TWI448519B - A fluorescent ink composition and a method for producing the same, and a method for producing the nanometer phosphor powder - Google Patents

Description

Fluorescent ink composition, method for producing the same, and method for producing nano fluorescent powder particles thereof

This application is a continuation-in-part of U.S. Patent Application Serial No. 13/103, the entire disclosure of which is hereby incorporated by reference.

The present invention generally relates to a fluorescent ink composition for LEDs and/or LED devices. In particular, the present invention relates to a fluorescent ink composition having nano-sized phosphor particles and a method of fabricating the same, which can efficiently convert light emitted by an LED from one wavelength to another.

A light emitting diode (LED) is a semiconductor light source. LEDs have many advantages over other light sources such as incandescent lamps. LEDs typically have a long life, good stability, fast switching characteristics, and low power consumption. The newly developed LEDs have comparable or higher luminous efficiency (lm/W) than fluorescent lamps.

When the forward bias of the LED exceeds its threshold voltage in the circuit, the LED illuminates due to the spontaneous recombination of the electron-hole pairs. The wavelength of the light produced depends on the band gap between the materials used in forming the p-n junction of the LED. The wavelength of light produced by an LED is typically in the range of infrared, visible or UV. Detailed information on LEDs can be found in "Light emitting diodes" by E. Fred Schubert, Cambridge University Press, which is incorporated herein by reference in its entirety. Detailed information on semiconductor optics can be found at Springer Press, Claus F. Klingshirn. Found in Semiconductor optics, which is incorporated herein by reference in its entirety.

To facilitate manufacturing, the most common form of LED is to place a micron-sized planar square LED wafer on a substrate. Such a semiconductor wafer is typically gallium nitride, and the substrate may be a metal such as aluminum, which also functions as a heat sink. The LED wafer is connected to the circuitry on the substrate by a fine metal wire. The LED wafer itself may be mounted on the surface of the substrate or may be mounted in a recess in the substrate.

There are various challenges in manufacturing high brightness LED light sources for human illumination. The first is to maximize the light extraction efficiency of the LED chip itself. Since semiconductor materials have a high refractive index, most of the light produced encounters total internal reflection (TIR) at the semiconductor-air interface. In the prior art, the amount of TIR light is reduced by reducing the difference in refractive index at the surface of the semiconductor. Since the refractive index of the semiconductor is a material property, the above effect is achieved by encapsulating the LED with a packaging material having a higher refractive index. In the past, epoxy materials were used, and tantalum resins have recently been used more because of their relatively high transparency, color stability, and thermal properties.

A single unpackaged LED produces monochromatic light. Due to the trend of using LEDs as illumination sources, recent research has focused on LED packaging technology, which enables LED chips to emit different colors of light. There has been considerable interest in the synthesis of white light. The most common way to produce white light from a single LED is to place a wavelength converting material, such as a yellow phosphor, on the light emitting surface of a blue emitting LED wafer. The layer of wavelength converting material on the LED wafer absorbs the photons emitted by some of the LEDs and down-converts them into light of visible wavelengths, producing a two-color source of light having blue and yellow wavelengths. If the resulting ratio of yellow and blue light is correct, then the human eye will feel white light.

In the prior art, a wavelength converting material is added to the encapsulation layer surrounding the LED wafer as an alternative to direct deposition on the wafer. There are different ways to use this packaging material. Some methods use molding or pre-molding to directly attach the packaging material to the substrate, and some methods are to build a dam around the LED wafer and then fill the dam. The latter is often referred to as dispensing because the encapsulating material is provided in liquid form and then cured. In fact, in this dispensing method, a fluorescent ink composition can be applied to the surface of an LED wafer.

Another method of applying a phosphor layer to an LED wafer in the prior art is to use an ink jet printer to eject the phosphor ink onto the surface of the LED wafer. Such an ink jet printing method is described in U.S. Patent Application Serial No. 13/103, the disclosure of which is incorporated herein by reference.

However, in the conventional packaging method, a large-sized phosphor powder having a particle diameter of 5 to 25 μm is usually used. However, the large-diameter phosphor powder is prone to the problem of phosphor powder sedimentation during use, so that the phosphor powder is unevenly distributed in the colloid, thereby causing the packaged LED to be prone to color deviation.

Therefore, it is necessary to improve the phosphor powder for dispensing or ink jet printing.

Large-sized phosphor powders having a particle diameter of 1 to 50 μm, particularly 5 to 25 μm, have high fluorescence conversion efficiency. However, phosphor particles in this particle size range have severe sedimentation problems, thereby causing inconsistencies in color temperature and color change of the packaged LEDs. Therefore, nanometer-sized phosphor particles have attracted interest due to their very small sedimentation rate. However, there is a serious problem with the current nanometer size phosphor powder particles, that is, the fluorescence conversion efficiency is reduced by more than 50% compared with the large particle size phosphor powder. The present invention provides a dispensing ink or ink jet printing fluorescent ink composition, The ink contains nano-fluorescent particles of the order of 100-1000 nm and can achieve high light conversion efficiency. The LED and/or LED device packaged with the fluorescent ink has excellent color temperature and/or color. Consistency and high brightness.

The present invention provides a phosphor ink composition deposited on an LED, the phosphor powder particles having a very small size and capable of achieving a high light conversion rate. The ink comprises a cured resin component and a phosphor powder component, and the phosphor powder component comprises nano-fluorescent powder particles of the order of 100 to 1000 nm. Nano-fluorescent particles are formed by pulverizing large phosphor particles of the order of 1 to 50 microns. Preferably, the comminution process is based on solvent wet milling.

After the pulverization process, the nano-fluorescent particles have a very small sedimentation rate. Therefore, they can be uniformly dispersed in the fluorescent ink composition, making it usable for dispensing or ink jet printing. Therefore, LEDs packaged with the ink can have a consistent correlated color temperature and/or color.

In addition, these nano-phosphor particles have very high light conversion efficiencies when converting LED light from one wavelength to another. Compared with large-sized phosphor particles having a size of 1 to 50 μm, particularly 5 to 25 μm, the light conversion efficiency of the nano-fluorescent particles of the present invention can be converted to those of large-sized phosphor particles. More than 90% efficiency. Other existing nano-fluorescent particles on the market are impossible to achieve.

The fluorescent ink used in the dispensing method can be obtained by mixing nano fluorescent powder particles and a curing resin (preferably, a thermosetting resin). The thermosetting resin may be a two-component resin.

The fluorescent ink used in the ink jet printing method includes the above-described phosphor powder component and a cured resin, and the cured resin is used as a polymer binder. The curing resin may be a UV curing resin and/or a thermosetting resin. To ensure the ink jet capability of the ink jet printer, the viscosity of the ink is maintained below about 50 centipoise. A sufficient amount of solvent is provided to control the viscosity of the entire fluorescent ink.

110~140, 210~240, 310~350‧‧‧ steps

Fig. 1 is a flow chart showing a method of forming nano fluorescent powder particles from large-diameter phosphor particles by solvent wet milling.

2A is a flow chart showing a method of producing a fluorescent ink composition based on the formation of nano-fluorescent powder particles from large-diameter phosphor particles in accordance with one embodiment of the present invention.

2B is a flow chart showing a method of producing a fluorescent ink composition based on the formation of nano-fluorescent powder particles from large-diameter phosphor particles in accordance with another embodiment of the present invention.

The ink of the present invention is described below with respect to a blue LED package having a combination of yellow phosphors to form a "white" LED. However, it should be understood that the present invention is applicable to applying any phosphor powder to LEDs of any color, thereby adjusting the color of the LEDs to be perceived by the human eye. Whether "fluorescent powder" as used herein is a "fluorescent powder" as conventionally referred to, the term "fluorescent powder" is used broadly to describe the absorption of light of one wavelength and the emission of light of another wavelength. Any wavelength conversion material. For blue LEDs, typical phosphors used to emit yellow light include yttrium aluminum garnet (YAG) based materials (optionally doped with antimony), yttrium aluminum garnet (TAG) based materials, and citrate based materials. Materials, sulfide materials, nitride materials or oxynitride materials. It is also possible to use an organic phosphor and an organic-inorganic composite luminescent material, which are referred to as "fluorescent powder" as described above for the sake of simplicity. The combination of a single wavelength converting material or a wavelength converting material can be selected based on the desired illumination of the entire packaged LED.

For LEDs, an acceptable range of acceptable particle size for the phosphor is typically between 1 micron and about 50 microns. For example, U.S. Patent No. 1,201,056,619 teaches a typical LED phosphor particle size between about 5 and 25 microns. As another example, U.S. Patent No. 8,125,139 suggests that the average particle size is preferably between 3 and 20 microns. again For example, U.S. Patent Nos. 8,048,338, U.S. Patent No. 7,878, 718, U.S. Patent No. 6, 862, 549, and U.S. Patent No. 7,524,437, the disclosure of each of each of each of each of each of

Although the phosphor powder having a particle diameter of 1 to 50 μm, especially 5 to 25 μm, has a high light conversion efficiency, the phosphor powder in the particle size range is prone to the problem of phosphor powder sedimentation during use. The uneven distribution of the phosphor powder in the colloid, thereby causing the packaged LED to be prone to color deviation. However, nano-sized phosphor particles have attracted attention due to their very small settling rate. However, there is a serious problem with the existing nano-sized phosphor particles, that is, the fluorescence conversion efficiency is reduced by more than 50% compared with the large-diameter phosphor powder.

As one of the developments, U.S. Patent Application No. US20070024173 discloses the use of nano-fluorescent particles having a size between 1 and 50 nm, preferably between 2 and 20 nm, in order to minimize the phosphor particles. The portion of the refracted or scattered light that does not undergo light conversion. It is also mentioned in the literature that phosphor powder particles having a size of 200 to 500 nm cause maximum light scattering, and thus this range of phosphor powder particles is not adopted.

The optimum range of phosphor particle size from 1 to 50 μm is supported by the detailed study of LED light output. Please refer to NTTran et al., "Effect of phosphor particle size on luminous efficacy of phosphor-converted white LED," IEEE Journal. Of Lightwave Technology, vol. 27, pp. 5145-5150, November 2009, incorporated herein by reference. From the simulation results, NTTran et al. (2009) have shown that when the particle size of the phosphor powder is increased from 50 nm to 100 nm, the light output is significantly reduced, and then in the range of 100 to 500 nm, light The output stays at a minimum, and then the light output increases slightly as the phosphor particle size increases to 1 micron. When As the toner particle size continues to increase from 1 micron, the light output continues to increase steadily. In the micron size range, when the phosphor particle size is about 20 microns, the light output reaches a maximum, and then the light output decreases. Similar to US20070024173, Tran et al. (2009) believe that the light output of the phosphor particle size in the range of 100 to 500 nm is the minimum because the light is significantly scattered by the phosphor particles.

Based on the above, those skilled in the art will not use phosphor powder having a phosphor particle size in the range of 100 to 1000 nm, particularly in the range of 100 to 500 nm, for LEDs. Recently, however, the inventors of the present application have experimentally proved that the phosphor powder has a particle size in the range of 100 to 1000 nm, and the phosphor powder can efficiently capture the LED light and convert the light from a wavelength to a photoluminescence. Another wavelength. The present inventors have found that light conversion of 100-1000 nm phosphor powder particles prepared according to the present invention is compared with large particle size phosphor particles having a size of 1 to 50 microns, particularly 5 to 25 microns. The efficiency can reach more than 90% of the conversion efficiency of those large particle size phosphor particles. This is not possible with other existing nano-fluorescent particles on the market, and their conversion efficiency is reduced by more than 50% as described above.

In light of this discovery, the inventors have noted that US 7,126,265 discloses a spherical phosphor particle formed by polymerizing a plurality of primary phosphor particles having an average particle size of from 100 to 1500 nm. The nano-fluorescent particles disclosed herein are not the primary phosphor particles disclosed in U.S. Patent 7,126,265. The nano-fluorescent particles disclosed herein are also not intended to form one or more spherical phosphor particles as mentioned in U.S. Patent No. 7,126,265.

The fluorescent ink of the present invention uses a phosphor component comprising nano fluorescent powder particles having a size of from 100 to 1000 nm, wherein the nano fluorescent powder particles are uniformly dispersed throughout the ink composition. In order to make the generated phosphor particles not only help to evenly disperse It also prevents the phosphor particles from sinking in the fluorescent ink, and requires precise pulverization technology. Nano-fluorescent particles are obtained by performing a size reduction process on a larger phosphor particle of about 1 to 50 microns. In particular, the comminution process is preferably based on solvent wet milling. Solvent wet milling is a wet milling process. For a description of the wet milling process, reference is made to T. F. Tadros, Dispersion of Powders in Liquids and Stabilization of Suspensions, Wiley, 2012, incorporated herein by reference. Regarding the solvent wet grinding, the parameters of the grinding process can be optimized in "T.-H. Hou et al. "Parameters optimization of a nano-particle wet milling process using the Taguchi method, response surface method and genetic algorithm," Powder Technology, Volume 173, Issue 3, pp. 153-162, 30 April 2007, which is incorporated herein by reference in its entirety. A discussion of solvent wet milling can also be found in WO/2000/056486.

The inventors have found through experiments that in addition to achieving high light conversion efficiency, nano-fluorescent particles have other advantages, compared with conventional phosphor powders of about 5 to 25 micron phosphor particle size. The sedimentation phenomenon of the powder in the cured resin is also improved. The size of the curing resin and the nano-fluorescent powder particles may be selected such that after the fluorescent ink composition is deposited on the LED, the sedimentation rate of the nano-fluorescent particles in the ink is relatively slow before final curing, thereby A cured phosphor layer uniformly distributed with phosphor powder is formed on the device or the LED package.

The nano-fluorescent powder and the fluorescent ink composition containing the nano-fluorescent powder and a method for producing the same will be described below.

In order to make a fluorescent ink containing fluorescent powder particles of a desired size range, The wet milling method carefully controls the phosphor particle size so that the resulting phosphor particle size range minimizes the deposition of the phosphor particles, i.e., remains dispersed. Figure 1 depicts the process of making larger phosphor particles into nano-fluorescent particles by solvent wet milling. The phosphor particles having a larger particle size are dispersed in a solvent to form a suspension. Alternatively, a dispersing agent may be added to the suspension to cause the larger phosphor particles to be dispersed in the solvent. The grinding ball media is then added to the suspension to form a mixture. The mixture is wet milled in an agitator/grinder until most of the larger phosphor particles have become particles of 100 to 1000 nm. Thus, nano-powder particles are formed in the mixture. To check/ensure that most of the larger phosphor particles have become nano-sized particles, a small portion of the sample mixture is taken for particle size measurement. After wet milling, the mixture is filtered using a screen such as a screen, the grinding ball medium is removed therefrom, and the particles are separated from other components in the mixture by, for example, a centrifuge to obtain nano-fluorescent particles.

Preferably, the fluorescent ink is produced without physical separation of the nano-powder particles and other components of the mixture. Fig. 2A shows an embodiment in which a fluorescent ink is produced, and the viscosity of the fluorescent ink can be adjusted to satisfy the viscosity required by the dispensing method or the ink jet printing method. First, the large-sized phosphor powder particles and the cured resin component are dispersed in a solvent to obtain a suspension.

The large-diameter phosphor powder may be a yttrium aluminum garnet (YAG)-based material (such as YAG:Ce), a yttrium aluminum garnet (TAG)-based material (such as TAG:Ce), or a citrate-based material (such as SrBaSiO ₄ : Eu), sulfide material (such as CaS:Eu, SrS:Eu, SrGa ₂ S ₄ :Eu, etc.), nitride material (such as Sr ₂ Si ₅ N ₈ :Eu, Ba ₂ Si ₅ N ₈ :Eu, etc.) or Nitrogen oxide material (such as Ca-α-SiAlON: Eu, SrSi ₂ O ₂ N ₂ :Eu, etc.).

The cured resin component may be a UV curable resin (such as Tego 2100, Tego 2200, etc.) Or a thermosetting resin (such as Dow Corning 6550, Dow Corning 6551, Shin-Etsu 9022, LPS5547, etc.), or a combination of the two. If a UV curable resin is included in the formulation, an initiator (such as Irgacure 2959, etc.) is required.

The solvent may be any conventional organic solvent such as ethanol, acetone, 2-pentanone, 1-pentanol, isopropanol or the like.

Optionally, a dispersing agent may be added to the suspension, and the dispersing agent may be Digo Tego 655, Digo Tego 710, Lubrizol Solsperse 22000, Zetasperse 2100, and the like.

The grinding ball media is then added to the suspension to form a first mixture. The first mixture is wet milled until most of the large particle size phosphor particles have become nanometer sized particles. As described above, a small portion of the sample of the first mixture is taken for particle size measurement to detect and ensure that most of the large particle size phosphor particles have become smaller. After wet milling, the first mixture is filtered using a screening program (which may be a screen) and the grinding ball media is removed from the first mixture to provide a second mixture. A portion of the solvent is evaporated from the second mixture until the viscosity of the second mixture approaches the desired viscosity value. Therefore, the fluorescent ink is obtained in the form of the second mixture after evaporation.

Figure 2B shows another embodiment of a fluorescent ink composition that produces the desired viscosity. This embodiment differs from the embodiment shown in Fig. 2A in that no cured resin component is added prior to wet milling. In the embodiment of Fig. 2B, the large particle size phosphor particles are first dispersed in a solvent to obtain a suspension. As described above, a dispersing agent can be added to the suspension. The grinding ball media is then added to the suspension to form a first mixture. The first mixture was wet milled until a small portion of the sample of the first mixture was measured for particle size and it was detected that most of the phosphor particles had turned into nano-sized particles. Then use the sieve The first mixture is filtered by a test program (which may be a screen) to remove the grinding ball media from the first mixture to obtain a second mixture. At this stage, a curing resin component is added to the second mixture and well dispersed in the second mixture to obtain a third mixture. A portion of the solvent is evaporated from the third mixture until the viscosity of the third mixture approaches a given viscosity value to obtain a fluorescent ink.

Depending on the LED packaging method, such as dispensing or inkjet printing, the composition of the fluorescent ink composition containing nano-sized phosphors may vary.

For the dispensing process, the composition of the ink composition is as follows:

The ink composition shown above is a suggested embodiment. However, it is to be understood that the ink composition for dispensing in the present invention is suitable for use in any type of phosphor powder, curing resin and dispersing agent of the prior art.

Since all the solvents in the ink composition evaporate for the dispensing process, the solvent components in the composition are not shown in the above table.

Specific examples of the preparation of the phosphor ink composition for dispensing will be given below based on the components and ratios listed in the above table.

Example 1: 6 g of a large particle size fluorescent powder YAG:Ce, 94 g of a cured resin Dow Corning Dow Corning 6550 was added to 200 cc of acetone to form a suspension, and then a grinding ball medium was added to the suspension to form a first mixture. The first mixture is wet milled until most of the large particle size phosphor particles are converted to nanometer sized particles. As described above, a small portion of the sample of the first mixture is taken for particle size measurement to detect and ensure that most of the large particle size phosphor particles are converted to nano-sized particles. After wet milling, the first mixture is filtered with a screen to remove the grinding ball media from the first mixture to provide a second mixture. All of the solvent in the second mixture was evaporated to give the final fluorescent ink formulation containing nano-sized phosphor powder for dispensing. The photoelectric detection parameters of the LED after being encapsulated by using the ink are as follows:

From the test data, the light conversion efficiency of the 100-1000 nm phosphor powder particles prepared by the invention can reach more than 90% of the conversion efficiency of those large particle size phosphor particles.

Example 2: 1 g of a large particle size fluorescent powder YAG:Ce, 99 g of a cured resin Dow Corning Dow Corning 6550 was added to 200 cc of acetone to form a suspension, and then a grinding ball medium was added to the suspension to form a first mixture. The first mixture is wet milled until most of the large particle size phosphor particles are converted to nanometer sized particles. As described above, a small portion of the sample of the first mixture is taken for particle size measurement to detect and ensure that most of the large particle size phosphor particles are converted to nano-sized particles. After wet milling, the first mixture is filtered with a screen to remove the grinding ball media from the first mixture to provide a second mixture. All of the solvent in the second mixture was evaporated to give the final fluorescent ink formulation containing nano-sized phosphor powder for dispensing.

Example 3: 60 g of a large particle size fluorescent powder TAG: Ce, 40 g of a cured resin Dow Corning Dow Corning 6551 was added to 200 cc of acetone to form a suspension, and then a grinding ball medium was added to the suspension to form a first mixture. Wet grinding the first mixture until Most of the bulk phosphor particles are converted into nanometer-sized particles. As described above, a small portion of the sample of the first mixture is taken for particle size measurement to detect and ensure that most of the large particle size phosphor particles are converted to nano-sized particles. After wet milling, the first mixture is filtered with a screen to remove the grinding ball media from the first mixture to provide a second mixture. All of the solvent in the second mixture was evaporated to give the final fluorescent ink formulation containing nano-sized phosphor powder for dispensing.

Example 4: Adding 54 g of large-diameter phosphor powder YAG:Ce, 6 g of Ca-α-SiAlON:Eu, 25 g of curable resin Shin-Etsu 9022, and 15 g of dispersant Digo Tego 655 to 200 cc of acetone to form a suspension, The grinding ball media is then added to the suspension to form a first mixture. The first mixture is wet milled until most of the large particle size phosphor particles are converted to nanometer sized particles. As described above, a small portion of the sample of the first mixture is taken for particle size measurement to detect and ensure that most of the bulk phosphor particles are converted to nano-sized particles. After wet milling, the first mixture is filtered with a screen to remove the grinding ball media from the first mixture to provide a second mixture. All of the solvent in the second mixture was evaporated to give the final fluorescent ink formulation containing nano-sized phosphor powder for dispensing.

Example 5: 30 g of a large-diameter phosphor powder YAG:Ce, 3 g of a dispersant Zetasperse 2100 was added to 200 cc of acetone to form a suspension, and then a grinding ball medium was added to the suspension to form a first mixture. The first mixture was wet milled until a small portion of the sample of the first mixture was subjected to particle size measurement and it was detected that most of the large particle size phosphor particles had been converted into nanometer-sized particles. The first mixture is then filtered using a screen to remove the grinding ball media from the first mixture to provide a second mixture. At this stage, 67 g of the cured resin component Shin-Etsu LPS 5547 was added and well dispersed in the second mixture to form a third mixture. Will be in the third mixture All solvents were evaporated to give the final fluorescent ink formulation containing nano-sized phosphor powder for dispensing.

For inkjet printing, the composition of the ink composition is as follows:

The ink composition shown above is a suggested embodiment. However, it will be appreciated that the ink compositions of the present invention for ink jet printing are suitable for use in any type of phosphor powder, curable resin and dispersant of the prior art.

Specific examples of the preparation of the phosphor ink composition for ink jet printing will be given below based on the components and ratios listed in the above table.

Example 6: 1 g of large-diameter phosphor powder YAG:Ce, 1 g of curable resin Digo 2100, 0.2 g of UV initiator, and 0.2 g of dispersant Lubrizol Solsperse 22000 were added to 300 cc of 2-pentanone to form a suspension. The grinding ball media is then added to the suspension to form a first mixture. The first mixture is wet milled until most of the large particle size phosphor particles are converted to nanometer sized particles. As described above, a small portion of the sample of the first mixture is taken for particle size measurement to detect and ensure that most of the large particle size phosphor particles are converted to nano-sized particles. After wet milling, the first mixture is filtered with a screen to remove the grinding ball media from the first mixture to provide a second mixture. A portion of the solvent in the second mixture was evaporated so that the remaining solvent weight was 97.6 g, resulting in a final fluorescent ink formulation containing nano-sized phosphor powder for ink jet printing.

Example 7: Adding 15 g of large particle size phosphor YAG:Ce, 15 g of cured resin Digo 2100, 4 g of UV initiator, 15 g of dispersant Digo Tego 710 to 300 cc of isopropanol, forming a suspension, and then in suspension A grinding ball medium is added to form a first mixture. The first mixture is wet milled until most of the large particle size phosphor particles are converted to nanometer sized particles. As described above, a small portion of the sample of the first mixture is taken for particle size measurement to detect and ensure that most of the large particle size phosphor particles are converted to nano-sized particles. After wet milling, the first mixture is filtered with a screen to remove the grinding ball media from the first mixture to provide a second mixture. A portion of the solvent in the second mixture was evaporated so that the remaining solvent weight was 51 g, resulting in a final fluorescent ink formulation containing nano-sized phosphor powder for ink jet printing.

Example 8: Adding 5 g of large-diameter phosphor powder SrBaSi:Eu, 10 g of curable resin Digo 2100, 1 g of UV initiator, and 1 g of dispersant Lubrizol Solsperse 22000 to 300 cc of 1-pentanol to form a suspension, and then Adding grinding ball medium to the suspension to form the first a mixture. The first mixture is wet milled until most of the large particle size phosphor particles are converted to nanometer sized particles. As described above, a small portion of the sample of the first mixture is taken for particle size measurement to detect and ensure that most of the large particle size phosphor particles are converted to nano-sized particles. After wet milling, the first mixture is filtered with a screen to remove the grinding ball media from the first mixture to provide a second mixture. A portion of the solvent in the second mixture was evaporated so that the remaining solvent weight was 83 g, resulting in a final fluorescent ink formulation containing nano-sized phosphor powder for ink jet printing.

Example 9: 10 g of large-diameter phosphor powder YAG:Ce, 1 g of Sr ₂ Si ₅ N ₈ :Eu, 3 g of dispersant Zetasperse 2100 was added to 300 cc of 1-pentanol to form a suspension, and then the suspension was added to the suspension. The ball medium forms a first mixture. The first mixture was wet milled until a small portion of the sample of the first mixture was subjected to particle size measurement and it was detected that most of the large particle size phosphor particles had been converted into nanometer-sized particles. The first mixture is then filtered using a screen to remove the grinding ball media from the first mixture to provide a second mixture. At this stage, 8 g of the cured resin component Digo 2200 and 0.4 g of UV initiator were added and dispersed well in the second mixture to form a third mixture. A portion of the solvent in the third mixture was evaporated so that the remaining solvent weight was 77.6 g, resulting in a final fluorescent ink formulation containing nano-sized phosphor powder for ink jet printing.

While the foregoing invention has been described in terms of the foregoing exemplary embodiments, it is understood that various modifications and variations are possible. Therefore, such modifications and variations are intended to fall within the scope of the invention as claimed.

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Claims (18)

A fluorescent ink composition for depositing on a light emitting diode (LED) or LED device, comprising: a cured resin component comprising a UV curable resin or a thermosetting resin or both, and a thermosetting resin component It is a two-component bismuth resin; a phosphor component comprising nano-fluorescent particles of the order of 100-1000 nm, the nano-fluorescent particles being uniformly distributed throughout the fluorescent ink composition. The fluorescent ink composition according to claim 1, wherein the nano fluorescent powder particles are formed by a pulverizing process for a larger particle size phosphor powder of the order of 1 to 50 μm. . The fluorescent ink composition of claim 2, wherein the pulverizing process is based on solvent wet milling. The fluorescent ink composition according to claim 1, wherein the phosphor component is selected from the group consisting of yttrium aluminum garnet (YAG) based materials, yttrium aluminum garnet (TAG) based materials, and bismuth silicate. Base material, sulfide material, nitride material or oxynitride material. The fluorescent ink composition of claim 1, wherein the phosphor component is contained in an amount of from about 1% by weight to about 60% by weight. The fluorescent ink composition according to claim 1, wherein the cured resin component is contained in an amount of from about 25% by weight to about 99% by weight. The fluorescent ink composition according to claim 1, wherein the cured resin component comprises a UV curable resin or a thermosetting resin or both, the fluorescent ink composition, There is a viscosity of less than about 50 centipoise such that the fluorescent ink composition can be printed using an ink jet printer. The fluorescent ink composition of claim 7, further comprising a photoinitiator for UV curing, wherein the photoinitiator is present in an amount from about 0.2% by weight to about 4% by weight. The fluorescent ink composition of claim 7, further comprising a solvent, wherein the solvent is contained in an amount of from about 51% by weight to about 97.6% by weight. The fluorescent ink composition of claim 9, wherein the solvent is selected from the group consisting of isopropyl alcohol, 2-pentanone, and 1-pentanol. The fluorescent ink composition of claim 7, further comprising a dispersing agent, wherein the dispersing agent is present in an amount of from about 0.2% by weight to about 15% by weight. The fluorescent ink composition of claim 7, wherein the phosphor component is contained in an amount of from about 1% by weight to about 15% by weight. The fluorescent ink composition according to claim 7, wherein the cured resin component is contained in an amount of from about 1% by weight to about 15% by weight. The fluorescent ink composition according to claim 1, wherein the cured resin component and the nano fluorescent powder particles are selected in such a size that the nano fluorescent powder particles are deposited, before curing, It is possible to settle extremely slowly in the fluorescent ink composition, so that a uniformly cured fluorescent layer can be formed in the LED device or the LED package. A method for preparing nano fluorescent powder particles, wherein the nano fluorescent powder particles are formed by pulverizing a large-sized phosphor powder particle, comprising: dispersing a large-sized phosphor powder particle in a solvent Forming a suspension; wet grinding the suspension until most of the larger particle size phosphor particles have been The phosphor powder particles are converted to nanometer order of magnitude, and the nano-powder particles are separated from other components in the suspension. A method of producing a fluorescent ink composition comprising a cured resin component and a nano-fluorescent powder particle, the method comprising: dispersing a larger particle size of the phosphor powder particles and the cured resin component In the solvent, a suspension is formed; the suspension is wet-milled until most of the larger-sized phosphor particles have been converted into nanometer-scale phosphor particles, thereby forming a nano-fluorescence-containing particle. The suspension of the powder particles; a portion of the solvent is evaporated from the suspension containing the nano-powder particles to form the fluorescent ink composition. A method for producing a fluorescent ink composition, the fluorescent ink composition comprising a cured resin component and a nano-fluorescent powder particle, the method comprising: dispersing a phosphor particle having a larger particle size in a solvent to form a suspension; the suspension is wet-milled until a majority of the larger particle size phosphor particles have been converted to nanometer-scale phosphor particles to form the suspension containing the nano-powder particles a liquid; adding the cured resin component to the suspension containing the nano-fluorescent powder particles to form a mixture; and evaporating a part of the solvent from the mixture to form the fluorescent ink composition. A fluorescent ink composition for deposition on a light emitting diode (LED) or LED device, comprising: a cured resin component comprising a UV curable resin or a thermosetting resin or both, and the UV curable resin is UV-curable enamel resin or organic bismuth acrylate; a phosphor component comprising nano-fluorescent particles of the order of 100-1000 nm The nano-fluorescent powder particles are uniformly distributed throughout the fluorescent ink composition.