KR101127061B1 - Oled with color change media - Google Patents

Abstract

The tuned OLED device according to the present invention comprises a light emitting layer for generating light, a translucent reflector, and a reflector layer disposed on opposite sides of the light emitting layer, and promotes on-axis light generated from the light emitting layer at one or more specific wavelengths to achieve the desired axial shape. Microcavity structures that produce a visible color but do not substantially enhance light of other wavelengths on the axis; And by an organic light emitting (OLED) device when viewed in the non-axial direction by reacting to light of a wavelength shorter than a specific wavelength by absorbing light of a wavelength shorter than a specific wavelength and emitting light of a color corresponding to the specific wavelength. And a layer comprising a color conversion medium that improves the color of the light.

Description

Organic light emitting device having a color conversion medium {OLED WITH COLOR CHANGE MEDIA}

The present invention relates to an organic electroluminescent device. More specifically, the present invention relates to electroluminescent devices with improved efficiency, color purity, and viewing angle.

Full color organic electroluminescent (EL) devices, also known as organic light-emitting devices (OLEDs), have recently come into the spotlight as new types of flat panel displays. OLED devices are of interest due to their low drive voltage, high brightness, wide viewing angle and their performance for full color flat panel light emitting displays. In its simplest form, an organic EL device consists of an anode for hole injection, a cathode for electron injection, and an organic EL medium sandwiched between the electrodes for sustaining the recombination of the charge-emitting charges. . One example of an organic EL device is described in commonly assigned US Pat. No. 4,356,429. Other examples are described in US Pat. Nos. 4,769,292 and 4,885,211 to Tang et al. In order to construct a pixelated useful display device such as a television, computer monitor, cellular phone display or digital camera display, individual organic EL elements can be arranged as an array of pixels in a matrix pattern. This pixel matrix can be electrically driven using a simple passive matrix or active matrix drive scheme. In the passive matrix, the organic EL layer is sandwiched between two sets of orthogonal electrodes arranged in columns and rows. One example of a passive matrix-driven organic EL device is disclosed in commonly assigned US Pat. No. 5,276,380. In an active matrix configuration, each pixel is driven by complex circuit elements such as transistors, capacitors, and signal lines. Examples of such active matrix organic EL devices are described in US Pat. Nos. 5,550,066 (usually assigned), 6,281,634, and 6,456,013.

One way to improve the efficiency of OLED devices is to use microcavity structures. The reflector and the translucent reflector act together with the layers between them to form microcavities so that the thickness and refractive index can be adjusted to resonate at the desired wavelength. Examples of microcavity structures are shown in US Pat. No. 6,406,801, US Pat. No. 5,780,174, and Japanese Patent (JP) 11-288786.

Due to the microcavity effect in the OLED device, offset light interference may occur, and may cause color distortion when the OLED device is viewed from a square. Microcavity devices are characteristic directional and are described, for example, in N. Takada, T. Tsutsui, and S. Saito, Appl. Phys. Lett. 63 (15) 2032 (1993), "Control of emission characteristics in organic thin film electroluminescent diodes using an optical microcavity structure." Likewise, the light emission intensity drops rapidly with the viewing angle.

Summary of the Invention

Therefore, it is an object of the present invention to provide an OLED device with reduced color distortion when viewed in an off-axis direction.

This object is achieved by a tuned OLED device, comprising: a) a light emitting layer for generating light, a translucent reflector, and a reflector layer disposed on opposite sides of the light emitting layer, the axial light being generated from the light emitting layer at one or more specific wavelengths; Microcavity structures that enhance to produce the desired on-axis visual color but do not substantially enhance light of other wavelengths on the axis; And b) the color of the light produced by the OLED device when viewed in the non-axial direction by reacting to light of a wavelength shorter than the specific wavelength by absorbing light of a wavelength shorter than the specific wavelength and emitting light of a color corresponding to the specific wavelength. And a layer comprising a color conversion medium that improves the resolution.

Advantages

An advantage of the present invention is that the present invention provides an efficient OLED device in which color distortion is reduced when viewed from a non-axis angle. A further advantage of the present invention is that the present invention can provide improved brightness in some embodiments, especially when viewed from off-axis angles.

1 is a cross-sectional view of a conventional microcavity OLED device showing luminescent effects in microcavities.

FIG. 2 is a diagram showing the emission spectrum of the prior art versus the unenhanced white emitting OLED device after microcavity enhancement.

3 is a cross-sectional view of one embodiment of an OLED device according to the invention.

4 is a cross-sectional view of another embodiment of an OLED device according to the invention.

Device features, such as layer thickness, are often scaled up to be easier to see than of precise dimensions because they are often in a range smaller than micrometers.

Explanation of symbols for main parts of the drawings

10 Tuned OLED Devices 15 Tuned OLED Devices

20 substrates 25 color conversion media

25a color conversion medium 25b color conversion medium

30 translucent reflectors / electrodes 35 transparent co-spacer layers

35a transparent co-spacer layer 35b transparent co-spacer layer

40 Hole injection layer 45 Hole transport layer

50 Emitting Layer 55 Electron Transport Layer

60 Electroinjection Layer 65 Tuned Multicolor OLED Devices

70 Microcavity Structure 75 Dielectric Stack

75a dielectric stack 75b dielectric stack

80a pixel 80b pixel

80c pixel 85 color filter

85a color filter 85b color filter

90 reflector layer / electrode 90a reflector layer

90b Reflector Layer 90c Reflector Layer

100 organic layer 105 light

110 reflected light 115 light

120 partially reflected light

125 partially transmitted on-axis light

125a axial light 125b axial light

125c on-axis light 130 partially reflected light

135 light 140 partially transmitted off-axis light

150 switching light 160 inter-pixel dielectric layer

170 Spectrum 175 Specific Wavelength

180 specific wavelength 185 specific wavelength

210 Active Matrix Circuit 211 Semiconductor Active Layer

212 gate dielectric 213 gate conductor

214 first insulating layer 215 power line

216 signal line 217 second insulating layer

The term "OLED device" or "organic light emitting display" is used in the sense recognized in the art to refer to a display device comprising an organic light emitting diode as a pixel. Color OLED devices emit light of one or more colors. The term "multi-color" is used to describe a display panel capable of emitting light of different hue in different areas. In particular, it is used to describe a display panel capable of displaying images of different colors. These regions do not necessarily need to be contiguous. The term “full color” is used to describe a multicolor display panel that can emit in the red, green and blue regions of the visible spectrum and can display an image in any combination of colors. Red, green, and blue constitute three primary colors, and all other colors can be produced by appropriate mixing of the three primary colors. However, additional colors may be used to extend the gamut of the device. The term "hue" refers to the profile of the luminescence intensity in the visible spectrum, where different colors represent differences in color that can be visually identified. The term "pixel" is used in the sense recognized in the art to refer to an area of the display panel that can be stimulated to independently emit light of another area. However, as will be appreciated, in a full color system several pixels of different colors may be used together to form a wide range of colors, and the observer may refer to this group of pixels as a single pixel. For the purposes of the present invention, this theoretical group will be referred to as "group of pixels" or "pixel group". In a full color display, the group of pixels generally includes three primary colors, red, green, and blue (RGB), which are the pixels that define the color gamut. As is well known, microcavity structures promote the emission of light in a relatively narrow range of wavelengths, and the term “specific wavelengths” is used to describe such enhanced range of wavelengths.

1 is a cross-sectional view of a prior art tuned OLED device showing the effect of luminescence in microcavity. Microcavity OLED devices have been reported to achieve enhanced chromaticity and luminous efficiency. Although the tuned OLED device 10 is shown as emitting light from the bottom (ie bottom emitting device), it will be appreciated that the tuned OLED device 10 may be a top emitting device.

The tuned OLED device 10 includes a microcavity structure 70 and includes a reflector layer 90 which is a highly reflective material at the wavelength at which the tuned OLED device 10 emits light. Preferred materials for the highly reflective reflector layer 90 include Ag, Al, Au or alloys of one or more such materials. The tuned OLED device 10 also includes a translucent reflector 30 that is partly reflective and partly transmissive. Suitable materials for the translucent reflector 30 include Ag, Au, or alloys of one or two of these materials selected to be translucent (ie, some are transmissive and some are reflective). The thickness can be, for example, in the range of 5 nm to 50 nm, more preferably 15 nm to 30 nm. Alternate translucent reflector structures consisting of alternating quarter wave stacks (QWS) of alternating high and low refractive indices are also known and can be used in the present invention by one skilled in the art. The reflector layer 90 and the translucent reflector 30 are located on opposite sides of the light emitting layer 50 and serve to produce light. As shown, in a bottom emitting device that sees light through the substrate 20, a translucent reflector 30 is positioned between the light emitting layer 50 and the substrate 20, and the reflector layer 90 is the substrate 20. And a translucent reflector 30 and a light emitting layer 50. Alternatively, in the top light emitting device that sees light in the opposite direction of the substrate 20, the reflector layer 90 is located between the light emitting layer 50 and the substrate 20, and the translucent reflector 30 is the substrate 20, It is disposed over the reflector layer 90 and the light emitting layer 50.

Reflector layer 90 and translucent reflector 30 may act to form microcavity structure 70 with layers therebetween so that thickness and refractive index may be adjusted to resonate at a desired wavelength. Examples of microcavity structures are described in US Pat. No. 6,406,801, US Pat. No. 5,780,174 A1, and Japanese Patent 11288786. Transparent co-spacer layer 35 may be used as additional means to adjust the microcavity structure resonance wavelength. Light is shown to be emitted at the interface between the hole transport layer 45 and the light emitting layer 50. The light 115 is on-axis light generated from the light emitting layer 50 in the direction of the translucent reflector 30, and is partially reflected as partially reflected light 120, and partially transmitted axial light 125. A part is transmitted as). Partially transmitted axial light 125 includes one or more narrow wavelength bands of light. That is, the microcavity structure 70 enhances the on-axis light generated from the light emitting layer 5 at one or more specific wavelengths of on-axis light to produce a desired on-axis visual color, but does not substantially enhance light of other wavelengths. Light 105 represents axial light emitted in the direction of reflector layer 90 and reflected as reflected light 110. This will be partially reflected and partially transmitted by the translucent reflector 30.

The thickness of the microcavity structure 70 comprising the transparent co-spacer layer 35 (if present) is selected to tune the microcavity OLED device 10 to resonate at a predetermined wavelength emitted from the device. The thickness satisfies Equation 1 below:

Where

n _i is the refractive index,

L _i is the thickness of the n th lower layer in the microcavity structure 70,

n _s is the refractive index,

L _s may be zero as the thickness of the transparent co-spacer layer 35,

Q _m1 and Q _m2 are the phase shifts (in radians) at the two organic EL device reflector interfaces, respectively.

λ is the predetermined wavelength of on-axis light promoted by the microcavity structure 70,

m is a nonnegative integer.

For example, the practitioner can select the effect of microcavity to promote on-axis light emission of the green light (partially transmitted on-axis light 125) for the desired on-axis visual color.

Light 135 represents light generated in the off-axis direction. This may be partially reflected by semi-transparent reflector 30 as partially reflected light 130 and partially transmitted as partially transmitted non-axial light 140. Light emitted in the non-axial direction by the microcavity structure (eg, partially transmitted non-emitter light 140) may have a wavelength different from that emitted from the axial light (eg, partially transmitted axial light 125). Will have brightness. In other words, the microcavity structure 70 will produce light with a broad spectrum visible at different viewing angles, even if the microcavity is tuned to promote a single wavelength of on-axis viewing color. Typically, the microcavity light emitted on the off-axis will have a shorter wavelength than the light generated on the on-axis.

2 shows the spectrum of on-axis emission after multi-mode microcavity enhancement versus the emission spectrum in unpromoted white light emitting OLED devices. Spectrum 170 is the emission spectrum in a white light emitting OLED device without axial microcavity enhancement. The use of multi-mode microcavities, such as those described in US Pat. No. 6,133,692 to Xu et al., Allows for certain wavelengths in the spectrum, such as specific wavelengths 175, 180 and 185, when viewed on the microcavity. Will promote. By selecting the thickness of the microcavity structure 70, the practitioner can form a microcavity structure that promotes on the axis a narrow single band of light wavelength.

In figure 3 a cross-sectional view of one embodiment of an OLED device according to the invention is shown. The tuned OLED device 15 may be part of a passive matrix device or an active matrix device. The tuned OLED device 15 has a microcavity structure 70 from the tuned OLED device 10 as its basic structure. The tuned OLED device 15 includes a reflector layer 90 and a translucent reflector 30 as described above. The reflector layer 90 and the translucent reflector 30 act as electrodes, but in other embodiments it is also possible for the reflector and the electrode to be separated. Although the bottom electrode, i.e., the electrode closest to the substrate 20, is mainly composed mainly as an anode, the present invention is not limited to the device of this structure. The tuned OLED device 15 further comprises a layer comprising a color conversion medium 25. The color conversion media layer is disposed above the translucent reflector 30. The color conversion medium 25 responds to light wavelengths shorter than the particular wavelength of on-axis light. The color conversion medium 25 absorbs these shorter wavelengths (e.g., partially transmitted off-axis light 140) and has light (e.g., corresponding to a particular wavelength of the partially transmitted axial light 125). To emit the diverted light 150. The corresponding color is in the same area as the visible spectrum, meaning that the viewer perceives the same or the same color. For example, the particular wavelength of on-axis light of the tuned OLED device 15 may be the spectrum of the green portion. The partially transmitted axial light 125 will comprise a narrow distribution of wavelengths that the viewer perceives as green. The partially transmitted off-axis light 140 is more blue than the partially transmitted off-axis light 125 but will be absorbed by the color converting medium 25 and re-emitted as diverted light 150. The diverted light 150 includes a broader wavelength distribution than the partially transmitted light 125, but will be in the same region as the partially visible light 125 generally in the visible spectrum, and the observer will perceive as green light. . This improves the color of light generated by the OLED device 15 when viewed in the non-axial direction. Similarly, the particular wavelength of on-axis light of the tuned OLED device 15 may be in the blue portion of the spectrum or in the red portion of the spectrum. The nature of the color conversion medium 25 will depend on the color of the tuned OLED device 15.

Color conversion media layers are described in US Pat. No. 6,084,347 and US Patent Application No. 2003/0127968 and include, for example, only fluorescent dyes or fluorescent dyes with binder resins, which include color conversion media. Fluorescent dyes will absorb light in one region of the spectrum and will emit light with longer wavelengths. Examples of fluorescent dyes that absorb light from near-ultraviolet to ultraviolet light and emit blue light are stilbene-based dyes such as 1,4-bis (2-methylstyryl) -benzene and trans-4,4'-diphenylstilbene. ; And coumarin-based dyes such as 7-hydroxy-4-methylcoumarin or combinations thereof. Examples of fluorescent dyes for absorbing light and emitting green light in the blue to blue green region include coumarin dyes such as 2,3,5,6-1H, 4H-tetrahydro-8-trifluoromethyl-quinolidino ( 9,9a, 1-ho) coumarin, 3- (2'-benzothiazolyl) -7-diethylaminocoumarin, 3- (2'-benzimidazolyl) -7-N, N-diethyl Aminocomarin; And naphthalimide dyes such as basic yellow 51, solvent yellow 11 and solvent yellow 116, or combinations thereof. Examples of fluorescent dyes for absorbing light in the blue to green region and for emitting orange to red light include cyanine dyes, such as 4-dimethylaminomethylene-2-methyl-6- (p-dimethylaminostyryl- 4H-pyran; pyridine dyes such as 1-ethyl-2- (4- (p-dimethylaminophenyl) -1,3-butadienyl) -pyridinium percholate; and rhodamine dyes such as rhodamine B and rhodamine 6G; oxazine-based dyes or combinations thereof, as long as it is fluorescent, various dyes may be used (eg, direct dyes, acid dyes, basic dyes and disperse dyes). For example, it is mixed with polymethacrylic acid ester, polyvinyl chloride, vinyl chloride / vinyl acetate copolymer, alkyd resin, aromatic sulfonamide resin, urea resin, melamine resin, benzoguanamine resin and the like to form a color conversion medium layer. To help.

The color converting medium 25 will emit in all directions including entering back into the tuned OLED device 15. To prevent this, a dielectric stack 75 may optionally be disposed between the layer of color converting media 25 and the translucent reflector 30. The dielectric stack 75 will reflect light and direct a larger fraction of the diverted light 150 emitted by the color conversion medium 25 to the viewer. Dielectric stack 75 (or known as quarter wave stack) includes alternating layers of high and low refractive index materials (eg, SiO ₂ and TiO ₂ ). Dielectric stack 75 is configured to reflect a substantial portion of the wavelength of diverted light 150, but must transmit a particular wavelength of relatively partially transmitted axial light 125. Techniques for producing dielectric stacks with desired properties are well known, for example, in Bonn and Wolf, "Principles of Optics", 6th ed., Pergamon Press, 1980.

Although not required, the tuned OLED device 15 may further comprise a color filter 85. The color filter 85 may be any known filter and is designed to remove any light of a wavelength shorter than a specific wavelength of on-axis light that is not absorbed by the color conversion medium 25 or any light of a wavelength longer than a specific wavelength of the on-axis light. do.

The tuned OLED device 15 and any pixels of the present invention are typically disposed as shown on the support substrate 20. The substrate 20 may be light transmissive or impermeable depending on the intended direction of light emission. Light transmissivity may be desirable for viewing EL emission through a substrate (ie, the bottom emitting device shown). Clear glass or plastic is mainly used in this case. In applications where the device is top emission, the permeability of the substrate 20 is not critical and may be light transmissive, light absorbing or light reflective. Substrates used in such cases include, but are not limited to, glass, plastics, semiconductor materials, silicon, ceramics, and circuit board materials.

The microcavity substrate 70 may include a transparent co-spacer layer 35 that may be disposed between one of the reflectors and the light emitting layer 50. It must transmit the emitted light and must be conductive to transfer charge between the electrode (reflector) and the light emitting layer 50 as shown. Since only the conductivity through the film is important, a bulk resistance of less than about 10 ⁸ ohm-cm is appropriate. Many metal oxides such as but not limited to indium tin oxide (ITO), zinc-tin oxide (ZTO), tin-oxide (SnO _x ), indium oxide (InO _x ), molybdenum oxide (MoO _x ), tellurium Oxides (TeO _x ), antimony oxides (SbO _x ), indium zinc oxide (IZO), and zinc oxides (ZnO _x ) may be used. If the transparent co-spacer layer 35 is not conductive, it can be formed over the transparent co-spacer layer 35 in such a way that the transparent electrode is in electrical contact with the circuit. The transparent electrode may be composed of the metal oxide described above. The thickness of the transparent co-spacer layer 35, the refractive index of the transparent co-spacer layer 35, or both are adjusted according to the thickness and refractive index of the layer of the tuned OLED device 15 to achieve the microcavity structure 70. Tune in color.

The tuned OLED device 15 further comprises an organic layer. There are a number of organic layers known in the art that can successfully practice the present invention, which includes a hole injection layer 40, a hole transport layer 45, a light emitting layer 50, an electron transport layer 55 and an electron injection Layer 60.

Although not necessary, it is often useful to provide the hole injection layer 40. The hole injection layer 40 may function to improve film formability of the subsequent organic layer and to facilitate hole injection into the hole transport layer 45. Suitable materials for use in the hole injection layer 40 are porphyrinic compounds described in US Pat. No. 4,720,432, plasma-deposited fluorocarbon polymers described in US Pat. Nos. 6,127,004, 6,208,075 and 6,208,077 and m. Some anti-aromatic amines, such as -MTDATA (4,4 ', 4 "-tris [(3-methylphenyl) phenylamino] triphenylamine), but are not limited to this. Another for organic EL devices Hole injection materials are described in European Patent Nos. 0 891 121 A1 and 1 029 909 A1.

The hole transport layer 45 contains one or more hole transport compounds, such as aromatic tertiary amines, and aromatic tertiary amines contain one or more trivalent nitrogen atoms bonded only to carbon atoms, at least one of which is an aromatic ring member. It is understood to be a compound. In one form, the aromatic tertiary amine may be an arylamine such as monoarylamine, diarylamine, triarylamine or polymerizable arylamine. Examples of monomeric triarylamines are illustrated in US Pat. No. 3,180,730 to Klupfel et al. Other suitable triarylamines substituted with one or more vinyl radicals and / or comprising one or more active hydrogen containing groups are disclosed in US Pat. Nos. 3,567,450 and 3,658,520 to Brantley et al.

A more preferred class of aromatic tertiary amines are those comprising two or more aromatic tertiary amine moieties as described in US Pat. Nos. 4,720,432 and 5,061,569. The hole transport layer 45 may be formed of a single aromatic tertiary amine compound or a mixture of these compounds. Examples of useful aromatic tertiary amines are as follows:

1,1-bis (4-di-p-tolylaminophenyl) cyclohexane;

1,1-bis (4-di-p-tolylaminophenyl) -4-phenylcyclohexane;

N, N, N ', N'-tetraphenyl-4,4' "-diamino-1,1 ': 4', 1": 4 ", 1 '"-quaterphenyl;

Bis (4-dimethylamino-2-methylphenyl) phenylmethane;

1,4-bis [2- [4- [N, N-di (p-tolyl) amino] phenyl] vinyl] benzene (BDTAPVB);

N, N, N ', N'-tetra-p-tolyl-4,4'-diaminobiphenyl;

N, N, N ', N'-tetraphenyl-4,4'-diaminobiphenyl;

N, N, N ', N'-tetra-1-naphthyl-4,4'-diaminobiphenyl;

N, N, N ', N'-tetra-2-naphthyl-4,4'-diaminobiphenyl;

N-phenylcarbazole;

4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPB);

4,4'-bis [N- (1-naphthyl) -N- (2-naphthyl) amino] biphenyl (TNB);

4,4'-bis [N- (1-naphthyl) -N-phenylamino] p-terphenyl;

4,4'-bis [N- (2-naphthyl) -N-phenylamino] biphenyl;

4,4'-bis [N- (3-acenaphthenyl) -N-phenylamino] biphenyl;

1,5-bis [N- (1-naphthyl) -N-phenylamino] naphthalene;

4,4'-bis [N- (9-anthryl) -N-phenylamino] biphenyl;

4,4'-bis [N- (1-antryl) -N-phenylamino] -p-terphenyl;

4,4'-bis [N- (2-phenanthryl) -N-phenylamino] biphenyl;

4,4'-bis [N- (8-fluoroantenyl) -N-phenylamino] biphenyl;

4,4'-bis [N- (2-pyrenyl) -N-phenylamino] biphenyl;

4,4'-bis [N- (2-naphthacenyl) -N-phenylamino] biphenyl;

4,4'-bis [N- (2-perylenyl) -N-phenylamino] biphenyl;

4,4'-bis [N- (1-coroneyl) -N-phenylamino] biphenyl;

2,6-bis (di-p-tolylamino) naphthalene;

2,6-bis [di- (1-naphthyl) amino] naphthalene;

2,6-bis [N- (1-naphthyl) -N- (2-naphthyl) amino] naphthalene;

N, N, N ', N'-tetra (2-naphthyl) -4,4'-diamino-p-terphenyl;

4,4'-bis {N-phenyl-N- [4- (1-naphthyl) -phenyl] amino} biphenyl;

2,6-bis [N, N-di (2-naphthyl) amino] fluorene;

4,4 ', 4'-tris [(3-methylphenyl) phenylamino] triphenylamine (MTDATA); And

4,4'-bis [N- (3-methylphenyl) -N-phenylamino] biphenyl (TPD).

Another class of useful hole transport materials includes the polycyclic aromatic compounds described in EP 1 009 041. Tertiary aromatic amines (including oligomeric materials) having more than two amine groups can be used. Poly (N-vinylcarbazole) (PVK), polythiophene, polypyrrole, polyaniline and copolymers such as poly (3,4-ethylenedioxythiophene) / poly (4-styrene, also called PEDOT / PSS Polymerizable hole transport materials, such as sulfonates)).

As described in more detail in US Pat. Nos. 4,769,292 and 5,935,721, the emissive layer 50 comprises a luminescent or fluorescent material in which electroluminescence is formed as a result of electron-hole pair recombination in this region to produce light. The light emitting layer 50 may be made of a single material, but more typically a guest compound or a host material doped with compounds, in which case the light emission is primarily from a dopant and may be of any color. The host material of the light emitting layer 50 may be an electron transport material as defined below, a hole transport material as defined above, or another material or combination of materials supporting hole electron recombination. Dopants are usually selected from highly fluorescent dyes, but phosphorescent compounds such as WO 98/55561, WO 00/18851, WO 00/57676 and WO patent Also useful are the transition metal complexes described in publication 00/70655. Dopants are typically coated into the host material at 0.01 to 10% by weight. Polymeric materials such as polyfluorene and polyvinylarylene (eg poly (p-phenylenevinylene), PPV) can also be used as host material. In this case, small molecular dopants may be molecularly dispersed into the polymerizable host, or the dopants may be added by copolymerizing trace components into the host polymer.

An important relationship in selecting dyes as dopants is the comparison of bandgap potentials, defined as the energy difference between the highest and lowest molecular orbitals occupied by the molecule. For efficient energy transfer from the host to the dopant molecule, a necessary condition is that the bandgap of the dopant must be smaller than the bandgap of the host material. For phosphorescent emitters, it is important that the host triplet energy level is high enough to transfer energy from the host to the dopant.

Host and release molecules known for this use are described in U.S. Pat. 5,755,999, 5,928,802, 5,935,720, 5,935,721 and 6,020,078, but are not limited to these.

Metal complexes and similar derivatives of 8-hydroxyquinoline (oxine) constitute a class of useful host compounds that can support electroluminescence. Examples of useful chelated oxynoid compounds are as follows:

CO-1: aluminum trisoxine (aka tris (8-quinolinolato) aluminum (III));

CO-2: magnesium bisoxine [aka bis (8-quinolinolato) magnesium (II)];

CO-3: bis [benzo {f} -8-quinolinolato] zinc (II);

CO-4: bis (2-methyl-8-quinolinolato) aluminum (III) -μ-oxo-bis (2-methyl-8-quinolinolato) aluminum (III);

CO-5: indium trisoxine (aka tris (8-quinolinolato) indium);

CO-6: aluminum tris (5-methyloxine) [aka tris (5-methyl-8-quinolinolato) aluminum (III)];

CO-7: lithium auxin [aka, (8-quinolinolato) lithium (I)];

CO-8: gallium auxin [aka tris (8-quinolinolato) gallium (III)]; And

CO-9: zirconium auxin [aka tetra (8-quinolinolato) zirconium (IV)].

Other classes of useful host materials include derivatives of anthracenes, such as 9,10-di- (2-naphthyl) anthracene and derivatives thereof described in US Pat. No. 5,935,721; Distyrylarylene derivatives described in US Pat. No. 5,121,029; And benzazole derivatives such as 2,2 ', 2 "-(1,3,5-phenylene) tris [1-phenyl-1H-benzimidazole]. Carbazole derivatives Is a particularly useful host for phosphorescent emitters.

Useful fluorescent dopants include anthracene, tetracene, xanthene, perylene, rubrene, coumarin, rhodamine and quinacridone, dicyanomethylenepyrane compounds, thiopyrane compounds, polymethine compounds, pyryllium and thiaryryllium compounds, Fluorene derivatives, periplanthene derivatives, indenoferylene derivatives, bis (azinyl) amine boron compounds, bis (azinyl) methane compounds, and derivatives of carbostyryl compounds, including but not limited to these.

Preferred thin film-forming materials for use in forming the electron transport layer 55 of the present invention are metal chelated oxynoid compounds, including chelates of auxin itself (commonly referred to as 8-quinolinol or 8-hydroxyquinoline). to be. These compounds help to inject and transport electrons, exhibit high performance levels, and are readily manufactured in thin film form. Exemplary oxynoid compounds have already been described.

Other electron transport materials include various butadiene derivatives disclosed in US Pat. No. 4,356,429 and various heterocyclic optical brighteners described in US Pat. No. 4,539,507. Benzazole and triazine are also useful electron transport materials.

An electron injection layer 60 may also be present between the cathode and the electron transport layer. Examples of electron injection materials include alkali or alkaline earth metals, alkali halide salts (such as LiF described above), or alkali or alkaline earth metal doped organic layers.

In some cases, the light emitting layer 50 and the electron transporting layer 55 may be selectively replaced by a single layer that functions to support both light emission and electron transport. It is known in the art that emitting dopants can be added to the hole transport layer 45 which can act as a host. To produce a white emitting OLED, a plurality of dopants may be added to one or more layers, for example, by combining blue- and yellow-emitting materials, cyanine- and red-emitting materials or red-, green- and blue-emitting materials. Can be added. For example, white emission devices in European Patent Nos. 1 187 235, European Patent No. 1 182 244, US Patent Application 2002/0025419 A1, US Patent Nos. 5,683,823, 5,503,910, 5,405,709 and 5,283,182 Is described. As described in commonly assigned European Patent No. 1 187 235 A2, a white emitting organic EL medium can be achieved by including the following layers: hole injection layer 40; A hole transport layer 45 disposed on the hole injection layer 40 and doped with a rubrene compound for emitting light in a yellow region of the spectrum; A light emitting layer 50 doped with a blue light emitting compound disposed on the hole transport layer 45; And an electron transport layer 55 disposed on the light emitting layer 50. Another embodiment using one or more different materials in the organic layer for different pixels may also be used in the present invention. This technique is applied to the tuned OLED device 15 so that the light emitting layer 50 produces white light (called broadband wavelength light).

Additional layers such as electron block layers or hole block layers as disclosed in the art can be used in the devices of the present invention. Hole block layers are commonly used to improve the efficiency of phosphorescent emitting devices, such as, for example, in US Patent Application 2002/0015859 A1.

The above-mentioned organic materials may be suitably deposited via vapor phase methods such as sublimation or from fluids such as solvents with optional binders to improve film formation, for example. If the material is a polymer, solvent deposition is useful, but other methods such as sputtering or heat transfer from the donor sheet can also be used. The material to be deposited by sublimation can often be vaporized from a sublimation 'boat' made of tantalum material, as described, for example, in US Pat. No. 6,237,529, or first coated onto a donor sheet and then sublimated closer to the substrate. have. The layer with the mixture of materials may utilize a separate sublimation boat, or the materials may be premixed and then coated from a single boat or donor sheet. Shadow masks, integrated shadow masks (US Pat. No. 5,294,870), spatially limited thermal dye transfer from donor sheets (US Pat. Nos. 5,688,551, 5,851,709 and 6,066,357) and inkjet methods (US Pat. No. 6,066,357). Can be used to achieve patterned deposition.

Most OLED devices are sensitive to moisture or oxygen, or both, so nitrogen, along with desiccants such as alumina, bauxite, calcium sulfate, clay, silica gel, zeolite, alkali metal oxides, alkaline earth metal oxides, sulfates or metal halides and perchlorates Or sealed in an inert atmosphere such as argon. Encapsulation and drying methods include, but are not limited to, those described in US Pat. No. 6,226,890. In addition, barrier layers such as SiO _x , Teflon and inorganic / polymer alternating layers are known in the encapsulation art.

The OLED device of the present invention may utilize various well-known optical effects, if necessary, in order to improve its characteristics. This optimizes layer thickness to produce maximum light transmission, provides a dielectric mirror structure, provides a glare or antireflective coating on a display, provides a polarizing medium on a display, or provides a medium density or Including but not limited to providing a color conversion filter.

4 is a cross-sectional view of a tuned multicolor OLED device having an array of light emitting pixels of different colors in accordance with another embodiment of the present invention. The tuned multicolor OLED device 65 is a top emission where light 125a, 125b, and 125c are emitted in a direction away from the substrate 20, but a bottom emission device can also be manufactured in this manner. Two or more different color pixels (e.g., pixels 80a and 80b) comprise layers comprising microcavity structures and color conversion media (e.g., color conversion media 25a and 25b). Each pixel including the microcavity structure includes a reflector layer (eg, reflector layer 90a in pixel 80a) that serves to form the bottom of the microcavity structure on substrate 20. Translucent reflector 30 forms the top of the microcavity structure in every pixel. This allows some of the light to be emitted from the top of the tuned multicolor OLED device 65. Reflector layer 90a and translucent reflector 30 also act as electrodes, reflector layer 90a for pixels 80a and translucent reflector 30 for pixels 80a, 80b and 80c, but are common electrodes in all pixels. Is a reflector and other structures are possible with separate translucent reflectors at each pixel. Other embodiments may also be envisioned where the reflector and the electrode are separate objects.

Different color pixels of various aspects are possible. The tuned OLED device 65 is a full color device, the specific wavelength of the on-axis light 125a is in the red region of the spectrum, the specific wavelength of the on-axis light 125b is in the green region of the spectrum, and the on-axis light 125c One useful combination is the particular wavelength of in the blue region of the spectrum. As shown, the tuned OLED device 65 includes a common light emitting layer 50 for the microcavity structure in each of the different color pixels having the microcavity structure. This is advantageous in manufacturing since it does not require patterning of the organic layer 100. If possible, the light emitting layer 50 in contact with the other layers described above will be configured to produce light of white or broadband wavelengths in this structure, and then other pixel colors as a result of the effects of microcavities, color filters, or both. Will be formed. Other embodiments are well known in which one or more OLED layers, such as emissive layer 50, are separately patterned for one or more pixels 80a, 80b, and 80c. In such a structure, each pixel may comprise a light emitting layer for a particular wavelength, such as a red, green and blue light emitting layer.

The tuned multicolor OLED device 65 includes the color conversion media 25a and 25b described above disposed above the translucent reflector 30. Color converting media 25a and 25b will emit light in all directions, including entering back into pixels 80a and 80b respectively. To prevent this, dielectric stacks 75a and 75b as described above may be selectively disposed between the color conversion media 25a and 25b and the translucent reflector 30, respectively. Dielectric stacks 75a and 75b must transmit relatively specific wavelengths (ie, on-axis light 125a and 125b) enhanced on the axis by the microcavity structure, respectively. Therefore, the characteristics of the dielectric stack will depend on the specific wavelength of the pixel.

Although not necessary, the color filters 85a and 85b described above may also be included. One or more pixels of the tuned OLED device 65 may include other color filters, the nature of which will depend on the desired on-axis visual color of the pixel. Black matrices (not shown) as known in the art may be located between or around the pixels or color filters to improve contrast.

Two or more different color pixels (eg, pixels 80a and 80b) of the tuned multicolor OLED device 65 include microcavity structures and color conversion media. Other different color pixels (eg, 80c) can be a variety of structures including microcavity structures with color conversion media, microcavity structures without color conversion media (shown in FIG. 4), or non-microcavity structures. Any of these pixels may optionally include a color filter or dielectric stack, or both.

The tuned multicolor OLED device 65 is an active matrix device having an active matrix circuit 210. The active matrix circuit 210 is formed over the substrate 20. The active matrix circuit 210 includes a first thin film transistor (TFT) including a semiconductor active layer 211, a gate dielectric 212, a gate conductor 213, a first insulating layer 214, and a second insulator 217. It includes. The active matrix circuit 210 also includes one signal line 216 having a luminance signal and one power line 215 for powering transistors. Methods of forming TFT circuits are well known in the art. Although only a single transistor, signal line, and power line are shown for each pixel, each pixel also includes a capacitor (not shown) and an additional selection line (not shown) as well as a second transistor (not shown). Typically have. It will be appreciated that many types of circuits with different numbers of circuit components and different structures are known in the art and many such circuits are used in the present invention. Examples of active matrix structures include US Pat. Nos. 5,550,066, 6,281,634, and 6,501,466. While the illustrated TFT is formed of the thin film semiconductor active layer 211, it will be understood that the substrate 20 together with the semiconductor substrate has substantially this function. 4 shows a top gate structure, that is, a structure in which the gate conductor 213 and the gate dielectric 212 are over the semiconductor active layer 211. However, it is also known that a TFT having a known inverse structure can be used as the bottom electrode to drive the organic EL device.

An interpixel dielectric layer 160 as described in US Pat. No. 6,246,179 can be used to cover the edges of transparent or translucent electrodes (eg, reflector layer 90c) to prevent short or strong electric fields in these areas. If the transparent co-spacer layer (eg 35a) is conductive or forms part of the electrode, the inter-pixel dielectric layer 160 may also cover the transparent co-spacer layer (eg 35a) as shown. Although it is preferable to use the inter-pixel dielectric layer 160, it is not necessary for successful implementation of the present invention.

Another embodiment in which the tuned multicolor OLED device 65 is a passive matrix device and does not have an active matrix circuit can be used in the present invention.

The pixel 80a functions as a microcavity structure in which light emitted to the light emitting layer 50 is reflected by the reflector layer 90a and a part (typically 25 to 75%) of light is reflected by the translucent reflector 30. . This enhances the on-axis light 125a emitted by the pixel 80a through the translucent reflector 30, where any wavelength of the on-axis light 125a will be enhanced as described above. The thickness of the organic layer 100 optimized for emission does not necessarily have an appropriate dimension to provide the desired wavelength of light 125a, but it is further desirable to include a transparent co-spacer layer to obtain the desired dimension. It may be desirable. Transparent co-spacer layer 35a is formed over reflector layer 90a. The thickness of the transparent co-spacer layer 35a, the refractive index of the transparent co-spacer layer 35a, or both are adjusted according to the thickness and refractive index of the organic layer 100 of the tuned OLED device 65 for the pixel 80a. The microcavity structure is tuned to resonate at the wavelength of the desired color of light. When two or more pixels comprise a transparent co-spacer layer, the thickness of the transparent co-spacer layer, the refractive index of the transparent co-spacer layer, or both are separately adjusted for each of the different color pixels so that the transparent co-spacer layer is different from each other. For example, it may vary depending on the transparent co-spacer layers 35a and 35b in pixels 80a and 80b, or in some pixels (pixels 80c without transparent co-spacer layers above reflector layer 90c). May not be included.

Although transparent co-spacer layers 35a and 35b are shown to exist between reflector layers 90a and 90b and organic layer 100, respectively, in another embodiment transparent co-spacer layers 35a and 35b are organic layers. It may be formed between the 100 and the semi-transparent reflector 30.

In another embodiment where one or more organic layers 100 are not common in all pixels and instead are patterned separately for one or more pixels, the transparent co-spacer layer is limited and one or more organic layers 100 for each pixel. The microcavity structure for the gamut-limited pixels can be tuned by separately tuning the thickness, index of refraction, or both.

Claims (31)

a) a desired on-axis visual color, comprising a light emitting layer for generating light, a translucent reflector, and a reflector layer disposed on opposite sides of the light emitting layer, and promoting on-axis light generated from the light emitting layer at one or more specific wavelengths; Microcavity structure that produces but does not substantially enhance light of other wavelengths on the axis; And b) light of the non-axial wavelength shorter than the specific wavelength on the axis by absorbing light of an off-axis wavelength shorter than the specific wavelength on the axis and emitting light of a color corresponding to the particular wavelength on the axis; And a layer comprising a color conversion medium responsive to and thereby improving the color of the light produced by the organic light emitting (OLED) device when viewed in the non-axial direction. The method of claim 1, Tuned OLED device wherein said light emitting layer produces light of a wide range of wavelengths. The method of claim 1, Tuned OLED device in which the specific wavelength of the on-axis light is in a red, green or blue region of the spectrum. The method of claim 1, And the color conversion medium layer is disposed on a translucent reflector. The method of claim 4, wherein And a dielectric stack disposed between the color conversion media layer and the translucent reflector. The method of claim 1, Tuned OLED device in which said reflector also acts as an electrode. The method of claim 1, Tuned OLED device wherein the translucent reflector also acts as an electrode. The method of claim 1, Tuned OLED device wherein said device is a passive matrix device. The method of claim 1, Tuned OLED device wherein said device is an active matrix device. The method of claim 1, And wherein said microcavity structure further comprises a transparent co-spacer layer. 11. The method of claim 10, A tuned OLED device in which the thickness of the transparent co-spacer layer, the refractive index of the transparent co-spacer layer, or both are adjusted with the layer thickness and refractive index of the tuned OLED device to tune the microcavity structure to the desired color. . The method of claim 1, Tuned OLED device wherein said device is bottom emitting. The method of claim 1, Tuned OLED device wherein said device is top emitting. The method of claim 1, Tuned OLED device further comprising a color filter. A tuned multicolor OLED (organic light emitting) device having an array of different color pixels, Two or more of the different color pixels, a) a light emitting layer for generating light, a semi-transparent reflector, and a reflector layer disposed on opposite sides of the light emitting layer, and promoting axial light generated from the light emitting layer at one or more specific wavelengths to produce the desired on-axis visual color but Microcavity structures that do not substantially enhance light of other wavelengths; And b) reacting to light of a wavelength shorter than the specific wavelength by absorbing light of a wavelength shorter than the specific wavelength and emitting light of a color corresponding to the specific wavelength, whereby organic light emission (OLED) when viewed in the non-axial direction ) A layer comprising a color conversion medium that improves the color of light produced by the device A tuned multicolor OLED device comprising a. The method of claim 15, A tuned multicolor OLED device having a common light emitting layer for microcavity structures in each of the two or more different color pixels. The method of claim 15, A tuned multicolor OLED device in which the light emitting layer generates light of a wideband wavelength. The method of claim 15, A tuned multicolor OLED device in which the specific wavelength of the on-axis light is in the red, green or blue region of the spectrum. The method of claim 15, A tuned multicolor OLED device with the color conversion media layer disposed on the translucent reflector. The method of claim 19, And a dielectric stack disposed between the color conversion media layer and the translucent reflector. The method of claim 15, A tuned multicolor OLED device in which the reflector also acts as an electrode for one or more pixels. The method of claim 15, And the translucent reflector also serves as an electrode for one or more pixels. The method of claim 15, A tuned multicolor OLED device wherein the device is a passive matrix device. The method of claim 15, A tuned multicolor OLED device wherein said device is an active matrix device. The method of claim 15, A tuned multicolor OLED device wherein at least one pixel further comprises a transparent co-spacer layer. The method of claim 25, Tuned multicolor OLEDs wherein the thickness of the transparent co-spacer layer, the refractive index of the transparent co-spacer layer, or both are adjusted with the thickness and refractive index of the tuned multicolor OLED device to tune the microcavity structure to the desired color. device. The method of claim 15, At least one of the OLED layers is patterned separately for at least one of the pixels. The method of claim 15, A tuned multicolor OLED device in which the device is bottom emitting. The method of claim 15, A tuned multicolor OLED device in which the device is top emitting. The method of claim 15, One or more of said pixels further comprising a different color filter. The method of claim 15, A tuned multicolor OLED device wherein said device is a full color device.

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