Patent Application
20060214556
1. Field of the Invention
The present invention relates to a light source (including a planar light source) comprising electron emitters each for emitting electrons from an emitter by applying a drive voltage to electrodes on the emitter.
2. Description of the Related Art
Recently, electron emitters having a drive electrode and a common electrode have been finding use in various applications such as field emission displays (FEDs) and backlight units. In an FED, a plurality of electron emitters are arranged in a two-dimensional array, and a plurality of phosphors are positioned in association with the respective electron emitters with a predetermined gap left therebetween.
Conventional electron emitters are disclosed in Japanese Laid-Open Patent Publication No. 1-311533, Japanese Laid-Open Patent Publication No. 7-147131, Japanese Laid-Open Patent Publication No. 2000-285801, Japanese Patent Publication No. 46-20944, and Japanese Patent Publication No. 44-26125, for example. All of these disclosed electron emitters are disadvantageous in that since no dielectric body is employed in the emitter, a forming process or a micromachining process is required between facing electrodes, a high voltage needs to be applied to emit electrons, and a panel fabrication process is complex and entails a high panel fabrication cost.
It has been considered to make an emitter of a dielectric material. Various theories about the emission of electrons from a dielectric material have been presented in the documents: Yasuoka and Ishii, “Pulsed Electron Source Using a Ferroelectric Cathode”, OYO BUTURI (A monthly publication of The Japan Society of Applied Physics), Vol. 68, No. 5, p. 546-550 (1999), and Puchkarev, Victor F. and Mesyats, Gannady A., “On the Mechanism of Emission from the Ferroelectric Ceramic Cathode, Journal of Applied Physics, Vol. 78, No. 9, 1 Nov., 1995, p. 5633-5637.
The development of light sources employing carbon nanowalls has also been promoted lately (see, for example, Japanese Laid-Open Patent Publication No. 2004-362960 and Japanese Laid-Open Patent Publication No. 2004-362959).
It is an object of the present invention to provide a light source comprising electron emitters for increasing the rate of utilization of phosphorescent light emission based on electrons emitted from the electron emitters to achieve high-luminance light emission.
A light source according to the present invention has a transparent substrate, a fixed substrate disposed in facing relation to the transparent substrate, at least one electron emitter disposed on the fixed substrate, a phosphor layer disposed on a surface of the transparent substrate which confronts the fixed substrate, a metal back layer disposed on a surface of the phosphor layer which confronts the fixed substrate, and a spreading electrode disposed on a portion of the fixed electrode which is free of the electron emitter. An electron flow emitted from the electron emitter is spread by an electric field generated by a voltage signal which is applied to the spreading electrode to reduce a surface density of the electron flow applied to the metal back layer to a peak value of at most 50 μA/cm2.
With the above arrangement, the phosphor layer is prevented from being saturated by an excessive amount of electrons impinging locally thereupon. The phosphor layer is capable of emitting phosphorescent light through an increased area for a spread uniform surface emission.
Another light source according to the present invention has a transparent substrate, a fixed substrate disposed in facing relation to the transparent substrate, at least one electron emitter disposed on the transparent substrate, a light reflecting film disposed on a surface of the fixed substrate which confronts the transparent substrate, a phosphor layer disposed on a surface of the light reflecting film which confronts the transparent substrate, and a spreading electrode disposed on a portion of the transparent electrode which is free of the electron emitter. An electron flow emitted from the electron emitter is spread by an electric field generated by a voltage signal which is applied to the spreading electrode to reduce a surface density of the electron flow applied to the phosphor layer to a peak value of at most 50 μA/cm2.
With the above arrangement, the phosphor layer is prevented from being saturated by an excessive amount of electrons impinging locally thereupon. The phosphor layer is capable of emitting phosphorescent light from its irradiated surface highly efficiently through an increased area for a spread uniform surface emission.
Still another light source according to the present invention has a transparent substrate, a fixed substrate disposed in facing relation to the transparent substrate, at least one electron emitter disposed on the fixed substrate, a phosphor layer disposed on a surface of the transparent substrate which confronts the fixed substrate, a metal back layer disposed on a surface of the phosphor layer which confronts the fixed substrate, and a spreading electrode disposed on a portion of the fixed electrode which is free of the electron emitter. The electron emitter emits an electron flow intermittently, and a pulsed electron flow (an electron flow pulse) emitted from the electron emitter is spread by an electric field generated by a voltage signal which is applied to the spreading electrode to reduce a surface density of the pulsed electron flow applied to the metal back layer to a peak value of at most 50 μA/cm2.
Yet another light source according to the present invention has a transparent substrate, a fixed substrate disposed in facing relation to the transparent substrate, at least one electron emitter disposed on the fixed substrate, a phosphor layer disposed on a surface of the transparent substrate which confronts the fixed substrate, a metal back layer disposed on a surface of the phosphor layer which confronts the fixed substrate, and a spreading electrode disposed on a portion of the fixed electrode which is free of the electron emitter. The electron emitter emits an electron flow intermittently, electron flow pulses emitted from the electron emitter are spread by an electric field generated by a voltage signal which is applied to the spreading electrode, and each of the electron flow pulses which are applied to the metal back layer has an amount of electrons of at most 1 nC/cm2.
With the above arrangement, the phosphor layer is prevented from being saturated by an excessive amount of electrons impinging locally thereupon. The phosphor layer is capable of emitting phosphorescent light through an increased area for a spread uniform surface emission. Because the pulsed electron flow is intermittently emitted at certain time intervals, the phosphor layer keeps its persistent phosphor emission even during periods in which the pulsed electron flow is not emitted, and the light source can emit light highly efficiently.
Yet still another light source according to the present invention has a transparent substrate, a fixed substrate disposed in facing relation to the transparent substrate, at least one electron emitter disposed on the transparent substrate, a light reflecting film disposed on a surface of the fixed substrate which confronts the transparent substrate, a phosphor layer disposed on a surface of the light reflecting film which confronts the transparent substrate, and a spreading electrode disposed on a portion of the transparent electrode which is free of the electron emitter. The electron emitter emits an electron flow intermittently, and a pulsed electron flow emitted from the electron emitter is spread by an electric field generated by a voltage signal which is applied to the spreading electrode to reduce a surface density of the pulsed electron flow applied to the phosphor layer to a peak value of at most 50 μA/cm2.
A further light source according to the present invention has a transparent substrate, a fixed substrate disposed in facing relation to the transparent substrate, at least one electron emitter disposed on the transparent substrate, a light reflecting film disposed on a surface of the fixed substrate which confronts the transparent substrate, a phosphor layer disposed on a surface of the light reflecting film which confronts the transparent substrate, and a spreading electrode disposed on a portion of the transparent electrode which is free of the electron emitter. The electron emitter emits an electron flow intermittently, electron flow pulses emitted from the electron emitter are spread by an electric field generated by a voltage signal which is applied to the spreading electrode, and each of the electron flow pulses which are applied to the phosphor layer has an amount of electrons of at most 1 nC/cm2.
With the above arrangement, the phosphor layer is prevented from being saturated by an excessive amount of electrons impinging locally thereupon. The phosphor layer is capable of emitting phosphorescent light through an increased area for a spread uniform surface emission. Because the pulsed electron flow is intermittently emitted at certain time intervals, the phosphor layer keeps its persistent phosphor emission even during periods in which the pulsed electron flow is not emitted, the light source can emit light highly efficiently.
A still further light source according to the present invention has a transparent substrate, a fixed substrate disposed in facing relation to the transparent substrate, at least two electron emitters disposed on the fixed substrate, a phosphor layer disposed on a surface of the transparent substrate which confronts the fixed substrate, a metal back layer disposed on a surface of the phosphor layer which confronts the fixed substrate, and a spreading electrode disposed on a portion of the fixed electrode which is free of the electron emitters. The electron emitters emit electron flows intermittently, pulsed electron flows emitted from the electron emitters are spread by an electric field generated by a voltage signal which is applied to the spreading electrode to reduce a surface density of the pulsed electron flow applied to the metal back layer to a peak value of at most 50 μA/cm2, and the pulsed electron flows emitted from the electron emitters irradiate the same area of the metal back layer and are emitted at different times from the electron emitters.
A yet further light source according to the present invention has a transparent substrate, a fixed substrate disposed in facing relation to the transparent substrate, at least two electron emitters disposed on the fixed substrate, a phosphor layer disposed on a surface of the transparent substrate which confronts the fixed substrate, a metal back layer disposed on a surface of the phosphor layer which confronts the fixed substrate, and a spreading electrode disposed on a portion of the fixed electrode which is free of the electron emitters. The electron emitter emits an electron flow intermittently, electron flow pulses emitted from the electron emitter are spread by an electric field generated by a voltage signal which is applied to the spreading electrode, each of the electron flow pulses which are applied to the metal back layer has an amount of electrons of at most 1 nC/cm2, and the electron flow pulses emitted from the electron emitters irradiate the same area of the metal back layer and are emitted at different times from the electron emitters.
With the above arrangement, the phosphor layer is prevented from being saturated by an excessive amount of electrons impinging locally thereupon. The phosphor layer is capable of emitting phosphorescent light through an increased area for a spread uniform surface emission. Since electron flow pulses having small peak values are emitted at different times from the electron emitters, the phosphor layer is prevented from being saturated and an electron flow required for phosphor emission is maintained for higher emission efficiency and higher luminance.
Still another light source according to the present invention has a transparent substrate, a fixed substrate disposed in facing relation to the transparent substrate, at least two electron emitters disposed on the transparent substrate, a light reflecting film disposed on a surface of the fixed substrate which confronts the transparent substrate, a phosphor layer disposed on a surface of the light reflecting film which confronts the transparent substrate, and a spreading electrode disposed on a portion of the transparent electrode which is free of the electron emitters. The electron emitters emit electron flows intermittently, pulsed electron flows emitted from the electron emitters are spread by an electric field generated by a voltage signal which is applied to the spreading electrode to reduce a surface density of the pulsed electron flow applied to the phosphor layer to a peak value of at most 50 μA/cm2, and the pulsed electron flows emitted from the electron emitters irradiate the same area of the phosphor layer and are emitted at different times from the electron emitters.
Yet another light source according to the present invention has a transparent substrate, a fixed substrate disposed in facing relation to the transparent substrate, at least two electron emitters disposed on the transparent substrate, a light reflecting film disposed on a surface of the fixed substrate which confronts the transparent substrate, a phosphor layer disposed on a surface of the light reflecting film which confronts the transparent substrate, and a spreading electrode disposed on a portion of the transparent electrode which is free of the electron emitters. The electron emitter emits an electron flow intermittently, electron flow pulses emitted from the electron emitter are spread by an electric field generated by a voltage signal which is applied to the spreading electrode, each of the electron flow pulses which are applied to the phosphor layer has an amount of electrons of at most 1 nC/cm2, and the electron flow pulses emitted from the electron emitters irradiate the same area of the phosphor layer and are emitted at different times from the electron emitters.
With the above arrangement, the phosphor layer is prevented from being saturated by an excessive amount of electrons impinging locally thereupon. The phosphor layer is capable of emitting phosphorescent light through an increased area for a spread uniform surface emission. Since electron flow pulses having small peak values are emitted at different times from the electron emitters, the phosphor layer is prevented from being saturated and an electron flow required for phosphor emission is maintained for higher emission efficiency and higher luminance.
Yet still another light source according to the present invention has a transparent substrate, a fixed substrate disposed in facing relation to the transparent substrate, at least one electron emitter disposed on the fixed substrate, a phosphor layer disposed on a surface of the transparent substrate which confronts the fixed substrate, and a trajectory deflector for deflecting the trajectory of a pulsed electron flow intermittently emitted from the electron emitter. The trajectory of the pulsed electron flow is deflected by the trajectory deflector to two-dimensionally scan a position of the phosphor layer which is irradiated with the pulsed electron flow for thereby spreading the pulsed electron flow. The light source is capable of emitting light highly efficiently based on the persistent light emission of the phosphor layer.
The trajectory deflector may comprise a plurality of spreading electrodes disposed around the electron emitter and the trajectory of the pulsed electron flow emitted from the electron emitter may be deflected with an electric field generated by voltage signals which are applied respectively to the spreading electrodes. The electron flow which tends to travel straight can be spread more than if the electron flow is spread under an electrostatic field, allowing the light source to emit light highly efficiently based on the persistent light emission of the phosphor layer.
The trajectory deflector may comprise a magnetic field generator and the trajectory of the pulsed electron flow emitted from the electron emitter may be deflected with a magnetic field generated by the magnetic field generator.
With the above arrangement, since the light source does not require a high voltage for deflecting the electron flow, the light source may have a less costly control circuit. Furthermore, the light source is capable of emitting light highly efficiently based on the persistent light emission of the phosphor layer.
The trajectory deflector may comprise a plurality of spreading electrodes disposed around the electron emitter and the magnetic field generator, and the trajectory of the pulsed electron flow emitted from the electron emitter may be deflected with an electric field generated by voltage signals which are applied respectively to the spreading electrodes and a magnetic field generated by the magnetic field generator.
With the above arrangement, since the light source does not require a high voltage for deflecting the electron flow, the light source may have a less costly control circuit. Furthermore, the light source is capable of emitting light highly efficiently based on the persistent light emission of the phosphor layer. It is also possible to increase the ratio at which the electron flow is spread, more than if the electron flow is deflected under an electric field or a magnetic field only.
If the pulsed electron flow emitted from the electron emitter has a level which changes with time in a single electron emission period, then the trajectory deflector may control a deflecting speed of the pulsed electron flow depending on the level of the pulsed electron flow to make constant an amount of electrons applied to the phosphor layer by the deflected pulsed electron flow when the trajectory deflector deflects the pulsed electron flow emitted from the electron emitter in a single electron emission period.
Consequently, it is possible to produce uniform phosphorescent light emission in a wide area. When an electron flow having a higher level is deflected, the same area of the phosphor layer is irradiated with the electron flow in a shorter period of time. When an electron flow having a lower level is deflected, the same area of the phosphor layer is irradiated with the electron flow in a longer period of time. In this manner, the amount of electrons applied to the same area of the phosphor layer is uniformized.
The trajectory deflector may have an electrode film disposed on a substrate on which the electron emitter is mounted, for applying an electric field, and/or a coil pattern disposed on the substrate on which the electron emitter is mounted, for generating a magnetic field. Alternatively, the trajectory deflector may have an electrode film disposed on the fixed substrate for applying an electric field and/or a coil pattern disposed on the fixed substrate for generating a magnetic field. For deflecting the trajectory of the electron flow, the trajectory deflector and the electron emitter need to be positioned highly accurately with respect to each other. If the electrode films and/or the coil pattern is formed on the fixed substrate based on the same reference positions by screen printing, for example, the electrode films and/or the coil pattern can be positioned highly accurately with respect to the electron emitter inexpensively and highly accurately.
The trajectory deflector may have an electrode film disposed on the fixed substrate for applying an electric field and/or a coil pattern disposed on the fixed substrate for generating a magnetic field, and the electron emitter may be mounted on the fixed substrate using the electrode film and/or the coil pattern as an alignment mark. For deflecting the trajectory of the electron flow, the trajectory deflector and the electron emitter need to be positioned highly accurately with respect to each other. If the electron emitter is mounted using the electrode film and/or the coil pattern as a positional reference, then the electrode film and/or the coil pattern can be positioned highly accurately with respect to the electron emitter inexpensively and highly accurately.
A further light source according to the present invention has a transparent substrate, a fixed substrate disposed in facing relation to the transparent substrate, a plurality of electron emitters disposed on the fixed substrate in the longitudinal direction along a plurality of columns, a phosphor layer disposed on a surface of the transparent substrate which confronts the fixed substrate, and a plurality of spreading electrodes disposed above the fixed substrate in the longitudinal direction along columns adjacent to the columns where the electron emitters are disposed on the fixed substrate. Electron flows emitted from the electron emitters are spread in the transverse direction by an electric field generated by a voltage signal which is applied to the spreading electrodes.
With the above arrangement, the phosphor layer is prevented from being saturated by an excessive amount of electrons impinging locally thereupon. The phosphor layer is capable of emitting phosphorescent light through an increased area for a spread uniform surface emission.
In the above arrangement, the voltage signal applied to the spreading electrodes may have a voltage level of 0 V. This is advantageous in lowering the cost and the height of the light source. Incidentally, the voltage signal applied to the spreading electrodes may have a voltage level of 100 V or less.
In the above arrangement, the spreading electrode may comprise a mesh electrode having a large number of openings, and the electron flows emitted from the electron emitters pass through the openings of the mesh electrode and are spread by an electric field generated by a voltage signal which is applied to the mesh electrode.
The mesh electrode may be rectangular in shape and disposed above the electron emitters. Since this requires only mounting the mesh electrode above the electron emitters, not require the highly accurate positioning, it is advantageous in simplifying the mounting work and reducing the cost of manufacturing.
The spreading electrode may comprise the rectangular mesh electrode which is rounded into a half-cylindrical shape, and may be disposed to cover the electron emitters. With this arrangement, the spreading electrode can easily be positioned with respect to the electron emitters, and the electron flows can substantially symmetrically be spread in the transverse direction. This is advantageous for a spread uniform surface emission.
A still further light source according to the present invention has a transparent substrate, a fixed substrate disposed in facing relation to the transparent substrate, at least one electron emitter disposed on the fixed substrate, a phosphor layer, and a spreading electrode, the transparent substrate having the phosphor layer and the spreading electrode. The transparent substrate comprises an upper plate facing the fixed substrate and at least two side plates interposed between the upper plate and the fixed substrate and is fixedly disposed to cover the electron emitter on the fixed substrate. The transparent substrate has a laminated assembly of the phosphor layer and the spreading electrode formed on internal surfaces of the upper plate and at least two of the side plates. An electron flow emitted from the electron emitter is spread by an electrical field generated by a voltage signal applied to the spreading electrode.
A yet further light source according to the present invention has a large fixed substrate, at least one light emitting tube disposed on the large fixed substrate, and a light reflecting film formed on a portion of the large fixed substrate which is free of the light emitting tube. The light emitting tube has a housing having a transparent substrate and a fixed substrate disposed in facing relation to the transparent substrate, at least one electron emitter disposed on the fixed substrate in the housing, a phosphor layer, and a spreading electrode, the transparent substrate having the phosphor layer and the spreading electrode. The transparent substrate comprises an upper plate facing the fixed substrate, and at least two side plates interposed between the upper plate and the fixed substrate. The transparent substrate is fixedly disposed to cover the electron emitter on the fixed substrate. The transparent substrate has a laminated assembly of the phosphor layer and the spreading electrode on internal surfaces of the upper plate and at least the two side plates. An electron flow emitted from the electron emitter is spread by an electric field generated by a voltage signal applied to the spreading electrode. In this arrangement, the light reflecting film may be formed on lower portions of the two side plates of an outer surface of the housing.
With this arrangement, light emits from the upper plate and the two side plates of each light emitting tube ahead of the light source. Light emits from the two side plates toward the large fixed substrate, and the light is reflected by the light reflecting layers to travel ahead of the light source. As a result, a spread uniform surface emission and a high-luminance light emission can be achieved, thereby easily manufacturing a structure for a spread uniform surface emission.
Additionally, since this does not require mounting a large transparent substrate facing the large fixed substrate and spacers (for supporting the large transparent substrate), reduction in weight, thickness and cost of the light source can be achieved.
In the above arrangement, the transparent substrate may have the phosphor layer formed on internal surfaces of the upper plate and at least two of the side plates, and the spreading electrode functioning as a metal back layer may be formed on the phosphor layer. Or the spreading electrode may have a transparent electrode, the transparent substrate may have the spreading electrode formed on internal surfaces of the upper plate and at least two of the side plates, and the phosphor layer may be formed on the spreading electrode.
Since the metal back layer or the transparent electrode also functions as the spreading electrode, simplified interconnects can be achieved.
With the above arrangement, a light spreading plate may be disposed on a surface of the transparent substrate opposite to the fixed substrate. As a result, the number of the disposed electron emitters on the fixed substrate can be significantly reduced, thereby reducing power consumption.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are shown by way of illustrative example.
Light sources according to embodiments of the present invention will be described below with reference to
As shown in
One electron emitter 12 may be assigned to each pixel, or a plurality of electron emitters 12 may be assigned to each pixel. In the present embodiment, it is assumed for the sake of brevity that one electron emitter 12 is assigned to each pixel.
The drive circuit 16 has a plurality of row selection lines 18 for selecting rows in the light emission section 14 and a plurality of signal lines 20 for supplying data signals Sd to the light emission section 14.
The drive circuit 16 also has a row selecting circuit 22 for supplying a selection signal Ss selectively to the row selection lines 18 to successively select a row of the electron emitters 12, a signal supplying circuit 24 for supplying parallel data signals Sd to the signal lines 20 to supply the data signals Sd to a row (selected row) selected by the row selecting circuit 22, and a signal control circuit 26 for controlling the row selecting circuit 22 and the signal supplying circuit 24 based on a control signal Sv (video signal or the like) and a synchronizing signal Sc that are input to the signal control circuit 26.
The electron emitters 12 in the light source 10 according to the present embodiment will be described below with reference to
As shown in
A drive voltage Va from the drive circuit 16 is applied between the upper electrode 32 and the lower electrode 34.
As shown in
The electron emitters 12 are placed in a vacuum. The vacuum level in the atmosphere should preferably in the range from 102 to 10−6 Pa and more preferably in the range from 10−3 to 10−5 Pa.
The reason for the above range is that in a lower vacuum, (1) many gas molecules would be present in the space, and a plasma can easily be generated and, if too intensive plasma were generated, many positive ions thereof would impinge upon the upper electrode 32 and damage the same, and (2) emitted electrons would tend to impinge upon gas molecules prior to arrival at the anode electrode 42, failing to sufficiently excite the phosphor layer 44 with electrons that are sufficiently accelerated under the bias voltage Vc.
In a higher vacuum, structural body supports and vacuum seals would be large in size, posing disadvantages on efforts to make the electron emitter smaller in size.
As shown in
As shown in
With the electron emitter 12, the upper electrode 32 has a thickness tc in the range of 0.01 μm≦tc≦10 μm, and the maximum angle θ between the upper surface of the emitter 30, i.e., the surface of the convexity 58 (which is also the inner wall surface of the concavity 52) of the grain boundary of the dielectric material, and the lower surface 54a of the overhanging portion 54 of the upper electrode 32 is in the range of 1°≦θ≦60°. The maximum distance d in the vertical direction between the surface of the convexity 58 (the inner wall surface of the concavity 52) of the grain boundary of the dielectric material of the emitter 30 and the lower surface 54a of the overhanging portion 54 of the upper electrode 32 is in the range of 0 μm≦d≦10 μm.
In the electron emitter 12, the shape of the through region 48, particularly the shape as seen from above, as shown in
The hole 60 has an average diameter ranging from 0.1 μm to 10 μm. The average diameter represents the average of the lengths of a plurality of different line segments passing through the center of the hole 60. If the through regions 48 are reduced in size by adjusting the material and/or sintering conditions of the upper electrode 32, then the average diameter of the hole 60 may be in the range from 0.05 μm to 0.1 μm. If the through regions 48 are reduced in size and highly integrated, then the amount of emitted electrons (the level of an electron flow) and the electron emission efficiency are increased.
The emitter 30 is made of a dielectric material. The dielectric material may preferably be a dielectric material having a relatively high dielectric constant, e.g., a dielectric constant of 1000 or higher. Dielectric materials of such a nature may be ceramics including barium titanate, lead zirconate, lead magnesium niobate, lead nickel niobate, lead zinc niobate, lead manganese niobate, lead magnesium tantalate, lead nickel tantalate, lead antimony stannate, lead titanate, lead magnesium tungstate, lead cobalt niobate, etc. or a combination of any of these materials, a material which chiefly contains 50 weight % or more of any of these materials, or such ceramics to which there is added an oxide of such as lanthanum, calcium, strontium, molybdenum, tungsten, barium, niobium, zinc, nickel, manganese, or the like, or a combination of these materials, or any of other compounds.
For example, a two-component material nPMN-mPT (n, m represent molar ratios) of lead magnesium niobate (PMN) and lead titanate (PT) has its Curie point lowered for a larger specific dielectric constant at room temperature if the molar ratio of PMN is increased.
Particularly, a dielectric material where n=0.85-1.0 and m=1.0-n is preferable because its specific dielectric constant is 3000 or higher. For example, a dielectric material where n=0.91 and m=0.09 has a specific dielectric constant of 15000 at room temperature, and a dielectric material where n=0.95 and m=0.05 has a specific dielectric constant of 20000 at room temperature.
For increasing the specific dielectric constant of a three-component dielectric material of lead magnesium niobate (PMN), lead titanate (PT), and lead zirconate (PZ), it is preferable to achieve a composition close to a morphotropic phase boundary (MPB) between a tetragonal system and a quasi-cubic system or a tetragonal system and a rhombohedral system, as well as to increase the molar ratio of PMN. For example, a dielectric material where PMN:PT:PZ=0.375:0.375:0.25 has a specific dielectric constant of 5500, and a dielectric material where PMN:PT:PZ=0.5:0.375:0.125 has a specific dielectric constant of 4500, which is particularly preferable. Furthermore, it is preferable to increase the dielectric constant by introducing a metal such as platinum into these dielectric materials within a range to keep them insulative. For example, a dielectric material may be mixed with 20 weight % of platinum.
The emitter 30 may be in the form of a piezoelectric/electrostrictive layer or an anti-ferroelectric layer. If the emitter 30 comprises a piezoelectric/electrostrictive layer, then it may be made of ceramics such as lead zirconate, lead magnesium niobate, lead nickel niobate, lead zinc niobate, lead manganese niobate, lead magnesium tantalate, lead nickel tantalate, lead antimony stannate, lead titanate, barium titanate, lead magnesium tungstate, lead cobalt niobate, or the like, or a combination of any of these materials.
The emitter 30 may be made of chief components including 50 wt % or more of any of the above compounds. Of the above ceramics, the ceramics including lead zirconate is mostly frequently used as a constituent of the piezoelectric/electrostrictive layer of the emitter 30.
If the piezoelectric/electrostrictive layer is made of ceramics, then lanthanum, calcium, strontium, molybdenum, tungsten, barium, niobium, zinc, nickel, manganese, or the like, or a combination of these materials, or any of other compounds may be added to the ceramics. Alternatively, ceramics produced by adding SiO2, CeO2, Pb5Ge3O11, or a combination of any of these compounds to the above ceramics may be used. Specifically, a material produced by adding 0.2 wt % of SiO2, 0.1 wt % of CeO2, or 1 to 2 wt % of Pb5Ge3O11 to a PT-PZ-PMN piezoelectric material is preferable.
For example, the piezoelectric/electrostrictive layer should preferably be made of ceramics including as chief components lead magnesium niobate, lead zirconate, and lead titanate, and also including lanthanum and strontium.
The piezoelectric/electrostrictive layer may be dense or porous. If the piezoelectric/electrostrictive layer is porous, then it should preferably have a porosity of 40% or less.
If the emitter 30 is in the form of an anti-ferroelectric layer, then the anti-ferroelectric layer may be made of lead zirconate as a chief component, lead zirconate and lead tin as chief components, lead zirconate with lanthanum oxide added thereto, or lead zirconate and lead tin as components with lead zirconate or lead niobate added thereto.
The anti-ferroelectric layer may be porous. If the anti-ferroelectric layer is porous, then it should preferably have a porosity of 30% or less.
If the emitter 30 is made of strontium tantalate bismuthate (SrBi2Ta2O9), then its polarization inversion fatigue is small. Materials whose polarization inversion fatigue is small are laminar ferroelectric compounds and expressed by the general formula of (BiO2)2+(Am−1BmO3m+1)2−. Ions of the metal A are Ca2+, Sr2+, Ba2+, Pb2+, Bi3+, La3+, etc., and ions of the metal B are Ti4+, Ta5+, Nb5+, etc. An additive may be added to piezoelectric ceramics of barium titanate, lead zirconate, and PZT to convert them into a semiconductor. In this case, it is possible to provide an irregular electric field distribution in the emitter 30 to concentrate an electric field in the vicinity of the interface with the upper electrode 32 which contributes to the emission of electrons.
The sintering temperature can be lowered by adding glass such as lead borosilicate glass or the like or other compounds of low melting point (e.g., bismuth oxide or the like) to the piezoelectric/electrostrictive/anti-ferroelectric ceramics.
If the emitter 30 is made of piezoelectric/electrostrictive/anti-ferroelectric ceramics, then it may be a sheet-like molded body, a sheet-like laminated body, or either one of such bodies stacked or bonded to another support substrate.
If the emitter 30 is made of a non-lead-based material, then it may be a material having a high melting point or a high evaporation temperature so as to be less liable to be damaged by the impingement of electrons or ions.
The emitter 30 may be made by any of various thick-film forming processes including screen printing, dipping, coating, electrophoresis, aerosol deposition, powder jet deposition (film growth based on high-speed ejection of fine particles under the atmospheric pressure), etc., or any of various thin-film forming processes including an ion beam process, sputtering, vacuum evaporation, ion plating, chemical vapor deposition (CVD), plating, etc. Particularly, it is preferable to form a powdery piezoelectric/electrostrictive material as the emitter 30 and impregnate the emitter 30 thus formed with glass of a low melting point or sol particles. According to this process, it is possible to form a film at a low temperature of 700° C. or lower or 600° C. or lower.
The upper electrode 32 should preferably be made of an organic metal paste which can produce a thin film after being baked. For example, a platinum resinate paste or the like should preferably be used. An oxide electrode for suppressing a polarization inversion fatigue, which is made of ruthenium oxide (RuO2), iridium oxide (IrO2), strontium ruthenate (SrRuO3), La1−xSrxCoO3 (e.g., x=0.3 or 0.5), La1−xCaxMnO3 (e.g., x=0.2), La1−xCaxMn1−yCoyO3 (e.g., x=0.2, y=0.05), or a mixture of any one of these compounds and a platinum resinate paste, for example, is preferable. A mixture of a platinum resinate paste and a gold resinate paste or an iridium resinate paste is also preferable as it allows small through regions 48 to be easily formed.
As shown in
The upper electrode 32 may be made of any of the above materials by any of thick-film forming processes including screen printing, spray coating, coating, dipping, electrophoresis, etc., or any of various thin-film forming processes including sputtering, an ion beam process, vacuum evaporation, ion plating, chemical vapor deposition (CVD), plating, etc. Preferably, the upper electrode 32 is made by any of the above thick-film forming processes.
The lower electrode 34 is made of an electrically conductive material, e.g., a metal such as platinum, molybdenum, tungsten, or the like. Alternatively, the lower electrode 34 is made of an electric conductor which is resistant to a high-temperature oxidizing atmosphere, e.g., a metal, an alloy, a mixture of insulative ceramics and a metal, a mixture of insulative ceramics and an alloy, or the like. Preferably, the lower electrode 34 should be made of a precious metal having a high melting point such as platinum, iridium, palladium, rhodium, molybdenum, or the like, or a material chiefly composed of an alloy of silver and palladium, silver and platinum, platinum and palladium, or the like, or a cermet of platinum and ceramics. Further preferably, the lower electrode 34 should be made of platinum only or a material chiefly composed of a platinum-base alloy.
The lower electrode 34 may be made of carbon or a graphite-base material. Ceramics to be added to the electrode material should preferably have a proportion ranging from 5 to 30 volume %. The lower electrode 34 may be made of the same material as the upper electrode 32, as described above.
The lower electrode 34 should preferably be formed by any of the various thick-film forming processes described above. The lower electrode 34 has a thickness of 20 μm or less or preferably a thickness of 5 μm or less.
Each time the emitter 30, the upper electrode 32, or the lower electrode 34 is formed, the assembly is heated (sintered) into an integral structure.
The sintering process for integrally combining the emitter 30, the upper electrode 32, and the lower electrode 34 may be carried out at a temperature ranging from 500 to 1400° C., preferably from 1000 to 1400° C. For heating the emitter 30 which is in the form of a film, the emitter 30 should be sintered together with its evaporation source while their atmosphere is being controlled so that the composition of the emitter 30 will not become unstable at high temperatures.
By performing the sintering process, the film which will serve as the upper electrode 32 is shrunk from the thickness of 10 μm to the thickness of 0.1 μm, and simultaneously a plurality of holes are formed therein. As a result, as shown in
The emitter 30 may be covered with a suitable member, and then sintered such that the surface of the emitter 30 will not be exposed directly to the sintering atmosphere.
The principles of electron emission of the electron emitter 12 will be described below. First, a drive voltage Va is applied between the upper electrode 32 and the lower electrode 34. The drive voltage Va is defined as a voltage, such as a pulse voltage or an alternating-current voltage, which abruptly changes with time from a voltage level that is higher or lower than a reference voltage (e.g., 0 V) to a voltage level that is lower or higher than the reference voltage.
A triple junction is formed in a region of contact between the upper surface of the emitter 30, the upper electrode 32, and a medium (e.g., a vacuum) around the electron emitter 12. The triple junction is defined as an electric field concentration region formed by a contact between the upper electrode 32, the emitter 30, and the vacuum. The triple junction includes a triple point where the upper electrode 32, the emitter 30, and the vacuum exist as one point. The vacuum level in the atmosphere should preferably be in the range from 102 to 10−6 Pa and more preferably in the range from 10−3 to 10−5 Pa.
With the electron emitter 12, the triple junction is formed on the overhanging portion 54 of the upper electrode 32 and the peripheral area of the upper electrode 32. Therefore, when the above drive voltage Va is applied between the upper electrode 32 and the lower electrode 34, an electric field concentration occurs at the triple junction.
A first electron emission process for the electron emitter 12 will be described below with reference to
In a second output period T2 (second stage), the voltage level of the drive voltage Va abruptly changes, i.e., the voltage V1 higher than the reference voltage is applied to the upper electrode 32, and the voltage V2 lower than the reference voltage is applied to the lower electrode 34. The electrons that have been accumulated in the portions of the emitter 30 which are exposed through the through region 48 of the upper electrode 32 and the regions near the outer peripheral portion of the upper electrode 32 are expelled from the emitter 30 by dipoles (whose negative poles appear on the surface of the emitter 30) in the emitter 30 whose polarization has been inverted in the opposite direction. As shown in
A second electron emission process will be described below. In a first output period T1 (first stage) shown in
The electron emitter 12 offers the following advantages: Since the upper electrode 32 has the plural through regions 48, electrons are uniformly emitted from each of the through regions 48 and the outer peripheral portions of the upper electrode 32. Thus, any variations in the overall electron emission characteristics of the electron emitter 12 are reduced, making it possible to facilitate the control of the electron emission and increase the electron emission efficiency.
Because the gap 56 is formed between the overhanging portion 54 of the upper electrode 32 and the emitter 30, when the drive voltage Va is applied, an electric field concentration tends to be produced in the region of the gap 56. This leads to a higher efficiency of the electron emission, making the drive voltage lower (emitting electrons at a lower voltage level).
As described above, since the upper electrode 32 has the overhanging portion 54 on the peripheral portion of the through region 48, together with the increased electric field concentration in the region of the gap 56, electrons are easily emitted from the overhanging portion 54 of the upper electrode 32. This leads to a larger output and higher efficiency of the electron emission, making the drive voltage Va lower. The light source 10, which has a number of arrayed electron emitters 12, has a higher level of luminance.
According to either the first electron emission process (which emits electrons accumulated in the emitter 30) or the second electron emission process (which emits secondary electrons by forcing primary electrons from the upper electrode 32 into impingement upon the emitter 30), as the overhanging portion 54 of the upper electrode 32 functions as a gate electrode (a control electrode, a focusing electronic lens, or the like), the tendency of the emitted electrons to travel straight can be increased. This is effective in reducing crosstalk if a number of electron emitters 12 are arrayed for use as an electron source of displays.
The electron emitter 12 is capable of easily developing a high electric field concentration, provides many electron emission regions, has a larger output and higher efficiency of the electron emission, and can be driven at a lower voltage (lower power consumption).
In particular, at least the upper surface of the emitter 30 has the uneven pattern 50 of the grain boundary of the dielectric material. As the upper electrode 32 has the through regions 48 in portions corresponding to the concavities 52 of the grain boundary of the dielectric material, the overhanging portions 54 of the upper electrode 32 can easily be realized.
The maximum angle θ between the upper surface of the emitter 30, i.e., the surface of the convexity 58 (which is also the inner wall surface of the concavity 52) of the grain boundary of the dielectric material, and the lower surface 54a of the overhanging portion 54 of the upper electrode 32 is in the range of 1°≦θ≦60°. The maximum distance d in the vertical direction between the surface of the convexity 58 (the inner wall surface of the concavity 52) of the grain boundary of the dielectric material of the emitter 30 and the lower surface 54a of the overhanging portion 54 of the upper electrode 32 is in the range of 0 μm<d≦10 μm. These arrangements make it possible to increase the degree of the electric field concentration in the region of the gap 56, resulting in a larger output and higher efficiency of the electron emission and making the drive voltage lower efficiently.
The through region 48 is in the shape of the hole 60. As shown in
If the upper electrode 32 comprises an alloy electrode chiefly made of a Pt resinate paste and the sintering conditions are adjusted, then the average diameter of the hole 60 may be less than 0.1 μm. Particularly, if the temperature is quickly increased in the sintering process, then it is possible to form holes 60 having an average diameter less than 0.1 μm at a high density. If the average diameter of the hole 60 is in excess of 10 μm, then the proportion (share) of the portion (second portion) 72 which contributes to the emission of electrons in the portion of the emitter 30 that is exposed through the through region 48 is reduced, resulting in a reduction in the electron emission efficiency.
As shown in
Actually, the capacitor C1 due to the emitter 30 is not directly connected in series to the capacitor C2 which comprises the cluster of capacitors Ca, but the capacitive component that is connected in series varies depending on the number of the through regions 48 formed in the upper electrode 32 and the overall area of the through regions 48.
Capacitance calculations will be performed on the assumption that 25% of the capacitor C1 due to the emitter 30 is connected in series to the capacitor C2 which comprises the cluster of capacitors Ca, as shown in
Because the series-connected portion and the remaining portion are connected parallel to each other, the overall capacitance is 27.5 pF. This capacitance is 78% of the capacitance 35.4 pF of the capacitor C1 due to the emitter 30. Therefore, the overall capacitance is smaller than the capacitance of the capacitor C1 due to the emitter 30.
Consequently, the capacitance of the cluster of capacitors Ca due to the gaps 56 is relatively small. Because of the voltage division between the cluster of capacitors Ca and the capacitor C1 due to the emitter 30, almost the entire applied voltage Va is applied across the gaps 56, which are effective to produce a larger output of the electron emission.
Since the capacitor C2 which comprises the cluster of capacitors Ca is connected in series to the capacitor C1 due to the emitter 30, the overall capacitance is smaller than the capacitance of the capacitor C1 due to the emitter 30. This is effective to provide such preferred characteristics that the electron emission is performed for a larger output and the overall power consumption is lower.
Three modifications of the electron emitter 12 will be described below with reference to
As shown in
As shown in
As shown in
The characteristics of the electron emitter 12, particularly, the voltage vs. charge quantity characteristics (the voltage vs. polarization quantity characteristics) thereof will be described below.
The electron emitter 12 is characterized by an asymmetric hysteresis curve based on the reference voltage=0 (V) in vacuum, as indicated by the characteristics shown in
The voltage vs. charge quantity characteristics will be described below. If a region of the emitter 30 from which electrons are emitted is defined as an electron emission region, then at a point p1 (initial state) where the reference voltage is applied, almost no electrons are stored in the electron emission region. Thereafter, when a negative voltage is applied, the amount of positive charges of dipoles whose polarization is inverted in the emitter 30 in the electron emission region increases, and electrons are emitted from the upper electrode 32 toward the electron emission region in the first stage, so that electrons are stored. When the absolute value of the negative voltage increases, electrons are progressively stored in the electron emission region until the amount of positive charges and the amount of electrons are held in equilibrium with each other at a point p2 of the negative voltage. As the absolute value of the negative voltage further increases, the stored amount of electrons increases, making the amount of negative charges greater than the amount of positive charges. The accumulation of electrons is saturated at a point P3. The amount of negative charges is the sum of the amount of electrons remaining to be stored and the amount of negative charges of the dipoles whose polarization is inverted in the emitter 30.
When the absolute value of the negative voltage subsequently decreases, and a positive voltage is applied in excess of the reference voltage, electrons start being emitted at a point p4 in the second stage. When the positive voltage increases in a positive direction, the amount of emitted electrons increases until the amount of positive charges and the amount of electrons are held in equilibrium with each other at a point p5. At a point p6, almost all the stored electrons are emitted, bringing the difference between the amount of positive charges and the amount of negative charges into substantial conformity with a value in the initial state. That is, almost all stored electrons are eliminated, and only the negative charges of dipoles whose polarization is inverted in the emitter 30 appear in the electron emission region.
The voltage vs. charge quantity characteristics have the following features:
(1) If the negative voltage at the point p2 where the amount of positive charges and the amount of electrons are held in equilibrium with each other is represented by V1 and the positive voltage at the point p5 is represented by V2, then these voltages satisfy the following relationship:
|V1|<|V2|
(2) More specifically, the relationship is expressed as
1.5×|V1|<|V2|
(3) If the rate of change of the amount of positive charges and the amount of electrons at the point p2 is represented by ΔQ1/ΔV1 and the rate of change of the amount of positive charges and the amount of electrons at the point p5 by ΔQ2/ΔV2, then these rates satisfy the following relationship:
(ΔQ1/ΔV1)>(ΔQ2/ΔV2)
(4) If the voltage at which the accumulation of electrons is saturated is represented by V3 and the voltage at which electrons start being emitted is represented by V4, then these voltages satisfy the following relationship:
1≦|V4|/|V3|≦1.5
The characteristics shown in
At the point p1 (initial state) where the reference voltage (e.g., 0 V) is applied as shown in
Thereafter, when a negative voltage is applied and the absolute value of the negative voltage is increased, the polarization starts being inverted substantially at the time the negative voltage exceeds a negative coercive voltage (see the point p2 in
Thereafter, when the absolute value of the negative voltage is reduced and a positive voltage is applied in excess of the reference voltage, the upper surface of the emitter 30 is kept charged up to a certain voltage level (see
The characteristics of the electron emitter 12 have the following features:
(A) If the negative coercive voltage is represented by v1 and the positive coercive voltage by v2, then
|v1|<|v2|
(B) More specifically, 1.5×|v1|<|v2|
(C) If the rate of change of the polarization at the time the negative coercive voltage v1 is applied is represented by Δq1/Δv1 and the rate of change of the polarization at the time the positive coercive voltage v2 is applied is represented by Δq2/Δv2, then
(Δq1/Δv1)>(Δq2/Δv2)
(D) If the voltage at which the accumulation of electrons is saturated is represented by v3 and the voltage at which electrons start being emitted is represented by v4, then
1≦|v4|/|v3|≦1.5
Since the electron emitter 12 has the above characteristics, it can easily be applied to the light source 10 which has a plurality of electron emitters 12 arrayed in association with a plurality of pixels, for emitting light due to the emission of electrons from the electron emitters 12.
The drive circuit 16 shown in
During the charge accumulation period Td, the row selecting circuit 22 outputs the selection signal Ss to the selected row and outputs a non-selection signal Sn to the unselected rows. During the electron emission period Th, the row selecting circuit 22 outputs a constant voltage (e.g., −350 V) which is the sum of a power supply voltage (e.g., 50 V) from the power supply circuit 90 and a voltage (e.g., −400 V) from the pulse power supply 92.
The signal supplying circuit 24 has a pulse generating circuit 94 and an amplitude modulating circuit 96. The pulse generating circuit 94 generates and outputs a pulse signal Sp having a constant pulse period and a constant amplitude (e.g., 50 V) during the charge accumulation period Td, and outputs a reference voltage (e.g., 0 V) during the electron emission period Th.
During the charge accumulation period Td, the amplitude modulating circuit 96 amplitude-modulates the pulse signal Sp from the pulse generating circuit 94 depending on the luminance levels of the light-emitting devices of the selected row, and outputs the amplitude-modulated pulse signal Sp as the data signal Sd for the light-emitting devices of the selected row. During the electron emission period Th, the amplitude modulating circuit 96 outputs the reference voltage from the pulse generating circuit 94 as it is. The timing control in the amplitude modulating circuit 96 and the supply of the luminance levels of the selected light-emitting devices to the amplitude modulating circuit 96 are performed through the signal supplying circuit 24.
For example, as indicated by three examples shown in
A modification of the signal supplying circuit 24 will be described below with reference to
As shown in
For example, as indicated by three examples shown in
Changes of the characteristics at the time when the level of the negative voltage for the accumulation of electrons is changed will be reviewed in relation to the three examples of amplitude modulation on the pulse signal Sp shown in
However, as shown in
A drive method for the light source 10 according to the present embodiment will be described below with reference to
As shown in
According to the drive method, all the electron emitters 12 are scanned in the charge accumulation period Td, and voltages depending on the luminance levels of corresponding light-emitting devices are applied to a plurality of electron emitters 12 which correspond to pixels to be turned on (to emit light), thereby accumulating charges (electrons) in amounts depending on the luminance levels of the corresponding light-emitting devices in the electron emitters 12 which correspond to the light-emitting devices to be turned on. Then, in the electron emission period Th, a constant voltage is applied to all the electron emitters 12 to cause the electron emitters 12 which correspond to the light-emitting devices to be turned on to emit electrons in amounts depending on the luminance levels of the corresponding light-emitting devices, thereby emitting light from the light-emitting devices to be turned on.
More specifically, as also shown in
Thus, a voltage ranging from −50 V to −20 V depending on the luminance level is applied between the upper and lower electrodes 32, 34 of the electron emitter 12 which corresponds to each of the light-emitting devices to be turned on in the first row. As a result, each electron emitter 12 accumulates electrons depending on the applied voltage. For example, the electron emitter 12 corresponding to the light-emitting device in the first row and the first column is in a state at the point p3 shown in
A data signal Sd supplied to the electron emitters 12 which correspond to light-emitting devices to be turned off (to extinguish light) has a voltage of 50 V, for example. Therefore, a voltage of 0 V is applied to the electron emitters 12 which correspond to light-emitting devices to be turned off, bringing those electron emitters 12 into a state at the point p1 shown in
After the supply of the data signal Sd to the first row is finished, in the selection period Ts for the second row, a selection signal Ss of 50 V is supplied to the row selection line 18 of the second row, and a non-selection signal Sn of 0 V is applied to the row selection lines 18 of the other rows. In this case, a voltage ranging from −50 V to −20 V depending on the luminance level is also applied between the upper and lower electrodes 32, 34 of the electron emitter 12 which corresponds to each of the light-emitting devices to be turned on. At this time, a voltage ranging from 0 V to 50 V is applied between the upper and lower electrodes 32, 34 of the electron emitter 12 which corresponds to each of unselected light-emitting devices in the first row, for example. Since this voltage is of a level not reaching the point 4 in
Similarly, in the selection period Ts for the nth row, a selection signal Ss of 50 V is supplied to the row selection line 18 of the nth row, and a non-selection signal Sn of 0 V is applied to the row selection lines 18 of the other rows. In this case, a voltage ranging from −50 V to −20 V depending on the luminance level is also applied between the upper and lower electrodes 32, 34 of the electron emitter 12 which corresponds to each of the light-emitting devices to be turned on. At this time, a voltage ranging from 0 V to 50 V is applied between the upper and lower electrodes 32, 34 of the electron emitter 12 which corresponds to each of unselected light-emitting devices in the first through (n−1)th rows. However, no electrons are emitted from the electron emitters 12 which correspond to the light-emitting devices to be turned on, of those unselected light-emitting devices.
After elapse of the selection period Ts for the nth row, it is followed by the electron emission period Th. In the electron emission period Th, a reference voltage (e.g., 0 V) is applied from the signal supplying circuit 24 to the upper electrodes 32 of all the electron emitters 12, and a voltage of −350 V (the sum of the voltage of −400 V from the pulse power supply 92 and the power supply voltage 50 V from the row selecting circuit 22) is applied to the lower electrodes 34 of all the electron emitters 12. Thus, a high voltage (+350 V) is applied between the upper and lower electrodes 32, 34 of all the electron emitters 12. All the electron emitters 12 are now brought into a state at the point p6 shown in
Electrons are thus emitted from the electron emitters 12 which correspond to the light-emitting devices to be turned on (to emit light), and the emitted electrons are led to the anode electrodes 42 which correspond to those electron emitters 12, exciting the corresponding phosphor layers 44 which emit light. The emitted light is radiated out through the surface of the transparent substrate 40.
Subsequently, electrons are accumulated in the electron emitters 12 which correspond to the light-emitting devices to be turned on (to emit light) in the charge accumulation period Td, and the accumulated electrons are emitted for phosphorescent light emission in the electron emission period Th, for thereby radiating emitted light through the surface of the transparent substrate 40.
According to the present embodiment, as described above, an electron flow is not emitted throughout one frame, but an electron flow is emitted in the electron emission period Th of one frame. Therefore, an electron flow is emitted in a pulsed fashion. Specifically, an electron flow that is emitted from the electron emitter 12 can be defined as a pulsed electron flow or electron flow pulses.
Preferred structures of the light source 10 according to the present embodiment which employs electron emitters 12 described above will be described below with reference to
As shown in
As shown in
As shown in
In the arrangement shown in
A plurality of lower electrode interconnects 120 are disposed on the principal surface of the fixed substrate 110. A frame 122 is mounted on the principal surface of the fixed substrate 110 where the lower electrode interconnects 120 are disposed. The frame 122 has a plurality of rectangular cribs, arranged a matrix, for example, which are defined by a plurality of walls 124 arranged in rows and columns. The electron emission units 112 are inserted respectively in the rectangular cribs. Each of the rectangular cribs as viewed in plan is slightly greater than a single electron emission unit 112, allowing the electron emission units 112 to be easily inserted respectively in the rectangular cribs. In
As shown in
The upper electrode interconnects 126 and the upper electrodes 32 of the electron emission units 112 are electrically connected to each other by leads 132 extending from the upper electrodes 32 in the fourth columns and electrically connected to the upper electrode interconnects 126 disposed on the walls 124 near the upper electrodes 32 in the fourth columns, by an electrically conductive paste 134.
The lower electrode interconnects 120 and the lower electrodes 34 (not shown) in each of the electron emission units 112 are electrically connected to each other by an electrically conductive paste (not shown) applied to the lower electrode interconnects 120 disposed on the principal surface of the fixed substrate 110 and the lower electrodes 34.
As shown in
The light source 10a according to the first specific example is capable of emitting phosphorescent light due to electron excitation in each of the electron emission units 112 at an emission efficiency higher than the emission efficiency of LED light emission. The light source 10a is also advantageous in that it has a reduced burden on the environment because it does not employ mercury.
In the above example, the electron emission unit 112 has 16 electron emitters 12. A light source 10b according to a second specific example shown in
Specifically, the light source 10b according to the second specific example has a lower electrode interconnect 120 and an upper electrode interconnect 126 provided on a fixed substrate 110 and spaced from and disposed adjacent to each other, and a plurality of electron emitters 12 disposed between and over the lower electrode interconnect 120 and the upper electrode interconnect 126. Each of the electron emitters 12 has an upper electrode 32 disposed on an upper surface of the ferroelectric chip 136 (emitter 30), and a lower electrode 34 (not shown) disposed on a lower surface of the ferroelectric chip 136. The upper electrode 32 and the upper electrode interconnect 126 are electrically connected to each other by an electrically conductive paste 138, and the lower electrode 34 (not shown) and the lower electrode interconnect 120 are electrically connected to each other by an electrically conductive paste 140.
In the above embodiment, the light source has a single light emission section 14 including all the electron emitters 12, and a single drive circuit 16 connected to the light emission section 14. A light source 10c according to a third specific example shown in
Each of the planar light source sections Z1 through Z6 can be controlled for energization/de-energization to perform stepwise light control (digital light control). Particularly, if the drive circuits 16 independently connected respectively to the planar light source sections Z1 through Z6 have modulation circuits, then the light emission distributions of the planar light source sections Z1 through Z6 can independently be controlled. That is, the light source 10c can perform analog light control as well as digital light control for fine light control applications.
In the example shown in
With the light sources 10c through 10f according to the third through sixth specific examples, the light emission section 14 is divided into the six planar light source sections Z1 through Z6. However, the number of planar light source sections is optional.
Light sources 10 according to various embodiments of the present invention will be described below with reference to
As shown in
A spreading electrode 150 is disposed on a portion of the principal surface of the fixed substrate 110 which is free of the electron emitters 12. A phosphor layer 44 is disposed substantially entirely on the reverse side of the transparent substrate 40 which confronts the fixed substrate 110, and an anode electrode 42 which comprises a metal film is disposed on the lower end face of the phosphor layer 44. The anode electrode 42 also functions as a metal back layer 152. The anode electrode 42 may be formed by sputtering or vacuum evaporation, or may be in the form of a metal foil applied to the phosphor layer 44. The metal film serving as the anode electrode 42 should preferably be made of Ag or Al as it has a high reflectance and is suitably flexible.
The electron emitters 12 and the phosphor layer 44 may be arrayed in a pattern as shown in
As shown in
The electron flow 146 is spread by an electric field generated by the spreading electrode 150 to excite the phosphor layer 44 on the transparent substrate 40. Therefore, the phosphor layer 44 is prevented from being saturated by an excessive amount of electrons impinging locally thereupon. The phosphor layer 44 is capable of emitting phosphorescent light from its irradiated surface highly efficiently through an increased area for a spread uniform surface emission.
In the present embodiment, if an acceleration voltage of 10 kV is applied to the anode electrode 42, then the pulsed electron flow (electron flow pulses) 146 that is applied to the phosphor layer 44 is spread to reduce its peak surface density to 50 μA/cm2 or lower. Consequently, the light-emission efficiency of the phosphor layer 44 is prevented from being lowered by its saturation due to an excessive amount of electrons impinging locally thereupon.
The voltage applied to the spreading electrode 150 can control the spreading of electrons emitted from the electron emitter 12. Therefore, the light source 10A can be desired for optimally spreading electrons emitted from the electron emitter 12. Furthermore, the surface of the spreading electrode 150 may be polished to a mirror finish, allowing the spreading electrode 150 to function as a light reflecting layer.
When the pulsed electron flow 146 is intermittently emitted at certain time intervals, since the phosphor layer 44 keeps its persistent phosphor emission even during periods in which the pulsed electron flow 146 is not emitted, the light source 10A can emit light highly efficiently.
As shown in
According to the second embodiment, the light source 10B can be designed with increased freedom for generating an electric field for spreading the electron flow 146 while keeping a desired insulating distance between the spreading electrode 156 and the drive electrodes and interconnects of the electron emitters 12. The insulating distance may also be maintained by a separate insulating substrate such as of glass or the like disposed between the electron emitters 12 and the fixed substrate 110.
As shown in
An anode electrode 42 which comprises a light reflecting film 142, for example, is disposed substantially entirely on the principal surface of the fixed substrate 110 which confronts the transparent substrate 40, and a phosphor layer 44 is disposed on the upper end face of the anode electrode 42.
When electrons emitted from the electron emitters 12 impinge upon the phosphor layer 44 on the principal surface of the fixed substrate 110, the phosphor layer 44 is excited to generate a phosphor emission 154. The phosphor emission 154 is reflected by the anode electrode 42 as the light reflecting film 142, travels toward the transparent substrate 40, and passes through the transparent substrate 40.
Since the phosphor emission 154 passes through the portion of the transparent substrate 40 which is free of the electron emitters 12, the phosphor emission 154 is effectively and highly efficiently utilized as display light from the surface of the transparent substrate 40. Accordingly, the portion of the transparent substrate 40 which is free of the electron emitters 12 is effectively utilized.
The electron flow 146 from the electron emitters 12 on the transparent substrate 40 is spread by an electric field that is generated by the spreading electrode 150, which comprises a transparent electrode, disposed on the transparent substrate 40, such that the surface density of the pulsed electron flow 146 that is applied to the phosphor layer 44 has a peak value of 50 μA/cm2. Therefore, the phosphor layer 44 is prevented from being saturated by an excessive amount of electrons impinging locally thereupon, and is capable of emitting phosphorescent light from its irradiated surface highly efficiently through an increased area for a spread uniform surface emission.
When the pulsed electron flow 146 is intermittently emitted at certain time intervals, since the phosphor layer 44 keeps its persistent phosphor emission even during periods in which the pulsed electron flow 146 is not emitted, the light source 10C can emit light highly efficiently.
As shown in
According to the fourth embodiment, the light source 10D can be designed with increased freedom for generating an electric field for spreading the electron flow 146 while keeping a desired insulating distance between the spreading electrode 156 and the drive electrodes and interconnects of the electron emitters 12.
Preferred embodiments which employ the spreading electrode 150, etc. will be described below with reference to
As shown in
When a positive control voltage Vf is applied to the first spreading electrode 150A and the second spreading electrode 150B through a first terminal 162A and a second terminal 162B thereof respectively, they generate an electrostatic lens in the emission path of the electron flow 146 for spreading the electron flow 146 from the electron emitter 12. The electron flow 146 emitted from the electron emitter 12 toward the metal back layer 152 is abruptly spread by the electrostatic lens disposed in the emission path of the electron flow 146, and then gradually spread as the electron flow 146 approaches the metal back layer 152. As a result, as shown in
(1) The enlargement ratio is greater as the distance between the first and second spreading electrodes 150A, 150B, i.e., the size of the electron emitter 12, is smaller.
(2) The enlargement ratio is greater as the distance between the first and second spreading electrodes 150A, 150B and the electron emitter 12 is smaller.
(3) The voltage applied to the first and second spreading electrodes 150A, 150B should preferably be equal to or lower than the accelerating voltage applied to the anode electrode 42. The voltage which is equal to the accelerating voltage should more preferably be applied to the first and second spreading electrodes 150A, 150B from the standpoint of the enlargement ratio.
(4) The enlargement ratio is greater as the distance between the first and second spreading electrodes 150A, 150B and the anode electrode 42 is greater.
If the accelerating voltage applied to the anode electrode 42 is 10 kV, then the electron flow 146 can be spread such that the surface density of the pulsed electron flow 146 applied to the phosphor layer 44 has a peak value of 50 μA/cm2 or lower. Therefore, the efficiency of the phosphor layer 44 is prevented from being lowered by being saturated by an excessive amount of electrons impinging locally thereupon. The enlarged irradiated area 164 is effective to prevent the phosphor layer 44 from being saturated, and the phosphor layer 44 is capable of emitting phosphorescent light from its irradiated surface highly efficiently through an increased area for a spread uniform surface emission.
The size of the irradiated area 164 can be changed by controlling the height ha of the first and second spreading electrodes 150A, 150B, i.e., the vertical distance from the horizontal position of the electron emission surface 160 of the electron emitter 12 to the horizontal position of the first and second spreading electrodes 150A, 150B, the horizontal distance da between the first and second spreading electrodes 150A, 150B, and the value of the control voltage Vf.
As shown in
The annular spreading electrode 150 has inner and outer profiles substantially similar to the outer profile of the electron emitter 12. In
When a positive control voltage Vf is applied to the spreading electrode 150 through a terminal 162 thereof, it generates an electrostatic lens in the emission path of the electron flow 146 (see
The size of the irradiated area 164 can be changed by controlling the height of the spreading electrode 150, the opening width db of the spreading electrode 150, and the value of the control voltage Vf.
As shown in
(1) The enlargement ratio is greater as the opening width db of the spreading electrode 150, i.e., the size of the electron emitter 12, is smaller.
(2) The enlargement ratio is greater as the distance between the spreading electrode 150 and the electron emitter 12 is smaller.
(3) The voltage applied to the spreading electrode 150 should preferably be equal to or lower than the accelerating voltage applied to the anode electrode 42. The voltage which is equal to the accelerating voltage should more preferably be applied to the spreading electrode 150 from the standpoint of the enlargement ratio.
(4) The enlargement ratio is greater as the distance between the spreading electrode 150 and the anode electrode 42 is greater.
As shown in
When a positive constant voltage +Vf is applied to the second spreading electrode 150B, the trajectory of the electron flow 146 emitted from the electron emitter 12 is deflected toward the second spreading electrode 150B. Conversely, when a negative constant voltage −Vf is applied to the second spreading electrode 150B, the trajectory of the electron flow 146 emitted from the electron emitter 12 is deflected toward the first spreading electrode 150A.
As shown in
At a time t0 in
Thereafter, as the absolute value of the negative voltage level of the sine wave Se gradually increases, the electron flow 146 is progressively deflected toward the first spreading electrode 150A. At a time t3 when the absolute value of the negative voltage level is maximum, the electron flow 146 is deflected a maximum distance toward the first spreading electrode 150A, irradiating a position P2 on the metal back layer 152, as shown in
When the sine wave Se is continuously applied, the position on the metal back layer 152 which is irradiated with the electron flow 146 reciprocates between the position P1 and the position P2 across the position P0.
If only the positive sine wave Se is applied to the second spreading electrode 150B, then the position on the metal back layer 152 which is irradiated with the electron flow 146 reciprocates between the position P0 and the position P1. Conversely, if only the negative sine wave Se is applied to the second spreading electrode 150B, then the position on the metal back layer 152 which is irradiated with the electron flow 146 reciprocates between the position P0 and the position P2.
With the light source 10G according to the seventh embodiment, as described above, inasmuch as the trajectory of the electron flow 146 is deflected by the electric field, the area 164 of the metal back layer 152 which is irradiated with the electron flow 146 is two-dimensionally scanned. The area that is irradiated with the electron flow 146 which tends to travel straight can be made greater than if the electron flow 146 is spread under the electrostatic field, allowing the light source 10G to produce a persistent phosphor emission highly efficiently.
As shown in
When voltages are applied to the respective first, second, third, and fourth spreading electrodes 150A through 150D through respective terminals, i.e., first, second, third, and fourth terminals 162A through 162D thereof, the electron flow 146 (see
A process (first process) for deflecting the electron flow 146 with voltages applied to the first, second, third, and fourth spreading electrodes 150A through 150D will be described below with reference to
According to this process, one cycle is established, and one deflective scanning sequence is finished in the cycle. For example, as shown in
The above annular deflective scanning sequence is achieved by applying positive high-frequency signal waves (convex signal waves) Seh with respective time delays to the respective first, second, third, and fourth terminals 162A through 162D, as shown in
As a result, as shown in
Similarly, at the time t13, the irradiated area 164 is in the position P12 closest to the second spreading electrode 150B. At a time t14 when the voltage applied to the second terminal 162B is substantially the same as the voltage applied to the third terminal 162C, the irradiated area 164 is in a position P22 between the second spreading electrode 150B and the third spreading electrode 150C, i.e., a position corresponding to a corner CN2 of the electron emission surface 160.
At the time t15, the irradiated area 164 is in the position P13 closest to the third spreading electrode 150C. At a time t16, the irradiated area 164 is in a position P23 between the third spreading electrode 150C and the fourth spreading electrode 150D, i.e., a position corresponding to a corner CN3 of the electron emission surface 160. At a time t17, the irradiated area 164 is in the position P14 closest to the fourth spreading electrode 150D. At a time t18, the irradiated area 164 is in a position P24 between the fourth spreading electrode 150D and the first spreading electrode 150A, i.e., a position corresponding to a corner CN4 of the electron emission surface 160.
As shown in
Another process (second process) for deflecting the electron flow 146 with voltages applied to the first, second, third, and fourth spreading electrodes 150A through 150D will be described below with reference to
As shown in
According to the second process, the speed at which the electron flow 146 is deflected is controlled depending on the level of the electron flow so that the amount of electrons applied to the phosphor layer 44 by the deflected electron flow 146 is made constant.
For example, the distribution waveform of the level of the electron flow shown in
As shown in
The timing for applying the high-frequency signal Seh to the first through fourth spreading electrodes 150A through 150D is thus controlled depending on the level of the electron flow for thereby making constant the amount of electrons applied from the deflected electron flow 146 to the phosphor layer 44.
According to the above second process, one electron emission period Th is divided into four regions. However, as with the first process, one electron emission period Th may be divided into a plurality of cycles, and the timing for applying the high-frequency signal Seh to the first through fourth spreading electrodes 150A through 150D in each of the cycles may be controlled depending on the level of the electron flow for thereby making constant the amount of electrons applied from the deflected electron flow 146 to the phosphor layer 44.
As shown in
The magnetic field generator 170 comprises a coil 174 wound around a substantially C-shaped core 172. The polarities appearing at the ends of the core 172 are changed depending on the direction in which a current flows through the coil 174. In
Consequently, when the direction of the magnetic field generated by the magnetic field generator 170 is changed with time, the trajectory of the electron flow 146 emitted from the electron emitter 12 can continuously be changed. The magnetic field generator 170 thus functions as a means for deflecting the trajectory of the electron flow 146, i.e., a deflector.
An example in which the electron flow 146 is deflected will be described below with reference to
The above process is repeated to cause the position on the metal back layer 152 which is irradiated with the electron flow 146 to reciprocate between the position P1 and the position P2 across the position P0.
The size of the irradiated area 164 can be changed depending on the gap of the core 172, i.e., the distance between the first core portion 172a and the second core portion 172b, the intensity of the magnetic field, the configuration of the space in which the magnetic field is applied, etc. The amount of deflection of the electron flow 146 can be controlled depending on whether the magnetic field generator 170 generates a magnetic field or not, the orientation of the generated magnetic field, and the intensity of the magnetic field.
With the light source 10I according to the ninth embodiment, since the trajectory of the electron flow 146 is deflected by the magnetic field, the irradiated area 164 on the metal back layer 152 can be two-dimensionally scanned. Since the light source 10I does not require a high voltage for deflecting the electron flow 146 unlike the arrangement for deflecting the electron flow 146 under an electric field, the light source 10I may have a less costly control circuit. Furthermore, the area that is irradiated with the electron flow 146 which tends to travel straight can be made greater than if the electron flow 146 is spread under the electrostatic field, allowing the light source 10I to produce a persistent phosphor emission highly efficiently.
As shown in
With the light source 10J, the magnetic field generated by the magnetic field generator 170 is not interrupted by the fixed substrate 110 or the like, but acts directly on the electron flow 146 for easily controlling the amount of deflection of the electron flow 146.
As shown in
A process of deflecting the electron flow 146 with a combination of the polarities of the core portions 172Aa, 172Ab, 172Ba, 172Bb will be described below with reference to
According to this process, one cycle is established, and one deflective scanning sequence is finished in the cycle. For example, as shown in
As shown in FIG., 56, the above annular deflective scanning sequence is achieved by developing polarities (e.g., N poles) with respective time delays at the first core portion 172Aa of the first magnetic field generator 170A, the first core portion 172Ba of the second magnetic field generator 170B, the second core portion 172Ab of the first magnetic field generator 170A, and the second core portion 172Bb of the second magnetic field generator 170B.
For example, in an interval from a time t50 to a time t52, the N pole is developed at the first core portion 172Aa of the first magnetic field generator 170A and the S pole is developed at the second core portion 172Ab of the first magnetic field generator 170A. In an interval from a time t51, which occurs between the time t50 and the time t52, to a time t54, the N pole is developed at the first core portion 172Ba of the second magnetic field generator 170B, and the S pole is developed at the second core portion 172Bb of the second magnetic field generator 170B. In an interval from the time t52 to a time t53, the coil of the first magnetic field generator 170A is de-energized. Thereafter, in an interval from the time t53 to a time t56, the S pole is developed at the first core portion 172Aa of the first magnetic field generator 170A and the N pole is developed at the second core portion 172Ab of the first magnetic field generator 170A. Similarly, in an interval from the time t54 to a time t55, the coil of the second magnetic field generator 170B is de-energized. Thereafter, in an interval from the time t55 to a time t57, the S pole is developed at the first core portion 172Ba of the second magnetic field generator 170B, and the N pole is developed at the second core portion 172Bb of the second magnetic field generator 170B.
As a result, as shown in
Similarly, in the interval from the time t54 to the time t55, the irradiated area 164 is in the position P33 closest to the second core portion 172Bb. In the interval from the time t55 to the time t56, the irradiated area 164 is in a position P43 between the second core portion 172Bb and the first core portion 172Aa, i.e., a position corresponding to the corner CN4 of the electron emission surface 160. In the interval from the time t56 to the time t57, the irradiated area 164 is in the position P34 closest to the first core portion 172Aa.
As shown in
In the eleventh embodiment, the polarities may be combined according to a process similar to the second process described above (see
As shown in
As shown in
When a current flows through the coil pattern 182, it generates an upward magnetic field 184 extending through the electron emitter 12 and the electrode films 180, i.e., extending from the fixed substrate 110 toward the transparent substrate 40.
The light source 10L according to the twelfth embodiment is capable of deflecting the electron flow 146 with a combination of an electric field that is generated by the first spreading electrode 150A and the second spreading electrode 150B and an upward magnetic field that is generated by the unillustrated magnetic field generator, i.e., the coil pattern 182 shown in
For example, a ground potential Vss is applied to the first spreading electrode 150A, and a constant positive voltage Vf is applied to the second spreading electrode 150B to give a horizontal velocity component to the electron flow 146. The electron flow 146 is deflected under a force due to a magnetic field depending on the horizontal velocity component, and travels toward the metal back layer 152 while in spiral motion. In this manner, the electron flow 146 is applied to a wide area of the metal back layer 152 to enable the phosphor layer 44 to emit light highly efficiently based on its persistent phosphor emission. Since no high voltage is required to spread the electron flow 146, the light source 10L may have a less costly control circuit.
As shown in
Specifically, as shown in
When a current flows through the coil pattern 188, it generates a magnetic field 190 extending from the first coil pattern portion 188a toward the second coil pattern portion 188b, for example. The magnetic field 190 is applied as a horizontal magnetic field to the electron emitter 12 and the electrode films 180.
The light source 10M according to the thirteenth embodiment is capable of deflecting the electron flow 146 with a combination of an electric field that is generated by the first spreading electrode 150A and the second spreading electrode 150B and a horizontal magnetic field 190 that is generated by the unillustrated magnetic field generator, i.e., the coil pattern 188 shown in
For example, a ground potential Vss is applied to the first spreading electrode 150A, and a constant positive voltage Vf is applied to the second spreading electrode 150B to give a horizontal velocity component to the electron flow 146. The electron flow 146 is accelerated by the vertical electric field and is deflected under a force proportional to the vertical velocity component. Inasmuch as the advantages of the deflection under the electric field and the deflection under the magnetic field are combined, the amount of deflection of the electron flow 146 is increased.
As shown in
For deflecting the trajectory of the electron flow 146 emitted from the electron emitter 12, it is necessary that the generator for generating an electric field and/or a magnetic field and the electron emitter 12 be positioned highly accurately with respect to each other. Since the electrode films 180 and the coil pattern 182 or 188 can be formed on the fixed substrate 110 based on the same reference positions by screen printing, for example, they can be positioned highly accurately with respect to the electron emitter 12 inexpensively and highly accurately, as shown in
Furthermore, as shown in
As shown in
In the light source 10N, pulsed electron flows 146 from the respective electron emitters 12A through 12D are applied to the same area of the metal back layer 152. However, the pulsed electron flows 146 for irradiating the same area of the metal back layer 152 are emitted at different times from the respective electron emitters 12A through 12D.
A study of the emission efficiency of a phosphor has indicated that, as shown in
For increasing the emission luminance, it is customary to increase the amount of electrons emitted from each electron emitter 12, and to apply a single pulsed electron flow 146 to the phosphor within a constant electron emission period Th, as indicated by the broken-line curve A in
However, the peak current density of the pulsed electron flow 146 as represented by the broken-line curve A is so high that the emission efficiency is low as shown in
In view of this, in
In this manner, the peak current densities of the first, second, third, and fourth electron emitters 12A through 12D are reduced to one quarter of the peak current density indicated by the broken-line curve A of the single electron emitter 12. For example, the peak current densities of the first, second, third, and fourth electron emitters 12A through 12D may be reduced to 10 μA/cm2 or less, or 5 μA/cm2 or less, for achieving an emission efficiency of 50 lm/W or higher.
By thus successively superposing the pulsed electron flows 146 of the low peak current densities emitted from the respective electron emitters 12, it is possible to obtain a necessary electron flow level for achieving both higher luminance and higher efficiency.
As shown in
According to the drive process shown in
Because the electron flow pulses 146 are produced in a time-division fashion from the respective electron emitters 12, the drive frequency of each of the electron emitters is not unnecessarily increased. Consequently, the service life of each of the electron emitters 12 is not unduly reduced.
Since the same area of the phosphor layer 44 is excited by the electron flow pulses 146 that are emitted in a time-division fashion from the respective electron emitters 12, a necessary electron flow level can be achieved for both higher luminance and higher efficiency.
The principles of the light source 10N according to the fourteenth embodiment are also applicable to the light sources 10A through 10M according to the first through thirteenth embodiments described above.
Other embodiments of the present invention which are effective to increase the emission efficiency of a phosphor will be described below with reference to
A study of the emission efficiency of a phosphor has indicated that, as shown in
As shown in
One frame is divided into four cycles, and operation of the light source 10O in one of the cycles (240 Hz, 4.1 msec.) will be described below with reference to
Therefore, the frequency of electron flow pulses 146 emitted from the single electron emitter 12 may be controlled to reduce the amount of electrons of each electron flow pulse 146 applied to the phosphor layer 44 to about 0.1 nC/cm2 for thereby increasing the emission efficiency of the phosphor layer 44.
As shown in
When a positive control voltage Vf is applied to the spreading electrode 150 through a terminal 162 thereof, it generates an electrostatic lens in the emission paths of the electron flows 146 for spreading the electron flows 146 from the electron emitters 12A through 12C. The electron flows 146 emitted from the electron emitters 12A through 12C toward the metal back layer 152 are abruptly spread by the electrostatic lens disposed in the emission paths of the electron flows 146, and then gradually spread as the electron flows 146 approach the metal back layer 152. As a result, as shown in
An experimental example will be described below. The light source 10P according to the sixteenth embodiment was fabricated under the manufacturing conditions shown below, and the ratio at which the irradiated area 164 of the metal back layer 152 is enlarged was confirmed. A red phosphor P22-RE1 (manufactured by Kasei Optonix, Ltd.), a green phosphor P22-GN4 (manufactured by Kasei Optonix, Ltd.), and a blue phosphor LDP-B3 (manufactured by Kasei Optonix, Ltd.) were mixed at a weight ratio of 1:1:1 into a phosphor layer 44. The phosphor layer 44 had a thickness represented by 6 mg/cm2, i.e., a weight per unit area. The metal back layer 152 had a thickness of 150 nm. The distance between the electron emitters 12A through 12C and the metal back layer 152 was 8 mm, and the distance between the electron emitters 12A through 12C and the spreading electrode 150 was 0.8 mm and 1.25 mm.
As a result, as shown in
The size of the irradiated area 164 can be changed by controlling the height of the spreading electrode 150, the width of the openings 200A through 200C in the spreading electrode 150, and the value of the control voltage Vf.
With the light source 10P according to the sixteenth embodiment, the electron flow pulses 146 emitted from the electron emitters 12A through 12C can be spread by the electric field that is generated by the spreading electrode 150, to reduce the amount of electrons of each electron flow pulse 146 applied to the phosphor layer 44 to about 0.1 nC/cm2 for thereby increasing the emission efficiency of the phosphor layer 44.
Incidentally, the process of driving the light source 10O according to the fifteenth embodiment described above, i.e., the process of increasing the frequency of electron flow pulses 146 emitted from the single electron emitter 12, may be applied to the light sources 10A through 10N according to the first through fourteenth embodiments and the light source 10P according to the sixteenth embodiment. Since the electron emitters 12 are two-dimensionally scanned and the electron flow pulses 146 are emitted at a high frequency from the electron emitters 12, the advantages (the increased emission efficiency of the phosphor layer 44 due to the spreading of the electron flow pulses 146) of the light sources 10A through 10N according to the first through fourteenth embodiments and the light source 10P according to the sixteenth embodiment, and the advantages (the increased emission efficiency of the phosphor layer 44 due to the high-frequency emission of the electron flow pulses 146) of the light source 10O according to the fifteenth embodiment are combined to further increase the emission efficiency of the phosphor layer 44 (synergistic advantages).
Though in the above embodiments, a plurality of electron emitters 12 are arranged in a matrix, the plurality of electron emitters 12 may be arranged in a staggered pattern, as in a light source 10Q according to a seventeenth embodiment of the present invention shown in FIGS. 75 to 77.
The arrangement of the light source 10Q according to the seventeenth embodiment will be described below with reference to FIGS. 75 to 77.
As shown in
The upper electrode interconnects 126 and the lower electrode interconnects 120 are alternately provided. The upper electrode interconnects 126 are electrically connected to the upper electrodes of the electron emitters 12, while the lower electrode interconnects 120 are electrically connected to the lower electrodes of the electron emitters 12.
The spreading electrode 150 is made of a single electrode plate, for example. A number of first openings 214 are provided at positions corresponding to the electron emitters 12, while a number of second openings 216 (see
A phosphor layer 44 and a metal back layer 152 (also as an anode electrode 42) are formed on a surface of the transparent substrate 40 in this order, the surface opposing the fixed substrate 110.
As shown in
A method of producing the light source 10Q according to the seventeenth embodiment will be described below with reference to
First, processes on the side of the fixed substrate 110 will be described with reference to
As shown in
Next, as shown in
By applying the bonding paste 224 (silver paste in this embodiment) to the electrode patterns (the upper electrode interconnects 126 and the lower electrode interconnects 120), the formed metal films (electrode patterns) to which the bonding paste 224 is applied also prevent the electron emitters 12 from detaching from the fixed substrate 110 (soda glass) due to the thermal expansion difference and avoid generation of cracks in the fixed substrate 110.
The formed electrode patterns (the upper electrode interconnects 126 and the lower electrode interconnects 120) generate a gap between the electron emitters 12 and the fixed substrate 110 (soda glass), thereby facilitating volatilization of solvent in the bonding paste 224. Accordingly, unnecessary spreading of the bonding paste 224 can be prevented when the bonding paste 224 is dried.
Then, as shown in
Alignment patterns indicating the predetermined positions for the electron emitters 12 are provided on the electrode patterns (the upper electrode interconnects 126 and the lower electrode interconnects 120). Alternatively, the predetermined positions may be indicated by the position of the bonding paste 224 on the electrode patterns. The intervals between the electron emitters 12 are determined so as to provide the light emitting regions (area) of the electron emitters 12 without any gap therebetween by measuring the light emitting region of one electron emitter 12.
Then, as shown in
Then, as shown in
Thereafter, the spreading electrode 150 is mounted on the spreading electrode spacers (the glass chip 230 and the glass bar 232) in a manner to cover part of the principal surface of the fixed substrate 110.
The spreading electrode 150 may be made of a metal plate (having its thickness of about 100 μm) such as SUS and invar 42. The spreading electrode 150 includes the first openings 214 having substantially the same size as the electron emitting surface of the electron emitter 12, the first openings 214 being positioned corresponding to the electron emitters 12 (overlapping the electron emitters 12). The spreading electrode 150 also includes the second opening 216 for supporting the first internal spacer 212a (see
Then, as shown in
The spreading electrode 150 is electrically connected to the interconnect pattern 234 formed on the upper surface of the glass bar 232 of the spreading electrode spacer through connecting wires 238.
Incidentally, the spreading electrode spacer (not shown) and the first internal spacer 212a may be integrated with each other and the bar may be made of metal instead of glass in order to decrease use of silver paste.
Then, as shown in
Comparing the circumferential spacer 210 with the internal spacers 212 (the first internal spacer 212a and the second internal spacer 212b), the internal spacers 212 are designed to be higher than the circumferential spacer 210 by 0.2 mm. When the transparent substrate 40 is attached to the fixed substrate 110, the internal spacer 212 defines the distance between the fixed substrate 110 and the transparent substrate 40. If a gap is generated at the circumference, the frit glass applied thereto compensates for the gap.
Next, processes on the side of the transparent substrate 40 will be described with reference to
As shown in
Then, as shown in
Then, as shown in
Next, an assembling process of the light source 10Q will be described with reference to
As shown in
Thereafter, the one surface of the transparent substrate 40 and the principal surface of the fixed substrate 110 are opposed to each other, and the circumferential spacer 210 and the circumference of the transparent substrate 40 are fixed to each other by the frit glass 244. Then, the fixed substrate 110 and the transparent substrate 40 are bonded to each other by heating at 475° C. to contact the surface of the first internal spacer 212a with the surface of the second internal spacer 212b.
Then, as shown in
According to the above processes, the light source 10Q according to the seventeenth embodiment can be manufactured.
A light source 10R according to an eighteenth embodiment of the present invention will be described below with reference to
As shown in
First, an upper surface of the fixed substrate 110 is divided into a plurality of regions (e.g., a plurality of columns Ln1, Ln2 . . . ). The direction (x-direction) in which each of columns (Ln1, Ln2, . . . ) extends is referred to as the longitudinal direction and the direction (y-direction) in which the columns (Ln1, Ln2, . . . ) are lined up is referred to as the transverse direction.
In the light source 10R, plate-like spreading electrodes 150 longitudinally extending are disposed above portions of the upper surface of the fixed substrate 110 which correspond to odd-numbered columns (Ln1, Ln3, Ln5, . . . ), for example, and a plurality of electron emitters 12 using ferroelectric chips 136 are longitudinally disposed on portions of the upper surface of the fixed substrate 110 which correspond to even-numbered columns (Ln2, Ln4, . . . ). Though not shown, the spreading electrodes 150 are disposed above portions corresponding to the first column and the last column respectively.
Specifically, there are spreading electrodes 150 above both sides of the column on which the electron emitters 12 are disposed. In
Therefore, electron flows 146 emitted from the electron emitters 12 are transversely spread by an electric field generated by the spreading electrodes 150. As shown in
Consequently, when the light source 10R is used for a backlight of a liquid crystal display (LCD), the light emitting region or regions 220 can be longitudinally displaced stepwise in a constant period (e.g., a period of vertical scanning signal of LCD) by controlling the electron emitters 12 by a row or rows at a time.
When moving images are displayed on LCD, a problem called image lag typically occurs. As described above, by longitudinally displacing the light emitting region or regions 220 of the light source 10R as a backlight, the image lag can be reduced and moving images can be displayed by a pseudo impulse display, which can improve the display properties of moving images on LCD.
A light source 10S according to a nineteenth embodiment of the present invention will be described below with reference to
As shown in
The width W1 of a spreading electrode 150a above a portion corresponding to the first column Ln1 is substantially equal to the width of a spreading electrode (not shown) above a portion corresponding to the last column. The width W2 of respective spreading electrodes 150b, 150c, . . . above each of columns between the columns of electron emitters 12 is substantially twice the width W1 of the spreading electrode 150a above the portion corresponding to the first column Ln1.
In
Similarly, the distance Dn3 between one end face 250c (the surface close to the third column Ln3) of the electron emitter 12 on the fourth column Ln4 and the center line Lma of the spreading electrode 150b above the portion corresponding to the third column Ln3 is also twice the transverse length Dn of the electron emitter 12. The distance Dn4 between the other end face 250d (the surface close to the fifth column Ln5) of the electron emitter 12 on the fourth column Ln4 and the center line Lmb of a spreading electrode 150c above a portion corresponding to the fifth column Ln5 is also twice the transverse length Dn of the electron emitter 12. Other columns are the same as above.
Further, according to the nineteenth embodiment shown in
In the above example, the ratio at which the light emitting region is enlarged with the electron flows 146 emitted from the electron emitter 12, i.e., the enlargement ratio, is 5 times in the transverse direction and also 5 times in the longitudinal direction. The enlargement ratio is however not limited to the above example. The enlargement ratio may optionally be selected depending on an applied voltage to the spreading electrodes 150, materials of the light spreading plate 254, the mounting location, etc.
A light source 10T according to a twentieth embodiment of the present invention will be described below with reference to
As shown in
A voltage of 0 V is constantly applied to the upper electrodes 32, and a control voltage Vf of about 5 kV is applied to the spreading electrodes 150. An electrostatic lens is generated in the emission paths of the electron flows 146 for spreading the electron flows 146. The electron flows 146 emitted from the electron emitters 12 toward the metal back layer 152 are abruptly spread by the electrostatic lens disposed in the emission paths of the electron flows 146, and then gradually spread as the electron flows 146 approach the metal back layer 152.
However, since this requires a high voltage power supply separately for applying the control voltage Vf of about 5 kV to the spreading electrodes 150, the cost disadvantageously tends to be high. Further, since this requires the large insulation distances between the lower electrode interconnect 120 and the spreading electrode 150, and the upper electrode 32 and the spreading electrode 150, this cannot allow the height of the light source 10T to be lowered.
As in a light source 10U according to a twenty-first embodiment of the present invention shown in
Namely, in the light source 10U according to the twenty-first embodiment, a voltage of 0 V is constantly applied to the upper electrodes 32, and a voltage of 0 V or a low voltage Vg of 100 V or the like is applied to the spreading electrodes 150. The electron flows 146 emitted from the electron emitters 12 then travel away from the spreading electrodes 150 toward the metal back layer 152. The electron flows 146 toward the metal back layer 152, then, intersect with each other above the center of the upper surface of the electron emitters 12. Thereafter the electron flows 146 are gradually spread as the electron flows 146 approach the metal back layer 152.
Since the voltage of 0 V or the low voltage Vg of 100 V or the like is applied to the spreading electrodes 150, this case does not require a high voltage power supply. If the low voltage Vg of 100 V or the like is applied to the spreading electrodes 150, this requires only installing a low-cost low voltage power supply. If the voltage of 0 V is applied to the spreading electrodes 150, even a low voltage power supply is not required. This is advantageous for reducing the cost. In addition, since this does not require the large insulation distances between the lower electrode interconnect 120 and the spreading electrode 150, and the upper electrode 32 and the spreading electrode 150, it is advantageous for lowering the height of the light source 10T.
As in a light source 10Ua according to a modification shown in
A light source 10V according to a twenty-second embodiment of the present invention will be described below with reference to
As shown in
The mesh electrode 260 comprises a rectangular or square-shaped metal mesh electrode which is rounded into a half-cylindrical shape. Both end faces of the mesh electrode 260 are secured on the upper surface of the fixed substrate 110 to dispose the mesh electrode 260 on the fixed substrate 110. The mesh electrode 260 is so positioned as to position the ferroelectric chip 256 directly below the top portion of the half-cylindrical shaped mesh electrode 260.
As shown in
The mesh electrode 260 comprises a mesh woven with metal wire having a wire diameter of F40 μm, for example. The mesh has preferably 200 mesh (i.e., 200 openings per inch) and an opening area of about 50%, for example.
The mesh count, opening area, wire diameter, etc. of the mesh electrode 260 may arbitrarily be selected depending on the spreading ratio of the electron flows 146, the size of the electron emitters 12 (an area of the electron emission surface), the gap between the fixed substrate 110 and the transparent substrate 40, the applied voltage to the mesh electrode 260, etc. Incidentally, the spreading ratio of the electron flows 146 can arbitrarily be changed by changing the radius of curvature of the mesh electrode 260.
If the mesh count is too small, the electron flows 146 are sparsely spread to form some light emitting regions separately. This results in deterioration of the display quality. If the mesh count is too large, most of the electron flows 146 emitted from the electron emitters 12 are captured by the mesh electrode 260, which functions as a shield electrode.
In the light source 10V according to the twenty-second embodiment, since the mesh electrode 260 is used as a spreading electrode 150 and both end faces of the mesh electrode 260 are secured on the fixed substrate 110, the spreading electrode 150 can easily be positioned with respect to the electron emitters 12, and the electron flows 146 can substantially symmetrically be spread in the transverse direction. This is advantageous for a spread uniform surface emission.
Modifications of the light source 10V according to the twenty-second embodiment will be described below with reference to
As shown in
In this case, the electron flows 146 emitted from the electron emitter 12 can be spread in all directions.
As shown in
In this case as with the twenty-second embodiment, the electron flows 146 passing through openings of the second mesh electrode 260B can be spread in the transverse direction. The spreading ratio of the electron flows 146 can arbitrarily be changed by adjusting a folding angle θb of the second mesh electrode 260B.
As shown in
In the light source 10Vc according to the third modification, the electron flows 146 passing through openings of the third mesh electrode 260C are randomly spread. As a result, a spread uniform surface emission can be achieved.
Incidentally, the third mesh electrode 260C for randomly spreading the electron flows 146 may comprise a third mesh electrode 260Ca having a corrugated shape or the like.
As shown in
When the spreading electrode 150 is mounted above the electron emitter 12, it typically requires the highly accurate positioning of the electron emitters 12 and the openings formed on the spreading electrode 150. As shown in
However, in the fourth modification, since the fourth mesh electrode 260D has a large number of openings, this requires only mounting the fourth rectangular mesh electrode 260D above the ferroelectric chips 256, not require the highly accurate positioning of each electron emitter 12 and each opening. Further, a particular process is not required on the fourth mesh electrode 260D. Therefore, the fourth modification is advantageous in simplifying the mounting work and reducing the cost of manufacturing.
As shown in
In this case, the electron flows 146 emitted from the electron emitters 12 also travel away from the fifth mesh electrodes 260E toward the metal back layer 152. The electron flows 146 toward the metal back layer 152 then intersect with each other above the center of the upper surface of the electron emitters 12. Thereafter the electron flows 146 are gradually spread as the electron flows 146 approach the metal back layer 152.
A light source 10W according to a twenty-third embodiment of the present invention will be described below with reference to
As shown in
The transparent substrate 40 comprises an upper plate 40a facing the fixed substrate 110 and two side plates (a first side plate 40b and a second side plate 40c) interposed between the upper plate 40a and the fixed substrate 110.
A phosphor layer 44 is formed on an inner wall of the transparent substrate 40, i.e. an internal surface of the upper plate 40a (the surface facing the fixed substrate 110), an upper portion of an internal surface of the first side plate 40b (the surface facing the second side plate 40c), and an upper portion of an internal surface of the second side plate 40c (the surface facing the first side plate 40b). Further, a metal back layer 152 (anode electrode 42) functioning as a spreading electrode 150 is formed on the phosphor layer 44.
The electron flows 146 emitted from the electron emitters 12 travel toward the metal back layer 152. Then, since the metal back layer 152 is formed on the three surfaces continuously, the electron flows 146 are gradually spread as the electron flows 146 approach the metal back layer 152. Light then emits on the upper plate 40a, the first side plate 40b, and the second side plate 40c of the transparent substrate 40.
This modification shows one light source 10W (a light emitting tube 266). However, in a large planar light source 270 having a large area for emitting light shown in
With this arrangement, light 276 emits ahead of the planar light source 270 from the upper plate 40a and the upper portions of the first side plate 40b and the second side plate 40c of each light emitting tube 266. Also, light 278 emits from the upper portions of the first side plate 40b and the second side plate 40c toward the large fixed substrate 272, and the light 278 is reflected by the light reflecting layers 274 to travel ahead of the planar light source 270. As a result, a spread uniform surface emission and a high-luminance light emission can be achieved. Thereby a structure can easily be manufactured for a spread uniform surface emission.
Additionally, since the planar light source 270 does not require mounting a large transparent substrate facing the large fixed substrate 272 and spacers (for supporting the large transparent substrate), reduction in weight, thickness and cost of the planar light source 270 can be achieved. Further, since the anode electrode 42 (the metal back layer 152) also functions as the spreading electrode 150, simplified interconnects can be achieved.
According to the above modification, the phosphor layer 44 is firstly formed on the inner wall of the transparent substrate 40, and then the metal back layer 152 is formed on the phosphor layer 44. Otherwise, in a light source 10Wa according to a modification shown in
Although certain preferred embodiments of the present invention have been shown and described in detail, it should be understood that various changes and modifications may be made therein without departing from the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-037567 | Feb 2006 | JP | national |
| Number | Date | Country | |
|---|---|---|---|
| 60665166 | Mar 2005 | US | |
| 60693193 | Jun 2005 | US | |
| 60702759 | Jul 2005 | US | |
| 60719331 | Sep 2005 | US |
