KR20070031329A - Direct-view display devices using vertical cavity laser arrays - Google Patents

Abstract

The display device for generating pixelated colored light includes a backlight unit 220 for providing pump-ray light. The apparatus also includes a microcavity light-generating array 100 responsive to pump-ray light and having pixels, wherein each pixel is a transparent substrate, a base dielectric stack that is reflective to light over a range of wavelengths, a display. An active region responsive to pump-ray light for producing light, and an upper dielectric stack spaced from the base dielectric stack and reflective to light over a range of wavelengths. The apparatus also includes an optical shutter 310 for passing selected display light from the microcavity light generating array, a polarization layer 305 disposed between the microcavity light generating array and the optical shutter, and disposed above the optical shutter. A light expanding layer 320 or color converting layer to increase the viewing angle cone of the display light.

Description

Direct-view display device using vertical cavity laser array {DIRECT-VIEW DISPLAY DEVICES USING VERTICAL CAVITY LASER ARRAYS}

The present invention relates to a display device for producing colored light using a microcavity device array.

The following terms are defined to facilitate reading of the specification. In the present invention, the optical axis refers to a direction in which propagating light does not show birefringence. In the present invention, polarizers and analyzers refer to elements that polarize electromagnetic waves. However, the one closer to the light source will be called the polarizer while the one closer to the observer will be called the analyzer. In the present invention, the polarizer refers to both the polarizer and the analyzer. Azimuth angle φ and tilt angle θ are used in the present invention to specify the direction of the optical axis. With respect to the transmission axis of the polarizing plate and the analyzer, since the inclination angle θ is 0, only the azimuth angle φ is used.

1 shows the definition of the azimuth angle φ and the inclination angle θ for specifying the direction of the optical axis 1 with respect to the x-y-z coordinate system 3. The x-y plane is parallel to the display surface 5 and the z-axis is parallel to the display normal direction 7. The azimuth angle φ is the angle between the y-axis and the optical axis 9 projection on the x-y plane. The inclination angle θ is an angle between the optical axis 1 and the x-y plane.

There are a number of ways to generate pixelated colored light for displays, for example using conventional passive or active matrix organic light emitting diode (OLED) devices. Another way is to use a liquid crystal display (LCD). In a typical LCD system, a liquid crystal cell is disposed between a pair of polarizers. Light entering the display is polarized by the initial polarizer. As the light passes through the liquid crystal cell, the molecular orientation of the liquid crystal material affects the polarized light such that the light passes through or is blocked by the analyzer. The orientation of liquid crystal molecules can be altered by applying a voltage across the cell, thus allowing the intensity of light of various magnitudes to pass through the LCD pixel. By using this principle, minimal energy is required to switch the LCD. This switching energy is typically much less than necessary for cathode ray tubes (CRTs) using cathode luminescent materials, which makes displays using liquid crystal materials very attractive.

Typical liquid crystal cells contain a color filter array (CFA) consisting of red, green and blue transmissive pixels. In order to transmit a large amount of light from the backlight unit BLU, the transmission spectrum of each of the CFA pixels must have a large half width (FWHM). As a result of the wide FWHM, the color range of the LCD is at most about 0.7 of the NTSC color range standard. In addition, as light impinges on the CFA, more than two thirds of the light is absorbed by the CFA, and less than one third is transmitted. Correspondingly, absorption of light outside the transmission spectrum of each of these pixels loses the overall display efficiency.

The transmissive LCD is exemplified by a backlight unit including a light source, a light guide plate (LGP), a reflective layer, a diffusion layer, an aiming film, and a reflective polarizing plate. The reflective polarizer is used for reproducing and reflecting light of undesirable polarization. However, not all undesirable polarized light is reproduced, and not all of the reproduced light exits the BLU with the correct polarization state. Thus, only a small portion of the light reflected from the reflective polarizer is reproduced in the correct polarization state. As a result, the unpolarized LBU light source produces nearly two efficiency losses when passing through the base polarizer.

LCDs are rapidly replacing electronic displays, televisions, and other office and home displays for CRTs and other types of computer monitors. However, LCDs suffer from poor contrast ratios at larger viewing angles. Unless the contrast ratio is improved at large viewing angles, LCDs will be limited in penetrating certain markets. The poor contrast ratio is typically due to the increased brightness of the dark state of the display. The LCD is optimized so that the display has the highest contrast ratio within a narrow viewing cone (at 0 degree viewing angle) concentrated on the axis. When looking at the display off-axis at a larger viewing angle, the dark state experiences an increase in brightness, thus reducing the contrast ratio. When looking at the full color display off the axis, the dark state not only increases the luminosity but also the color of the dark and light state all shift. In the past, this loss of hue shift and contrast ratio has been attempted to be improved by various methods, for example by introducing a compensation film into the display, segmenting pixels, or even further using multiple domains. However, these methods slightly improve hue shift and contrast ratio for only limited viewing cones. In addition, the fabrication of compensation films and multi-domain liquid crystal cells is typically expensive, thus increasing the overall cost of the display.

Other flat panel displays seek to solve the viewing angle problem by integrating a photoluminescent (PL) screen on the front of the LCD (called PL-LCD) (W. Crossland, SID Digest 837 (1997)). Such displays use a backlight unit having a narrow band frequency, a liquid crystal modulator, and a photoluminescent output screen for color generation. The PL-LCD light source utilizes a wavelength in UV that accelerates the destruction of the liquid crystal material. In addition, the PL-LCD light source is much less efficient than the standard cold cathode fluorescent lamps (CCFLs) used in typical LCD displays.

In general, it would be advantageous to manufacture a display without the problems associated with a typical LCD display. As discussed above, these drawbacks are loss of efficiency (due to the use of unpolarized backlights and CFAs), insufficient color range, and loss of contrast and color at larger viewing angles. OLED displays overcome some of these drawbacks, but the current short lifespan and greater manufacturing costs are problematic. Some of the larger manufacturing costs are inherent in OLED designs, such as the need for pixelation of the OLED emitter portion and the greater complexity of thin film transistors (TFTs) for current driven devices.

Summary of the Invention

It is therefore an object of the present invention to provide a display that overcomes the disadvantages inherent in a typical LCD display, such as loss of efficiency, less color gamut, and lower contrast and color at larger viewing angles.

The purpose is

a) a backlight unit for providing pump-ray light;

b) a microcavity light-generating array responsive to pump-ray light and having pixels, wherein each pixel is

i) a transparent substrate;

ii) a base dielectric stack reflective to light over a range of wavelengths;

iii) an active region responsive to pump-ray light for producing display light;

iv) an upper dielectric stack spaced from the base dielectric stack and reflective to light over a range of wavelengths

It includes);

c) an optical shutter for passing display light selected from said microcavity light-generating array;

d) a polarization layer disposed between said microcavity light-generating array and an optical shutter; And

e) a beam expanding layer for increasing the viewing angle cone of display light, disposed above the optical shutter.

Is achieved by a display device for generation of pixelated colored light.

Advantage of the invention

An advantage of the present invention is the use of a pixelated two dimensional microcavity device array as a light source for liquid crystal displays. Microcavity devices have the useful feature of reducing the divergence angle of the output light to less than 10-15 ° through proper engineering of the device design. This small divergence angle enables a 1: 1 correspondence between the color element of the microcavity and the color element of the liquid crystal display. Correspondingly, it is no longer necessary to include a color filter array as one of the LCD film components.

Since the microcavity light passes through an LC switch that is almost on axis, the problems associated with contrast and color shift are limited for large viewing angles. An additional feature of near collimation of the light source is that liquid crystal viewing angle compensation film can be removed from the display structure. It is also common to include a collimating film as part of the LCD component; Since the microcavity device output from the two-dimensional array is naturally collimated (<10 to 15 ° divergence angle), the film can be removed.

A further advantage of the present invention comes from the fact that the light output from each color element is spectroscopically narrow. This property greatly improves the color range of the liquid crystal display. In applications where limited viewing angles are desired, for example private viewing, the near collimation of the light source produces much improved on-axis viewing brightness in the display compared to typical ones. These improvements can be traded for either significantly increasing display brightness or for greatly increased display power efficiency (which can significantly increase battery life).

1 shows a perspective view useful for understanding the definition of the tilt and azimuth angles to specify the optical axis direction.

Figure 2 shows a schematic side cross-sectional view of an optically pumped two dimensional microcavity device array light source.

3 shows a top view of a two dimensional microcavity device array light source containing red, green and blue emission components.

4 is a simplified schematic diagram of a display device containing a microcavity device array light source.

5 is a simplified schematic diagram of a planar LED-array driven backlight unit pumping microcavity device array light sources.

6 is a simplified schematic diagram of a planar LED-array driven backlight unit pumping microcavity device array light sources.

7 is a simplified schematic diagram of a cold cathode fluorescent lamp driven backlight unit pumping microcavity device array light sources.

8 is a simplified schematic diagram of another embodiment of a cold cathode fluorescent lamp driven backlight unit pumping a microcavity device array light source.

9 is a simplified schematic diagram of its components, including a liquid crystal cell and an analyzer.

10 is a simplified schematic diagram of another embodiment of a display device containing a microcavity device array light source.

Explanation of Drawings

1: optical axis

3: x-y-z coordinate system

5: display surface

7: Display normal direction

9: optical axis

100: Microcavity Array Device

105: blue-emitting microcavity array device

110: substrate

120: base dielectric stack

130: active area

140: top dielectric stack

160: periodic gain range

170: spacing layer

180: pump-ray light

190: microcavity release

205: emission element

220: backlight unit

230: light emitting diode

240: diffusion layer

250: linear array

260 waveguide

270: flat array

280: cold cathode fluorescent lamp

300: row

305: polarizer

310: optical shutter layer

315: red / green dielectric stack

320: ray expanding layer

325: color transition layer

330: liquid crystal cell

340: Prospector

350: liquid crystal substrate

360: transparent conductor layer

370: alignment layer of liquid crystal molecules

380: liquid crystal material

φ: azimuth

θ: tilt angle

The present invention is made possible by near collimating and spectroscopically narrow light sources. In addition, the light source should contain red, green and blue emitting elements from conventional substrates of size 80 × 240 μm. A light source that meets these criteria is a two dimensional microcavity array device 100 as schematically shown in FIG. 2. 3 shows a top view of the microcavity array device 100 in which red, green and blue (RGB) emitting elements 205 need to be present on the surface of the microcavity device. In order to generate red, green and blue microcavity light from a conventional substrate, the active region 130 may be composed of an organic substrate gain medium. Also, a recent study (RN Bhargava, Phys. Stat. Sol. 229, 897 (2002)) points out the possibility of obtaining visible wavelength emission from inorganic based nanoparticles. One possibility is (less than the preferred diameter 10 ㎚) or is not doped, or impurities, such as Mn ²⁺ or ZnO nanoparticles doped with Eu ^{2 +.} As a further example, the colloidal CdSe / CdS heterostructure quantum dots proved to be at least 80% quantum yield (AP Alivisatos, MRS Bulletin 18 (1998)).

2 again, the substrate 110 should be light transmissive. As a result, the substrate 110 may be transparent glass or plastic. A base dielectric stack 120 is disposed on the substrate 110, which stack is composed of alternating high and low refractive index dielectric materials. Generally, the base dielectric stack 120 is designed to be reflective to microcavity light over a range of wavelengths. Typical high and low refractive index materials are TiO ₂ and SiO _2, respectively. The base dielectric stack 120 may be deposited by plasma-promoted chemical vapor deposition, electron-ray (e-ray) deposition, or sputtering. Additional methods are polymer extrusion, and sol-gel and colloidal deposition as commonly practiced in the art.

Active region 130 is deposited on base dielectric stack 120. 2 shows that the active region 130 is not a bulk layer but a multilayered composite. The active region 130 contains one or more periodic gain portions 160, which are separated by the spacing layer 170. The thickness of the periodic gain portion 160 is typically less than 50 nm, with a preferred thickness of 5 to 30 nm. The thickness of the spacer layer 170 is selected such that the periodic gain portion (s) are aligned with the antinodes of the microcavity fixed electromagnetic field (e-field). The use of the periodic gain portion (s) 160 in the active region 130 results in greater power conversion efficiency and a greater reduction in unnecessary spontaneous emissions. In summary, the active region 130 is disposed on one or more periodic gain portions 160 and on either side of the periodic gain portion (s) and the periodic gain portion (s) is a standing wave electromagnetic field of the device. A spacing layer 170 arranged to align with the fractures of the substrate.

The periodic gain portion (s) 160 consists of small molecular weight organic material, polymeric organic material, or inorganic based nanoparticles (fluorescing with high quantum efficiency). The small molecular weight organic materials are typically deposited by high vacuum ( ^10-6 Torr) thermal evaporation, while conjugated polymers and inorganic nanoparticles are usually formed by rotary casting.

Unless specifically indicated otherwise, the use of the term "substituted" or "substituent" means any group or atom other than hydrogen. In addition, when the term "group" is used, it means that when a substituent group contains a substitutable hydrogen, as long as the group does not destroy the unsubstituted form of the substituent as well as the properties necessary for device utility. It is meant to include those forms further substituted by any substituent group or groups as mentioned in the present invention. Suitably the substituent group may be halogen or bonded to the rest of the molecule by atoms of carbon, silicon, oxygen, nitrogen, phosphorus, sulfur, selenium or boron. Such substituents may be, for example, halogen, for example chloro, bromo or fluoro; Nitro; Hydroxyl; Cyano; Carboxyl; Or alkyl, including straight or branched or cyclic alkyl groups which may be further substituted, for example methyl, trifluoromethyl, ethyl, t-butyl, 3- (2,4-di-t- Pentylphenoxy) propyl, and tetradecyl; Alkenyl such as ethylene, 2-butene; Alkoxy, for example methoxy, ethoxy, propoxy, butoxy, 2-methoxyethoxy, secondary-butoxy, hexyloxy, 2-ethylhexyloxy, tetradecyloxy, 2- (2 , 4-di-t-pentylphenoxy) ethoxy, and 2-dodecyloxyethoxy; Aryl such as phenyl, 4-t-butylphenyl, 2,4,6-trimethylphenyl, naphthyl; Aryloxy such as phenoxy, 2-methylphenoxy, alpha- or beta-naphthyloxy, and 4-tolyloxy; Carbon amido, for example acetamido, benzamido, butyramido, tetradecane amido, alpha- (2,4-di-t-pentyl-phenoxy) acetamido, alpha- (2, 4-di-t-pentylphenoxy) butyramido, alpha- (3-pentadedecylphenoxy) -hexaneamido, alpha- (4-hydroxy-3-t-butylphenoxy) -tetradecaneami FIG. 2, 2-oxo-pyrrolidin-1-yl, 2-oxo-5-tetradecylpyrroline-1-yl, N-methyltetradecaneamido, N-succinimido, N-phthalimido, 2 , 5-dioxo-1-oxazolidinyl, 3-dodecyl-2,5-dioxo-1-imidazolyl, and N-acetyl-N-dodecylamino, ethoxycarbonylamino, phenoxycarbo Nylamino, benzyloxycarbonylamino, hexadecyloxycarbonylamino, 2,4-di-t-butylphenoxycarbonylamino, phenylcarbonylamino, 2,5- (di-t-pentylphenyl) carbonyl Amino, p-dodecyl-phenylcarbonylamino, p-tolylcarbonylamino, N-methylureido, N, N-dimethylureido, N-methyl-N- Decyl ureido, N-hexadecyl ureido, N, N-dioctacyl ureido, N, N-dioctyl-N'-ethyl ureido, N-phenyl ureido, N, N-diphenyl ureido, N-phenyl-Np-tolylureido, N- (m-hexadecylphenyl) ureido, N, N- (2,5-di-t-pentylphenyl) -N'-ethylureido, and t-butyl Carbon amido; Sulfonamido, for example methylsulfonamido, benzenesulfonamido, p-tolylsulfonamido, p-dodecylbenzenesulfonamido, N-methyltetradecylsulfonamido, N, N-dipropyl-sulfa Moylamino and hexadecylsulfonamido; Sulfamoyls such as N-methylsulfamoyl, N-ethylsulfamoyl, N, N-dipropylsulfamoyl, N-hexadecylsulfamoyl, N, N-dimethylsulfamoyl, N- [3- (dode Siloxy) propyl] sulfamoyl, N- [4- (2,4-di-t-pentylphenoxy) butyl] sulfamoyl, N-methyl-N-tetradecylsulfamoyl, and N-dodecylsulfamoyl; Carbamoyl, for example N-methylcarbamoyl, N, N-dibutylcarbamoyl, N-octadecylcarbamoyl, N- [4- (2,4-di-t-pentylphenoxy) butyl] carbamoyl , N-methyl-N-tetradecylcarbamoyl, and N, N-dioctylcarbamoyl; Acyl, for example acetyl, (2,4-di-t-amylphenoxy) acetyl, phenoxycarbonyl, p-dodecyloxyphenoxycarbonyl methoxycarbonyl, butoxycarbonyl, tetradecyloxycarbon Neyl, ethoxycarbonyl, benzyloxycarbonyl, 3-pentadedecyloxycarbonyl, and dodecyloxycarbonyl; Sulfonyl, for example methoxysulfonyl, octyloxysulfonyl, tetradecyloxysulfonyl, 2-ethylhexyloxysulfonyl, phenoxysulfonyl, 2,4-di-t-pentylphenoxysulfonyl, methylsulfonyl, Octylsulfonyl, 2-ethylhexylsulfonyl, dodecylsulfonyl, hexadecylsulfonyl, phenylsulfonyl, 4-nonylphenylsulfonyl, and p-tolylsulfonyl; Sulfonyloxy, such as dodecylsulfonyloxy, and hexadecylsulfonyloxy; Sulfinyl, for example methylsulfinyl, octylsulfinyl, 2-ethylhexylsulfinyl, dodecylsulfinyl, hexadecylsulfinyl, phenylsulfinyl, 4-nonylphenylsulfinyl, and p-tolylsulfinyl; Thio, for example ethylthio, octylthio, benzylthio, tetradecylthio, 2- (2,4-di-t-pentylphenoxy) ethylthio, phenylthio, 2-butoxy-5-t-octylphenyl Thio, and p-tolylthio; Acyloxy such as acetyloxy, benzoyloxy, octadecanoyloxy, p-dodecylamidobenzoyloxy, N-phenylcarbamoyloxy, N-ethylcarbamoyloxy and cyclohexylcarbonyloxy; Amines such as phenylanilino, 2-chloroanilino, diethylamine, dodecylamine; Imino, such as 1 (N-phenylimido) ethyl, N-succinimido, or 3-benzylhydantoinyl; Phosphates such as dimethyl phosphate and ethyl butyl phosphate; Phosphites such as diethyl and dihexylphosphite; Heterocyclic group, heterocyclic oxy group or heterocyclic thio group, each of which may be substituted and is a 3-7 membered member consisting of carbon atoms and one or more heteroatoms selected from the group consisting of oxygen, nitrogen, sulfur, phosphorus and boron Heterocyclic rings), for example 2-furyl, 2-thienyl, 2-benzimidazolyloxy or 2-benzothiazolyl; Quaternary ammonium such as triethylammonium; Quaternary phosphoniums such as triphenylphosphonium; And silyloxy, for example trimethylsilyloxy.

In some cases, the substituents themselves may be further substituted one or more times with the disclosed substituent groups. The specific substituents used may be selected by those skilled in the art to obtain the desired properties desired for a particular use, and may include, for example, electron recovery groups, electron donor groups, and steric groups. Where a molecule may have two or more substituents, unless otherwise provided, the substituents may be joined together to form a ring, such as a condensed ring. Generally, the group and its substituents may have up to 48 carbon atoms, typically from 1 to 36 carbon atoms, usually less than 24 carbon atoms, but may be larger depending on the particular substituent selected. Substitutions may include condensed ring derivatives, such as but not limited to benzo-, dibenzo-, naphtha-, or dynaphtho-condensed derivatives. Such condensed ring derivatives may also be further substituted.

The organic-based periodic gain portion (s) 160 (or emitter material) may consist of a single host material, but more typically a guest compound (dopant) or luminescence mainly comes from the dopant and optionally It includes a host material doped with a compound that can have a color of. Such host-dopant combinations are advantageous because they produce very little unpumped scattering / absorption loss (which may be less than 1 cm ⁻¹ ) for the organic substrate gain medium. The dopant is usually selected from among highly fluorescent dyes, but phosphorescent compounds such as transition metal complexes as disclosed for OLED applications in WO 98/55561, WO 00/18851, WO 00/57676 and WO 00/70655 It is also useful. Dopants are typically coated at 0.01 to 10% by weight in the host material, which may be selected to provide light emission with a red, green or blue tint. Examples of host-dopant combinations useful for the red emitting layer include Alq as host material and 1% L39 [4- (dicyanomethylene) -2-t-butyl-6- (1,1,7,7 as dopant -Tetramethyljulrolidyl-9-enyl) -4H-pyran].

An important relationship in choosing a dye as a dopant is to compare the absorption of the dopant material and the release of the host material. For efficient energy transfer from the host to the dopant molecules (via Forster energy transfer), the necessary condition is that the absorption of the dopant overlaps with the release of the host material. Those skilled in the art are familiar with the concept of Foster energy transfer, which involves energy transfer in the absence of radiation between the host and dopant molecules. An important relationship in selecting the host material is that the absorption of the host material significantly overlaps the emission spectrum of the pump-ray 180 light. It is also desirable that the absorption of the host material or host material + dopant is small at the microcavity emission wavelength of the microcavity array device 100. Acceptable absorption levels are those in which the absorption coefficient of the host + dopant combination is less than 1000 cm ⁻¹ at the microcavity emission wavelength.

Useful fluorescence emitting materials are described in I.B. Berlman, "Handbook of Fluorescence Spectra of Aromatic Molecular," Academic Press, New York, 1971 and polycyclic aromatic compounds as disclosed in EP 1 009 041. Tertiary aromatic amines having more than two amine groups can be used, including oligomeric materials.

Another class of useful emissive materials (for hosts or dopants) include aromatic tertiary amines, wherein the amine is one or more trivalent nitrogen atoms bonded only to carbon atoms, one or more of which are members of the aromatic ring It is understood that it is a compound containing. In one form the aromatic tertiary amine may be an arylamine, for example monoarylamine, diarylamine, triarylamine, or oligomeric arylamine. Typical 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 by Brantley et al.

A more preferred class of aromatic tertiary amines are those comprising two or more aromatic tertiary amine residues as disclosed in US Pat. Nos. 4,720,432 and 5,061,569. Such compounds include those represented by Formula A:

Where

Q ₁ and Q ₂ are independently selected aromatic tertiary amine residues,

G is a bonding group, for example arylene, cycloalkylene, or an alkylene group of carbon-carbon bonds.

In one embodiment, at least one of Q ₁ and Q ₂ contains a polycyclic condensed ring structure, such as naphthalene. When G is an aryl group, this is for convenience a phenylene, biphenylene or naphthalene moiety.

A useful class of triarylamines that satisfy Formula A and contain two triarylamine residues are represented by Formula B:

Where

R ₁ and R ₂ each independently represent a hydrogen atom, an aryl group, or an alkyl group, or R ₁ and R ₂ together represent an atom that together completes a cycloalkyl group;

R ₃ and R ₄ each independently represent an aryl group, which in turn is substituted with a diaryl substituted amino group, as represented by Formula C:

Where

R ₅ and R ₆ are independently selected aryl groups.

In one embodiment, at least one of R ₅ and R ₆ contains a polycyclic condensed ring structure, such as naphthalene.

The host material may comprise a substituted or unsubstituted triarylamine compound. Another class of aromatic tertiary amines are tetraaryldiamines. Preferred tetraaryldiamines include two diarylamino groups, for example a group as represented by Formula C, joined via an arylene group. Useful tetraaryldiamines include those represented by the following formula (D):

Each Are is an independently selected arylene group such as phenylene or anthracene residues,

n is an integer from 1 to 4,

Ar, R ₇ , R ₈ and R ₉ are independently selected aryl groups.

In a typical embodiment, at least one of Ar, R ₇ , R ₈ and R ₉ is a polycyclic condensed ring structure, for example naphthalene.

In turn, the various alkyl, alkylene, aryl and arylene moieties of Formulas A, B, C, and D may each be substituted. Typical substituents include alkyl groups, alkoxy groups, aryl groups, aryloxy groups and halogens such as fluorides, chlorides and bromides. These various alkyl and alkylene moieties typically contain about 1 to 6 carbon atoms. The cycloalkyl moiety may contain from 3 to about 10 carbon atoms, but typically 5, 6 or 7 ring-carbon atoms, for example cyclopentyl, cyclohexyl and cycloheptyl ring structures. The aryl and arylene moieties are typically phenyl and phenylene moieties.

The emissive material can be formed either alone or as a mixture of these compounds. Specifically, triarylamines, for example triarylamines satisfying Formula B, can be used together with tetraaryldiamines, for example as represented by Formula D. The host material may comprise a substituted or unsubstituted dicarbazole-biphenyl compound. Exemplary useful aromatic tertiary amines are as follows:

4,4'-N, N'-dicarbazole-1,1'-biphenyl (CBP) (D1);

4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (D2);

4,4'-bis [N- (1-naphthyl) -N- (2-naphthyl) amino] biphenyl) (D3);

4,4'-bis [N- (2-naphthyl) -N-p-tolylamino] biphenyl (D4);

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

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

4,4'-bis (diphenylamino) quadriphenyl;

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

N, N, N-tri (p-tolyl) amine;

4- (di-p-tolylamino) -4 '-[4 (di-p-tolylamino) -styryl] stilbene;

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] 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-peryleneyl) -N-phenylamino] biphenyl;

4,4'-bis [N- (1-coronylyl) -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;

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

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

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

4,4 ', 4 "-tris [(3-methylphenyl) phenylamino] triphenylamine.

The host material may comprise a substituted or unsubstituted aza-aromatic compound. For example, the host material may include substituted or unsubstituted acridine, quinoline, purine, phenazine, phenoxazine or phenanthroline compounds. Carbazole derivatives are useful hosts. Useful examples of phenanthroline materials include 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline and 4,7-diphenyl-1,10-phenanthroline.

Host and dopant molecules include, but are not limited to, U.S. Pat.

Metal complexes of 8-hydroxyquinoline and similar derivatives (Formula E) constitute a class of useful host compounds capable of supporting electroluminescence and are capable of luminescence at wavelengths greater than 500 nm, for example green, yellow, orange and red. Especially suitable for:

Where

M represents a metal;

n is an integer from 1 to 4;

Z independently represents in each case the atoms that complete the nucleus having two or more condensed aromatic rings.

From the above, it is apparent that the metal may be a monovalent, divalent, trivalent or tetravalent metal. The metal may for example be an alkali metal such as lithium, sodium or potassium; Alkaline earth metals such as magnesium or calcium; Trivalent metal such as aluminum or gallium, or another metal such as zinc or zirconium. In general, any monovalent, divalent, trivalent or tetravalent metal known to be a useful chelate metal can be used.

Z completes a heterocyclic nucleus containing two or more condensed aromatic rings, at least one of which is an azole or azine ring. Additional rings, including both aliphatic and aromatic rings, may optionally be condensed with the two required rings. The number of ring atoms is usually kept below 18 to avoid increasing the molecular volume without improving the action.

The host material may comprise a substituted or unsubstituted chelated oxynoid compound.

Exemplary 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)]

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

The host material may comprise a substituted or unsubstituted anthracene compound.

Derivatives of 9,10-di- (2-naphthyl) anthracene (formula F) constitute a class of useful hosts capable of supporting electroluminescence and have wavelengths above 400 nm, for example blue, green, yellow, orange Or particularly suitable for emitting red light:

Where

R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ represent one or more substituents on each ring, wherein each substituent is individually selected from the following groups:

Group 1: hydrogen, typically alkyl having 1 to 24 carbon atoms;

Group 2: aryl or substituted aryl having 5 to 20 carbon atoms;

Group 3: 4 to 24 carbon atoms necessary to complete the condensed aromatic ring of anthracenyl, pyrenyl or perylene;

Group 4: heteroaryl or substituted heteroaryl having 5 to 24 carbon atoms necessary to complete the condensed heteroatom ring of a furyl, thienyl, pyridyl, quinolinyl or other heterocyclic system;

Group 5: alkoxylamino, alkylamino or arylamino having 1 to 24 carbon atoms; And

Group 6: fluorine, chlorine, bromine or cyano.

Illustrative examples are 9,10-di- (2-naphthyl) anthracene (F1) and 2-t-butyl-9,10-di- (2-naphthyl) anthracene (F2). Other anthracene derivatives may be useful as hosts, including, for example, derivatives of 9,10-bis [4- (2,2-diphenylethenyl) phenyl] anthracene.

Benzazole derivatives (formula G) constitute another class of useful hosts capable of supporting photoluminescence and are particularly suitable for luminescence at wavelengths above 400 nm, for example blue, green, yellow, orange or red:

Where

n is an integer from 3 to 8;

Z is O, NR or S;

R and R 'are individually hydrogen; Alkyl having 1 to 24 carbon atoms such as propyl, t-butyl, heptyl and the like; Aryl or hetero atom substituted aryl having 5 to 20 carbon atoms such as phenyl and naphthyl, furyl, thienyl, pyridyl, quinolinyl and other heterocyclic systems; Or halo, for example chloro, fluoro; Or atoms necessary to complete the condensed aromatic ring;

L is a binding unit comprising alkyl, aryl, substituted alkyl, or substituted aryl, which conjugately or unconjugates a plurality of benzazoles together. Examples of useful benzazoles are 2,2 ', 2 "-(1,3,5-phenylene) tris [1-phenyl-1H-benzimidazole].

The host material may include a substituted or unsubstituted benzoxazole compound, a substituted or unsubstituted benzthiazole compound, or a substituted or unsubstituted benzimidazole compound. The host material may include a substituted or unsubstituted oxazole compound, a substituted or unsubstituted triazole compound, or a substituted or unsubstituted oxadiazole compound. Useful examples of oxazole compounds include 1,4-bis (5-phenyloxazol-2-yl) benzene, 1,4-bis (4-methyl-5-phenyloxazol-2-yl) benzene and 1,4 -Bis (5- (p-biphenyl) oxazol-2-yl) benzene. Useful examples of oxadiazole compounds include 2- (4-biphenylyl) -5-phenyl-1,3,4-oxadiazole and 2- (4-biphenylyl) -5- (4-tert- Butylphenyl) -1,3,4-oxadiazole. Useful examples of triazole compounds include 3- (4-biphenylyl) -4-phenyl-5-tert-butylphenyl-1,2,4-triazole.

Distyrylarylene derivatives are also useful as host materials or dopant materials. Many examples are disclosed in US Pat. No. 5,121,029. Useful release materials (hosts and dopants) may have the formula H or I:

X-CH = CH-Y-CH = CH-Z

X- (CH = CH) _n -Z

In the above formulas,

X and Z are independently substituted or unsubstituted aromatic groups or substituted or unsubstituted aromatic complex ring groups having one nitrogen atom;

n is 1, 2 or 3;

Y is a divalent aromatic group or a divalent aromatic complex ring group having one nitrogen atom. Useful examples include 1,4-bis (2-methylstyryl) -benzene, 4,4 '-(9,10-anthracenediyldi-2,1-ethenediyl) bis (N, N-bis (4 -Methylphenyl) -benzeneamine, 4,4 '-(1,4-naphthalenediyldi-2,1-ethenediyl) bis (N, N-bis (4-methylphenyl) benzeneamine, and 4,4' -(1,4-phenylenedi-2,1-ethenediyl) bis (N, N- (4-tolyl)) benzeneamine.

The organic substrate dopant is chosen to provide an emission of 300-1700 nm. The dopant may be selected from fluorescent or phosphorescent dyes. Useful fluorescent dopants include materials as disclosed above as host material. Other useful fluorescent dopants include, but are not limited to, substituted or unsubstituted anthracene, tetracene, xanthene, perylene, rubrene, coumarin, rhodamine, and derivatives of quinacridone, dicyanomethylenepyran compound, thiopyran compound, Polymethine compounds, pyryllium and thiapiryllium compounds, fluorene derivatives, periplanthene derivatives, indenoferylene derivatives, bis (azinyl) amine boron compounds, bis (azinyl) methane compounds, naphthyridine, fluoranthenes, Furan, indole, thiaphene, benzoxanthene, pyrene, ferropyrene, terphenyl, quarterphenyl, quinquephenyl, sexyphenyl, anthrene, bisantrene compound, N, N, N ', N'-substituted benz Den derivatives, N, N, N ', N'-tetraarylbenziden derivatives and carbostyryl compounds or combinations thereof. Derivatives of this class of substances can also serve as useful host materials or combinations thereof. The host material will often be a compound containing three or more phenylene moieties.

Exemplary useful dopants include, but are not limited to the following:

Other emissive materials include various heterocyclic fluorescent brighteners as disclosed in US Pat. No. 4,539,507.

The release material may also be a polymeric material, a blend of two or more polymeric materials, or a doped polymer or polymer blend. The release material may also include more than one nonpolymeric and polymeric material with or without a dopant. Typical dopants are listed above for nonpolymeric molecules. Non-polymeric dopants can be dispersed molecularly within the polymeric host or added by copolymerizing the dopant with a few components into the host polymer. Typical polymeric materials include, but are not limited to, substituted and unsubstituted poly (p-phenylenevinylene) (PPV) derivatives, substituted and unsubstituted poly (p-phenylene) (PPP) derivatives, substituted and unsubstituted poly Fluorene (PF) derivatives, substituted and unsubstituted poly (p-pyridine), substituted and unsubstituted poly (p-pyridalvinylene) derivatives, and substituted, unsubstituted poly (p-phenylene) ladders and Step-ladder polymers, and copolymers thereof (Diaz-Garcia, et al., US Pat. No. 5,881,083 and references therein). Such substituents include, but are not limited to, alkyl, cycloalkyl, alkenyl, aryl, heteroaryl, alkoxy, aryloxy, amino, nitro, thio, halo, hydroxy and cyano. Typical polymers include poly (p-phenylene vinylene), dialkyl-, diaryl-, diamino-, or dialkoxy-substituted PPV, mono alkyl-mono alkoxy-substituted PPV, mono aryl-substituted PPV, 9,9'-dialkyl or diaryl-substituted PF, 9,9'-mono alkyl-mono aryl substituted PF, 9-mono alkyl or aryl substituted PF, PPP, dialkyl-, diamino-, dia Aryl-, or dialkoxy-substituted PPP, mono alkyl-, aryl-, alkoxy-, or amino-substituted PPP. Also polymeric materials such as poly (N-vinylcarbazole) (PVK), polythiophene, polypyrrole, polyaniline and copolymers such as poly (3,4-ethylenedioxythiophene) / poly (4 Styrenesulfonate) (also called PEDOT / PSS) can be used.

The above-mentioned organic materials are suitably deposited through sublimation, but can be deposited from a solvent with any binder to improve film formation. If the material is a polymer, solvent deposition is usually preferred. The material deposited by sublimation is often vaporized from a sublimer “boat” made of tantalum material, for example as disclosed in US Pat. No. 6,237,529, or first coated onto a donor sheet and then sublimed very close to the substrate. You can. The layer with the mixture of materials may be using a separate sublimer boat or premixing the materials and coating from a single boat or donor sheet.

As shown in FIG. 3 and discussed above, the microcavity device array contains red, green, and blue emission pixels having dimensions on the order of 80 × 240 μm. The emission color is measured by the combination of the length of the emission path and the fluorescence spectrum of the gain medium contained in the periodic gain portion 160. Patterned deposition of the gain medium contained in the periodic gain portion 160 allows for the use of shadow masks, integrated shadow masks (US Pat. No. 5,294,870), space-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). If the periodic gain portion 160 is more than one layer, it is necessary to repeat the patterned deposition correspondingly.

Most organic based microcavity devices are sensitive to moisture or oxygen, or both, so that the device is typically sealed under an inert atmosphere, such as nitrogen or argon. Desiccants such as alumina, bauxite, calcium sulfate, clay, silica gel, zeolites, alkaline metal oxides, alkaline earth metal oxides, sulfates or metal halides and perchlorates can be incorporated into the enclosed device. Encapsulation and drying methods include, but are not limited to, those disclosed in US Pat. No. 6,226,890. In addition, barrier layers such as SiO _x , Teflon, and alternating inorganic / polymer layers are known in the art for encapsulation.

For the spacing layer 170, it is desirable to use a material that is very transparent to both microcavity emission 190 and pump-rays 180. In this embodiment, 1,1-bis- (4-bis (4-methyl-phenyl) -amino-phenyl) -cyclohexane (TAPC) is chosen as the spacing material because it is visible and adjacent UV spectrum This is because it has a very low absorption throughout and its refractive index is slightly lower than that of most organic host materials. This refractive index difference is useful because it helps to maximize the overlap between the fixed e-field rupture and the periodic gain portion (s) 160. In addition to the organic spacer material, the spacer layer 170 may also consist of an inorganic material, for example SiO ₂ , because it has a low absorption and its refractive index is smaller than that of the organic host material. When using an inorganic substrate spacer layer, the material can be deposited by thermal evaporation, e-rays at low deposition temperatures (about 70 ° C.), or colloidal methods.

Growth of the active region 130 is followed by deposition of the upper dielectric stack 140. The upper dielectric stack 140 is spaced apart from the base dielectric stack 120 and is reflective to light over a range of wavelengths. Its composition is similar to that of the base dielectric stack. Because the upper dielectric stack 140 is deposited over the active region 130 containing organic material (in the case of organic substrate gain medium), its deposition temperature avoids melting of the organic material and prevents sample breakage upon cooling to room temperature. It should be kept low to avoid thermal expansion mismatches (between organic materials and inorganic dielectric stack materials) that occur. As a result, the typical deposition temperature of the upper dielectric stack 140 is 100 degrees Celsius or less. The upper dielectric stack can be deposited in a conventional manner, for example by e-rays, low-energy sputtering or colloidal deposition. In order to achieve effective microcavity device performance, the peak reflectivity of the base dielectric stack 120 is greater than 99% while the peak reflectance of the upper dielectric stack 140 is preferably less than 90%.

The microcavity array device 100 is optically driven by an incident pump-ray source 180 and emits a microcavity emission 190. The pump-ray light 180 may be non-coherent LED light. 2 shows microcavity emission 190 passed through top dielectric stack 140. On the other hand, the microcavity structure can be optically pumped through the upper dielectric stack 140 along with the microcavity emission 190 passing through the substrate 110 by a suitable design of dielectric stack reflectance properties. Operation of the microcavity array device 100 takes place in the following manner. Pump-rays 180 pass through substrate 110 and base dielectric stack 120 and are absorbed by periodic gain portion (s) 160, where a portion of the pump-ray energy is longer wavelength microcavities. It is emitted again as light. When the pump-rays 180 enter through the substrate 110, the upper dielectric stack peak reflectance is reduced to the base dielectric stack (to allow the microcavity emission 190 to exit primarily through the upper dielectric stack 140). 120) It needs to be smaller than the peak reflectance. In order to improve the power conversion efficiency of the device, the top dielectric stack 140 is typically additional dielectric such that the top dielectric stack 140 is highly reflective to the pump-rays 180 and the base dielectric stack 120 is highly transmissive to the pump-rays 180. A layer is applied to both dielectric stacks.

By the invention of the display containing the microcavity array device 100, a simplified liquid crystal display can be manufactured. A more simplified LCD, as shown in FIG. 4, typically contains a backlight unit 220, a microcavity array device 100, a polarizer 305, an optical shutter layer 310, and a beam expanding layer 320. do. The backlight unit 220 provides the pump-ray light 180 to the microcavity array device 100. The microcavity array device 100 provides a colored, pixelated, polarized light source with the polarizer 305 to the optical shutter layer 310. The optical shutter layer 310 passes or blocks light of the pixelated structure. The light expanding layer 320 takes light exiting the light shutter layer 310 and extends its viewing cone.

To generate the pump-ray light 180, the backlight unit 220, as shown in FIGS. 5 to 8, includes a diffusion layer 240 and a light emitting diode (LED) 230 or a cold cathode fluorescent lamp (CCFL) 280. It is composed of The diffusion layer 240 homogenizes light incident on the microcavity array device 100. The LED 230 is typically a linear array 250 that illuminates the edge of the waveguide 260 and then readjusts light to illuminate the microcavity array device 100, or directly illuminates the microcavity array device 100. Planar array 270. The CCFL 280 typically readjusts the light to rim the waveguide 260 and illuminate the microcavity array device 100, or is oriented in a column 300 directly below the diffuse layer to provide microcavity array device 100. Light it up directly.

The small divergence angle of the microcavity array device 100 enables a 1: 1 correspondence between the emitting element 205 of the microcavity array and the color element of the optical shutter layer 310. Correspondingly, it is no longer necessary to include an array of color filters as one of the components of the optical shutter layer 310. The optical shutter layer 310 is only needed to adjust the colored light incident from the microcavity array device 100; This limits the efficiency losses associated with color filter arrays. An additional feature of near collimation of light output from microcavity array device 100 is that the viewing angle compensation film can be removed from the display structure. In addition, due to the natural collimation (<10-15 ° divergence angle) of the microcavity array device 100 light output, it is possible to remove the collimating film typically included in the backlight unit 220. As a result of removing the viewing angle compensation film and the collimating film from the display structure, the cost of the liquid crystal display device can be reduced. However, in order to prevent light leakage from neighboring pixels, a small divergence of the light output of the microcavity array device 100 should be considered. To prevent inaccurate light from escaping through neighboring pixels, the size of the emissive element 205 of the microcavity array is approximately 80 x as the microcavity light traverses into the optical shutter layer 310. It should be slightly reduced to achieve a suitable pixel dimension of 240 μm. The size of the emissive element can be controlled by selectively depositing metal between the base dielectric stack 120 and the substrate 110. Preferred metals are Al or Ag, which can be selectively deposited by well known evaporation techniques. This metal will highly reflect pump-ray light 180 and will recycle the light until the pump-ray light 180 passes between the metal deposits.

The optical shutter layer 310 as shown in FIG. 9 is typically a liquid crystal cell 330 having an analyzer 340 at the furthest side from the microcavity array device 100. The liquid crystal cell 330 is similar to a conventional liquid crystal cell except that it does not contain CFA. The liquid crystal cell 330 does not require CFA since the light output from the microcavity array device 100 is pixelated with red, green and blue microcavity emission. The liquid crystal cell 330 includes a liquid crystal substrate 350 at the top and the base thereof. The liquid crystal substrate 350 of the liquid crystal cell 330 may include a glass plate or a plastic substrate. The thickness of the liquid crystal substrate 350 should be thin enough to prevent parallax that causes light leakage through adjacent pixels. The thickness of the liquid crystal substrate 350 should preferably be less than 0.5 mm. Both liquid crystal substrates 350 are coated with a patterned transparent conductor layer 360. Typical transparent conductor is tin indium oxide. An alignment layer 370 is coated on top of each of the transparent conductor layers 360. Finally, a liquid crystal material 380 is coated between the two alignment layers 370. The liquid crystal cell 330 adjusts the intensity of light output from the microcavity array device 100 by aligning liquid crystal molecules according to an application of a selective voltage. The liquid crystal cell 330 may also contain thin film transistors at each pixel location to cause the display to be actively driven. However, the present invention does not require a particular drive design. The optical shutter layer 310 also contains an analyzer 340 that decomposes the polarized light output from the liquid crystal cell 330.

Those skilled in the art will appreciate that other optical shutters can be used in the present invention. An example is an optical shutter manufactured by electrowetting. In such optical switches, as demonstrated in Hayes, et al., Nature, 425, 383 (2003), application of an electric field changes the extent to which dye-containing oil droplets cover the surface of each pixel. In fact, the electric field alters the hydrophobicity of the pixel surface. Hayes et al., Nature, 425, 383 (2003) envisioned a switch for use in reflective displays, where the reflection is produced by a white reflective layer behind the oil droplets. The electrowetting switch can also be used for transmission instead of reflection when the back is clean.

Since the light output of the microcavity array device 100 is near collimated, it is necessary to include the light expanding layer 320 as the final element of the LCD device of FIG. 4 in order to increase each cone of the colored light output. Possible components comprising the beam expanding layer 320 may be diffusion layer elements or microlens arrays. The component should allow it to increase the viewing cone while preserving the sharpness on the display. More specifically, when exiting the ray expanding layer 320, each pixel should be clearly distinguishable as before entering the ray expanding layer 320. Depending on the intended viewing application, the expansion of the viewing cone can be correspondingly controlled by the ray expanding layer 320.

Another embodiment of a liquid crystal display device as shown in FIG. 10 includes a backlight unit 220, a blue emitting microcavity array device 105, a polarizer 305, an optical shutter layer 310, a red / green dielectric stack ( 315 and color conversion layer 325. The backlight unit 220 provides pump ray light 180 to the blue-emitting microcavity array device 105. The blue emitting microcavity array device 105 together with the polarizer provides a blue polarized light source to the optical shutter layer 310. For the blue emitting microcavity array device 105, its composition and operation are similar to those discussed above, except that it only outputs blue microcavity light. The optical shutter layer 310 passes or blocks blue light having a pixelated structure. The color conversion layer 325 selectively absorbs blue microcavity light and converts it down to red and green light at the location of the red and green display pixels. The red / green dielectric stack 315 is disposed between the color conversion layer 325 and the light shutter layer 315 such that the red and green light propagates only in the direction of the observer. At the position of the blue display pixel, no down conversion occurs. As a result, the color shifting layer 325 at the location of the blue display pixel contains a forward scattering element to increase each emission cone of collimated blue microcavity light.

In the case of emitting only blue from the blue emitting microcavity array device 105, the optical shutter layer 310 can be slightly modified to optimize its operation. More specifically, liquid crystal cell 330 modulates the blue light intensity output from blue emitting microcavity array device 105 by orienting liquid crystal molecules upon application of a selective voltage. The liquid crystal cell 330 must be tuned so that the dark state is optimized for the center wavelength of the blue microcavity incidence angle from the blue emitting microcavity array device 105. In this way, the contrast of the display device can be increased.

The color conversion layer 325 selectively absorbs modulated blue microcavity light and converts it down to red and green light at the location of the red and green display pixels. In order to convert blue light down into red and green light, the layer may comprise red and green emitting organic fluorescent dyes, respectively, in the solid substrate. Organic fluorescent dyes have the advantages of high fluorescence quantum efficiency and high absorption cross section. It can also be deposited by cost effective deposition techniques, for example by spin coating. Candidates for the red and green high quantum efficiency organic dyes were [4- (dicyanomethylene) -2-t-butyl-6- (1,1,7,7-tetramethylzololidyl-9-enyl)-, respectively 4H-pyran] (DCJTB) and [10- (2-benzothiazolyl) -2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H, 5H, 11H- [1] Benzopyrano [6,7,8-ij] quinolizine-11-one] (coumarin 545T). Both have a fluorescence quantum efficiency close to 100% (in solid film) and a large absorption cross section in the 460-480 nm wavelength range, where the blue emitting microcavity array device 105 will emit. In addition to using organic fluorescent dyes as downconversion agents, recent results point out the possibility of using inorganic quantum dots as fluorescent compounds in the color conversion layer 325. For example, colloidal CdSe / CdS heterostructure quantum dots have demonstrated quantum yields in excess of 80% (A.P. Alivisatos, MRS Bulletin 18 (1998)). Solid substrates containing such organic or inorganic fluorescent materials should be able to be deposited by a transparent and inexpensive process in visible wavelength light. Preferred solid substrates are transparent plastics such as poly-vinyl acetate or PMMA. In doping the substrate with an organic dye, it is necessary to keep the dye concentration just below the concentration at which concentration inhibition occurs. The doping concentration will itself range from 0.5 to 2% for DCJTB and coumarin 545T.

Although the internal quantum efficiency is almost 100% for the selected organic fluorescent dye, the external quantum efficiency can be limited as a result of light trapping in the solid substrate. A preferred method of increasing external quantum efficiency is to include a scattering center with the particles when the dye particles are deposited with the solid substrate material. The scattering particles should have an index of about half the emission wavelength (red and green), a different index than the solid substrate, and be transparent throughout the visible spectral range. Preferred particles may be TiO ₂ as a result of transparency and broad refractive index throughout the visible spectrum.

Since the display light needs to face the viewer, a red / green dielectric stack 315 is disposed between the color conversion layer 325 and the light shutter layer 310. The red / green dielectric layer 315 must reflect more than 80% of the red and green emission and pass at least 90% of the blue microcavity light. It is desirable to deposit the red / green dielectric stack 315 by inexpensive methods, for example by polymer extrusion, colloidal deposition or plasma promoted chemical vapor deposition. Other methods commonly practiced in the art are also possible.

As described above, the color conversion layer 325 contains blue pixels that pass blue laser light without downconversion. Due to the narrow divergence angle of the blue microcavity light, the blue pixel needs to incorporate a material that increases the angular emission cone of blue light. As is well known in the art, scattering particles may be selected that preferentially scatter blue microcavity light in the forward direction. For green and red pixels, the scattering particles should be transparent and have an index different from that of the solid substrate. Both the size and refractive index of the scattering particles are selected according to well known ways of enhancing forward scattering. In addition to increasing each emission cone by including scattering particles in a blue pixel substrate, other methods commonly practiced in the art are possible.

The blue, green and red pixels of the color conversion layer 325 need to be sized according to the display application (given display area and resolution) and selectively deposited using a cost effective process. One method is to incorporate fluorescent particles and scattering particles into the photoresist formulation. This type of approach was used to prepare dyed photoimaging photoresists (CFAs are typically deposited by this technique), where the dyed particles are added to the photoresist formulation. Using this approach, the blue, green and red portions of color conversion layer 325 can be selectively deposited using photolithography techniques well known in the art. In addition to selective deposition by photolithography of the color conversion layer 325, other methods commonly practiced in the art may be used.

In addition to the efficiency gain obtained by the removal of CFA from the optical shutter layer 310 having a large area, the blue emitting microcavity array device as a light source brings other advantages. Since the blue microcavity light emission is near collimated, both the viewing angle compensation film and the collimating film (typically found in the backlight unit 220) can be removed from the display structure. As a result of removing the viewing angle compensation film and the collimating film from the display structure, the cost of the liquid crystal display device can be reduced.

Claims (32)

a) a backlight unit for providing pump-ray light; b) generating display light in response to pump-ray light and having pixels, each pixel being i) a transparent substrate, ii) a base dielectric stack reflective to light over a range of wavelengths, iii) responsive to pump-ray light A microcavity light-generating array comprising an active region for activating, and iv) an upper dielectric stack spaced from the base dielectric stack and reflective to light over a range of wavelengths; c) an optical shutter for passing display light selected from said microcavity light-generating array; d) a polarization layer disposed between said microcavity light-generating array and an optical shutter; And e) a light expanding layer disposed over said optical shutter for increasing the viewing angle cone of display light; And a display device for generating pixelated colored light. The method of claim 1, And wherein said active region of different pixels generates display light of different colors in response to pump-ray light. The method of claim 1, A display device that transmits pump-ray light and introduces it through one or more of the dielectric stacks into the active region. The method of claim 1, At least one layer having a liquid crystal responsive to a field applied to pass the selected display light, and means for applying the field to a selected portion of the liquid crystal layer. The method of claim 1, And the optical shutter comprises at least one polarizing film layer. The method of claim 1, And the optical shutter comprises at least one layer having an electrowetting switch. The method of claim 1, And the backlight unit includes a light emitting diode or a cold cathode fluorescent lamp. The method of claim 1, The active region is disposed on either or more sides of one or more periodic gain portion (s) and the periodic gain portion (s) and the periodic gain portion (s) is an antinode of the standing wave electromagnetic field of the device. And a spacing layer arranged to align with the plurality of layers. The method of claim 8, And wherein said periodic gain portion (s) of different pixels produce red, green or blue light. The method of claim 8, And the periodic gain portion (s) comprise an organic host material and a dopant. The method of claim 8, And the spacing layer is substantially transparent to pump-ray light and the microcavity light. The method of claim 11, And the spacer layer comprises 1,1-bis- (4-bis (4-methyl-phenyl) -amino-phenyl) -cyclohexane or silicon dioxide. The method of claim 10, Part of the periodic gain moiety (s) that produces green light is the host material of aluminum tris (8-hydroxyquinoline) and [10- (2-benzothiazolyl) -2,3,6,7-tetrahydro A display device comprising a dopant of -1,1,7,7-tetramethyl-1H, 5H, 11H- [1] benzopyrano [6,7,8-ij] quinolizine-11-one]. The method of claim 10, Some of the periodic gain moiety (s) that produce red light are the host material of aluminum tris (8-hydroxyquinoline) and [4- (dicyanomethylene) -2-t-butyl-6- (1, 1,7,7-tetramethylzulolidil-9-enyl) -4H-pyran]. The method of claim 10, Part of the periodic gain moiety (s) that produces blue light is the host material of 2-3-butyl-9,10-di-naphthalen-2-yl-anthracene and 2,5,8,11-tetrakis A display device comprising a dopant of (1,1-dimethylethyl) -perylene. The method of claim 8, And the periodic gain portion (s) comprise a polymeric material. The method of claim 8, And the periodic gain portion (s) comprise inorganic nanoparticles. a) a backlight unit for providing pump-ray light; b) responsive to pump-ray light, each pixel having i) a transparent substrate, ii) a base dielectric stack reflective to light over a range of wavelengths, iii) blue light in response to pump-ray light A microcavity light-generating array comprising an active region for producing and iv) an upper dielectric stack spaced from the base dielectric stack and reflective to light over a range of wavelengths; c) an optical shutter for passing colored light selected from said microcavity light-generating array; d) a polarization layer disposed between said microcavity light-generating array and an optical shutter; And e) a color shifting layer adapted to increase the viewing angle cone of the selected colored light, wherein the selected different parts comprise different parts producing different colored light in response to the blue light; And a display device for generating pixelated colored light. The method of claim 18, And the color shifting layer comprises different color changing materials to produce red and green display light. The method of claim 18, And a third dielectric stack disposed on top of the optical shutter for reflecting red and green light from the color conversion layer. The method of claim 18, A display device that transmits pump-ray light and introduces it through one or more of the dielectric stacks into the active region. The method of claim 18, At least one layer having a liquid crystal responsive to a field applied to pass the selected display light, and means for applying the field to a selected portion of the liquid crystal layer. The method of claim 18, And the optical shutter comprises at least one polarizing film layer. The method of claim 18, And the optical shutter comprises at least one layer having an electrowetting switch. The method of claim 18, And the backlight unit includes a light emitting diode or a cold cathode fluorescent lamp. The method of claim 18, The active region is disposed on one or more of the periodic gain portion (s) and on either side of the periodic gain portion (s) and arranged such that the periodic gain portion (s) are aligned with the waves of the standing wave electromagnetic field of the device. A display device comprising spaced apart layers. The method of claim 26, And the periodic gain portion (s) comprise an organic host material and a dopant. The method of claim 26, And the spacing layer is substantially transparent to pump-ray light and the microcavity light. The method of claim 28, And the spacer layer comprises 1,1-bis- (4-bis (4-methyl-phenyl) -amino-phenyl) -cyclohexane or silicon dioxide. The method of claim 27, Part of the periodic gain moiety (s) that produces blue light is the host material of 2-3-butyl-9,10-di-naphthalen-2-yl-anthracene and 2,5,8,11-tetrakis A display device comprising a dopant of (1,1-dimethylethyl) -perylene. The method of claim 26, And the periodic gain portion (s) comprise a polymeric material. The method of claim 26, And the periodic gain portion (s) comprise inorganic nanoparticles.

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