, an organic electroluminescence device (hereinafter referred to as “organic EL device”) having an organic functional layer is known. Such an organic EL device generally includes a light emitting element having a light emitting layer between an anode and a cathode. Furthermore, in order to improve the hole injection property and the electron injection property, a structure in which a hole injection / transport layer is disposed between the anode and the light emitting layer, or an electron injection layer or a hole blocking layer between the light emitting layer and the cathode. A configuration in which is arranged is proposed.

  Incidentally, an organic EL device used for a display or the like that performs full-color display includes a light emitting element having an emission wavelength band corresponding to each color of red (R), green (G), and blue (B). In the case where white and any color display are performed by combining light emission from light emitting elements emitting red (R), green (G), and blue (B), the CIE (International Commission on Illumination) standard coordinates In order to obtain the desired white (white balance) of the target coordinate point on the system, it is necessary to balance the chromaticity and luminance of each color.

On the other hand, when the light emission lifetimes of the light emitting elements of the organic EL device are compared, it is known that the lifetime of blue (B) is shorter than that of red (R) or green (G). This is a problem common to fluorescence and phosphorescence, but in comparison, fluorescence emission often has a longer lifetime than phosphorescence emission. Therefore, among red (R), green (G), and blue (B), red (R) and green (G) are phosphorescent, and only blue (B) having the shortest emission lifetime is made fluorescent, so that white balance is achieved. In addition, a long-life organic EL device is manufactured (see, for example, Patent Documents 1 to 5).
Japanese Patent Laid-Open No. 2003-77665 JP 2004-265755 A JP 2005-158676 A JP 2006-156258 A JP 2006-156848 A

However, in the above-described organic EL device, the phosphorescent blue (B) having the shortest emission lifetime is replaced with the fluorescent blue (B) so that the lifetime of the organic EL device is extended while maintaining the white balance. However, assuming an organic EL device that performs full-color display in which three colors are emitted simultaneously, the light emitting lifetimes of the light emitting elements are different. For example, red (R), green ( One of the short-lived ones of G) deteriorates next, and there is a problem that the white balance gradually collapses as time passes.
In such a case, there is a method of correcting the driving circuit, but in active matrix driving or the like, the aperture ratio is lowered due to an increase in TFT or the like, and the function as a display is also deteriorated.

  In view of the circumstances as described above, an object of the present invention is to provide an organic electroluminescence device capable of maintaining white balance even if it is subjected to deterioration over time of a light emitting element, a method for manufacturing the organic electroluminescence device, and an electronic apparatus. There is to do.

In order to achieve the above object, an organic electroluminescence device according to the present invention includes an organic electroluminescence device including a plurality of light emitting elements in which an organic functional layer is sandwiched between a first electrode and a second electrode. The thickness of the organic functional layer of the light emitting element having the shortest light emission lifetime among the plurality of light emitting elements is formed to an optimum film thickness that maximizes the light emission lifetime, and at least one of the other light emitting elements The thickness of the organic functional layer is different from the optimum thickness that maximizes the light emission lifetime.
According to this configuration, the light emitting lifetime of each light emitting element can be changed by adjusting the film thickness of the organic functional layer of each light emitting element. It is possible to approach the emission lifetime of. Thereby, even if the light emitting element is deteriorated over time, the difference in luminance and chromaticity of each light emitting element can be suppressed, so that white balance can be maintained for a long time.

In addition, a plurality of red light emitting elements emitting red light, green light emitting elements emitting green light, and blue light emitting elements emitting blue light, in which an organic functional layer is sandwiched between the first electrode and the second electrode In the organic electroluminescence device including a light emitting element, the thickness of the organic functional layer of the light emitting element having the shortest light emission lifetime among the light emitting elements of the red light emitting element, the green light emitting element, and the blue light emitting element is In addition, the film thickness of the organic functional layer of the light emitting element of at least one other color is different from the film thickness of the optimal film thickness with the longest light emission lifetime. It is formed.
According to this configuration, the thickness of the organic functional layer of the light emitting element having the shortest light emission lifetime is formed to an optimum film thickness that maximizes the light emission lifetime, whereas at least another light emitting element of one color. By adjusting the film thickness of the organic functional layer to a film thickness different from the optimum film thickness so as to shorten the light emission lifetime, the light emission lifetime of at least the other color light emitting device is the light emitting device with the shortest light emission lifetime. It is possible to approach the emission lifetime of. Thereby, even if the light emitting element is deteriorated over time, the difference in luminance and chromaticity of each light emitting element can be suppressed, so that white balance can be maintained for a long time.

The organic functional layer includes at least a light emitting layer and a hole injecting and transporting layer, and emits a color having the shortest emission lifetime among the light emitting elements of the red light emitting element, the green light emitting element, and the blue light emitting element. The film thickness of the light emitting layer of the light emitting element is formed to an optimum film thickness that maximizes the light emission lifetime, and the film thickness of the light emitting element of the light emitting element that emits another color has the longest light emission lifetime. It is characterized by being formed thin with respect to the optimum film thickness.
According to this configuration, only by adjusting the film thickness of the light emitting layer, the light emitting layer thickness of the light emitting element of the light emitting element with the shortest light emitting lifetime is formed to the optimum film thickness that maximizes the light emitting lifetime. On the other hand, the light emitting layers of the other two colors of light emitting elements are formed to have a film thickness different from the optimum film thickness, so that the light emitting lifetimes of the other two colors of light emitting elements can be maximized. The light emission life of a short light emitting element can be approached. Therefore, white balance can be maintained for a long time even if each light emitting element is deteriorated with time.

In addition, the chromaticity and luminance shift caused by changing the film thickness of the light emitting layer with a film thickness other than the light emitting layer of each light emitting element is corrected.
According to this configuration, by adjusting the film thickness other than the light emitting layer, the interference state of the light emitted from the light emitting element is adjusted, and the spectrum shape after the interference is emitted with desired luminance and chromaticity. It can be easily optimized. That is, the luminance and chromaticity of each light emitting element can be adjusted in a state where the light emitting lifetime of each light emitting element is most approximated.

Further, the film thickness of the first electrode is set based on the wavelength of light emitted from each of the light emitting layers.
According to this configuration, by adjusting the film thickness of the first electrode, it is possible to adjust the chromaticity of each light emitting element while suppressing the influence on the light emission characteristics of the light emitting element. The white balance can be maintained for a long period of time even if it is deteriorated over time.

Further, the deviation of the light emission lifetime of each light emitting element is within 30%.
According to this configuration, even if each light emitting element is deteriorated with time, white balance can be maintained until the light emitting function is lost.

On the other hand, the manufacturing method of the organic electroluminescence device according to the present invention is a manufacturing method of an organic electroluminescence device including a plurality of light emitting elements in which an organic functional layer is sandwiched between a first electrode and a second electrode. The step of forming each light emitting element includes the step of forming the film thickness of the organic functional layer of the light emitting element having the shortest light emission lifetime among the plurality of light emitting elements to an optimum film thickness that maximizes the light emission lifetime. The method further comprises the step of forming the thickness of the organic functional layer of the other light emitting element to a thickness different from the optimum thickness that maximizes the light emission lifetime.
According to this configuration, since the light emitting lifetime of each light emitting element can be changed by forming the organic functional layer with a different thickness depending on the light emitting lifetime of each light emitting element, the light emitting lifetime of each light emitting element is maximized. The light emission life of a light emitting element having a short light emission lifetime can be approached. Therefore, even if the light emitting element is deteriorated with time, the difference in luminance and chromaticity of each light emitting element can be suppressed, so that white balance can be maintained for a long time.

The step of forming each light emitting layer is a step of applying a liquid material for forming the light emitting layer of each color by an ink jet method.
According to this configuration, it is possible to reliably arrange a predetermined amount of the forming material of each light emitting layer at a predetermined position while suppressing the manufacturing cost.

On the other hand, an electronic apparatus according to the present invention includes the organic electroluminescence device.
According to this configuration, since the organic electroluminescence device is provided, it is possible to provide an electronic device that is excellent in white balance even if each light emitting element is deteriorated with time.

  Embodiments of the present invention will be described below with reference to the drawings. The present embodiment shows a part of the present invention, and does not limit the present invention, and can be arbitrarily changed within the scope of the technical idea of the present invention. Moreover, in each figure shown below, in order to make each layer and each member the size which can be recognized on drawing, the scale is varied for each layer and each member.

(First embodiment of organic EL device)
FIG. 1 is an equivalent circuit diagram of the organic EL device (organic electroluminescence device) of the present embodiment. In FIG. 1, reference numeral 1 denotes an organic EL device.

This organic EL device 1 is of an active matrix type using a thin film transistor (hereinafter referred to as TFT) as a switching element, and intersects a plurality of scanning lines 101 at right angles to each scanning line 101. And a plurality of power lines 103 extending in parallel to each signal line 102, and in the vicinity of the intersections of the scanning lines 101 and the signal lines 102. Pixel regions X are formed.
Of course, according to the technical idea of the present invention, an active matrix using TFT or the like is not indispensable. Even if the present invention is implemented using an element substrate for a simple matrix and the simple matrix is driven, the same effect can be obtained at low cost. can get.

  A data line driving circuit 100 including a shift register, a level shifter, a video line, and an analog switch is connected to the signal line 102. Further, a scanning line driving circuit 80 including a shift register and a level shifter is connected to the scanning line 101.

  Further, in each pixel region X, a switching TFT (switching element) 112 to which a scanning signal is supplied to the gate electrode via the scanning line 101 and a pixel shared from the signal line 102 via the switching TFT 112 are provided. A holding capacitor 113 for holding a signal, a driving TFT (switching element) 123 to which a pixel signal held by the holding capacitor 113 is supplied to a gate electrode, and the power supply line 103 through the driving TFT 123 are electrically connected A pixel electrode 111 (first electrode) through which a driving current flows from the power supply line 103 when connected, and a light emitting layer 70 sandwiched between the pixel electrode 111 and the cathode 12 (second electrode) are provided. ing.

  According to the organic EL device 1, when the scanning line 101 is driven and the switching TFT 112 is turned on, the potential of the signal line 102 at that time is held in the holding capacitor 113, and according to the state of the holding capacitor 113. The on / off state of the driving TFT 123 is determined. Then, a current flows from the power supply line 103 to the pixel electrode 111 via the channel of the driving TFT 123, and further a current flows to the cathode 12 (second electrode) via the light emitting layer 70. The light emitting layer 70 emits light according to the amount of current flowing through it.

  Next, specific modes of the organic EL device 1 of the present embodiment will be described with reference to FIGS. Here, FIG. 2 is a plan view schematically showing the configuration of the organic EL device. FIG. 3 is a cross-sectional view schematically showing an organic EL device.

First, the configuration of the organic EL device 1 will be described with reference to FIG.
FIG. 2 is a diagram showing a TFT element substrate (hereinafter referred to as “substrate”) 2 that causes the light emitting layer 12 to emit light by the above-described various wirings, TFTs, and various circuits formed on the substrate body 20.
The substrate 2 of the organic EL device 1 includes an actual display area 4 (inside the two-dot chain line in FIG. 2) in the center and a dummy area 5 (between the one-dot chain line and the two-dot chain line) arranged around the actual display area 4. Area).

  One of red (R), green (G), and blue (B) light is extracted from the pixel region X shown in FIG. 1, and the display region RGB shown in FIG. 2 is formed. In the actual display area 4, the display areas RGB are arranged in a matrix. In addition, each of the display areas RGB is arranged in the same color in the vertical direction of the paper, and constitutes a so-called stripe arrangement. The display area RGB is combined into one display unit pixel, and the display unit pixel mixes RGB light emission to perform full color display.

  Scan line drive circuits 80 and 80 are arranged on both sides of the actual display area 4 in FIG. 2 and on the lower layer side of the dummy area 5. Further, an inspection circuit 90 is disposed above the actual display area 4 in FIG. 2 and below the dummy area 5. This inspection circuit 90 is a circuit for inspecting the operating state of the organic EL device 1, and includes, for example, inspection information output means (not shown) for outputting the inspection result to the outside, and the organic EL during production or at the time of shipment. The apparatus 1 is configured to be able to inspect the quality and defects.

Next, a cross-sectional structure of the organic EL device 1 will be described with reference to FIG.
As shown in FIG. 3, the organic EL device 1 includes a circuit element unit 14 and an organic EL element unit 10 including the light emitting element 3 on the circuit element unit 14 in the thickness direction of the substrate 2. In the circuit element section 14, the above-described scanning line, signal line, storage capacitor, switching TFT, driving TFT 123, and the like are formed.

  In the organic EL device 1 of the present embodiment, light emitted from the light emitting layer 70 to the substrate 2 side is transmitted through the circuit element unit 14 and the substrate 2 and emitted to the outside (observer side) of the substrate 2, and light is emitted. The light emitted from the layer 70 to the side opposite to the substrate 2 is also reflected by the cathode 12, passes through the circuit element unit 14 and the substrate 2, and is emitted to the outside (observer side) of the substrate 2. It has become. Therefore, a transparent or translucent substrate is used as the substrate 2. For example, glass, quartz, resin (plastic, plastic film), and the like can be cited. In this embodiment, a glass substrate is used.

  Further, in the case of a so-called top emission type in which the light emitted from the light emitting layer 70 is extracted from the cathode 12 side, the configuration is such that the emitted light is extracted from the sealing substrate side opposite to the substrate 2. Either an opaque substrate or an opaque substrate can be used. Examples of the opaque substrate include a thermosetting resin and a thermoplastic resin in addition to a ceramic sheet such as alumina and a metal sheet such as stainless steel that has been subjected to an insulation treatment such as surface oxidation.

In the circuit element portion 14, a base protective layer 281 mainly composed of SiO ₂ is formed on the substrate 2 as a base, and a silicon layer 241 is formed thereon. A gate insulating layer 282 mainly composed of SiO ₂ and / or SiN is formed on the surface of the silicon layer 241.

In the silicon layer 241, a region overlapping with the gate electrode 242 with the gate insulating layer 282 interposed therebetween is a channel region 241a. The gate electrode 242 is a part of a scanning line (not shown). On the other hand, a first interlayer insulating layer 283 mainly composed of SiO ₂ is formed on the surface of the gate insulating layer 282 that covers the silicon layer 241 and on which the gate electrode 242 is formed.

  Further, in the silicon layer 241, a low concentration source region 241b and a high concentration source region 241S are provided on the source side of the channel region 241a, while a low concentration drain region 241c and a high concentration drain are provided on the drain side of the channel region 241a. The region 241D is provided to form a so-called LDD (Lightly Doped Drain) structure. Among these, the high-concentration source region 241S is connected to the source electrode 243 through a contact hole 243a that opens over the gate insulating layer 282 and the first interlayer insulating layer 283. The source electrode 243 is configured as a part of a power supply line (not shown). On the other hand, the high-concentration drain region 241D is connected to the drain electrode 244 made of the same layer as the source electrode 243 through a contact hole 244a opened through the gate insulating layer 282 and the first interlayer insulating layer 283.

  A planarization film 284 is formed on the first interlayer insulating layer 283 where the source electrode 243 and the drain electrode 244 are formed. The planarizing film 284 is formed of a heat-resistant insulating resin such as acrylic or polyimide, and is formed to eliminate surface irregularities due to the driving TFT 123, the source electrode 243, the drain electrode 244, and the like. Are known.

  The organic EL device 1 includes the organic EL element unit 10 on the surface of the planarizing film 284. The organic EL element unit 10 includes a plurality of light emitting elements 3 in which an organic functional layer 110 is sandwiched between a pixel electrode 111 and a cathode 12. The light emitting element 3 is configured as a red light emitting element 3R that emits red light, a green light emitting element 3G that emits green light, and a blue light emitting element 3B that emits blue light.

  A pixel electrode 111 is formed on the planarization film 284 of the circuit element unit 14 described above. The pixel electrode 111 is formed with a thickness of, for example, 800 mm, and is connected to the drain electrode 244 through a contact hole 111 a provided in the planarization film 284. That is, the pixel electrode 111 is connected to the high concentration drain region 241D of the silicon layer 241 through the drain electrode 244. In this embodiment, which is a bottom emission type, the pixel electrode 111 is formed of a transparent conductive material, and specifically, ITO (Indium Tin Oxide) is preferably used.

On the surface of the planarization film 284 on which the pixel electrode 111 is formed, the pixel electrode 111 and an inorganic partition wall 25 that covers the peripheral edge of the pixel electrode 111 are formed. Further, an organic partition wall 221 is formed on the inorganic partition wall 25. Is formed. Here, the inorganic partition wall 25 is made of SiO ₂ or the like, and the organic partition wall 221 is made of a heat-resistant insulating resin such as acrylic or polyimide.
On the pixel electrode 111, the hole injection transport layer 60 and the light emitting layer 70 are formed inside the opening 25 a formed in the inorganic partition wall 25 and the opening 221 a formed in the organic partition wall 221, that is, in the pixel region. Are stacked in this order from the pixel electrode 111 side, whereby the organic functional layer 110 is configured.

The hole injecting and transporting layer 60 is for injecting and transporting holes of the pixel electrode 111 to the light emitting layer 70. The hole injecting and transporting layer 60 is formed with a thickness of, for example, 500 mm, and is formed on the pixel electrode 111 so as to be positioned in the opening 25 a of the inorganic partition wall 25. As a material for forming the hole injecting and transporting layer 60, an aqueous dispersion of 3,4-polyethylenedioxythiophene / polystyrene sulfonic acid (PEDOT / PSS) is particularly preferably used.
In addition, as a forming material of the positive hole injection transport layer 60, various things can be used without being limited to the above-mentioned thing. For example, a material obtained by dispersing polystyrene, polypyrrole, polyaniline, polyacetylene or a derivative thereof in an appropriate dispersion medium such as the aforementioned polystyrene sulfonic acid can be used.

  The light emitting layer 70 is divided by an organic barrier 221 formed on the inorganic barrier 25, and a red light emitting layer 70R, a green light emitting layer 70G, and a blue light emitting layer 70B having emission wavelength bands corresponding to the respective colors are formed on each pixel electrode 111. I have. By providing the red light emitting layer 70R, the green light emitting layer 70G, and the blue light emitting layer 70B for each pixel electrode 111, one full-color display pixel is formed, and these emit light in gradation, whereby the organic EL device 1 As a whole, a full color display is made.

  As a material for forming the light emitting layer 70, a known light emitting material capable of emitting fluorescence or phosphorescence can be used. In the present embodiment, each of the light emitting layers 70R, 70G, and 70B is made of a phosphorescent material. Yes. For example, a CBP (4,4-dicarbazole-4,4-biphenyl) derivative or the like is used as a phosphorescent host material, a PtOEP (platinum porphyrin complex) derivative as a red phosphorescent material, and Ir (ppy) 3 as a green phosphorescent material. (Iridium complex) derivative, FIrpic (iridium complex) derivative, etc. as blue phosphorescent material dissolved in organic solvent such as cyclohexylbenzene, dihaliderobenzofuran, trimethylbenzene, tetramethylbenzene or their mixed solvent Can be used.

  Here, the film thickness of each light emitting layer 70R, 70G, 70B is formed to be different for each color. As described above, among the light emission lifetimes of the light emitting layers 70R, 70G, and 70B, the blue light emission layer 70B tends to be shorter than the light emission lifetimes of the red light emission layer 70R and the green light emission layer 70G. Specifically, each of the light emitting layers 70R, 70G, and 70B has an optimum film thickness that maximizes the light emission lifetime, and when the film thickness of each of the light emitting layers 70R, 70G, and 70B is made thicker than the optimum film thickness. There is a tendency to shorten the life, and there is a tendency to shorten the life even if the film thickness is reduced. Therefore, in the present embodiment, the blue light emitting layer 70B is adjusted to an optimum film thickness, and the red light emitting layer 70R and the green light emitting layer 70G are formed to be thinner than the optimum film thickness, whereby each light emitting layer 70R, The light emission lifetimes of 70G and 70B are approximated. As an example, the thickness of the red light emitting layer 70R is 100 mm, and the thickness of the green light emitting layer 70G is 300 mm. And the film thickness of the blue light emitting layer 70B is 400 mm.

  An electron injection layer 30 is formed on each of the light emitting layers 70R, 70G, and 70B. The electron injection layer 30 plays a role of injecting electrons into the light emitting layers 70R, 70G, and 70B, and has a film thickness of, for example, 350 mm. The material for forming the electron injection layer 30 includes oxazole derivatives, phenanthrolin derivatives, oxadiazole derivatives, anthraquinodimethane and derivatives thereof, benzoquinone and derivatives thereof, naphthoquinone and derivatives thereof, anthraquinone and derivatives thereof, tetracyanoanthraquinodimethane. And derivatives thereof, fluorenone derivatives, diphenyldicyanoethylene and derivatives thereof, diphenoquinone derivatives, metal complexes of 8-hydroxyquinoline and derivatives thereof, and the like can be used.

  A hole blocking layer may be formed between the light emitting layers 70R, 70G, and 70B and the electron injection layer 30. The hole blocking layer is for confining holes injected / transported from the pixel electrode 111 in each of the light emitting layers 70R, 70G, and 70B, and has a function of increasing the light emission efficiency. The hole blocking layer is formed when each of the light emitting layers 70R, 70G, and 70B is formed of a phosphorescent material. Further, as a material for forming the hole block layer, a triazole derivative, polyvinyl pyridine, polyvinyl pyrrolidone, or the like is used.

The cathode 12 is formed so as to cover the entire surface of each of the light emitting layers 70R, 70G, and 70B. For example, Ca is formed to a thickness of about 5 nm, and Al is formed to a thickness of about 300 nm thereon. It is a thing. Since the electrode has such a laminated structure, particularly Al functions as a reflective layer. If a transparent material is used for the cathode 12 as well, the emitted light can be emitted from the cathode side. As the transparent material, ITO, Pt, Ir, Ni, or Pd can be used. The film thickness is preferably about 75 nm in order to ensure transparency, and more preferably thinner than this film thickness.
Further, a sealing substrate (not shown) is stuck on the cathode 12 via an adhesive layer 51.

Next, the relationship between the film thickness of the light emitting layer, the light emission lifetime of the light emitting element, and the luminance will be described.
Conventionally, the optimum film thickness of each light emitting layer is set to about 500 mm for the red light emitting layer, 500 mm for the green light emitting layer, and about 400 mm for the blue light emitting layer. However, when each light emitting layer is set to an optimum film thickness in this way, the light emitting life of the blue light emitting layer is usually shorter than the light emitting life of the red light emitting layer and the green light emitting layer. As a result, the chromaticity and luminance of each light emitting element will deteriorate over time. Specifically, as described above, when the thickness of each light emitting layer is increased, the life of the light emitting element tends to be shortened, and even when the thickness is decreased, the life is likely to be shortened.

  Further, by changing the film thickness of each light emitting layer, the voltage required for emitting the optimum luminance of each light emitting element also changes. This is because the resistance of each light emitting layer is changed by changing the film thickness of each light emitting layer. Specifically, as each light emitting layer becomes thinner, the resistance becomes smaller and the voltage becomes lower, and when the film thickness becomes thicker, the resistance becomes larger and a high voltage is required.

FIG. 9 shows a light emitting device in the case where the thickness of each light emitting layer is formed with an optimum film thickness (500 mm (red), 500 mm (green), 400 mm (blue)) having the longest light emission lifetime as in the prior art. It is a graph which shows the relationship between the drive time [T] and the brightness | luminance of each light emitting element. In FIG. 9, the red light emitting element is red R ′, the green light emitting element is green G ′, and the blue light emitting element is blue B ′. In the graph of FIG. 9, the vertical axis represents the luminance normalized by the initial luminance.
As shown in FIG. 9, at the time T0, the luminance of each light emitting element is adjusted, and the white balance is optimized. However, as time elapses, the brightness of each color R ′, G ′, B ′ decreases, but it can be seen that there is a difference in this deterioration curve. As a result, the white balance starts to collapse from the time point T1, and the difference increases as T2 and T3 elapse. For the blue color B ′, the light emitting function is lost when T2 elapses. In other words, even if red R ′ and green G ′ have a long lifetime, the white balance optimized at the time T0 starts to collapse at the time T1, so that the organic EL device has a short lifetime. become.

  Here, in the present embodiment, among the light emitting layers of the red light emitting element, the green light emitting element, and the blue light emitting element, the thickness of the blue light emitting layer having the shortest light emitting life is set to have the longest light emitting life (400 mm). In addition, the red light emitting layer (100 mm) and the green light emitting layer (300 mm) are formed thinner than the optimum film thickness with the longest light emission lifetime. The film thickness of each light emitting layer is adjusted so that the light emission lifetime of the element is shortened to approach the light emission lifetime of the blue light emitting element.

  FIG. 4 shows the relationship between the driving time [T] of the light emitting element and the luminance when the film thickness of each light emitting layer is 100 mm (red), 300 mm (green), and 400 mm (blue) as in this embodiment. It is a graph which shows. In FIG. 4, the red light emitting element 3R is red R, the green light emitting element 3G is green G, and the blue light emitting element 3B is blue B. Also, the broken lines in FIG. 4 indicate the deterioration curves of red R ′ and green G ′ in FIG. 9 described above. Similarly to the graph of FIG. 9 described above, the vertical axis in the graph of FIG. 4 is the luminance normalized by the initial luminance.

As shown in FIG. 4, at the time T0, the luminance of each light emitting element is adjusted, and the white balance is optimized. As the time elapses, the luminance of each color R, G, B decreases, but there is no difference in the deterioration curves in each color R, G, B, and white balance until the light emitting function of each light emitting element is lost. It is possible to emit light while maintaining the above.
In addition, it is preferable that the shift | offset | difference of the light emission lifetime of each light emitting element is less than 30%. Thereby, white balance can be maintained until the light emitting function of any light emitting element is lost.

(Method for manufacturing organic EL device)
Next, a method for manufacturing the organic EL device according to this embodiment will be described with reference to FIGS. Here, FIGS. 5 and 6 are process diagrams of the organic EL device, and show portions corresponding to FIG. In the following description, the process up to the step of forming the pixel electrode 111 is the same as that of the prior art, and thus the description thereof is omitted.

First, as shown in FIG. 5A, an inorganic insulating material such as SiO ₂ is formed on the pixel electrode 111 and the planarizing film 284 by a CVD method or the like to form a partition layer (not shown). Subsequently, the partition wall layer is patterned using a known photolithography technique and etching technique. As a result, as shown in FIG. 5B, an opening 25a (not shown) is formed for each pixel region of the light emitting element 3 to be formed, and at the same time, an inorganic partition wall 25 is formed.

Next, as shown in FIG. 5C, an organic partition 221 is formed with a resin or the like at a predetermined position of the inorganic partition 25, specifically, a position surrounding the pixel region.
Next, the surface on which the pixel electrode 111, the inorganic partition wall 25, and the organic partition wall 221 are formed in this manner is subjected to oxygen plasma treatment, and contaminants such as organic substances attached to the surface are removed to improve wettability. Specifically, the substrate 2 is heated to a predetermined temperature, for example, about 70 to 80 ° C., and then plasma processing (O ₂ plasma processing) using oxygen as a reaction gas under atmospheric pressure is performed.

Next, the wettability of the upper surface and the side surface of the organic partition wall 221 is lowered by performing a liquid repellent treatment. Specifically, plasma treatment (CF ₄ plasma treatment) using tetrafluoromethane as a reaction gas under atmospheric pressure is performed, and then the substrate 2 heated for the plasma treatment is cooled to room temperature, whereby organic The upper surface and side surfaces of the partition wall 221 are made liquid repellent, and the wettability is lowered.
In this CF ₄ plasma treatment, the exposed surface of the pixel electrode 111 and the inorganic partition wall 25 are also somewhat affected, but the ITO that is the material of the pixel electrode 111 and the SiO ₂ that is the constituent material of the inorganic partition wall 25 are Since the affinity for fluorine is poor, the wettability of the surface improved by oxygen plasma treatment is maintained.

  Next, a hole injecting and transporting layer 60 is formed in a region surrounded by the organic partition 221. In the step of forming the hole injecting and transporting layer 60, a liquid phase method such as a spin coating method or an ink jet method is adopted. In this embodiment, the hole injecting and transporting layer 60 is formed in a region surrounded by the organic partition 221. An ink jet method is preferably employed because the formation material needs to be selectively disposed. By this inkjet method, a dispersion of PEDOT-PSS, which is a material for forming the hole injecting and transporting layer 60, is disposed on the exposed surface of the pixel electrode 111, and then heat treatment (drying treatment) is performed, so that the thickness becomes 500 mm. The hole injection transport layer 60 is formed. In addition, as a dispersion of PEDOT-PSS, for example, PEDOT: PSS is 1:10 (weight ratio), solid content concentration is 0.5% by weight, diethylene glycol monobutyl ether is 70% by weight as a solvent (dispersion medium), The remaining amount is pure water.

  Next, as shown in FIG. 6A, the light emitting layer 70 is formed on the hole injecting and transporting layer 60. As a method for forming the light emitting layer 70, an ink jet method is suitably employed as in the method for forming the hole injection transport layer 60. Specifically, the material for forming each of the light emitting layers 70R, 70G, and 70B described above is discharged to a region surrounded by the organic partition 221. At this time, the light emitting layers 70R, 70G, and 70B are selectively applied so that the red light emitting layer 70R, the green light emitting layer 70G, and the blue light emitting layer 70B are arranged in the order of the above-described film thicknesses. Thereafter, heat treatment is performed at 100 ° C. for about 1 hour in a nitrogen atmosphere. As described above, when the full-color organic EL device 1 (see FIG. 3) is manufactured, the light-emitting layer 70 is formed by the ink jet method, thereby reducing the manufacturing cost and forming the light-emitting layers 70R, 70G, and 70B. Can be reliably disposed at a predetermined position in a predetermined amount. In addition to the ink jet method, the light emitting layer 70 can be formed by a dispensing method, a printing method, or the like.

  Next, as shown in FIG. 6B, the electron injection layer 30 is formed on each of the light emitting layers 70R, 70G, and 70B. Specifically, the ink jet method is suitably employed in the same manner as the method for forming the hole injection transport layer 60 and the light emitting layer 70. Specifically, it is selectively applied on the light emitting layer 70 surrounded by the organic partition wall 221, and then heat treatment is performed in a nitrogen atmosphere.

Next, as shown in FIG. 6C, the cathode 12 is formed by stacking, for example, calcium with a thickness of about 5 nm and aluminum with a thickness of about 300 nm so as to cover the light emitting layer 70 and the organic partition 221. Specifically, unlike the formation of the hole injecting and transporting layer 60 and the light emitting layer 70, by performing the vapor deposition method, the sputtering method, or the like, it is not selectively formed only in the pixel region, but on almost the entire surface of the substrate 2. A cathode 12 is formed.
Thereafter, an adhesive layer 51 is formed on the cathode 12, and a sealing substrate (not shown) is further adhered by the adhesive layer 51 to perform sealing. Thereby, the organic EL device 1 of the present embodiment can be obtained.

As described above, in the present embodiment, the blue light emitting layer 70B is formed to have a film thickness that maximizes the light emission lifetime, and the red light emission layer 70R and the green light emission layer 70G have the longest light emission lifetime. Since the light emitting lifetimes of the red light emitting element 3R and the green light emitting element 3G are shortened by forming a thin film with respect to the film thickness, the red light emitting element 3R and the green light emitting element 3G have the longest light emitting lifetime. The light emission life of the blue light emitting element 3B having a short life can be approached.
Thereby, each of the light emitting layers 70R, 70G, and 70B can be adjusted by adjusting the film thickness of each light emitting layer 70R, 70G, and 70B without reducing the aperture ratio by correcting the driving circuit and changing the material for forming each light emitting layer. Even if the light emitting elements 3R, 3G, and 3B are deteriorated with time, the white balance of the organic EL device 1 can be maintained for a long time.

(Second Embodiment of Organic EL Device)
Next, a second embodiment of the present invention will be described based on FIG.
The second embodiment of the present invention is different from the first embodiment in that in addition to adjusting the thickness of each light emitting layer, the thickness of the pixel electrode is also adjusted.
FIG. 7 is a cross-sectional view schematically showing an organic EL device according to the second embodiment. In addition, in this embodiment, the same code | symbol is attached | subjected about the part similar to 1st Embodiment, and the detailed description is abbreviate | omitted.

  As shown in FIG. 7, the pixel electrodes 111R, 111G, and 111B corresponding to the light emitting elements 3R, 3G, and 3B are formed to have different film thicknesses. Specifically, the pixel electrodes 111R and 111G of the red light emitting element 3R and the green light emitting element 3G are formed with, for example, 800 mm as in the first embodiment. Here, the film thickness of the pixel electrode 111B of the blue light emitting element 3B is formed thinner than the film thickness of the pixel electrodes 111R and 111G, for example, 500 mm.

  Further, the light emitting layers 70R, 70G, and 70B are formed to have different thicknesses. Specifically, the red light emitting layer 70R is formed with 150 mm, for example, the green light emitting layer 70G is formed with 300 mm, and the blue light emitting layer 70B is formed with 500 mm, for example.

Here, the relationship between the thickness of the light emitting layer of the light emitting element and the chromaticity will be described. In addition, the following description is the same also about each layer in which the light light-emitted by a light emitting layer propagates.
In the present embodiment, the film thicknesses of the light emitting layers 70R, 70G, and 70B (150 Å (red), 300 Å (green), and 500 Å (blue)) are light that can be emitted with the light emission lifetime of each light emitting element and the optimum chromaticity of each color. Are formed on the basis of the wavelength and luminance. Specifically, the light emitted from each of the light emitting layers 70R, 70G, and 70B is divided into a light component emitted directly to the substrate 2 side and a light component emitted from the cathode 12 to the substrate 2 side. In the following description, the light that is directly emitted from the light emitting layers 70R, 70G, and 70B to the substrate 2 side is referred to as “first light”, and the light that is reflected from the cathode 12 side and then emitted to the substrate 2 side is referred to as “second light”. "Light".

  The light emitted from the substrate 2 side exhibits different spectra depending on the interference state between the first light and the second light. That is, the first and second lights propagate through each layer including the light emitting layer 70 (for example, the hole injection transport layer 60 and the pixel electrode 111) before being emitted from the substrate 2 side, but the respective light emitting layers 70R and 70G. , 70B, the respective distances of the first and second light traveling through the light emitting layers 70R, 70G, 70B vary. Accordingly, the mutual phases of the first and second lights emitted from the substrate 2 side change in accordance with the film thicknesses of the respective light emitting layers 70R, 70G, and 70B. The interference state (light emission state) of the second light also changes according to the film thickness of each light emitting layer 70R, 70G, 70B. Note that the interference state between the first light and the second light also changes depending on the refractive index when the light passes through the interface of each layer.

  Therefore, when a voltage is applied to each light emitting layer 70R, 70G, 70B (each light emitting element 3R, 3G, 3B), the spectrum of light emitted from each light emitting layer 70R, 70G, 70B is the light emitting layer 70R, 70G. , 70B. Specifically, by increasing the film thickness of each of the light emitting layers 70R, 70G, and 70B, the peak of the spectrum from each of the light emitting layers 70R, 70G, and 70B shifts to the longer wavelength side and the spectrum width becomes wider. Therefore, the desired chromaticity cannot be obtained. On the other hand, when the film thickness is reduced, the peak of the spectrum shifts to the short wavelength side, and thus desired chromaticity cannot be obtained even in this case.

In the first embodiment, the white balance of each light emitting element 3R, 3G, 3B is adjusted by adjusting the film thickness of each light emitting layer 70R, 70G, 70B and bringing the light emitting life of each light emitting element 3R, 3G, 3B closer. However, when the desired luminance and chromaticity cannot be obtained for the above-described reason with the light emission lifetimes of the light emitting layers 70R, 70G, and 70B being most approximated, the pixel electrodes 111R, 111G , 111B is adjusted to adjust the interference state of the light emitted from each of the light emitting layers 70R, 70G, 70B, and the spectrum shape after the interference of each of the light emitting elements 3R, 3G, 3B is set to a desired luminance and It can be adjusted to be emitted with chromaticity.
Accordingly, in addition to the same effects as those of the first embodiment, the chromaticity can be adjusted without changing the optimized light emission lifetime of each of the light emitting elements 3R, 3G, 3B. The white balance of the device 1 can be adjusted with higher accuracy.

  In addition, by adjusting the luminance and chromaticity according to the film thickness of the pixel electrode 111 as described above, it is possible to maintain the white balance by the light emitting elements 3R, 3G, and 3B while suppressing the influence on the light emission characteristics. In addition to the pixel electrode 111, it is also possible to adjust the thickness of each layer through which light emitted from the light emitting layer 70 is propagated, such as the hole injection transport layer 60 and the electron injection layer 30. Thereby, since the interference state of the light emitted from the light emitting layer can be adjusted similarly to the present embodiment, the white balance by each light emitting element can be maintained for a long time.

  In the above embodiment, an example in which the present invention is applied to a so-called bottom emission type organic EL device that emits light emitted from the light emitting layer from the substrate side is shown. The present invention can also be applied to a so-called top emission type organic EL device that emits light from a light source. When the top emission type is adopted, the chromaticity can be adjusted by changing the film thickness of the cathode by each light emitting element.

(Electronics)
Next, a specific example of an electronic apparatus provided with the organic EL device 1 of the present embodiment will be described.
FIG. 8A is a perspective view showing an example of a mobile phone. In FIG. 8A, reference numeral 1000 indicates a mobile phone body, and reference numeral 1001 indicates a display unit including the organic EL device 1.
FIG. 8B is a perspective view showing an example of a wristwatch type electronic device. In FIG. 8B, reference numeral 1100 indicates a watch body, and reference numeral 1101 indicates a display unit including the organic EL device 1.
FIG. 8C is a perspective view showing an example of a portable information processing apparatus such as a word processor or a personal computer. In FIG. 8C, reference numeral 1200 denotes an information processing apparatus, reference numeral 1202 denotes an input unit such as a keyboard, reference numeral 1204 denotes an information processing apparatus body, and reference numeral 1206 denotes a display unit including the organic EL device 1.
FIG. 8D is a perspective view showing an example of a thin large-screen television. In FIG. 8D, the thin large-screen television 1300 includes a thin large-screen television main body (housing) 1302, an audio output unit 1304 such as a speaker, and a display unit 1306 including the organic EL device 1.

  Since the electronic devices 1000, 1100, 1200, and 1300 shown in FIGS. 8A to 8D include the organic EL device 1, the display units 1001, 1101, 1206, and 1306 of the organic EL device 1 are included. Since the reduction in luminous efficiency is prevented and the lifetime is extended, the display units 1001, 1101, 1206, and 1306 also have extended lifetimes in the electronic devices 1000, 1100, 1200, and 1300 themselves.

In addition, this invention is not restricted to the said embodiment, In the range which does not deviate from the summary of this invention, it can change suitably.
For example, in the above-described embodiment, the case where a phosphorescent material is used as the material for forming the light emitting layer has been described. However, a fluorescent material having a longer emission lifetime than the phosphorescent material may be used for all the light emitting layers.
Further, it is possible to form the red light emitting layer and the green light emitting layer with a phosphorescent material and form only the blue light emitting layer with a fluorescent material. In these cases as well, the interference state of the light emitted from the light emitting element is adjusted with the light emitting element's light emission life most approximated, and the spectrum shape after interference of each light emitting element is emitted with the desired luminance and chromaticity. Then, the light emitting layer, the pixel electrode, and the like are adjusted.

It is explanatory drawing which shows the wiring structure of the organic electroluminescent apparatus of this embodiment. FIG. 2 is a schematic plan view of the organic EL device in FIG. 1. It is a principal part cross-sectional schematic diagram of the organic electroluminescent apparatus of FIG. 1 which concerns on 1st Embodiment. It is a graph which shows the relationship between the drive time of the light emitting element which concerns on 1st embodiment, and a brightness | luminance. (A)-(c) is process drawing explaining the manufacturing method of the organic electroluminescent apparatus of FIG. (A)-(c) is process drawing explaining the manufacturing method following FIG. It is a principal part cross-sectional schematic diagram of the organic electroluminescent apparatus of FIG. 1 which concerns on 2nd Embodiment. (A)-(d) is a perspective view which shows embodiment of the electronic device of this invention. It is a graph which shows the relationship between the drive time of a conventional light emitting element, and a brightness | luminance.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Organic EL apparatus (organic electroluminescent apparatus) 3 ... Light emitting element 3R ... Red light emitting element 3G ... Green light emitting element 3B ... Blue light emitting element 12 ... Cathode (2nd electrode) 60 ... Hole injection transport layer 70 ... Light emitting layer 70R ... Red light emitting layer 70G ... Green light emitting layer 70B ... Blue light emitting layer 110 ... Organic functional layer 111 ... Pixel electrode (first electrode)

Claims (9)

In an organic electroluminescence device including a plurality of light-emitting elements in which an organic functional layer is sandwiched between a first electrode and a second electrode,
The film thickness of the organic functional layer of the light emitting element with the shortest light emission lifetime among the plurality of light emitting elements is formed to an optimum film thickness with the longest light emission lifetime,
An organic electroluminescence device, wherein the thickness of the organic functional layer of at least one of the other light emitting elements is different from the optimum thickness that maximizes the light emission lifetime. A plurality of light emitting elements having a red light emitting element that emits red light, an organic functional layer sandwiched between the first electrode and the second electrode, a green light emitting element that emits green light, and a blue light emitting element that emits blue light In an organic electroluminescence device comprising:
Among the light emitting elements of the red light emitting element, the green light emitting element, and the blue light emitting element, the film thickness of the organic functional layer of the light emitting element having the shortest light emitting lifetime is the optimum film thickness that maximizes the light emitting lifetime. As it is formed,
An organic electroluminescent device, wherein the thickness of the organic functional layer of the light emitting element of at least one other color is different from the optimum thickness that maximizes the light emission lifetime. The organic functional layer includes at least a light emitting layer and a hole injection transport layer,
Of the light emitting elements of the red light emitting element, the green light emitting element, and the blue light emitting element, the film thickness of the light emitting layer of the light emitting element that emits the color with the shortest light emitting lifetime is the optimum film thickness with the longest light emitting lifetime. And formed
The organic light-emitting device according to claim 1 or 2, wherein the light-emitting layer of the light-emitting element that emits another color has a thin film thickness with respect to an optimum film thickness that maximizes a light emission lifetime. Electroluminescence device.   4. The chromaticity and luminance shift caused by changing the film thickness of the light emitting layer with a film thickness other than the light emitting layer of each light emitting element is corrected. 5. 2. The organic electroluminescence device according to item 1.   5. The organic electroluminescence according to claim 1, wherein the film thickness of the first electrode is set based on the wavelength of light emitted from each of the light emitting layers. apparatus.   The organic electroluminescence device according to any one of claims 1 to 5, wherein a deviation in light emission lifetime of each of the light emitting elements is within 30%. A method of manufacturing an organic electroluminescence device including a plurality of light emitting elements in which an organic functional layer is sandwiched between a first electrode and a second electrode,
The step of forming each light emitting element is a step of forming the film thickness of the organic functional layer of the light emitting element having the shortest light emission lifetime among the plurality of light emitting elements to an optimum film thickness that provides the longest light emission lifetime;
Forming the thickness of the organic functional layer of at least one of the other light-emitting elements to a thickness different from the optimum thickness that maximizes the light emission lifetime. Method.   8. The method of manufacturing an organic electroluminescent device according to claim 7, wherein the step of forming each light emitting element is a step of applying a liquid material for forming each organic functional layer by an ink jet method.   An electronic apparatus comprising the organic electroluminescence device according to any one of claims 1 to 6.

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