WO2003098691A2

WO2003098691A2 - Display

Info

Publication number: WO2003098691A2
Application number: PCT/GB2003/002116
Authority: WO
Inventors: Poopathy Kathirgamanathan
Original assignee: Elam-T Limited
Priority date: 2002-05-17
Filing date: 2003-05-16
Publication date: 2003-11-27
Also published as: AU2003227941A1; WO2003098691A3; GB0211324D0

Abstract

A screen structure is a transparent electro-optic substrate e.g. of silicon on which there is a VLSI (1) which is back lit by a layer of an electroluminescent material (3). There is a collimator (2) which focuses the light from the electroluminescent layer.

Description

Display

The present invention relates to a display screen for displaying visual images.

Small display screens e.g. of the order of one centimetre square are known which comprise a NLSI circuit on a substrate. The substrate is lit by light emitting diodes and the image produced can be seen. These small screens are used in a variety of applications one of which is for screens which are viewed close to the eye; for example in goggles, spectacles etc. and in virtual reality applications. As the size of an image depends on the angle the image subtends at the eye, the closer proximity to the eye the larger the image seen by the user.

A particular type of this screen is made by OPSIS S.A. of 1 Rue du Pare Foulon F- 91140 Nillebon/Y France who use a transparent silicon substrate on which the NLSI circuit is deposited. Light can then be transmitted through the substrate to the screen. The use of LED as the light source places a limit on the minimum size and weight of the screen and the power requirements can make it awkward to use in some circumstances.

We have now devised an electroluminescent structure which can be used as an improved small screen.

According to the invention there is provided a structure comprising sequentially :-

(i) an electroluminescent layer

(ii) a collimator and (iii) a transparent electro-optic substrate on which there is an integrated circuit.

The integrated circuit is preferably a very large scale integrated circuit (VLSI). The NLSI is connected to an electric signal source which generates the image to be viewed; this can be via an electromagnetic signal such as in a television transmission or via a wire or from any other source as in conventional screens.

The transparent substrate is preferably a transparent silicon wafer which is thin enough to let light pass through, but has the physical properties to enable the integrated circuit or NLSI to be deposited on its surface. As stated above such electro- optic materials are commercially available.

In a chip of the type useful in the present there can be a transparent substrate on which is formed the integrated circuit which contains the active functional elements and which supports the transparent passive functional elements which generate the image; this is back lit by a light source.

The structure forms a transmissive screen-chip associated with an electroluminescent lighting means situated on the side remote from that through which it must be observed, either directly or by projection.

US Patent 6433362 discloses chips formed on an original substrate of the low-cost SOI type, having an insulating and transparent support and whose structure allows the use of standard manufacturing processes.

This is an integrated circuit device or "chip", of the type comprising an original support and microscopic active and passive functional elements present in a thin layer of monocrystalline semiconductor material. The original support is refractory and transparent and is covered on one of its faces with a thin layer of transparent and insulating inorganic refractory material; this thin layer itself being covered with a thin layer of inorganic monocrystalline semiconductor material, in particular of the silicon or silicon-germanium type, which contains the active functional elements and which supports the transparent passive functional elements, other opaque functional elements being punctually arranged to allow transparent cells to remain, through which light of the visible spectrum can freely pass through the entire chip.

In a preferred chip the original support is made of refractory glass; the glass has a coefficient of expansion adapted to that of the thin layer of semiconductor material; the original support is covered on all of its faces with a refractory and transparent layer having a barrier effect with respect to certain chemical elements present in the support, in order to confine them therein; the original support carries an opaque layer on its face which is remote from the one carrying the semiconductor layer; the semiconductor layer is formed of monocrystalline silicon or silicon-germanium whose thickness is sufficiently thin so that the said layer is transparent; microelectronic elements such as transistors are disposed on the periphery of the transparent zones; liquid crystals are integrated with a thin material, in order to constitute a unit structure interposed between the chip itself and a transparent counter-electrode formed by a thin layer applied against a transparent window, this assembly constituting a transmissive screen-chip. The device is associated with lighting means situated on the side remote from that through which it must be observed, either directly or by projection.

In the present invention the lighting means is an electroluminescent layer.

The collimator is preferably a diffraction grating which collimates the light and acts as micro lenses so that the light is focussed onto the integrated circuit or NLSI .

In use there is a transparent electro-optic substrate on which there is an integrated circuit or VLSI which is back lit by the layer of an electroluminescent material. The collimator focuses the light from the electroluminescent layer.

Electroluminescent compounds which can be used in the present invention are of general formula (Lα)_nM where M is a rare earth, lanthanide or an actinide. Lα is an organic complex and n is the valence state of M. Other fluorescent compounds which can be used in the present invention are of formula

where Lα and Lp are organic ligands, M is a rare earth, transition metal, lanthanide or an actinide and n is the valence state of the metal M. The ligands Lα can be the same or different and there can be a plurality of ligands Lp which can be the same or different.

For example (Lι)(L )(L₃)(L..)M(Lp) where M is a rare earth, transition metal, lanthanide or an actinide and (Lι)(L₂)(L₃)(L...) are the same or different organic complexes and (Lp) is a neutral ligand. The total charge of the ligands (Li)(L₂)(L₃)(L..) is equal to the valence state of the metal M. Where there are 3 groups Lα which corresponds to the III valence state of M the complex has the formula (L₁)(L χL₃)M (Lp) and the different groups (Lι)(L₂)(L₃) may be the same or different.

Lp can be monodentate, bidentate or polydentate and there can be one or more ligands Lp.

Preferably M is metal ion having an unfilled inner shell and the preferred metals are selected from Sm(III)₅ Eu(II), Eu(III), Tb(III), Dy(III), Yb(III), Lu(III), Gd (III), Gd(III) U(III), Tm(III), Ce (III), Pr(III), Nd(IH), Pm(III), Dy(III), Ho(III), Er(IIι), Yb(III) and more preferably Eu(III), Tb(III), Dy(III), Gd (III), Er (III), Yt(III).

Further fluorescent compounds which can be used in the present invention are of general formula (Lα)_nMιM₂ where M-_. is the same as M above, M₂ is a non rare earth metal, Lα is a as above and n is the combined valence state of Mi and M₂. The complex can also comprise one or more neutral ligands Lp so the complex has the general formula (Lα)_n Mi M₂ (Lp), where Lp is as above. The metal M₂ can be any metal which is not a rare earth, transition metal, lanthanide or an actinide examples of metals which can be used include lithium, sodium, potassium, rubidium, caesium, beryllium, magnesium, calcium, strontium, barium, copper (I), copper (II), silver, gold, zinc, cadmium, boron, aluminium, gallium, indium, germanium, tin (II), tin (IV), antimony (II), antimony (TV), lead (II), lead (IN) and metals of the first, second and third groups of transition metals in different valence states e.g. manganese, iron, ruthenium, osmium, cobalt, nickel, palladium(ιl). palladium(IV), platinum(II), platinum(ιN), cadmium, cliromium. titanium, vanadium, zirconium, tantalum, molybdenum, rhodium, iridium, titanium, niobium, scandium, yttrium.

For example (Lι)(L₂)(L₃)(L..)M (Lp) where M is a rare earth, transition metal, lanthanide or an actinide and (Lι)(L₂)(L₃)(L...) and (Lp) are the same or different organic complexes.

Further organometallic complexes which can be used in the present invention are binuclear, trinuclear and polynuclear organometallic complexes e.g. of formula

(Lm M^ M- f Lre ),

where L is a bridging ligand and where Mi is a rare earth metal and M₂ is Mi or a non rare earth metal, Lm and Ln are the same or different organic ligands Lα as defined above, x is the valence state of Mi and y is the valence state of M₂.

In these complexes there can be a metal to metal bond or there can be one or more bridging ligands between Mi and M₂ and the groups Lm and Ln can be the same or different. By trinuclear is meant there are three rare earth metals joined by a metal to metal bond i.e. of formula

(Lm)_xM ₁ M₃(_Ln)_y— M₂(_Lp)_z

or

where M-i , M₂ and M₃ are the same or different rare earth metals and Lm, Ln and Lp are organic ligands Lα and x is the valence state of M-j, y is the valence state of M₂ and z is the valence state of M₃. Lp can be the same as Lm and Ln or different.

The rare earth metals and the non rare earth metals can be joined together by a metal to metal bond and/or via an intermediate bridging atom, ligand or molecular group.

For example the metals can be linked by bridging ligands e.g.

(Lm)_xM ₁ M₃(_Ln)_y M₂(_Lp)_z

or

where L is a bridging ligand.

By polynuclear is meant there are more than three metals joined by metal to metal bonds and/or via intermediate ligands

M₁ M₂ M₃ M₄ or

M« M, M„ M, or

or

M₁ M₂ M₄ M₃ _L X_LX ^L where M*_., M₂, M₃ and M are rare earth metals and L is a bridging ligand.

Preferably Lα is selected from β diketones such as those of formulae

(I) (II) (III) where Ri_, R₂ and R₃ can be the same or different and are selected from hydrogen, and substituted and unsubstituted hydrocarbyl groups such as substituted and unsubstituted aliphatic groups, substituted and unsubstituted aromatic, heterocyclic and polycyclic ring structures, fluorocarbons such as trifluoryl methyl groups, halogens such as fluorine or thiophenyl groups; Ri, R and R₃ can also form substituted and unsubstituted fused aromatic, heterocyclic and polycyclic ring structures and can be copolymerisable with a monomer e.g. styrene. X is Se, S or O, Y can be hydrogen, substituted or unsubstituted hydrocarbyl groups, such as substituted and unsubstituted aromatic, heterocyclic and polycyclic ring structures, fluorine, fluorocarbons such as trifluoryl methyl groups, halogens such as fluorine or thiophenyl groups or nitrile.

Examples of Ri and/or R₂ and/or R₃ include aliphatic, aromatic and heterocyclic alkoxy, aryloxy and carboxy groups, substituted and substituted phenyl, fluorophenyl, biphenyl, phenanthrene, anthracene, naphthyl and fluorene groups alkyl groups such as t-butyl, heterocyclic groups such as carbazole.

Some of the different groups Lα may also be the same or different charged groups such as carboxylate groups so that the group Li can be as defined above and the groups L₂, L₃... can be charged groups such as

(IN) where R is Ri as defined above or the groups Li, L₂ can be as defined above and L₃. etc. are other charged groups.

Ri R and R₃ can also be

X where X is O, S, Se orNH.

(V)

A preferred moiety Ri is trifluoromethyl CF₃ and examples of such diketones are, banzoyltrifluoroacetone, p-chlorobenzoyltrifluoroacetone, p-bromotrifluoroacetone, p-phenyltrifluoroacetone, 1 -naphthoyltrifluoroacetone, 2-naphthoyltrifTuoroacetone, 2-phenathoyltrifluoroacetone, 3-phenanthoyltrifluoroacetone, 9- anthroyltrifluoroacetonetrifluoroacetone, cinnamoyltrifluoroacetone, and 2- thenoyltrifluoroacetone.

The different groups Lα may be the same or different ligands of formulae

(NI) where X is O, S, or Se and Ri R₂ and R are as above.

The different groups Lα may be the same or different quinolate derivatives such as

(VII) (VIII) where R is hydrocarbyl, aliphatic, aromatic or heterocyclic carboxy, aryloxy, hydroxy or alkoxy e.g. the 8 hydroxy quinolate derivatives or

(LX) (X) where R, R_ls and R are as above or are H or F e.g. Ri and R₂ are alkyl or alkoxy groups

As stated above the different groups Lα may also be the same or different carboxylate groups e.g.

(XIII) where R₅ is a substituted or unsubstituted aromatic, polycyclic or heterocyclic ring a polypyridyl group, R₅ can also be a 2-ethyl hexyl group so L_n is 2-ethylhexanoate or R₅ can be a chair structure so that L_n is 2-acetyl cyclohexanoate or Lα can be

where R is as above e.g. alkyl, allenyl, amino or a fused ring such as a cyclic or polycyclic ring.

The different groups Lα may also be

(XN) (XVI)

(XVII) (XVIIa)

Where R, Ri and R₂ are as above.

The groups Lp can be selected from

Ph Ph

O Ν Ph

Ph Ph

(XVIII) Where each Ph which can be the same or different and can be a phenyl (OPΝP) or a substituted phenyl group, other substituted or unsubstituted aromatic group, a substituted or unsubstituted heterocyclic or polycyclic group, a substituted or unsubstituted fused aromatic group such as a naphthyl, anthracene, phenanthrene or pyrene group. The substituents can be for example an alkyl, aralkyl, alkoxy, aromatic, heterocyclic, polycyclic group, halogen such as fluorine, cyano, amino. Substituted amino etc. Examples are given in figs. 1 and 2 of the drawings where R, Ri_, R_2; R₃ and R₄ can be the same or different and are selected from hydrogen, hydrocarbyl groups, substituted and unsubstituted aromatic, heterocyclic and polycyclic ring structures, fluorocarbons such as trifluoryl methyl groups, halogens such as fluorine or thiophenyl groups; R, Ri, R_2; R₃ and _t can also form substituted and unsubstituted fused aromatic, heterocyclic and polycyclic ring structures and can be copolymerisable with a monomer e.g. styrene. R, R_1; R_2; R₃ and R₄ can also be unsaturated alkylene groups such as vinyl groups or groups

where R is as above.

L_p can also be compounds of formulae

(xvrv) (XX) (xxi) where Ri, R₂ and R₃ are as referred to above, for example bathophen shown in fig. 3 of the drawings in which R is as above or

(XXII) (XXIII) where Ri, R₂ and R₃ are as referred to above.

L_p can also be

Ph Ph Ph Ph

N- 0^: N- O

Ph Ph or Ph Ph

(XXIV) (XXV) where Ph is as above.

Other examples of L_p chelates are as shown in figs. 4 and fluorene and fluorene derivatives e.g. a shown in figs. 5 and compounds of formulae as shown as shown in figs. 6 to 8.

Specific examples of Lα and Lp are tripyridyl and TMHD, and TMHD complexes, α, α , α" tripyridyl, crown ethers, cyclans, cryptans phthalocyanans, porphoryins ethylene diamine tetramine (EDTA), DCTA, DTP A and TTHA. Where TMHD is 2,2,6,6-tetramethyl-3,5-heptanedionato and OPNP is diphenylphosphonimide triphenyl phosphorane. The formulae of the polyamines are shown in fig. 9.

Other fluorescent materials which can be used include metal quinolates such as lithium quinolate, and non rare earth metal complexes such as aluminium, magnesium, zinc and scandium complexes such as complexes of β-diketones e.g. Tris -(l,3-diphenyl-l-3-propanedione) (DBM) and suitable metal complexes are A1(DBM)₃, Zn(DBM)₂ and Mg(DBM)_2„ Sc(DBM)₃ etc.

Other fluorescent materials which can be used include the metal complexes of formula

(XXVI)

where M is a metal other than a rare earth, a transition metal, a lanthanide or an actinide; n is the valency of M; Ri, R₂ and R₃ which may be the same or different are selected from hydrogen, hydrocarbyl groups, substituted and unsubstituted aliphatic groups substituted and unsubstituted aromatic, heterocyclic and polycyclic ring structures, fluorocarbons such as trifluoryl methyl groups, halogens such as fluorine or thiophenyl groups or nitrile; Rι_; and R can also be form ring structures and R_l5 R₂ and R₃ can be copolymerisable with a monomer e.g. styrene. Preferably M is aluminium and R₃ is a phenyl or substituted phenyl group.

In order to improve the performance of the electroluminescent layer there can be a hole transporting layer between the anode and the electroluminescent layer and an electron transmitting layer between the cathode and the electroluminescent layer. Hole transporting materials and electron transmitting materials are well known and are described in WO 03/006573 the contents of which are incorporated herein by reference.

The electroluminescent material operates generally at a voltage of about 5 to 15 volts and for a 1cm square screen will take a current of only a few milliamps and generate substantially no heat. This makes devices based on the structure of the present invention very useful in a wide variety of applications.

In use a signal is received and an image produced on the VLSI and a current is simultaneously passed through the electroluminescent layer so that the image is back lit and easy to see. Alternatively the current to the electroluminescent layer is independently controlled.

One use is in connection with mobile telephones. In mobile telephones there is a screen which forms part of the telephone on which message and images are displayed; this screen uses liquid crystals. As mobile telephones are compact and occupy a small space, the screen must also be small. Mobile telephones are powered by re-chargeable batteries which have a limited capacity and are expensive so that a useful life per charge is only possible if low current is drawn from the battery. The display of visual images takes a relatively large amount of power and in practice this limits the type of display which is possible. For example the display is normally black on a lighter background and consists of words which can be difficult to read in bright light.

The device can be integrated with an apparatus such as a portable radio-telephone; the device can constitute a detachable plug-in assembly provided with devices for connection to an apparatus such as a radio-telephone or the device is associated with a spectacle frame, with one for each eye in a symmetrical and axial but not central arrangement or the device is associated with a mini-projector with a screen having a decimetric surface area.

With the advent of WAP, more information will become available to mobile telephone users and there will be a need for better and brighter displays. The display of the present invention is particularly useful for use with mobile phones as it is compact, has low power consumption and can give bright displays and display a lot of data or images. It is possible to obtain images with a high definition and brightness so that the image can be magnified to a larger size; in this way a mobile telephone can be a practical way of accessing the World Wide Web and displaying complex images.

The invention is illustrated in the accompanying drawings in which :-

Fig. 10 shows a device incorporating a structure according to the invention and Fig. 11 shows a mobile telephone using the device.

Referring to fig. 10 the structure comprises a first layer (1) which is a VLSI formed on a transparent silicon wafer substrate; next to the layer (1) is a collimator (2) which is a diffraction grating and next to layer (2) is a film of an electroluminescent layer. The layers are encapsulated in an inert transparent plastic coating (4).

In use a signal is received by the VLSI to be displayed on (1) in the conventional way; a current is passed through the layer (3) which backlights the image so that it is displayed.

Referring to fig. 11 a mobile telephone (10) is connected to a screen according to the invention (11) which has associated hardware and software attached to it at (14) and a mouse or other keyboard device (12). In use information received by the telephone can be passed to the screen (11) which is controlled by the hardware/software of (14) so that it is displayed on the screen. The mouse or other device (12) is also controlled by (14) so that the arrangement can function as a portable computer etc. The use of the screen of the invention with its low power requirements and good visual display enables the mobile telephone to be used to receive, display and manipulate data in a way not possible with the screens incorporated in mobile telephones.

Claims

1. A structure comprising sequentially :-

(i) an electroluminescent layer

(ii) a collimator (iii) a transparent electro-optic substrate on which there is an integrated circuit.

2. A structure as claimed in claim 1 in which the transparent substrate is a transparent silicon wafer.

3. A structure as claimed in claim 1 or 2 in which the collimator is a diffraction grating which collimates the light so that the light is focused onto the integrated circuit.

4. A structure as claimed in claim 1, 2 or 3 in which the integrated circuit is a VLSI.

5. A structure as claimed in any one of claims 1 to 4 in which the electroluminescent layer is an electroluminescent material of general formula

where Lα and Lp are organic ligands, M is a rare earth, transition metal, lanthanide or an actinide as specified herein and n is the valence state of the metal M; the ligands Lα can be the same or different and there can be a plurality of ligands Lp which can be the same or different.

6. A structure as claimed in any one of the preceding claims in which the electroluminescent layer is an electroluminescent material of general formula (Lα)_nM₁M₂ where Mi is the same as M above, M is a non rare earth metal, Lα is as specified herein and n is the combined valence state of Mi and M₂.

7. A structure as claimed claim 6 in which the complex also comprises one or more neutral ligands Lp and the complex has the general formula (Lα)_nMιM₂ (Lp).

8. A structure as claimed in claims 5, 6 or 7 in which Lα and Lp are selected from compounds of formula (I) to (XXVI) herein.

9. A structure as claimed in any one of claims 1 to 4 in which the electroluminescent layer is an electroluminescent material selected from binuclear, trinclear and polynuclear organometallic complexes of formula

( Lm )_X M, ^L M₂ (_Ln ),

where L is a bridging ligand and where Mi is a rare earth metal and M₂ is Mi or a non rare earth metal, Lm and Ln are the same or different organic ligands Lα as defined above, x is the valence state of Mi and y is the valence state of M₂ or

(Lm)_xM M- (Ln )_y— M₂ ( _Lp )_z

or

where M-i, M₂ and M₃ are the same or different rare earth metals and Lm, Ln and Lp are organic ligands Lα and x is the valence state of M-i, y is the valence state of M2 and z is the valence state of M₃ and Lp can be the same as Lm and Ln or different or

^-L- _^

(l_m)_xM M, (Ln )_y ^M ₂ ( Lp )_z

N/ A

or

where L is a bridging ligand and in which the rare earth metals and the non rare earth metals can be joined together by a metal to metal bond and/or via an intermediate bridging atom, ligand or molecular group or in which there are more than three metals joined by metal to metal bonds and/or via intermediate ligands.

10. A structure as claimed in any one of claims 6 to 9 in which the metal M₂ is any metal which is not a rare earth, transition metal, lanthanide or an actinide.

11. A structure as claimed in any one of claims 6 to 9 in which the metal M₂ is selected from lithium, sodium, potassium, rubidium, caesium, beryllium, magnesium, calcium, strontium, barium, copper (I), copper (II), silver, gold, zinc, cadmium, boron, aluminium, gallium, indium, germanium, tin (II), tin (IV), antimony (II), antimony (IV), lead (II), lead (IV) and metals of the first, second and third groups of transition metals in different valence states e.g. manganese, iron, ruthenium, osmium, cobalt, nickel, palladium(II), palladium(ιV), platinum(II), platinum(ιV), cadmium, chromium, titanium, vanadium, zirconium, tantulum, molybdenum, rhodium, iridium, titanium, niobium, scandium and yttrium.

12. A structure as claimed in any one of the preceding claims in which the integrated circuit is connected to a circuit which generates an image to be viewed.

13. A structure as claimed in claim 12 in which the signal is generated via an electromagnetic signal or via a wire.

14. A structure as claimed in claim 12 or 13 in which the electro-optic substrate, on which there is an integrated circuit or NLSI, is transparent and is back lit by the electroluminescent layer.

15. A structure as claimed in any one of the preceding claims which is encapsulated in an inert plastic or glass.

16. A structure as claimed in any one of the preceding claims attached to a mobile telephone receiver.

17. A structure as claimed in any one of the preceding claims associated with a spectacle frame, with one structure for each eye in a symmetrical and axial but not central arrangement.

18 A structure as claimed in any one of the preceding claims associated with a mini- projector with a screen having a decimetric surface area.