CN1141691A - Improvement for back lighting and improvement relating to it - Google Patents

Abstract

A backlighting arrangement comprises a discharge lamp envelope (10) and a spirally formed inductive winding (2), the winding formed in a single layer. The electromagnetic field generated when an alternating voltage is supplied to the winding (2) couples into the envelope (10) wherein a plasma arc is established.

Description

To the improvement of back lighting and relevant with it improvement

The present invention relates to back lighting, and, although right and wrong are exclusive, relate in particular to the back lighting of LCD (LCD).

Compared with early voluminous life and have a very big emulative cathode ray tube (CRT) technology, one of major advantage of LCD technology is the compactedness on the gauge, and above-mentioned compactedness makes LCD become unique feasible solution in some display application.In other extensive application, become and be not desired for the huge CRT of making of aesthetic reason CRT.

Although CRT is comprising the light source of himself effectively, and LCD needs ambient lighting.Sometimes this can reach by ambient lighting, and LCD comes down to reflexive in this case.But more frequently, LCD needs back lighting, and backside illumination technology must not can be damaged the compactedness on the above-mentioned gauge excessively.But also the brightness that requires back lighting is uniformly basically, is economical on power consumption and has the acceptable life-span.

Having carried out many effort is the effective and compact background light source of LCD development, and the background light source that is made of fluorescent tube and diffusion pipe is known.In addition, for example at JP-A-63150850, JP-A-63208543, JP-A-62150647 and US-A-4, many suggestions that improve equipment are disclosed in 872,741.

Above-mentioned all documents all openly adopt the background light source of the relative thin of electrodeless lamp technology.JP-A-63150850 and JP-A-63208543 are disclosed in and use a plurality of tubulose electrodeless lamps on the public support, and these lamps are encouraged by different loop constructions.On the other hand, JP-A-62150647 and US-A-4,872, the 741 open electrodeless lamps of forming by single plane big envelope (unitary flat envelopes) that adopt.

Very clear for back lighting LCD need adopt electrodeless technology, this is because electrodeless technology can be sent the light output that has excellent homogeneity and high-brightness light and have the long-life and have potential compactedness on gauge.

But the electrodeless lamp that contains gas filler also exists difficulty, for make the excitation of this lamp need of work it, and in order to trigger and this lamp that turns round need be applied to radio-frequency (RF) energy on the actuator element and again and is coupled in the gas filler.This lamp is moved reliably and have strong uniform luminance, the efficient of this coupling is primary importance.This aspect institute of the present invention just major concern of electrodeless backside illumination technology.

JP-A-62150647 proposes to arrange coupling element along the periphery of the electrodeless background light source of rectangle.But, in case this layout can not be by the required uniformity exciter when background light source plane surpasses certain relatively little size.On the other hand, US-A-4,872,741 propose to adopt the Circumferential coils array that distributes along the rear surface of rectangle background light source.But this layout may cause the restriction that lamp is excited, in addition because the thickness of Circumferential coils has increased the gross thickness size of background light source, so it has also damaged the compactedness of assembly to a certain extent.And past contact meeting causes lacking the control to the gas discharge shape that is produced, thereby has limited the uniformity performance.

According to the electrodeless background light source that the invention provides a kind of illuminated displays, this background light source comprises a flat basically assembly, for consistent with the size of display, this assembly is that its third dimension is being represented the thickness of this assembly by two-dimentional configuration, this assembly has at least one big envelope gas filler that contains gas filler and can respond the radio-frequency (RF) energy that it is applied and produce electromagnetic radiation, this electromagnetic radiation encourages conversion medium to produce visible light conversely again, this background light source is characterised in that the device that is used for described radio-frequency (RF) energy is applied to described gas filler comprises one or more drive units of being made up of electric conducting material, drive unit and consistent along the predetermined image of described two dimension extension, and drive unit only enlarges the thickness of described electric conducting material basically on the described third dimension, described pattern be roughly spiral-shaped and and described big envelope arranged side by side.

In order clearly to understand the present invention and to implement the present invention easily, existing some only as an example execution modes that illustrate with reference to the accompanying drawings, accompanying drawing is:

Fig. 1 schematically illustrates first execution mode of the present invention;

Fig. 2 schematically illustrates interchangeable spiral coil;

Fig. 3 schematically illustrates the effect on the plasma arc of replaceable coil;

Fig. 4 schematically illustrates the interchangeable pattern of spiral coil;

Fig. 5 schematically illustrates the circuit that is used for driving according to a coil of the present invention;

Fig. 6 schematically illustrates the layout according to non-planar of the present invention;

Fig. 7 schematically illustrates and directly constitute helical coil on a bulb big envelope;

How Fig. 8 (a) and (b) and 8 (c) expressions is configured for the background light source of large area display by some independent, relative little background light sources that respectively have self screw electrode (or electrode group);

Fig. 9 represents the background illumination structure of the part be made up of hexagon background light source setting-in pattern;

Figure 10 and Figure 11 represent typical structure according to the circular background light source of one embodiment of the present invention by perspective view and exploded view respectively; And

Figure 12 represents the custom circuit layout of radio-frequency (RF) driver circuit.

At first, on circuit board substrate 4, form the inductance coil 2 that constitutes by electric conducting material (being copper) as can be seen spirally under this situation referring to Fig. 1.At first copper is plated at least one first type surface of circuit board 4, by the metallic plate printing technology of standard copper is removed then, be essentially the coil 2 of spiral pattern with formation.

Plate 4 is put in the seal glass big envelope 10 that contains gas filler very closely.The character of gas filler is that the optical characteristics that will be generated by background light source is determined, but big envelope 10 contains one or more inert gases that reduce pressure (≈ 2mbar) and contains a spot of mercury usually.Have fluoresent coating on the inboard of in two first type surfaces of this big envelope (this first type surface is from plate 4 that surface farthest under this situation, promptly towards the front surface of illuminated LCD).When plate 4 shown in the dotted line among Fig. 1 12 and big envelope 10 adjoin each other, and make coil 2 mutually arranged side by side, provide the radio frequency alternating voltage from the voltage source (not shown) to coil 2 through contact point 6,8 with big envelope 10.Helical coil 2 must not be unidirectional as shown in FIG., and the electric current that importantly makes in the gas filler to be responded to is not cancelled out each other.Be readily appreciated that for this requirement of those skilled in the art.As known, in big envelope 10, cause the plasma arc that produces ultra-violet radiation, but the wavelength activating fluorescent material that this ultra-violet radiation had is to send visible radiation.Background light source produces the visible light of the LCD that can be used for throwing light on by this way.

Another first type surface (if needs, and some subsurfaces) of knowing very much big envelope 10 also can apply fluorescent material.Usually big envelope 10 usefulness glass are made, and will be coated in fluorescent material the inside of big envelope in this case, thereby this is because if the outer glass that fluorescent material is coated in big envelope 10 can absorb the validity that ultra-violet radiation greatly reduces device.But, if big envelope 10 is to make as quartz with the material of not obvious absorption ultra-violet radiation, then can adopt outside fluorescent material coating, this external skin is than the easy realization of coated inside.

In described any structure, can on the rear surface of big envelope 10 or near the rear surface, reflecting material be set, so that any visible light or ultra-violet radiation that meeting is revealed from the rear surface thereby that can slattern reflect back among the big envelope.In the example of Fig. 1, it is that how much helicals by single standard form spirally that coil 2 is represented as.It can also be seen that for coil to have different many interchangeable helical rib by reference Fig. 2, respectively have different advantages with respect to known non-helical these shapes of shape inductance coil.But and the common advantage that the spiral pattern of these broad sense is consistent is that it can easier and excitation discharge more reliably.This gives the credit to the electric field that these generalized helix shape patterns are produced and has radial character.

Fig. 2 (a) expression annulus helical winding 2 identical as can be seen as Fig. 1, Fig. 2 (b) represents ellipse spiral formula coil 2, Fig. 2 (c) is a square coil and Fig. 2 (d) is multiple ceoncentrically wound coil." spirally " that is clearly adopted here and " spiral " term not only comprise crooked but also comprise helix wire, heterogeneous and multiple.And the characteristics of each " helix " are to be as the criterion with " radius " of the average increase of each complete turn of coil or circle from central point.

Although the shape of spiral coil 2 is arbitrarily to a certain extent as shown in Figure 2, every kind of shape produces its feature plasma arc in the gas filler of big envelope 10.With reference to Fig. 1,2 and 3, with several such features of explanation.

In each figure of Fig. 3 (a) 3 (b) and 3 (c) by Fig. 1 in the direction indication of arrow go out the section A BCD of big envelope 10, its middle conductor CD is along this big envelope of one side five equilibrium of length maximum.The example of the plasma arc discharge in the gas filler of the difform coil 2 of each figure expression among Fig. 3.Solid line 13 among the section A BCD is electron density contours of plasma arc.

US-A-4 is pressed in Fig. 3 (a) expression, the non-homogeneous discharge that the making toroidal coil of 872,741 suggestions produces.This coil has its section of round shape shown in reference number 12.

As Fig. 3 (b) midship section 14 is the master screw shape coil 2 as shown in Fig. 2 (a).The high electron density contour of Fig. 3 (b) distributes along big envelope more equably than the contour of Fig. 3 (a) as can be seen.This is because the flat wound characteristic of this coil determines.

Similarly, the section 1b of Fig. 3 (c) is the section of the spiral coil 2 of Fig. 2 (d).Can clearly be seen that from isocontour shape on the principle that it provides uniform electronic density distribution and the output of the most uniform light in each coil layout shown in Figure 3.But, preferably adopt among round screw thread layout among Fig. 2 (a) or Fig. 2 (b) a kind of in the oval layout in practice.

Although characteristics of the present invention spiral coil according to the present invention is an individual layer, thereby the 2 D-coil that can provide ratio such as annulus to occupy less space effectively, but might as shown in Figure 4 many such individual layers be piled up and/or be piled up.

Fig. 4 (a) represents many square spiral shape coils 18, and the many hexagon spiral coils 20 of Fig. 4 (b) expression.As top especially discuss with reference to Fig. 3, these various layouts will cause the plasma arc of each tool characteristic in big envelope 10.In Fig. 4 (c) of expression round spiral coil, the coil 22 on structure foreground on the example of plate 4, and on the opposite side of plate 4, construct coil 24.

Schematically illustrate referring now to Fig. 5 and to be applicable to the circuit of driving according to coil of the present invention.Be connected with voltage source 30 by contact 6,8 coils 2 through capacitor 26,28.It is the alternating voltage of 13.56MHz that power supply 30 produces frequency, and capacitor 26 is 54pF for 19pF capacitor 28.Coil 2 is processed as (in known mode) and has the size of 2.5mH inductance.

Although must in individual layer, constitute according to spiral coil of the present invention, whether must be as top example, this layer can not be plane, and this big envelope can not be plane also.Therefore as to need this layer may be crooked or distortion certainly, for the shape of the single layer coil that effectively is coupled between background light source and coil should be consistent with the shape of background light source.In Fig. 6, shown such example, among Fig. 6 with similar parts in identical digitized representation and the above-mentioned example.As can be seen from Figure 6, coil 2 still on the individual layer on the plate 4, but plate 4 be crooked rather than as shown above be planar shaped.

In superincumbent each example, coil 2 is expressed as structure on plate 4, although coil 2 is adjacent with big envelope 10, coil and big envelope separate.But as shown in Figure 7, needn't be like this, can on big envelope 10, construct coil 2 and become as a whole, can provide the layout more elongated like this than layout that the front is described.

Though those skilled in the art can recognize for spiral coil-its shape how-needn't force it to have uniform turn-to-turn spacing.Thereby the present invention is intended to obtain than adopting known individual layer spiral coil to have the thinner background light source of more even light output.

For those skilled in the art's this point also is significantly, and spiral coil promptly according to the present invention always exists gap or at interval between each the adjacent circle of conductive component or circle.For example can be by electrical insulating material being coated on the conductive component between each circle, to stay the air gap and this soft-body is obtained this gap or interval by spiral around self winding up.

When background light source that one of structure is used for large-area relatively display (as 6 inches * 8 inches), with several less, respectively having the background light source light source that self encourages spiral electrode or electrode group, to set up this overall background light source be easy.For example, the background light source of one 6 " * 8 " can be made of the big envelope of four 6 " * 2 ", as shown in the layout of Fig. 8 (a), 8 (b) and 8 (c), one of these big envelope arranging against a ground and each each drive by one, two or three spiral electrodes.

Very clear, big envelope needs not to be rectangle, and if they be rectangle they also needn't and Fig. 8 (a), 8 (b) and 8 (c) shown in layout consistent.For example, the big envelope of the most handy eight 3 " * 2 ", rather than be configured for the background light source of 6 " * 8 " display with the big envelope of four 6 " * 2 ", and correspondingly the layout of each spiral electrode also may be different.But the quantity that usually preferably makes each big envelope that is used for constructing the combined background light source class of being discussed in this section and the previous paragraphs is for minimum, because joint between each different big envelopes or connecting line can cause the inhomogeneities of light output.Can compensate this inhomogeneities by various opticses such as diffuser or microlens array when needed, can be more cheap and easier but do not use extra parts manufacturing to make up background light source.

The combined light source that each hexagon big envelope is set into alveolate texture and constitutes is a kind of suitable especially layout, and it is well-regulated but be that the distribution mode of non-linear connecting line makes the non-linear of whole surf zone glazed thread output at display distribute by an acceptable pattern.In Fig. 9, schematically represented this layout.

In all execution modes, although this method is not absolutely necessary, by being easy to carrying out the etch configuration spiral electrode such as the copper coating on the non-conductive substrate of printed circuit board (PCB).It is that photoetching process according to standard carries out that the thickness of copper typically is 30 to 60 microns and etching.Because typically spiral electrode is to be that 13.56MHz and power are approximately 20 watts power drives by frequency, substrate material must can tolerate significant heating, preferably adopt ceramic substrate in some cases.Another program is, as described above, spiral electrode or electrode group can directly be configured on the surface of big envelope self, and this big envelope is normally with glass or quartzy formulate.

As can be seen from Figure 5, the circuit that each capacitor is used for and has the spiral electrode inductance under this situation carries out tuning.These capacitor structures are placed on not using on the zone of copper coating suit, make them away from the zone that occupies by spiral electrode or electrode group, especially more should be like this when adopting the two-sided substrate that all has a copper coating.In this case, can keep the overlay area of substrate opposite face copper coating and be used to set up capacitor.Under any circumstance, a kind of fine tuning ability is set suits, it can adopt the form of the trimmer capacitor of portable staggered element, and with respect to power supply and electrode (or electrode group) this fine setting container is installed suitably.

Figure 10 represents that diameter is the typical structure of the circular background light source member of 70mm, and it comprises a main shell 34 that contains short and thick circular cylinder formula background light source big envelope 36 in essence.As can be from more easily finding out Figure 11 exploded view, be that parts 34 and 36 have increased spiral electrode 38 that type was described and direct current to radio frequency converter and power match drive circuit 40 at afterbody, the latter is installed within the main shell 34.In addition, different protecting components is arranged on different positions, as afterbody binding 42 and member backboard 44, and at anterior binding 46, neoprene buffering spacer 48, transparent protective shield curtain 50 and the big envelope fixed head 52 of member front portion.A model and sequence number board 54 have also been added in the front portion of main shell 34.DC power supply is provided in main engine bed 34 and DC power supply is connected on the circuit 40 by socket 56.

The frequency that Figure 12 represents to drive top illustrated spiral electrode is the suitable circuit arrangement of 20 watts power supply for 13.56MHz power.

This circuit arrangement is predetermined to be contained in the die casting box (not shown), constructed this die casting box in order to use together with the illustrated circular lamp (not shown) relevant with Figure 10 and Figure 11 in front, voltage height to 30 volt of this circuit arrangement requirement electric current is 1.25 amperes a DC power supply.The fin that is fixed on this die casting box outside allows the circuit continuous operation.

This circuit has a piezo-oscillator 58 that drives single-stage terminal amplifier 60.This Amplifier Design becomes when the efficient from the direct current to the radio frequency that obtains 80% with 50 ohm load impedance by the work of E class A amplifier A.When under other impedance, driving, may obtain lower efficient.

Used two field-effect transistors (FET) 62 and 64 in the circuit, in the oscillator model of FET62 be 2N7000 and in the output amplifier model of FET64 be IRF510.The initial bias voltage of 2N7000 is that the voltage divider 66 by 1M/100K ohm provides, and 68 provide grid voltage.Need a power supply that is about 25 volts in order to start vibration, thereby and when in case after starting vibration can reduce this power supply if desired above starting bias voltage.The feedback of keeping vibration is that the crystal 72 by the resistor 70 of the 4K7 between the drain electrode grid of FET62 and 13.56MHz provides.Phase angle by capacitor 74 feedback signals of the 33pF that is connected with ground is optimized.The tuned load of this grade is to be provided by the capacitor 78 of the inductor 76 of 0.68 μ H, 220pF and the grid capacitance of FET64.

In order to obtain required output, need about 10 ohm output impedance, thereby connected a low pass " L " type circuit section impedance transformer.The series inductance of this converter and the series reactor of output network combine and provide a simple component.It is variable to allow circuit adjustment and tolerance that this inductor is made.

The feed through capacitor 80 of 10nF and the capacitor 82 of the 100nF between feed line and the ground have reduced radio frequency along the former conduction of electricity.

Although E class circuit is simple and effective, sort circuit has applied high voltage and high electric current on transistor.Peak current almost is three times of average and crest voltage will exceed three times of supply voltage.The supply voltage of maximum should be limited in 30 volts when adopting 100 volts transistor.

For integrality, list the value of other element of circuit shown in Figure 12 below:

Resistor 84 ... 1M

Resistor 86 ... 100K

Resistor 88 ... 120

Capacitor 90 ... 4n7

Resistor 92 ... 1K

Inductor 94 ... 4 μ H

Capacitor 96 ... 150p

Capacitor 98 ... 470p

Inductor 100 ... 0.6 μ H is variable

Capacitor 102 ... 180p

Capacitor 104 ... 330p

Discuss now a kind of can be applicable to need be very high brightness and the further improvement in the extraordinary uniformity lighting condition, fluorescent material coating before can removing in this case (being that background light source faces toward the coating on that first type surface of display).The manufacturing of this layer coating is difficult especially, because for the forward direction ultra-violet radiation that discharge is generated causes that useful visible light is changed this layer must be enough thick, but for this layer of forward direction visible light by the generation of rear portion fluorescent material of hyperabsorption again can not be too not thick.

It is very difficult will reaching these targets in practice simultaneously, thereby must take a kind of half measure, this half measure relates to the not really thin fluorescent material of employing so that all ultra-violet radiations that arrive on the anterior fluorescent material all are converted to visible radiation.Final this may mean that on brightness or uniformity background light source can not reach its whole potentiality.In addition, production has thick rear portion fluorescent material and wants the big envelope of the thin anterior fluorescent material of fine control to cause very big manufacture difficulty, especially when employing has the glass big envelope of inner fluorescent material.

If the outside or inner phosphor layer of individual layer only is set at the rear portion of big envelope then can overcomes or reduce these difficulties.This fluorescence coating can be enough thick in to guarantee along forwards produce visible radiation to (promptly towards display) maximumly.Settle a dichronic mirror (it must be transmission to ultra-violet radiation) in place near the big envelope front surface, the characteristic that this dichronic mirror had is a transmissive in the (radiation of wavelength＞400nm) and be reflected in the radiation of the ultraviolet portion (wavelength＜400nm, especially near the main ultraviolet ray place the 254nm that the low-pressure mercury discharge is produced) of wave spectrum of the visible light part of wave spectrum.Can form like this produce by the posterior face fluorescent material and directly from background light source with minimum decay along forwards to the useful visible radiation that transmits by plasma generation.And from plasma forwards to the ultra-violet radiation ripple be reflected back to plasma, and reuptake or propagate and help the emission of rear surface fluorescent material by plasma through plasma.In such a way from plasma forwards to the overwhelming majority of ultra-violet radiation will be used for optically encouraging plasma discharge (thereby reducing to drive the required radio-frequency power of this discharge) or be used to increase the total amount of the visible radiation that the rear portion fluorescent material produces.Can obtain now that a part at wave spectrum has very high transmittance and have the dichronic mirror of this desirable characteristics of highly reflective on another part of wave spectrum.

Claims (12)

1. electrodeless background light source that is used for illuminated displays, this background light source comprises a flat basically assembly, for with consistent this background light source of the size of display be the thickness of representing this assembly by its third dimension of two-dimentional configuration, this background light source has at least one big envelope that contains gas filler, gas filler can respond its radio frequency that applies (RF) energy is produced electromagnetic radiation, this electromagnetic radiation encourages conversion medium to produce visible light conversely again, it is characterized in that: be used for the device that described radio-frequency (RF) energy is applied on the described gas filler is comprised one or more drive units of being made up of electric conducting material, drive unit and the predetermined pattern that extends along described two dimension are consistent, and drive unit only enlarges the thickness of described electric conducting material basically on the described third dimension; Described pattern is to be generally screw type shape and mutually arranged side by side with described big envelope.

2. according to the background light source of claim 1, wherein said big envelope be constitute with glass and at it at least one extends along described two dimension and scribble inner fluorescent material coating facing on the surface of described display.

3. according to the background light source of claim 1, wherein said big envelope be constitute with the ultraviolet material of transmissive and at it at least one extends along described two dimension and scribble outside fluorescent material coating facing on the surface of described display.

4. according to the background light source of above-mentioned arbitrary claim, wherein saidly predetermined be generally screw type pattern and be essentially round figure and conform to one.

5. according to each background light source in the claim 1,2 or 3, wherein saidly predetermined be generally screw type pattern and be essentially oval figure and conform to one.

6. according to each background light source in the claim 1,2 or 3, the wherein said predetermined screw type pattern that is generally conforms to a figure that is essentially rectangle.

7. according to the background light source of above-mentioned arbitrary claim, the wherein said predetermined pattern that is generally spiral contains the scrambling at least a radial spacing between its adjacent each circle.

8. according to the background light source of above-mentioned arbitrary claim, wherein said electric conducting material is the copper of thickness between 30 microns to 60 microns.

9. background light source according to Claim 8, wherein said copper-clad is drawn together the metal coating on the non-metal base.

10. according to the background light source of claim 9, wherein be used at least one capacitor that described radio-frequency (RF) energy is applied on the described drive unit is made of the described copper coating of a part.

11. comprise background light source layout according to the assembly of the background light source of above-mentioned arbitrary claim.

12. according to a kind of layout of claim 11, wherein each background light source in this assembly is made of the hexagon big envelope.

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