WO2011079325A1

WO2011079325A1 - Uniform film-layered structure that converts the wavelength of emitted light and method for forming the same

Info

Publication number: WO2011079325A1
Application number: PCT/US2010/062129
Authority: WO
Inventors: Peiching Ling
Original assignee: Achrolux Inc.
Priority date: 2009-12-26
Filing date: 2010-12-27
Publication date: 2011-06-30
Also published as: JP5639662B2; GB2488936B; GB201210550D0; EP2517272A1; KR20150036785A; GB2488936A; KR20120083936A; DE112010004424T5; CN102812570A; JP2013516074A; TW201135982A; EP2517272A4; TWI452733B

Abstract

A method for forming a uniform film structure and a uniform film-layered structure that converts the wavelength of emitted light. The method includes providing a first surface of an article; forming on the first surface at least a layer of phosphor particles that are phosphor powders or have phosphor powders and a binder material; and forming on the layer of phosphor particles a first binder layer, to secure the layer of phosphor particles, the phosphor powders occupying more than 75% in volume of the layer of phosphor particles.

Description

UNIFORM FILM-LAYERED STRUCTURE THAT CONVERTS THE WAVELENGTH OF EMITTED LIGHT AND METHOD FOR FORMING THE SAME

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No.

61/284,792, filed on December 26, 2009 by Peiching Ling, which is commonly owned and incorporated by reference in its entirety herein for all purposes. This application is also related to U.S. Application No. 12/587,290, filed on October 5, 2009, by Peiching Ling, U.S. Application No. 12/587,281 , filed on October 5, 2009, by Peiching Ling, and U.S. Application No. 12/587,291, filed on October 5, 2009, by Peiching Ling, all of which are commonly owned and incorporated herein by reference in their entirety for all purposes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to methods of forming uniform film structures, and, more particularly, to a uniform film-layered structure that converts the wavelength of light emitted by a light emitted diode and a method for forming the uniform film-layered structure.

2. Description of Related Art

The present invention relates generally to material processing and optical apparatus techniques. More particularly, embodiments of the present invention provide methods and systems for forming a uniform layer of material that can be used in an optical device, such as a phosphor layer for a lens in an LED device. As used herein, "phosphor" refers to any luminescent materials, which absorb light of one wavelength and emit light of a different wavelength. In this usage, "phosphor" and "wavelength conversion material" are used interchangeably. Phosphor materials have been widely used in LED package for producing white light, or various colors of light (e.g. phosphor-converted green or red) with blue pump LEDs. The conventional methods of depositing a phosphor material over a blue LED chip or package assembly include:

-Slurry methods: phosphor particles are dispersed into silicone, epoxy or solvent filler material to form a phosphor mixture, applying said phosphor mixture to LED surface or package lens material by various techniques such as spray coating, dipping coating, dispensing, phosphor-in-cup, or over molding on a support structure and so on.

-Electrophoretic deposition (EPD): phosphor particles are dispersed into electrochemical solution, and deposited on LED wafer with a bias voltage across

LED wafer.

Problems with the conventional method are variation of thickness uniformity over LED surface or inside the LED package. The slurry method usually forms a particle layer with varying thickness, which results in inconsistency of color points, and poor color uniformity of phosphor-converted LED to LED. Further, even forming a uniform layer of phosphor layer on non-flat surface with these conventional methods is difficult. It becomes very challenge for the conventional methods to meet requirements in the lighting application.

One of known problems of applying phosphor silicone to LED non-planner encapsulation surface for a remote phosphor is phosphor coating uniformity. Because the viscosity of phosphor-silicone mixture is generally higher than that of cured LED encapsulant, and as a result, the curvature of phosphor silicone is larger, i.e. the phosphor layer is thicker in the central zones than outer edges. Same challenge exists for having a uniform phosphor coating on LED secondary optics for remote phosphor application as well. Therefore, how to provide a uniform film-layered structure that converts emitted light, in order to improve the optical quality of an LED, is becoming one of the most popular issues in the art. SUMMARY OF THE INVENTION

The present invention provides manufacturing methods at high production rate for depositing uniform phosphor particles layer onto a wide variety of LED encapsulation structures or LED chip. Some of the embodiments in the present invention can be applied for coating phosphor on a LED secondary optics as well. As used herein, "phosphor" refers to any luminescent materials, which absorb light of one wavelength and emit light of a different wavelength.

The present invention provides a method for forming a uniform film structure. The method comprises: providing a first surface of an anticle; forming on the first surface at least a layer of phosphor particles in a manner that none of the phosphor particles is completely separate from adjacent ones; and forming on the layer of phosphor particles a first binder layer to secure the layer of phosphor particles.

In a embodiment of the present invention, the first binder layer is a layer of binder particles.

The present invention further provides another of forming a uniform film structure. The another method comprises: providing a first surface; forming on the first surface at least a layer of phosphor particles that include phosphor powders and a binder material; and binding the phosphor particles.

In an embodiment in which the phosphor particles comprise the phosphor powders and the binder material, the phosphor particles are a mixture of the phosphor powders and the binder material, or are formed by encapsulating the phosphor powders with the binder material, wherein binding the phosphor particles includes heating the binder material so as to bind the phosphor particles, and wherein the phosphor powders occupy more than 75% in volume of the layer of the phosphor particles in which the phosphor particles are bound. The method may further comprises forming on the layer of phosphor particles a first binder layer and heating the binder material and the first binder layer, to secure the layer of phosphor particles.

In an embodiment of the present invention, the first surface of the article is provided by a viscous second binder layer. In another embodiment of the present invention, the first binder layer is a moisture resistant layer such as parylene.

In an embodiment of the present invention, the method may further comprise transferring the secured layer of phosphor particles on or above a second surface of another article, or transferring the layer of cured phosphor particles on or above a second surface of another article. The second surface may be a surface of an LED lens, a secondary optics, an LED package, an LED chip or an LED wafer.

In an embodiment of the present invention, the first binder layer may have a surface that is not in contact with the layer of phosphor particles that has a lens profile. In an embodiment in which the phosphor particles comprises the phosphor powders and the binder material, if a first binder layer is formed on the layer of phosphor particles, the first binder layer may also have a surface with a lens profile and not in contact with the layer of phosphor particles.

The present invention further provides a uniform film-layered structure that converts the wavelength of emitted light. The structure comprises a first binder layer; and a layer of phosphor particles that is formed on and secured to the first binder layer, the phosphor particles comprising phosphor powders and a binder material, the phosphor powders occupying more than 75% in volume of the layer of phosphor particles.

The first binder layer is a moisture resistant layer such as parylene. In an embodiment of the present invention, the structure further comprises a carrier connected via the first binder layer to the layer of phosphor particles, wherein the binder layer is between the carrier and the layer of phosphor particles, and the carrier is an LED lens, a secondary optics, an LED package, an LED chip or an LED wafer.

In an embodiment of the present invention, the first binder layer has a surface with a lens profile and not in contact with the layer of phosphor particles.

Compared with the conventional methods, in which phosphors are usually scattered in silicon resin or liquid and then disposed on an LED surface or package, such that the phosphor particles are not evenly scattered in the silicon resin or liquid and, after the silicon resin or liquid in which phosphor particles are evenly scattered are coated on LEDs or packages, the phosphor particles cannot be controlled to scatter evenly, which results in the conglomeration of some of the phosphor particles in the formed phosphor particle layer and independence of the others, which results the inconsistency of color points of LED products and poor color uniformity of phosphor-converted LED to LED, embodiments of the invention provide methods and systems to form a substantially uniform film structure on LED package surface or surface of secondary optics or surface of LED die or LED surface can overcome the above-mentioned problems of the prior art, and can one or more of the following steps:

(1) forming a uniform layer of phosphor particle on a first surface,

(2) minimizing particle movement on the first surface during curing process; and

(3) transferring the phosphor layer to a desired surface such as LED package surface or LED surface. The transfer may be done with molding process, attaching with a glue layer or applying isotropic forces to encapsulation surface i.e., normal pressure to surface, to eliminate shear force, which may cause distortion of particle distribution formed on the surface of presser tool. BRIEF DESCRIPTION OF DRAWINGS

The invention can be more fully understood by reading the following detailed description of the preferred embodiments, with reference made to the accompanying drawings, wherein:

FIGS. 1A and IB are schematic diagrams of a method for forming a uniform film structure of a first embodiment according to the present invention;

FIG. IB' is a schematic diagram of a first bonding layer that is a bonding particle layer;

FIG. 2 is a schematic diagram of a method for forming a uniform film structure of a second embodiment according to the present invention;

FIGS. 3 A and 3B are schematic diagrams of a method for forming a uniform film structure and its structure of a third embodiment according to the present invention;

FIG. 4 shows a method of transferring a layer of phosphor particles on or above a desired second surface;

FIGS. 5A-5C are schematic diagrams illustrating a layer of phosphor particles transferred by a mold;

FIGS. 6A-6C are schematic diagrams illustrating a layer of phosphor particles that is transferred on various surfaces;

FIG. 7 is a schematic diagram of a first surface array for mass production;

FIGS. 8 A and 8B are cross-sectional views of a method and device that applies isotropic pressures between two surfaces; and

FIGS. 9A-9D illustrate phosphor particle packing structures according to embodiments of the present invention in comparison with phosphor distribution formed by slurry methods. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following illustrative embodiments are provided to illustrate the disclosure of the present invention, these and other advantages and effects can be apparently understood by those in the art after reading the disclosure of this specification. The present invention can also be performed or applied by other different embodiments. The details of the specification may be on the basis of different points and applications, and numerous modifications and variations can be devised without departing from the spirit of the present invention.

FIGS. 1A and IB are schematic diagrams of a method for forming a uniform film structure of a first embodiment according to the present invention. The method comprises: forming on a first surface 101 of a mold at least a layer of phosphor particles 10 having phosphor particles that are constituted by phosphor powders; and forming on the layer of phosphor particles 10 a first binder layer 12 to secure the layer of phosphor particles 10.

Phosphors are used for converting or altering light wavelength, e.g., for LED-based light sources. Common phosphors for these purposes include yttrium aluminum garnet (YAG) materials, terbium aluminum garnet (TAG) materials, ZnSeS+ materials, and silicon aluminum oxynitride (SiAION) materials (such as . a-SiAION), etc. According to embodiments of the present invention, however, any material that converts or alters wavelength of incident light can be used as a phosphor material. As used herein, the term "phosphor" represents all materials that are capable of converting or altering a wavelength of light to another wavelength, including mixture or combination of different wavelength converting or wavelength altering materials. In the first embodiment, the phosphor particles indicate powder-formed phosphors themselves.

Forming a substantially uniform layer of phosphor particles 10 is critical for achieving high quality of light conversion. In the first embodiment, an electrostatic charging process is adopted for deposition of a substantially uniform layer of phosphor on the first surface 101 such as a mold, as illustrated in FIG. 1A. Details of electrostatic charging process for forming uniform layers of phosphor particles can be referred to US Patent Application No. 12/587,290, which is incorporated by reference herein. For instance, the layer of phosphor particles 10 is formed by forming electrostatic charges on a first surface 101 and moving the first surface 101 to be close to and attract the phosphor particle, to form the layer of phosphor particles 10. In an embodiment, the electrostatic charging process is carried out in a nonliquid environment, which is different from the conventional electrochemical charging process in a slurry environment. In some embodiments of the methods, the deposition process does not require keeping the even distribution of particle powders and binders in liquid suspension form, and doe not suffer this problem. Instead, in some embodiments, particle powders and binder materials are separately formed on or applied to the first surface of the mold.

Therefore, the electrostatic charge process applied in the present invention can accurately control packing density and layer thickness of phosphor particles. In an embodiment, the coating process is repeatable on the same surface to create a single or multiple uniform particle containing layers of luminescent materials on a hemispherical surface, concave or convex surface of different shapes, or flat surfaces. As a result, particle layers with a high packing density are formed and uniformly distributed on the surface of an article or element. The phosphor particles attracted in a single layer may comprise different types of phosphor powders, i.e., phosphor powders having different colors. The different types of phosphor powders may also formed on different layers. The process may be repeatable for multi-layered of phosphor particles. The layer of phosphor particles may comprise phosphor particles and other filling particles.

As shown in FIG. IB, after the layer of phosphor particles 10 is formed, the layer of phosphor particles 10 is secured by the first binder layer 12, so as to minimize the moving of the phosphor particles. The first binder layer 12 may be a curable material, such as silicone, epoxy, glass, softens, or any suitable material for LED encapsulation. In some embodiments, a thin film such as a dielectric layer may be deposited over the layer of phosphor particles. For example, a dielectric layer, e.g., Si02 layer, or parylene may be deposited using CVD, PVD, electro beam evaporation or other deposition methods. In one embodiment, the deposited layer coats the internal region of the layer of phosphor particle, such as voids between the phosphor particles. In another embodiment, the first binder layer is formed on the layer of phosphor particles, to provide sufficient binding force during subsequent processes.

One of the advantages of using a dielectric film to secure particles is that refractive index of the deposited film is adjustable for index matching to maximize light extraction. The dielectric material film is preferred to be deposited at low processing temperatures, so that the film is fairly porous. The porous dielectric film is sufficient to hold particles to eliminate particle movement during subsequent processes, and also allows adhesive material, which is used to attach particles to LED encapsulations, penetrating through to fill up voids within particle powders.

In another embodiment, the first binder layer 12 may also have high thermal conductivity to facilitate heat dissipation efficiency from the layer of phosphor particles.

In another embodiment, the first binder layer 12 may have strong moisture resistance to prevent phosphor or LED from degradation during wet/hot operation conditions.

In another embodiment of the first binder layer 12, as shown in FIG. IB', the first binder layer 12 is a layer of binder particles 12a.

The binder particles, such as silicone or epoxy compounds or thermoplastic or glass may be attracted on the top surface of the layer of phosphor particles 10. The attraction of binder particles may be used electrostatic charging process as the above described for forming phosphor particle layer. The first surface 101 may be optionally heated up at predetermined temperature during binder attraction process. This is to soften the binder particles 12a as soon as being in contact with layer of phosphor particles 10 on the first surface 101.

After that, the layer of phosphor particles 10 on the first surface of the mold and the binder particles 12a may be cured at a predetermined temperature to bind phosphor particles to each other.

FIG. 2 is a schematic diagram of a method for forming a uniform film structure of a second embodiment according to the present invention.

The second embodiment differs from the first embodiment only in that the first surface 101 of the mold in the second embodiment is provided by a viscous second binder layer 14. Specifically, the layer of phosphor particles 10 is formed on a surface of the second binder layer 14 (i.e., the first surface), and is sandwiched between the first binder layer 12 and the second binder layer 14. The second binder layer 14 may have the same material, formation method and aspects as previously described.

FIGS. 3A and 3B are schematic diagrams of a method for forming a uniform film structure and its structure of a third embodiment according to the present invention. The method comprises: forming on the first surface 101 at least a layer of phosphor particles 10' that include phosphor powders and a binder material; and binding the phosphor particles.

In the third embodiment, pre-coated phosphor particles are prepared. The phosphor particles are a mixture of the phosphor powders 10a and a binder material 10b, or are coated with the polymer binder material 10b, such as silicone, epoxy, thermosetting or thermoplastic. The phosphor particles may be coated with the polymer binder material in a rolling suspension, and then dry out the solvent to form powders. Alternatively, the binder coating process may be performed in the way similar to forming polymer molding compounds where combining polymers and additives to obtain a mixture of necessary physical and chemical properties. In this embodiment, phosphor particles can be treated as filler material. The phosphor-polymer mixture may be manufactured into liquid, rubber, sheet, solid or powder form depending on chosen process techniques. One of the advantages of the pre-coated phosphor particles is the ease of manufacturing process for phosphor deposition process over LED chip surface or onto LED encapsulation structure, which can be achieved even with existing molding process techniques.

The layer of phosphor particles is formed by forming on the first surface 101 electrostatic charges; and moving the first surface 101 to be close to and attract the pre-coated phosphor particles, so as to form the layer of phosphor particles. The pre-coated phosphor particles may be charged with electrostatic charges or non-charged, and then attracted on the first surface 101 which may be charged with electrostatic charges. Heating up to soften the binder material can bind the phosphor particles. The phosphor powders occupy more than 75% in volume of the layer of phosphor particles in which the phosphor particles are bound. After the layer of phosphor particles that has a predetermined thickness, the first surface 11 is then heated up to a predetermined temperature to cure the binder material. The phosphor particles are then bound to each other, and can effectively eliminate particle movement during the subsequent processes.

In the third embodiment, a first binder layer 12 is further formed on the layer of phosphor particles, as shown in FIG. 3B. In an embodiment of the present invention, the first binder layer is parylene. Then, the binder material 10b and the first binder layer 12 are heated up, to secure the layer of phosphor particles 10'.

Similarly, the coating process is repeatable on the same surface to create a single or multiple uniform particle containing layers of luminescent materials on a hemispherical surface, concave or convex surface of different shapes, or flat surfaces. As a result, particle layers with a high packing density are formed and uniformly distributed on the surface. The phosphor particles attracted in a single layer may comprise different types of phosphor powders, i.e., phosphor powders having different colors. The different types of phosphor powders may also formed on different layers of different colors. The process may be repeatable for multi-layered of phosphor particles. The layer of phosphor particles may comprise phosphor particles and other filling particles.

The present invention further provides a uniform film-layered structure that converts the wavelength of emitted light. The uniform film-layered structure comprises a first binder layer 12, and a layer of phosphor particles 10' that is formed and secured on the first binder layer, the phosphor particles comprising phosphor powders and a binder material, and the phosphor powders occupying more than 75% in volume of the layer of phosphor particles.

Please refer to FIGS. 4 and 5, which illustrate a method of forming a uniform film structure of a fourth embodiment according to the present invention. The method transfers the layer of phosphor particles on or above a desired second surface of a device or article. In the fourth embodiment, the cured layer of phosphor particles in the first or second embodiment, or the layer of phosphor particles in which the phosphor particles are bound in the third embodiment is transferred on or above the second surface of another device or article.

As shown in FIG. 4, the first surface 101 is pressed against to the second surface 102 with an appropriate glue layer 5 under a certain pressure to form phosphor layers on the second surface 102, and cured at a predetermined temperature. As shown in FIG. 4, the second surface 102 is a surface of an LED lens, which is a lens that transfers the layer of phosphor particles on the second surface 102, and is, as a whole, called a transfer lens. The second surface 102 may also be a surface of a secondary optics, an LED package, an LED die or an LED wafer. The second surface 102 and/or other surfaces of the LED lens may be coated with a moisture resistant film such as parylene.

If the layer of phosphor particles is formed based on the third embodiment, the glue layer 5 may be the first binder layer 12 of FIG. 3. Accordingly, the first binder layer 12 needs to be cured only during the transfer step.

A uniform film-layered structure obtained by the method that converts the wavelength of emitted light further includes a carrier of the second surface 102. In an embodiment of the present invention, the carrier is an LED lens, a secondary optics, an LED package, an LED die or an LED wafer. The carrier is connected to the layer of phosphor particles 10 via the first binder layer 12 ( or the glue layer 5). Accordingly, the first binder layer 12 is between the carrier and the layer of phosphor particles 10. In an embodiment of the present invention, the carrier is an LED lens, and the LED lens is coated with a moisture resistant film such as parylene.

Please refer to FIG. 5, which illustrates another method of transferring the layer of phosphor particles on the second surface 102 of another device or element. The first surface 101 may be one of the surface of a first mold 51, as shown in FIGS. 5A-5C. A molding chamber formed when the first mold 51 is engaged with a second mold 52 may be filled with a heat-curable material 6, such as silicone, epoxy or even thermoplastic or glass that can be melted and reformed at a raised temperature. The first mold 51 and the second mold 52 may be formed of metal or non-conductive material.

The first mold 51 with the layer of phosphor particles 10 (or 10') is pressed against to a second mold 52, so that the layer of phosphor particles 10 is implemented into a chamber that is in the shape of a lens. During the compression process, the layer of phosphor particles 10 is still held on the surface of the surface of the first mold 51 , so the distribution of the phosphor particles is not disturbed during compression process. The mold is heated to harden the heat-curable material 6, and then the first mold 51 and the second mold 52 are separated, as shown in FIG. 5C. After the separation, the layer of phosphor particles 10 is formed on the surface of encapsulation such as lens. The lens shown in FIG. 5C is also an aspect of a transfer lens. If the layer of phosphor particles 10 is formed based on the first embodiment, the steps of FIGS. IB and 5A-5C may be integrated to complete the first binder layer, so as to obtain the first binder layer having a lens profile. In other words, the first binder layer has a surface not in contact with the layer of phosphor particles 10 that has the lens profile.

If the layer of phosphor particles 10 is formed based on the third embodiment, the heat-curable material 6 may be directly connected on the layer of phosphor particles 10 to act as the first binder layer. Accordingly, a surface 6a of the first binder layer that is not contact with the layer of phosphor particles 10 may also have a lens profile. In a uniform film-layered structure that converts the wavelength of emitted light, the surface of the first binder layer that is not in contact with the layer of phosphor particles 10 has a lens profile.

The process techniques can be extended for applying layers of phosphor particle to various shapes of surfaces with an appropriate counterpart presser tool, such as,

Concave surface, e.g. inner surface of lens or cover, as illustrated in FIG. 6A;

Convex surface like outer surface of lens or cover, as illustrated in FIG. 6B; and Flat surface or a plate, as illustrate in FIG. 6C.

As shown in FIG. 7, the first surface 101 in a fifth embodiment may be configured into an array for mass production. The head surface of the first surface 101 may be shaped to a contour corresponding phosphor layer on encapsulation surface according to the present invention.

In a sixth embodiment, methods of applying isotropic pressure between two surfaces is provided. These methods can be used in transferring a phosphor layer on a curved surface, such as the secured layer of phosphor particles 10 as shown in FIG. 1 to another curved encapsulation surface for providing normal pressure between the two surfaces and without a shear force.

In an embodiment shown in FIG. 8A, an expandable material 81 is disposed inside a curved surface layer of a holder 80. The outer surface of the head 82 is a flexible material such as silicone, which is expandable according to the expandable material 81 inside the holder 80. When the volume of the expandable material 81 is expanded when its temperature is raised, exerting an isotropic force on the curved surface layer. In a specific embodiment, a layer of phosphor particles 10 is formed on the curved surface layer using, e.g., one of the methods described above. The curved surface layer is positioned adjacent to a receiving surface, e.g., a lens or an encapsulation material. The temperature of the expandable material is raised, causing the phosphor layer to be pressed against the receiving surface. The pressure between the two surfaces causes the phosphor layer to be transferred to the receiving surface.

Depending on the embodiments, the distance between the two surfaces is selectable.

In an example, the two surfaces can be in contact. In another example, there can be a space between the two surfaces. The spaced can be a few microns to 200 microns or larger. In either case, the expandable material 81 is configured to cause a substantially uniform pressure between the two surfaces. Examples of the expandable material 81 include expancel, other suitable material that expands at elevated temperatures, or combination of materials.

In one embodiment, the phosphor layer 10 is on a convex surface, which can be pushed out by the expandable material 81. In another embodiment, the layer of phosphor particles 10 is in a concave surface as illustrated in FIG. 8B, which can be pushed inwards by a layer of the expandable material disposed on the outside of the layer of phosphor particles 10.

Applying a normal force to surface is essential to eliminate shear force, which may cause distortion of particle distribution formed on the surface of presser tool during particle attachment to encapsulation surface.

In one of embodiments as illustrated in FIG. 8A, the presser head 82 is made of an expansible material such as silicone. An expansion vessel is embedded in the inside of the presser head 82. The expansion vessel may be filled with liquid or expancel or liquid together with expancel. As the above described, phosphor particles are formed a uniform layer on the head region. In an embodiment, a fiber-guided blue LED may be installed inside the presser head to in-situ monitor the amount of phosphor powder attracted on the presser head for a desired color point.

During phosphor particle transfer, the tool head with phosphor particles is then pressed again the encapsulation surface meanwhile the tool head is expanded by heating up, or injecting air into the head. Once the head is expanded, the presser head provides an isotropic force, normal to the surface of encapsulation, eliminating particle movement during the curing process.

A similar method of providing isotropic force for transferring the layer of phosphor particles to another surface can be applied for various surface with an appropriate design of expansion head, such as head design for concave surface as shown in FIG. 8B.

Please refer to FIGS. 9A-9D, which illustrate phosphor particle packing structures according to embodiments of the present invention in comparison with phosphor distribution formed by slurry methods. In the packing structure of the deposited phosphor particles according to the embodiment of the present invention as shown in FIG. 9A, phosphor particles 18 are highly packed on surface. The phosphor powders occupy more than 75% in volume of the layer of phosphor particles. This is difficult to be realized with slurry methods in which phosphor particles are distributed within phosphor mixture, phosphor-silicone mixture as illustrated in FIG. 9B. Such high density packed phosphor as illustrated in FIG. 9A can enhance heat dissipation generated from light conversion within phosphor particles. This is because the generated heated can be dissipated through particles connected with one another, instead of passing through silicone between particles in the slurry method which still needs solvent filler material to form a phosphor mixture. The enhanced heat dissipation can also increase conversion efficiency, and improve light degradation from heat.

For application containing multi-phosphor layers of different optical properties according to embodiments of the present invention, different phosphors can be deposited in layered structure as illustrated in FIG. 9C, Phosphor particles 19 is separated from phosphor particles 18 in a layer structure. In slurry methods, different phosphor particles are distributed in silicone layer, phosphor-silicone mixture as illustrated in FIG. 9D.

Such layered structure in FIG.9C according to embodiments of the present invention can enhance color quality by optimizing the ordering of different properties of phosphor particles to minimize light re-absorption between different optical properties of phosphor particles, enhancing light conversion efficiency as well.

The foregoing descriptions of the detailed embodiments are only illustrated to disclose the features and functions of the present invention and not restrictive of the scope of the present invention. It should be understood to those in the art that all modifications and variations according to the spirit and principle in the disclosure of the present invention should fall within the scope of the appended claims.

Claims

CLAIMS What is claimed is:

1. A method for forming a uniform film structure, comprising the steps of:

providing a first surface of an article;

forming on the first surface at least a layer of phosphor particles in a manner that none of the phosphor particles is completely separate from adjacent ones; and

forming on the layer of phosphor particles a first binder layer to secure the layer of phosphor particles.

2. The method of claim 1 , wherein the first surface is provided by a viscous second binder layer.

3. The method of claim 1 , wherein the first binder layer is a layer of binder particles.

4. The method of claim 3, wherein the layer of binder particles are attracted by electrostatic charges.

5. The method of claim 1, wherein the layer of phosphor particles are formed by:

forming on the first surface electrostatic charges; and

moving the first surface to be close to and attract the phosphor particles, to form the layer of phosphor particles.

6. The method of claim 1 , wherein the first binder layer is parylene.

7. The method of claim 1, wherein the phosphor particles include different types of phosphor powders.

8. The method of claim 1 , further comprising transferring the secured layer of phosphor particles on a second surface of another article.

9. The method of claim 1 , wherein the first binder layer has a surface with a lens profile and not in contact with the layer of phosphor particles.

10. A method of forming a uniform film structure, comprising:

providing a first surface; forming on the first surface at least a layer of phosphor particles that include phosphor powders and a binder material; and

binding the phosphor particles.

11. The method of claim 10, wherein the phosphor particles are a mixture of the phosphor powders and the binder material, or are formed by encapsulating the phosphor powders with the binder material; wherein the binder material are heated so as to bind the phosphor particles; and wherein the phosphor powders occupy more than 75% in volume of the layer of the phosphor particles in which the phosphor particles are bound.

12. The method of claim 10, wherein the first surface is provided by a viscous second binder layer.

13. The method of claim 10, further comprising:

forming on the layer of phosphor particles a first binder layer; and

heating the binder material and the first binder layer, to secure the layer of phosphor particles.

14. The method of claim 13, wherein the first binder layer has a surface not in contact with the layer of phosphor particles that has a lens profile.

15. The method of claim 13, wherein the first binder layer is parylene.

16. The method of claim 10, wherein the layer of phosphor particles are formed by:

forming on the first surface electrostatic charges; and

17. The method of claim 10, wherein the phosphor particles include different types of phosphor powders.

18. The method of claim 10, further comprising transferring the layer of phosphor particles in which the phosphor particles are bound on a second surface.

19. The method of claim 18, wherein the second surface is a surface of an LED lens, a secondary optics, an LED package, an LED die or an LED wafer.

20. The method of claim 19, wherein the second surface of the LED lens is covered by a moisture resistant film.

21. A uniform film- layered structure that converts a wavelength of emitted light, the uniform film-layered structure comprising:

a first binder layer formed on a first surface of an article; and

a layer of phosphor particles that is formed on and secured to the first binder layer, the phosphor particles comprising phosphor powders and a binder material, the phosphor powders occupying more than 75% in volume of the layer of phosphor particles, and the phosphor particles being arranged in a manner that none of them is completely separating from adjacent ones.

22. The uniform film-layered structure of claim 21, wherein the first binder layer is parylene.

23. The uniform film-layered structure of claim 21 , wherein the phosphor particles comprises different types of phosphor powders.

24. The uniform film- layered structure of claim 21 , wherein the article is used for the first binder layer to connect the layer of phosphor particles, wherein the binder layer is between the article and the layer of phosphor particles, and the article is an LED lens, a secondary optics, an LED package, an LED die or an LED wafer.

25. The uniform film- layered structure of claim 21 , wherein the article is the LED lens, and the LED lens is covered with a moisture resistant film.

26. The uniform film-layered structure of claim 21, wherein the first binder layer has a surface with a lens profile and not in contact with the layer of phosphor particles.