LED light bulb and LED filament thereof

An LED filament and an LED light bulb applying the same are disclosed. The LED filament includes LED chips, conductive electrodes disposed corresponding to the LED chips, and a light conversion coating. The LED chips are electrically connected together and the conductive electrodes are electrically connected with the LED chips. The light conversion coating includes an adhesive and a plurality of phosphors. The light conversion coating coats on at least two sides of the LED chips and the conductive electrodes. The light conversion coating exposes a portion of two of the conductive electrodes. Accordingly, the LED filament is capable of emitting light similar to that a point light source does and the LED light bulb may emit omnidirectional light.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to the following Chinese Patent Applications No. CN 201510502630.3 filed on 2015 Aug. 17, CN 201510966906.3 filed on 2015 Dec. 19, CN 201610041667.5 filed on 2016 Jan. 22, CN 201610272153.0 filed on 2016 Apr. 27, CN 201610281600.9 filed on 2016 Apr. 29, CN 201610394610.3 field on 2016 Jun. 3, and CN 201610586388.7 filed on 2016 Jul. 22, the disclosures of which are incorporated herein in their entirety by reference.

TECHNICAL FIELD

The instant disclosure relates to illumination field, and more particularly, to an LED light bulb and an LED filament thereof.

RELATED ART

The LED has advantages of environmental protection, energy saving, high efficiency and long lifespan, and therefore it attracts widespread attention in recent years and gradually replaces traditional lighting lamps. However, due that the luminescence of the LED has directivity, current LED lamps is unable to provide with an illumination with a wide angle range like traditional lamps. Accordingly, how to design LED lamps with similar wide range for illumination to the traditional lamps challenges the industries.

In order to provide with an illumination with a wide range, optical components like lenses, prisms, reflectors are utilized to adjust light distribution emitted originally from the LED. However, the optical components for adjusting the light distribution decrease the overall optical efficiency of LED lamps. Consequently, how to improve the optical efficiency and provide with wide range for illumination are important tasks in the lighting industry.

Next, an LED die without package can be deemed as a full-angle light source and is capable of providing with full-range illumination. However, the package of LED narrows the illumination angle and decreases optical efficiency.

Further, a lamp with a LED filament is more possible to provide wide-range illumination and its outlook is closer to that of the traditional incandescent (tungsten) light bulbs. This is also one of advantages of light bulb with a LED filament.

One of the challenges of LED light bulbs is omnidirectional lighting. Current LED light bulbs utilize LED filaments. The LED filament has LED chips on a strip substrate and mixtures of silica gel with phosphor coated on the LED chips. The substrate is usually a glass substrate or a metal substrate. The glass substrate has the advantages of not blocking light emitted from LED chips; however, its disadvantages include that the thermal conductivity of the glass substrate is not good and the glass substrate is fragile. Likewise, the LED chips are disposed on the metal substrate having excellent thermal conductivity, but light emitted from the LED chips will be blocked from the metal substrate side. Additionally, the substrates of conventional LED filaments are hard and not bendable. Accordingly, in order to provide with omnidirectional lighting, the conventional LED light bulb utilizes a number of LED filaments symmetrically positioned inside a bulb shell. The utilization of multiple LED filaments increases the cost of the LED bulb because of its complicated manufacturing processes, complex assembly procedures and low yield rate. Additionally, the more LED filaments in a light bulb, the more soldering spots between filaments and filament supports there are as well as the higher possibility soldering defects happens.

US patent publication number 20130058080A1 discloses an LED light bulb and an LED light-emitting strip capable of emitting 4π (light. The LED light bulb comprises an LED light bulb shell, a core column with an exhaust tube and a bracket, at least one LED light emitting strip with LED chips therein emitting 4π (light, a driver, and an electrical connector. The LED light bulb shell is vacuum sealed with the core column so as to form a vacuum sealed chamber. The vacuum sealed chamber is filled with a gas having a low coefficient of viscosity and a high coefficient of thermal conductivity. The bracket and the LED light emitting strips fixed on the bracket are housed in the vacuum sealed chamber. The LED light emitting strip is in turn electrically connected to the driver, the electrical connector, while the electrical connector is used to be electrically connected to an external power supply, so as to light the LED light emitting strips.

SUMMARY

To address the issues, the instant disclosure provides with embodiments of an LED filament, a manufacturing method therefor, and an LED light bulb utilizing the LED filament.

According to an embodiment, an LED filament comprising a plurality of LED chips, at least two conductive electrodes disposed corresponding to the plurality of LED chips, and a light conversion coating. The plurality of LED chips and the conductive electrodes are electrically connected therebetween. The light conversion coating comprises an adhesive and a plurality of phosphors. The light conversion coating coats on at least two sides of the LED chips and the conductive electrodes. The light conversion coating exposes a portion of two of the conductive electrodes. The phosphors in the light conversion coating are capable of emitting light after absorbing some form of radiation.

According to an embodiment, the LED filament further comprises a plurality of conductive wires electrically and correspondingly connected among the plurality of LED chips and the conductive electrodes. The light conversion coating covers the plurality of conductive wires.

According to an embodiment, the LED filament further comprises a plurality of circuit films electrically and correspondingly connected among the plurality of LED chips and the conductive electrodes. The light conversion coating covers the plurality of the circuit films.

According to an embodiment, each of the circuit films comprises a first film and a conductive circuit disposed thereon. The conductive circuits are electrically and correspondingly connected among the plurality of LED chips and the conductive electrodes.

According to an embodiment, the light conversion coating comprises a base layer and a top layer. The plurality of LED chips is on a side of the base layer. The Shore D Hardness of the base layer is at least 60 HD.

According to an embodiment, the light conversion coating further comprises oxidized nanoparticles. The size of the oxidized nanoparticles is substantially smaller than the size of the phosphors.

According to an embodiment, the Young's Modulus of the LED filament is between 0.1×1010Pa to 0.3×1010Pa. The composition ratio of the plurality of the phosphors to the adhesive is between 1:1 and 99:1.

According to an embodiment, an LED light bulb comprises a bulb shell, a bulb base connected with the bulb shell, at least two conductive supports disposed in the bulb shell, and a single LED filament disposed in the light bulb. The LED filament comprises a plurality of LED chips, at least two conductive electrodes disposed corresponding to the plurality of LED chips, and a light conversion coating. The plurality of LED chips and the conductive electrodes are electrically connected therebetween. The conductive electrodes are electrically and respectively connected with the conductive supports. The light conversion coating coats on at least two sides of the LED chips and the conductive electrodes. The light conversion coating exposes a portion of two of the conductive electrodes. The light conversion coating comprises an adhesive and a plurality of phosphors.

According to an embodiment, the LED light bulb further comprises a stem in the bulb shell and a heat dissipating element between the bulb shell and bulb base. The heat dissipating element is connected with the stem. The LED filament connected with the stem.

According to some embodiments, each of the surfaces of the LED chips is covered by the light conversion coating. The phosphors of light conversion coating may absorb light out of the surfaces of the LED chips and emit light with longer wavelength. Since the LED chips are surrounded by the light conversion coating to form the main body of the LED filament, the LED filament is capable of emitting light from the sides of the filament having the light conversion coating, and being bended with adequate rigidity. The LED light bulb is capable of emitting omnidirectional light with the single LED filament.

DETAILED DESCRIPTION

The instant disclosure provides an LED filament and an LED light bulb to solve the abovementioned problems. The instant disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the disclosure are shown. This disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Like reference numerals refer to like elements throughout.

It will be understood that the term “and/or” includes any and all combinations of one or more of the associated listed items. It will also be understood that, although the terms first, second, third etc. may be used herein to describe various elements, components, regions, parts and/or sections, these elements, components, regions, parts and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, part or section from another element, component, region, layer or section. Thus, a first element, component, region, part or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present disclosure.

The following description with reference to the accompanying drawings is provided to explain the exemplary embodiments of the disclosure. Note that in the case of no conflict, the embodiments of the present disclosure and the features of the embodiments may be arbitrarily combined with each other.

As indicated in the section of the cross-reference, the instant disclosure claims priority of several Chinese patent applications, and the disclosures of which are incorporated herein in their entirety by reference. When it comes to claim construction, the claims, specification, and prosecution history of the instant disclosure controls if any inconsistency between the instant disclosure and the incorporated disclosures exists.

Please refer toFIGS. 1 and 2.FIG. 1illustrates a perspective view of an LED filament with partial sectional view according to a first embodiment of the present disclosure whileFIG. 2illustrates a partial cross-sectional view at section2-2ofFIG. 1. According to the first embodiment, the LED filament100comprises a plurality of LED chips102,104, at least two conductive electrodes110,112, and a light conversion coating120. The conductive electrodes110,112are disposed corresponding to the plurality of LED chips102,104. The LED chips102,104are electrically connected together. The conductive electrodes112,114are electrically connected with the plurality of LED chips102,104. The light conversion coating120coats on at least two sides of the LED chips102,104and the conductive electrodes110,112. The light conversion coating120exposes a portion of two of the conductive electrodes110,112. The light conversion coating120comprises an adhesive122and a plurality of phosphors124.

LED filament100emits light while the conductive electrodes110,112are applied with electrical power (electrical current sources or electrical voltage sources). In this embodiment, the light emitted from the LED filament100is substantially close to 360 degrees light like that from a point light source. An LED light bulb10a,10b, illustrated is inFIGS. 12A and 12B, utilizing the LED filament100is capable of emitting omnidirectional light, which will be described in detailed in the followings.

As illustrated in theFIG. 1, the cross-sectional outline of the LED filament100is rectangular. However, the cross-sectional outline of the LED filament100is not limited to rectangular, but may be triangle, circle, ellipse, square, diamond, or square with chamfers.

Each of LED chips102,104may comprise a single LED die or a plurality of LED dies. The outline of the LED chip102,104may be, but not limited to, a strip shape which does not have the problem of current diffusion uniform distribution. Therefore, extended electrodes are not required on the electrodes of the LED chip102,104to help the current diffusion. The extended electrodes may shield the illumination of the LED chip, thereby affecting the illumination efficiency. In addition, the LED chips102,104may be coated on their surfaces with a conductive and transparent layer of Indium Tim Oxide (ITO). The metal oxide layer contributes to uniform distribution of the current diffusion and to increase of illumination efficiency. Specifically, the aspect ratio of the LED chip may be 2:1 to 10:1; for example, but not limited to, 14×28 or 10×20. Further, the LED chips102,104may be high power LED dies and are operated at low electrical current to provide sufficient illumination but less heat.

The LED chips102,104may comprise sapphire substrate or transparent substrate. Consequently, the substrates of the LED chips102,104do not shield/block light emitted from the LED chips102,104. In other words, the LED chips102,104are capable of emitting light from each side of the LED chips102,104.

The electrical connections among the plurality of LED chips102,104and the conductive electrodes112,114, in this embodiment, may be shown inFIG. 1. The LED chips102,104are connected in series and the conductive electrodes112,114are disposed on and electrically and respectively connected with the two ends of the series-connected LED chips102,104. However, the connections between the LED chips102,104are not limited to that inFIG. 1. Alternatively, the connections may be that two adjacent LED chips102,104are connected in parallel and then the parallel-connected pairs are connected in series.

According to this embodiment, the conductive electrodes110,112may be, but not limited to, metal electrodes. The conductive electrodes110,112are disposed at two ends of the series-connected LED chips102,104and a portion of each of the conductive electrodes110,112are exposed out of the light conversion coating120. In an embodiment of at least three conductive electrodes110,112, a portion of two of the conductive electrodes110,112are exposed out of the light conversion coating120. Please refer toFIGS. 3A and 3Bwhich illustrate disposition of metal electrodes and a plurality of LED chips according to other embodiments of the LED filament. In the embodiment ofFIG. 3A, the LED chips102,104are connected in series and the two ends of the series-connected LED chips102,104are positioned at the same side of the LED filament100to form an U shape. Accordingly, the two conductive electrodes110,112are positioned at the same side as the ends of the series-connected LED chips102,104. According to the embodiment ofFIG. 3B, the LED chips102,104are disposed along two parallel LED strips and the LED chips102,104along the same LED strip are connected in series. Two conductive electrodes110,112are disposed at two ends of the series-connected LED chips102,104and electrically connected to each of ends of the series-connected LED chips102,104. In this embodiment ofFIG. 3B, there are, but not limited to, only two conductive electrodes110,112. For examples, the LED filament100, in practices, may comprise four sub-electrodes. The four sub-electrodes are connected to four ends of the series-connected LED chips102,104, respectively. The sub-electrodes may be connected to anode and ground as desired. Alternatively, one of two conductive electrodes110,112may be replaced with two sub-electrodes, depending upon the design needs.

Please further refer toFIG. 12A. The conductive electrodes110,112has through holes111,113(shown inFIG. 1) on the exposed portion for being connected with the conductive supports14a,14bof the LED light bulb10a.

Please refer toFIGS. 1 and 2again. According to this embodiment, the LED filament100further comprises conductive wires140for electrically connecting the adjacent LED chips102,104and conductive electrodes110,112. The conductive wires140may be gold wires formed by a wire bond of the LED package process, like Q-type. According toFIG. 2, the conductive wires140are of M shape. The M shape here is not to describe that the shape of the conductive wires140exactly looks like letter M, but to describe a shape which prevents the wires from being tight and provides buffers when the conductive wires140or the LED filament100is stretched or bended. Specifically, the M shape may be any shape formed by a conductive wire140whose length is longer than the length of a wire which naturally arched between two adjacent LED chips102,104. The M shape includes any shape which could provide buffers while the conductive wires104are bended or stretched.

The light conversion coating120comprises adhesive122and phosphors122. The light conversion coating120may, in this embodiment, wrap or encapsulate the LED chips102,104and the conductive electrodes110,112. In other words, in this embodiment, each of six sides of the LED chips102,104is coated with the light conversion coating120; preferably, but not limited to, is in direct contact with the light conversion coating120. However, at least two sides of the LED chips102,104may be coated with the light conversion coating120. Preferably, the light conversion coating120may directly contact at least two sides of the LED chips102,104. The two directly-contacted sides may be the major surfaces which the LED chips emit light. Referring toFIG. 1, the major two surfaces may be the top and the bottom surfaces. In other words, the light conversion coating120may directly contact the top and the bottom surfaces of the LED chips102,104(upper and lower surfaces of the LED chips102,104shown inFIG. 2). Said contact between each of six sides of the LED chips102,104and the light conversion coating120may be that the light conversion coating120directly or indirectly contacts at least a portion of each side of the LED chips102,104. Specifically, one or two sides of the LED chips102,104may be in contact with the light conversion coating120through die bond glue. In some embodiments, the die bond glue may be mixed with phosphors to increase efficiency of light conversion. The die bond glue may be silica gel mixed with silver powder or heat dissipating powder to increase effect of heat dissipation thereof. The adhesive122may be silica gel. In addition, the silica gel may be partially or totally replaced with polyimide or resin materials to improve the toughness of the light conversion coating120and to reduce possibility of cracking or embrittlement.

The phosphors124of the light conversion coating120absorb some form of radiation to emit light. For instance, the phosphors124absorb light with shorter wavelength and then emit light with longer wavelength. In one embodiment, the phosphors124absorb blue light and then emit yellow light. The blue light which is not absorbed by the phosphors124mixes with the yellow light to form white light. According to the embodiment where six sides of the LED chips102,104are coated with the light conversion coating120, the phosphors124absorb light with shorter wavelength out of each of the sides of the LED chips102,104and emit light with longer wavelength. The mixed light (longer and shorter wavelength) is emitted from the outer surface of the light conversion coating120which surrounds the LED chips102,104to form the main body of the LED filament100. In other words, each of sides of the LED filament100emits the mixed light.

The light conversion coating120may expose a portion of two of the conductive electrodes110,112. Phosphors124is harder than the adhesive122. The size of the phosphors124may be 1 to 30 um (micrometer) or 5 to 20 um. The size of the same phosphors124are generally the same. InFIG. 2, the reason why the cross-sectional sizes of the phosphors124are different is the positions of the cross-section for the phosphors124are different. The adhesive122may be transparent, for example, epoxy resin, modified resin or silica gel, and so on.

The composition ratio of the phosphors124to the adhesive122may be 1:1 to 99:1, or 1:1 to 50:1. The composition ratio may be volume ratio or weight ratio. Please refer toFIG. 2again. The amount of the phosphors124is greater than the adhesive122to increase the density of the phosphors124and to increase direct contacts among phosphors124. The arrow lines onFIG. 2show thermal conduction paths from LED chips102,104to the outer surfaces of the LED filament100. The thermal conduction paths are formed by the adjacent and contacted phosphors. The more direct contacts among the phosphors124, the more thermal conduction paths forms, the greater the heat dissipating effect the LED filament100has, and the less the light conversion coating becomes yellow. Additionally, the light conversion rate of the phosphors124may reach 30% to 70% and the total luminance efficiency of the LED light bulb10a,10bis increased. Further, the hardness of the LED filament100is increased, too. Accordingly, the LED filament100may stand alone without any embedded supporting component like rigid substrates. Furthermore, the surfaces of cured LED filament100are not flat due to the protrusion of some of the phosphors124. In other words, the roughness of the surfaces and the total surface area are increased. The increased roughness of the surfaces improves the amount of light passing the surfaces. The increased surface area enhances the heat dissipating effect. As a result, the overall luminance efficiency of the LED light filament100is raised.

Next, LED chips102,104may comprise LED dies which emit blue light. The phosphors124may be yellow phosphors (for example Garnet series phosphors, YAG phosphors), so that the LED filament100may emit white light. In practices, the composition ratio of phosphors124to the adhesive122may be adjusted to make the spectrum of the white light emitted from the LED filament100closer to that emitted from incandescent bulbs. Alternatively, the phosphors124may be powders which absorb blue light (light with shorter wavelength) and emit yellow green light (hereinafter referred to yellow green powders) or emit red light (hereinafter referred to red powders) (light with longer wavelength). The light conversion coating120may comprise less red powders and more yellow green powders, so that the CCT (corrected color temperature) of the light emitted from the LED filament100may close to 2,400 to 2,600 K (incandescent light).

As mention above, a desired deflection of the LED filament100may be achieved by the adjustment of the ratio of phosphors124to the adhesive122. For instance, the Young's Modulus (Y) of the LED filament100may be between 0.1×1010to 0.3×1010Pa. If necessary, the Young's Modulus of the LED filament100may be between 0.15×1010to 0.25×1010Pa. Consequently, the LED filament100would not be easily broken and still possess adequate rigidity and deflection.

Please refer toFIGS. 4 to 5.FIG. 4illustrates a perspective view of an LED light bulb with partial sectional view according to a second embodiment of the LED filament andFIG. 5illustrates a partial cross-sectional view at section5-5ofFIG. 4.

According to the second embodiment of the LED filament200, the LED filament200comprises a plurality of LED chips202,204, at least two conductive electrodes210,212, and a light conversion coating220. The conductive electrodes210,212are disposed corresponding to the plurality of LED chips202,204. The plurality of LED chips202,204and the conductive electrodes212,214are electrically connected therebetween. The light conversion coating220coats on at least two sides of the LED chips202,204and the conductive electrodes210,212. The light conversion coating220exposes a portion of two of the conductive electrodes210,212. The light conversion coating220comprises an adhesive222, a plurality of inorganic oxide nanoparticles226and a plurality of phosphors224.

The size of the plurality of inorganic oxide nanoparticles226is around 10 to 300 nanometers (nm) or majorly is around 20 to 100 nm. The size of the plurality of inorganic oxide nanoparticles226is lesser than that of the phosphors224. The plurality of the inorganic oxide nanoparticles226may be, but not limited to, aluminium oxides (Al2O3), silicon oxide (SiO2), zirconium oxide (Zirconia, ZrO2), titanic oxide (TiO2), Calcium oxide (CaO), strontium oxide (SrO), and Barium oxide (BaO).

As shown inFIG. 5, the inorganic oxide nanoparticles226and the phosphors224are mixed with the adhesive222. The unit prices and the hardnesses of the inorganic oxide nanoparticles226and the phosphors224are different. Therefore, a desired deflection, thermal conductivity, hardness, and cost of the LED filament200may be reached by adjustment of the ratio of the adhesive222, phosphors224to the inorganic oxide nanoparticles226affects. In addition, due that the size of the inorganic oxide nanoparticles226is lesser than that of the phosphors224, the inorganic oxide nanoparticles226may fill into the gaps among the phosphors224. Hence, the contact area among the phosphors224and the inorganic oxide nanoparticles226is increased and thermal conduction paths are increased as shown by arrow lines onFIG. 5, too. Further, the inorganic oxide nanoparticles226may deflect or scatter light incident thereon. The light deflection and scattering make the light emitted from phosphors224mixed more uniformly and the characteristics of the LED filament200becomes even better. Furthermore, the impedance of the inorganic oxide nanoparticles226is high and no electrical leakage would happen through the inorganic oxide nanoparticles226.

In some embodiments, the phosphors224are substantially uniformly distributed in the adhesive222(for instance, in silica gel, the polyimide or resin materials). Each of the phosphors224may be partially or totally wrapped by the adhesive222to improve the cracking or embrittlement of the light conversion coating220. In the case that not each of the phosphors224is totally wrapped by the adhesive222, the cracking or embrittlement of the light conversion coating220is still improved. In some embodiments, silica gel may be mixed with the polyimide or resin materials to form the light conversion coating220.

The LED filament200further comprises a plurality of circuit film240(or call as transparent circuit film) for electrically and correspondingly connected among the plurality of LED chips and the conductive electrodes. Specifically, the plurality of circuit film240is electrically connecting the adjacent LED chips202,204and conductive electrodes210,212. The light conversion coating220may encapsulate the plurality of circuit film240.

Please refer toFIG. 6A.FIG. 6Aillustrates a first embodiment of the uncut circuit film according to the second embodiment of the LED filament200. Each of the circuit films240comprises a first film242and a conductive circuit244disposed on the first film242. The first film242in one embodiment may be, but not limited to, a thin film. In order to be easily understood the embodiments, the following description uses thin film as an example for the first film242. However, the thin film242is not the only embodiment for the first film242. The thin film242may be a transparent or translucent film. The transparent film may allow light emitted from the LED chips202,204and/or phosphors124to pass. The conductive circuits244are electrically and correspondingly connected among the plurality of LED chips202,204and the conductive electrodes210,212. In this embodiment, the conductive circuits244are of bar shape and substantially parallel to each other. However, the conductive circuits244may be in other shape or pattern. Please refer toFIG. 7Awhich illustrates a second embodiment of the uncut circuit film according to the second embodiment of the LED filament. Each of the circuit films240acomprises a thin film242aand a conductive circuit244adisposed on the thin film242a. The conductive circuits244aare substantially parallel lines electrically connected with pads of adjacent LED chips202,204as shown inFIG. 7B. Please refer toFIG. 8Awhich illustrates a third embodiment of the uncut circuit film according to the second embodiment of the LED filament. Each of the circuit films240bcomprises a thin film242band a conductive circuit244bdisposed on the thin film242b. The conductive circuits244bare crossover lines electrically connected with pads of adjacent LED chips202b,204bas shown inFIG. 8B. The width of the lines may be 10 micrometers (um) and the thickness of the lines may be 2 um. The pattern or shape of the conductive circuits244,244a,244bare not limited to the above-mentioned embodiments, any pattern or shape which is capable of connecting pads of adjacent LED chips202,204and conductive electrodes210,212are feasible.

The thin film242may be, but not limited to, Polyimide film (PI film). Transmittance of the polyimide film is above 92%. The material of the conductive circuit244may be, but not limited to, indium tin oxide (ITO), nano-silver plasma, metal grids, or nano-tubes. The advantages of Silver include good reflection and low light absorption. Nano-scaled silver lines in grid shape have advantages of low resistance and high penetration of light. In addition, gold-dopped nano-silver lines may enhance the adherence between the pads of the LED chips202,204and the sliver lines (conductive circuits).

Please refer toFIG. 6Aagain. The circuit film240may be made by firstly forming conductive circuits244on a thin film242, and then forming slots246on the thin film242with the conductive circuits244.

Please refer toFIG. 6A. The conductive circuits244do not cover the whole surface of the thin film242. Consequently, light emitted from the LED chips202,204can pass through the circuit film240at least from the portion of the thin film242where the conductive circuits244do not occupy. In the second embodiment, the circuit film240is used to electrically connect with adjacent LED chips202,204and the conductive electrodes210,212. The circuit film240has the advantages of wider conductive lines, better deflection, and better toughness (less possibility of being broken) than the conductive wires140in the first embodiments.

Regarding the electrical connection among the circuit film240, LED chips202,204, and the conductive electrodes210,212, conductive glues may be applied on the surfaces of the LED chips202,204and the conductive electrodes210,212where the conductive circuits244are going to electrically connect. The conductive glues may be, but not limited to, silver paste, solder paste (tin paste), or conductive glues doped with conductive particles. Then, dispose the circuit film240on the LED chips202,204and the conductive electrodes210,212with adequate alignment and cure the circuit film240and the conductive glues by heat or UV.

Please refer toFIGS. 9A to 9Ewhich illustrate a manufacturing method of an LED filament according to a first embodiment. The manufacturing method of the LED filament200comprises:

S22: electrically connect the LED chips202,204with the conductive electrodes210,212, referring toFIG. 9B; and

S24: dispose a light conversion coating220on the LED chips202,204and the conductive electrodes210,212. The light conversion coating220coats on at least two sides of the LED chips202,204and the conductive electrodes210,212. The light conversion coating220exposes a portion of at least two of the conductive electrodes210,212. The light conversion coating220comprises adhesive222and a plurality of phosphors224, referring toFIGS. 9C to 9E.

In S20, the plurality of LED chips202,204are disposed in a rectangular array. Each column of the LED chips202,204, at the end of the manufacturing process, may be cut into a single LED filament200. During disposition of the LED chips202,204, the anodes and cathodes of the LED chips202,204should be properly orientated for later connected in series or parallel. The carrier280may be, but not limited to, glass substrate or metal substrate. The carrier280may be, but not limited to, a plate like that shown inFIG. 9A, or a plate with a groove like the carrier180shown inFIG. 10. The groove is for being disposed with the base layer120b.

In S22, the uncut circuit film240ais similar to the circuit film240ashown inFIG. 7A. The LED chips202,204and the conductive circuit210,212are electrically connected by the parallel conductive lines. Alternatively, the circuit film240,240bshown, respectively, inFIG. 6A or 8Amay be used in S22. The conductive wires140shown inFIG. 2can be used in S22, too.

In S24, the light conversion coating220may be coated on the LED chips202,204and the conductive electrodes210,212by different method. Firstly, takingFIGS. 9C to 9Eas an example, the manufacturing method of S24comprises:

S240: coat a light conversion sub-layer (top layer220a) on a surface of the LED chips202,204and the conductive electrodes210,212which is not contact with the carrier280;

S242: flip over the LED chips202,204and the conductive electrodes210,212disposed with the top layer220a; and

S244: coat a light conversion sub-layer (base layer220b) on a surface of the LED chips202,204and the conductive electrodes210,212which are not coated with the top layer220a.

In order to distinguish the light conversion sub-layers in S240and in S244, the light conversion sub-layer in S240is referred to top layer220aand the light conversion sub-layer in S244is referred to base layer220bhereinafter.

In S240, after the LED chips202,204and the conductive electrodes210,212are coated with the top layer220a, the adhesive222and the phosphors224will fill out the gaps among the LED chips202,204and the conductive electrodes210,212. Then, proceed with a curing process to harden the top layer which encapsulates the upper part of the LED chips202,204and the conductive electrodes210,212and exposes a portion of at least two of the conductive electrodes210,212. The curing process may be done by heat or UV.

In S242, the flip-over of the semi-finished piece may be done by two different ways in accordance with different situations. Concerning the first flip-over way, the LED chips202,204and the conductive electrodes210,212are disposed on the carrier280without any adherences with the carrier280. S242can be done by flip the cured semi-finished piece over directly. Then, place the flipped-over semi-finished piece on the carrier280again. (The semi-finished piece is the cured the LED chips202,204and the conductive electrodes210,212covered with the top layer220a.)

As for the second way, glues are applied on the carrier280. The glues are, for instance, photoresist in semiconductor process, or die bond glues. The glues (photoresist or die bond glues) is for temporarily fixing the LED chips202,204and the conductive electrodes210,212on the carrier280. The glue may be removed by acetone or solvent and the semi-finished piece is separated from the carrier280. If necessary, the remained glues may be removed by an additional cleaning process.

In S244, referring toFIG. 9E, cure the base layer220bafter the base layer220bis coated on the surface of the LED chips202,204and the conductive electrodes210,212.

Referring toFIG. 9C, the top layer220ais slightly greater than the uncut circuit film240a. However, it is not a requirement. The sizes of the top layer220amay be the same as or lesser than that of the uncut circuit film240a. Referring toFIG. 9E, the area of the top layer220ais substantially the same as that of the base layer220b. It is not a requirement, either. In implementation, the area of the top layer220amay be greater or lesser than the area of the base layer220b.FIG. 9Eillustrates a semi-finished LED filament where a plurality of LED filaments200are integrated into one piece.

After S24, the method may further comprise S26: cut the semi-finished LED filament along the dot-and-dash lines shown inFIG. 9E. Each cut portion is an LED filament200. The semi-finished LED may be cut every other two dot-and-dash lines.

The method ofFIGS. 9A to 9Eillustrates each LED filament are disposed in a rectangular array manner. Alternatively, the disposition of S20may be a single column of LED chips202,204. In the consequence, S26may be omitted.

Please refer toFIG. 10for the second embodiment of the manufacturing method for the LED filament200. The method comprises:

S20A: coat a light conversion sub-layer (a base layer120b) on a carrier180;

S22: electrically connect the LED chips102,104with the conductive electrodes110,112; and

S24: coat a light conversion sub-layer (top layer120a) on the LED chips102,104and the conductive electrodes110,112. The top layer120acoats on the LED chips102,104and the conductive electrodes110,112. The top layer120aand the base layer120bexpose a portion of at least two of the conductive electrodes110,112. The light conversion coating120(top layer120aand the base layer120b) comprises adhesive122and a plurality of phosphors124.

As shown inFIG. 10, the base layer120bis a part of the light conversion coating120and comprises an adhesive122and phosphors124. In the embodiment ofFIG. 10, the base layer120bis, but not limited to, coated on the carrier180with a groove. Alternatively, the carrier180can be omitted. In other words, the base layer120bmay be place on a work table without any carrier180. The LED chips102,104and the conductive electrodes110,112are disposed on the base layer120b.

The thickness of the base layer120bmay be 50 to 100 um. The composition ratio of phosphors124to the adhesive122can be adjusted and the thickness of the base layer120bmay be around 60 to 80 um. After S20, a pre-curing process may be used to slightly cure the base layer120bso that the LED chips102,104and the conductive electrodes110,112can be fixed on the base layer120b. Besides, the LED chips102,104and the conductive electrodes110,112may be fixed on the base layer120bby die bond glues.

After the electrical connection of S22, the top layer120ais coated on the LED chips102,104and the conductive electrodes110,112and then a curing process is proceeded with to cure the top layer120a. Consequently, the flip-over of S242and glue-removing process are omitted.

According to the embodiment ofFIG. 10, after S24, the process of S26may be proceeded with.

The base layer120bis used for carrying the LED chips102,104and the conductive electrodes110,112and its thickness may be 0.5 to 3 minimeters (mm) or 1 to 2 mm.

The composition ratio of phosphors124to the adhesive122may be adjusted accordingly to make the base layer120bhard enough to sufficiently carry the LED chips102,104and the conductive electrodes110,112and for the following process like wire bond. The Shore D Hardness of the base layer120bmay be at least 60 HD. Hence, the overall LED filament10awill have enough hardness, rigidity and deflection. The electrical conductivity of the connection among the LED chips102,104and the conductive electrodes110,112can be maintained even though the LED filament10ais bent.

In accordance with the embodiment ofFIG. 10, the hardness of the cured base layer120bis better to be sufficient to carry the LED chips102,104and the conductive electrodes110,112and to support for the wire bonding process. However, the top layer120ais not required to have the same hardness as the base layer120b. Accordingly, the adjustment of ratio of the phosphors124to the adhesive122is more flexible. Alternatively, the light conversion coating120may comprise inorganic oxide nanoparticles224(not shown inFIG. 10).

Next, please refer toFIGS. 11A to 11Dwhich illustrate a manufacturing method of an LED filament according to a third embodiment. The manufacturing method for an Led filament10acomprises:

S204: dispose a plurality of LED chips102,104and a plurality of conductive electrodes110,112on the conductive foil130, referring toFIG. 11B;

S22: electrically connect the LED chips102,104with the conductive electrodes110,112, referring toFIG. 11C; and

S24: coat a light conversion sub-layer (top layer120a) on the surfaces of the LED chips102,104and the conductive electrode110,112where are not in contact with the base layer120b. The light conversion coating120(including the base layer120band the top layer120a) coats on at least two sides of the LED chips102,104and the conductive electrodes110,112. The light conversion coating120exposes a portion of at least two of the plurality of conductive electrodes110,112. The light conversion coating120comprises adhesive122and phosphors124.

Please refer toFIG. 11A, the light conversion coating of S202is called as the base layer120b. The conductive foil130may have a plurality of openings132. The width of each of the openings132may be lesser than the length of the LED chips102,104and each of the openings132is aligned with the portion of the LED chips102,104which emits light. Therefore, light emitted from LED may pass through the openings132without any shielding or blocking.

The conductive foil130may be, but not limited to, a copper foil coated with silver. The openings132may be formed by punching or stamping on a copper foil.

Before S202, the method may comprise a pre-step: dispose the base layer120bon a carrier (like180ofFIG. 10) or on a work table.

In S204, please refer toFIG. 11B. The LED chips102,104and the conductive electrodes110,112are disposed on the conductive foil130. As above-mentioned, the light emitting portions of the LED chips102,104are better to align with the openings132.

Please refer toFIG. 11C. The electrical connection of S22may be accomplished by wire bonding process like that shown inFIG. 1. As shown inFIG. 11C, the LED chips102,104and the conductive electrodes110,112are electrically connected together in series.

Next, please refer toFIG. 11D. Like the embodiment ofFIG. 10, the light conversion sub-layer may be referred to top layer120a. The top layer120afills out the gaps among the LED chips102,104and the conductive electrodes110,112including the gaps under the LED chips102,104and the openings132.

Regarding the disposition of the top layer120a, there are a few method to proceed with. The first one is to coat a mixture of the adhesive122and the phosphors124on the LED chips102,104and the conductive electrodes110,112. The second one is to firstly coat a layer of adhesive122on the LED chips102,104and the conductive electrodes110,112, and secondly coat a layer of phosphors124on the layer of the adhesive122(two disposition steps). Thereafter, cure the layer of adhesive122and the layer of phosphors124. The third one is to repeat the above two disposition steps until a required thickness is reached. Thereafter, a curing process is proceeded with. In comparison with the three methods, the uniformity of the light conversion coating120done by the third method might be better. Additionally, the disposition (coat) of the adhesive122or the phosphors124may be done by spraying.

After S24, a cut process may be proceeded with, referring toFIG. 11E. Cut LED filaments100are manufactured as shown inFIG. 11E.

In accordance with the embodiment ofFIGS. 11A to 11E, the LED chips102,104and the conductive electrodes110,112are electrically connected together through conductive foil130and conductive wire140. The flexibility of the electrical connections is enhanced. Accordingly, when the LED filament100is bent, the electrical connections would not be easily broken.

Please refer toFIGS. 12A and 12Bwhich illustrate a perspective view of LED light bulb applying the LED filaments according to a first and a second embodiments. The LED light bulb10a,10bcomprises a bulb shell12, a bulb base16connected with the bulb shell12, at least two conductive supports14a,14bdisposed in the bulb shell12, a driving circuit18electrically connected with both the conductive supports14a,14band the bulb base16, and a single LED filament100.

The conductive supports14a,14bare used for electrically connecting with the conductive electrodes110,112and for supporting the weight of the LED filament100. The bulb base16is used to receive electrical power. The driving circuit18receives the power from the bulb base16and drives the LED filament100to emit light. Due that the LED filament100emits light like the way a point light source does, the LED bulb10a,10bmay emit omnidirectional light. In this embodiment, the driving circuit18is disposed inside the LED light bulb. However, in some embodiments, the driving circuit18may be disposed outside the LED bulb.

The definition of the omnidirectional light depends upon the area the bulb is used and varies over time. The definition of the omnidirectional light may be, but not limited to, the following example. Page 24 of Eligibility Criteria version 1.0 of US Energy Star Program Requirements for Lamps (Light Bulbs) defines omnidirectional lamp in base-up position requires that light emitted from the zone of 135 degree to 180 degree should be at least 5% of total flux (lm), and 90% of the measured intensity values may vary by no more than 25% from the average of all measured values in all planes (luminous intensity (cd) is measured within each vertical plane at a 5 degree vertical angle increment (maximum) from 0 degree to 135 degree). JEL 801 of Japan regulates the flux from the zone within 120 degrees along the light axis should be not less than 70% of total flux of the bulb.

In the embodiment ofFIG. 12A, the LED light bulb10acomprises two conductive supports14a,14b. In an embodiment, the LED light bulb may comprise more than two conductive supports14a,14bdepending upon the design.

The bulb shell12may be shell having better light transmittance and thermal conductivity; for example, but not limited to, glass or plastic shell. Considering a requirement of low color temperature light bulb on the market, the interior of the bulb shell12may be appropriately doped with a golden yellow material or a surface inside the bulb shell12may be plated a golden yellow thin film for appropriately absorbing a trace of blue light emitted by a part of the LED chips102,104, so as to downgrade the color temperature performance of the LED bulb10a,10b. A vacuum pump may swap the air as the nitrogen gas or a mixture of nitrogen gas and helium gas in an appropriate proportion in the interior of the bulb shell12, so as to improve the thermal conductivity of the gas inside the bulb shell12and also remove the water mist in the air. The air filled within the bulb shell12may be at least one selected from the group substantially consisting of helium (He), and hydrogen (H2). The volume ratio of Hydrogen to the overall volume of the bulb shell12is from 5% to 50%. The air pressure inside the bulb shell may be 0.4 to 1.0 atm (atmosphere).

According to the embodiments ofFIGS. 12A and 12B, each of the LED light bulbs10a,10bcomprises a stem19in the bulb shell12and a heat dissipating element17between the bulb shell12and the bulb base16. The LED filament100is connected with the stem19through the conductive supports14a,14b. The stem19may be used to swap the air inside the bulb shell12with nitrogen gas or a mixture of nitrogen gas and helium gas. The stem19may further provide heat conduction effect from the LED filament100to outside of the bulb shell12. The heat dissipating element17may be a hollow cylinder surrounding the opening of the bulb shell12, and the interior of the heat dissipating element17may be equipped with the driving circuit18. The material of the heat dissipating element17may be at least one selected from a metal, a ceramic, and a plastic with a good thermal conductivity effect. The heat dissipating element17and the stem19may be integrally formed in one piece to obtain better thermal conductivity in comparison with the traditional LED light bulb whose thermal resistance is increased due that the screw of the bulb base is glued with the heat dissipating element.

Referring toFIG. 12A, the height of the heat dissipating element17is L1and the height from the bottom of the heat dissipating element17to the top of the bulb shell12is L2. The ratio of L1to L2is from 1/30 to 1/3. The lower the ratio, the higher the cutoff angle of illumination of the light bulb. In other words, the lower ratio increases the higher light-emission angle and the light from the bulb is closer to omnidirectional light.

Please referring toFIG. 12B, the LED filament100is bent to form a portion of a contour and to form a wave shape. In order to appropriately support the LED filament100, the LED light bulb10bfurther comprises a plurality of supporting arms15which are connected with and supports the LED filament100. The supporting arms15may be connected with the wave crest and wave trough of the waved shaped LED filament100. In this embodiment, the arc formed by the filament100is around 270 degrees. However, in other embodiment, the arc formed by the filament100may be approximately 360 degrees. Alternatively, one LED light bulb10bmay comprise two LED filaments100or more. For example, one LED light bulb10bmay comprise two LED filaments100and each of the LED filaments100is bent to form approximately 180 degrees arc (semicircle). Two semicircle LED filaments100are disposed together to form an approximately 360 circle. By the way of adjusting the arc formed by the LED filament100, the LED filament100may provide with omnidirectional light. Further, the structure of one-piece filament simplifies the manufacturing and assembly procedures and reduces the overall cost.

In some embodiment, the supporting arm15and the stem19may be coated with high reflective materials, for example, a material with white color. Taking heat dissipating characteristics into consideration, the high reflective materials may be a material having good absorption for heat radiation like graphene. Specifically, the supporting arm15and the stem19may be coated with a thin film of graphene.

Please refer toFIG. 13AandFIG. 14A.FIG. 13Aillustrates a perspective view of an LED light bulb according to a third embodiment of the present disclosure.FIG. 14Aillustrates a cross-sectional view of an LED light bulb according to a fourth embodiment of the present disclosure. According to the third embodiment, the LED light bulb10ccomprises a bulb shell12, a bulb base16connected with the bulb shell12, two conductive supports14a,14bdisposed in the bulb shell12, a driving circuit18electrically connected with both the conductive supports14a,14band the bulb base16, a stem19, supporting arms15and a single LED filament100. The LED light bulb10dof the fourth embodiment is similar to the third embodiment illustrated inFIG. 13Aand comprises two LED filaments100a,100barranged at the different vertical level inFIG. 14A. The LED filaments100a,100bare bent to form a contour from the top view ofFIG. 14A.

The cross-sectional size of the LED filaments100,100a,100bis small than that in the embodiments ofFIGS. 12A and 12B. The conductive electrodes110,112of the LED filaments100,100a,100bare electrically connected with the conductive supports14a,14bto receive the electrical power from the driving circuit18. The connection between the conductive supports14a,14band the conductive electrodes110,112may be a mechanical pressed connection or soldering connection. The mechanical connection may be formed by firstly passing the conductive supports14a,14bthrough the through holes111,113(shown inFIG. 1and secondly bending the free end of the conductive supports14a,14bto grip the conductive electrodes110,112. The soldering connection may be done by a soldering process with a silver-based alloy, a silver solder, a tin solder.

Similar to the first and second embodiments shown inFIGS. 12A and 12B, each of the LED filaments100,100a,100bis bent to form a contour from the top view ofFIGS. 13A and 14A. In the embodiments ofFIGS. 13A, 14A, each of the LED filaments100,100a,100bis bent to form a wave shape from side view. The shape of the LED filament100is novel and makes the illumination more uniform. In comparison with a LED bulb having multiple LED filaments, single LED filament100has less connecting spots. In implementation, single LED filament100has only two connecting spots such that the probability of defect soldering or defect mechanical pressing is decreased.

The stem19has a stand19aextending to the center of the bulb shell12. The stand19supports the supporting arms15. The first end of each of the supporting arms15is connected with the stand19awhile the second end of each of the supporting arms15is connected with the LED filament100,100a,100b. Please refer toFIG. 13Bwhich illustrates an enlarged cross-sectional view of the dashed-line circle ofFIG. 13A. The second end of each of the supporting arms15has a clamping portion15awhich clamps the body of the LED filament100,100a,100b. The clamping portion15amay, but not limited to, clamp at either the wave crest or the wave trough. Alternatively, the clamping portion15amay clamp at the portion between the wave crest and the wave trough. The shape of the clamping portion15amay be tightly fitted with the outer shape of the cross-section of the LED filament100,100a,100b. The dimension of the inner shape (through hole) of the clamping portion15amay be a little bit smaller than the outer shape of the cross-section of the LED filament100,100a,100b. During manufacturing process, the LED filament100,100a,100bmay be passed through the inner shape of the clamping portion15ato form a tight fit. Alternatively, the clamping portion15amay be formed by a bending process. Specifically, the LED filament100,100a,100bmay be placed on the second end of the supporting arm15and a clamping tooling is used to bend the second end into the clamping portion to clamp the LED filament100,100a,100b.

The supporting arms15may be, but not limited to, made of carbon steel spring to provide with adequate rigidity and flexibility so that the shock to the LED light bulb caused by external vibrations is absorbed and the LED filament100is not easily to be deformed. Since the stand19aextending to the center of the bulb shell12and the supporting arms15are connected to the stand19a, the position of the LED filaments100is at the level close to the center of the bulb shell12. Accordingly, the illumination characteristics of the LED light bulb10care close to that of the traditional light bulb including illumination brightness. The illumination uniformity of LED light bulb10cis better.

In the embodiment, the first end of the supporting arm15is connected with the stand19aof the stem19. The clamping portion of the second end of the supporting arm15is connected with the outer insulation surface of the LED filaments100,100a,100bsuch that the supporting arms15are not used as connections for electrical power transmission. In an embodiment where the stem19is made of glass, the stem19would not be cracked or exploded because of the thermal expansion of the supporting arms15of the LED light bulb10c.

Since the inner shape (shape of through hole) of the clamping portion15afits the outer shape of the cross-section of the LED filament100, the orientation of the cross-section of the LED filament100, if necessary, may be properly adjusted. As shown inFIG. 13B, the top layer120ais fixed to face around ten o'clock direction such that illumination surfaces of the LED filament100are facing substantially the same direction.

Please refer toFIG. 14Bwhich illustrates the circuit board of the driving circuit of the LED light bulb from the top view ofFIG. 14Aaccording to the fourth embodiment of the present disclosure. The driving circuit18comprises a circuit board18awhich is fixed to the bulb base16. The conductive supports14a,14bare electrically connected with the circuit board18aand passes through the stand19ato be electrically connected with the conductive electrodes110,112of the LED filament100a,100b. The circuit board18acomprises notches18b. The notches18bare of hook shape. The size of the tip of the notches18bis slightly smaller than that of the cross-section of the conductive supports14a,14bfor fixing the conductive supports14a,14b. The tip of the notches18bis beneficial to the soldering between the circuit board18aand the conductive supports14a,14b.

In the embodiments ofFIGS. 13A and 14A, the length of the conductive supports14a,14bis better to meet the below equation to prevent two conductive supports14a,14bfrom short circuit or to prevent the conductive supports14a,14bfrom unable to reach the circuit board18a.
L=A+√{square root over ( )}((B−3.2)^2+H^2)

Wherein, referring toFIG. 14A, 3.2is the electricity safety spacing; L is the calculated length of the conductive supports14a,14band its unit is mini-meter; A is the sum of the thickness of the circuit board18aand the height of the portion of the conductive supports14a,14bexposed from the surface of the circuit board18a; B is the horizontal distance between the two conductive supports14a,14b; and H is the height from the circuit board18ato the point the conductive supports14a,14benters the stem19. The actual length of the conductive supports14a,14bmay be, but not limited to, between 0.5 L and 2 L, and more particularly between 0.75 L and 1.5 L.

In the embodiment ofFIG. 14A, the LED light bulb10dhas two LED filaments100a,100bdisposed on different vertical levels. The conductive supports14a,14bfor the upper LED filaments100ahas a length Z=L+Y. Y is the distance between the upper LED filament100aand the lower LED filament100b.

While the instant disclosure related to an LED filament and LED light bulb has been described by way of examples and in terms of the preferred embodiments, it is to be understood that the instant disclosure needs not be limited to the disclosed embodiments. For anyone skilled in the art, various modifications and improvements within the spirit of the instant disclosure are covered under the scope of the instant disclosure. The covered scope of the instant disclosure is based on the appended claims.