LED ENCAPSULANT COMPRISING RARE EARTH METAL OXIDE PARTICLES

Abstract

The present invention relates to an LED encapsulant including rare-earth metal oxide particles and, more particularly, to an LED encapsulant including a compound represented by Chemical Formula 1 below in a polymer resin.

M.sub.a(OH).sub.b(CO.sub.3).sub.cO.sub.d [Chemical Formula 1]

In Chemical Formula 1, M is Sc, Y, La, Al, Lu, Ga, Zn, V, Zr, Ca, Sr, Ba, Sn, Mn, Bi or Ac, a is 1 or 2, b is 0 to 2, c is 0 to 3, and d is 0 to 3, wherein b, c, and d are not simultaneously zero, and b and c are either simultaneously zero or simultaneously not zero.

Claims

1. An LED (Light-Emitting Diode) encapsulant, comprising a compound represented by Chemical Formula 1 below in a polymer resin.
M.sub.a(OH).sub.b(CO.sub.3).sub.cO.sub.d [Chemical Formula 1] wherein M is Sc, Y, La, Al, Lu, Ga, Zn, V, Zr, Ca, Sr, Ba, Sn, Mn, Bi or Ac, a is 1 or 2, b is 0 to 2, c is 0 to 3, and d is 0 to 3, wherein b, c, and d are not simultaneously zero, and b and c are either simultaneously zero or simultaneously not zero.

2. The LED encapsulant of claim 1, wherein the compound represented by Chemical Formula 1 is Y(OH)CO.sub.3.

3. The LED encapsulant of claim 1, wherein the compound represented by Chemical Formula 1 is Y.sub.2O.sub.3.

4. The LED encapsulant of claim 1, wherein the compound represented by Chemical Formula 1 has a refractive index ranging from 1.6 to 2.3.

5. The LED encapsulant of claim 1, wherein the polymer resin is least one selected from the group consisting of a silicone-based resin, a phenol-based resin, an acrylic resin, polystyrene, polyurethane, a benzoguanamine resin, and an epoxy-based resin.

6. The LED encapsulant of claim 1, further comprising phosphor particles.

Description

DESCRIPTION OF DRAWINGS

[0030] FIG. 1 is an SEM (Scanning Electron Microscope) image showing rare-earth oxide particles (Y(OH)CO.sub.3 particles) according to the present invention; and

[0031] FIG. 2 is an SEM image showing rare-earth oxide particles (Y.sub.2O.sub.3 particles) according to the present invention.

MODE FOR INVENTION 36 Hereinafter, a detailed description will be given of the present invention.

[0032] The present invention pertains to a resin and a rare-earth metal oxide additive for use in encapsulation of an LED package exhibiting improved light extraction efficiency and, more particularly, to a resin for an LED encapsulant including rare-earth metal oxide nanoparticles, which serves to extract light rays that are confined between an LED package chip and an encapsulant, among the light rays generated in an LED package, to the outside, thereby manifesting high luminous efficiency.

[0033] Accordingly, the present invention comprises a compound represented by Chemical Formula 1 below in a polyer resin.

M.sub.a(OH).sub.b(CO.sub.3).sub.cO.sub.d [Chemical Formula 1]

[0034] wherein, M is Sc, Y, La, Al, Lu, Ga, Zn, V, Zr, Ca, Sr, Ba, Sn, Mn, Bi or Ac.

[0035] a is 1 or 2, b is 0 to 2, c is 0 to 3, and d is 0 to 3.

[0036] Here, b, c, and d are not simultaneously zero, and b and c are either simultaneously zero or simultaneously not zero.

[0037] The compound of Chemical Formula 1 is preferably Y(OH)CO.sub.3 or Y.sub.2O.sub.3, and more preferably Y(OH)CO.sub.3 with respect to light extraction efficiency. This may be understood in greater detail through the Examples and Experimental Example, which will be described hereafter.

[0038] It is preferable for the compound of Chemical Formula 1 to have a refractive index in the range of 1.6 to 2.3. If the refractive index is less than 1.6 or greater than 2.3, light extraction efficiency may not be increased. The reason is that the refractive index of a typical silicone encapsulant is about 1.5 and the refractive index of a GaN chip is about 2.4.

[0039] In a light-emitting element package chip, total reflection occurs at boundaries between the element and external air or silicone which is an external encapsulant, or the like. According to Snell's law, the critical angle (crit) at which the light or waves passing through two isotropic media having different refractive indices can be emitted from the media to the outside is obtained using the following Equation.

[00001]$.Math.c.Math..Math.r.Math..Math.i.Math..Math.t=\arcsin \left(\frac{n.Math.2}{n.Math.1}\right)$

[0040] The refractive index of GaN is about 2.5, which is largely different from that of air (n.sub.air=1) and silicone (n.sub.silicone=1.5). Accordingly, the critical angle at which light generated in the light-emitting element package can be emitted to the outside is limited (.sub.GaN/air=23 and .sub.GaN/Silicone=37, respectively). Therefore, light extraction efficiency is only about 15%.

[0041] The polymer resin is not particularly limited, so long as polymer resin widely used in the art is used. For example, at least one selected from among a silicone-based resin, a phenol-based resin, an acrylic resin, polystyrene, polyurethane, a benzoguanamine resin, and an epoxy-based resin may be used. The silicone-based resin may be any one selected from among polysilane, polysiloxane, and a combination thereof. The phenol-based resin may be at least one phenol resin selected from among a bisphenol-type phenol resin, a resol-type phenol resin, and a resol-type naphthol resin. The epoxy-based resin may be at least one epoxy resin selected from among bisphenol F-type epoxy, bisphenol A-type epoxy, phenol novolak-type epoxy, and cresol novolak-type epoxy.

[0042] The encapsulant composition according to the present invention may further include phosphor particles so as to exhibit a desired color.

[0043] The present invention is described in more detail through the following examples, which are set forth to illustrate, but are not to be construed to limit the scope of the present invention.

EXAMPLES

Example 1

[0044] Y(OH)CO.sub.3 particles were manufactured with 100 mL of distilled water as the standard. Specifically, 2 g of yttrium nitrate hydrate and 40 g of urea were dissolved in 100 mL of distilled water and then mixed by sufficiently stirring for 30 min. After stirring, the pH of the resulting solution was adjusted to 5 to 6 using nitric acid and ammonium hydroxide as a base. The mixed solution was heated to 90 C. and stirred for 1 hr, filtered, and washed three times with distilled water. The washed Y(OH)CO.sub.3 particles were dried in an oven at 70 C. for 3 hrs, to manufacture particles having a size of 200 nm or less.

[0045] FIG. 1 shows an SEM image of the manufactured particles.

[0046] The Y(OH)CO.sub.3 particles were added to a silicone-based resin (a mixture comprising OE 6631 A and OE 6631 B at a ratio of 1:2) (97 wt % of the silicone-based resin and 3 wt % of the Y(OH)CO.sub.3), after which the resulting mixture was placed in a homogenizer and homogenized, to prepare an encapsulant composition.

Example 2

[0047] Y.sub.2O.sub.3 particles were obtained by manufacturing and then firing Y(OH)CO.sub.3. 100 mL of distilled water was used as a standard for Y(OH)CO.sub.3. Specifically, 2 g of yttrium nitrate hydrate and 40 g of urea were dissolved in 100 mL of distilled water and then mixed by sufficiently stirring for 30 min. After stirring, the pH of the resulting solution was adjusted to 5 to 6 using nitric acid and ammonium hydroxide as a base. The mixed solution was heated to 90 C. and stirred for 1 hr, filtered, and washed three times with distilled water. The washed Y(OH)CO.sub.3 particles were dried in an oven at 70 C. for 3 hrs. Then the dried Y(OH)CO.sub.3 particles were fired at 900 C. for 3 hrs in an oxidizing atmosphere, to obtain Y.sub.2O.sub.3 particles having a size of 200 nm or less.

[0048] FIG. 2 shows an SEM image of the manufactured particles.

[0049] The Y.sub.2O.sub.3 particles were added to a silicone-based resin (a mixture comprising OE 6631 A and OE 6631 B at a ratio of 1:2) (97 wt % of the silicone-based resin and 3 wt % of the Y.sub.2O.sub.3), after which the resulting mixture was placed in a homogenizer and homogenized, to prepare an encapsulant composition.

COMPARATIVE EXAMPLE

[0050] A 100 wt % encapsulant composition was prepared by mixing a silicone-based resin OE 6631 A and OE 6631 B at a ratio of 1:2.

EXPERIMENTAL EXAMPLE

[0051] The encapsulant compositions of Examples 1 and 2 and Comparative Example were mounted in an LED package having a blue LED (a wavelength of 450 nm) chip, and then the rate of increase in luminance was measured. In the LED package, the chip connected on a lead frame through die bonding was used as a light-emitting source. The LED package is configured such that the LED and the lead frame are electrically connected through metal wire bonding and then molded with an encapsulant consisting of a silicone resin, which is material for transparent encapsulant, and inorganic nanoparticles dispersed therein. As for the luminance increase rate, the degree of increase in luminance compared with the Comparative Example was expressed as a percentage. Luminance was measured using a DARSA Pro 5200 PL system from the Professional Scientific Instrument Company, Korea.

[0052] The results are given in Table 1 below.

TABLE-US-00001 TABLE 1 Comparative Example Example 1 Example 2 Luminance increase 0 5.9 2.6 rate (%)

[0053] As is apparent from Table 1, when the rare-earth metal oxide inorganic particles were contained in the encapsulant composition, the luminance was found to be drastically increased. Particularly, in the case of Y(OH)CO.sub.3 particles, when the amount of the particles was 3 wt %, luminance was increased by more than about two times compared to the same amount of Y.sub.2O.sub.3 particles.