LIGHT EMITTING DEVICE AND METHOD FOR PRODUCING SAME

Abstract

A light emitting device 10 includes: a lead frame 12a serving as a mounting portion having a cup 13; a light emitting element 14, mounted on the bottom face 13a of the cup, for emitting light having a predetermined peak wavelength; a layer of large phosphor particles 16, absorbed and formed on the light emitting element, for absorbing light emitted from the light emitting element and for emitting light having a longer peak wavelength than that of the light emitted from the light emitting element; small phosphor particles 18, which have a smaller particle diameter than that of the large phosphor particles, for absorbing at least one of light emitted from the large phosphor particles and light emitted from the light emitting element and for emitting light having a longer peak wavelength than that of the at least one of the light emitted from the large phosphor particles and the light emitted from the light emitting element; and a sealing member 20, in which the small phosphor particles are dispersed, for sealing the light emitting element and the layer of large phosphor particles in the cup.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detailed description given herebelow and from the accompanying drawings of the preferred embodiments of the invention. However, the drawings are not intended to imply limitation of the invention to a specific embodiment, but are for explanation and understanding only.

In the drawings:

FIG. 1 is a sectional view schematically showing the preferred embodiment of a light emitting device according to the present invention;

FIG. 2 is an enlarged sectional view of a cup portion of one lead frame on which a light emitting element of the light emitting device of FIG. 1 is mounted;

FIG. 3 is a graph showing the relationship between the mean particle diameter of phosphor particles used in a light emitting device and the relative intensity of emission of the light emitting device;

FIG. 4 is an illustration for explaining an electrostatic adsorption process for large phosphor particles in the preferred embodiment of a method for producing a light emitting device according to the present invention;

FIG. 5 is an illustration for explaining the structure in a cup of a lead frame of a light emitting device in Example;

FIG. 6 is a graph showing the relationship between the observation angle and correlated color temperature of the light emitting device in Example;

FIG. 7 is a graph showing the relationship between the observation angle and color rendering index of the light emitting device in Example;

FIG. 8 is an illustration for explaining the structure in a cup of a lead frame of a light emitting device in Comparative Example 1;

FIG. 9 is a graph showing the relationship between the observation angle and correlated color temperature of the light emitting device in Comparative Example 1;

FIG. 10 is an illustration for explaining the structure in a cup of a lead frame of a light emitting device in Comparative Example 2;

FIG. 11 is a graph showing the relationship between the observation angle and correlated color temperature of the light emitting device in Comparative Example 2;

FIG. 12 is an illustration for explaining the structure in a cup of a lead frame of a light emitting device in Comparative Example 3;

FIG. 13 is a graph showing the relationship between the observation angle and correlated color temperature of the light emitting device in Comparative Example 3;

FIG. 14 is an illustration for explaining the structure in a cup of a lead frame of a light emitting device in Comparative Example 4;

FIG. 15 is a graph showing the relationship between the observation angle and correlated color temperature of the light emitting device in Comparative Example 4;

FIG. 16 is an illustration for explaining the structure in a cup of a lead frame of a light emitting device in Comparative Example 5;

FIG. 17 is a graph showing the relationship between the observation angle and correlated color temperature of the light emitting device in Comparative Example 5;

FIG. 18 is an illustration for explaining the structure in a cup of a lead frame of a light emitting device in Comparative Example 6;

FIG. 19 is a graph showing the relationship between the observation angle and correlated color temperature of the light emitting device in Comparative Example 6;

FIG. 20 is an illustration for explaining the observation angle for correlated color temperature; and

FIG. 21 is a graph showing emission spectrum at the observation angle of 90° in the light emitting device in Example.

Claims

1. A method for producing a light emitting device, the method comprising the steps of: preparing a light emitting element for emitting light having a predetermined peak wavelength;preparing large phosphor particles for absorbing light emitted from the light emitting element and for emitting light having a different peak wavelength from that of the light emitted from the light emitting element;preparing small phosphor particles, which have a smaller particle diameter than that of the large phosphor particles, for absorbing light emitted from the light emitting element and for emitting light having a different peak wavelength from that of the light emitted from the light emitting element;causing the large phosphor particles to be absorbed on the surface of the light emitting element to form a layer of the large phosphor particles thereon; andsealing the light emitting element and the large phosphor particles by means of a sealing member containing the small phosphor particles.

2. A method for producing a light emitting device as set forth in claim 1, wherein said large phosphor particles are absorbed by electrostatic absorption.

3. A method for producing a light emitting device as set forth in claim 1, wherein said large phosphor particles have a particle diameter of not less than 10 μm and of less than 50 μm, and said small phosphor particles have a particle diameter of not less than 1 μm and of less than 10 μm.

4. A method for producing a light emitting device as set forth in claim 1, wherein said small phosphor particles are dispersed in said sealing member.

5. A light emitting device comprising: a mounting portion having a recessed portion;a light emitting element, mounted on a bottom face of the recessed portion of the mounting portion, for emitting light having a predetermined peak wavelength;a layer of large phosphor particles, formed on the light emitting element, for absorbing light emitted from the light emitting element and for emitting light having a different peak wavelength from that of the light emitted from the light emitting element;small phosphor particles, which have a smaller particle diameter than that of the large phosphor particles, for absorbing light emitted from the light emitting element and for emitting light having a different peak wavelength from that of the light emitted from the light emitting element; anda sealing member, in which said small phosphor particles are dispersed, for sealing the light emitting element and the layer of large phosphor particles in the recessed portion of the mounting portion,wherein a difference between the maximum and minimum values of correlated color temperatures is not greater than 500K when the correlated color temperatures of light emitted from the surface of the sealing member are measured every 10° in the range of from 10° to 170° with respect to the tangent plane at the center of the surface of the sealing member.

6. A light emitting device as set forth in claim 5, wherein said large phosphor particles have a particle diameter of not less than 10 μm and of less than 50 μm, and said small phosphor particles have a particle diameter of not less than 1 μm and of less than 10 μm.

7. A light emitting device as set forth in claim 5, which has a general color rendering index of not less than 90.

8. A method for producing a light emitting device, the method comprising the steps of: preparing a light emitting element for emitting light having a predetermined peak wavelength;preparing large phosphor particles for absorbing light emitted from the light emitting element and for emitting light having a longer peak wavelength than that of the light emitted from the light emitting element;preparing small phosphor particles, which have a smaller particle diameter than that of the large phosphor particles, for absorbing at least one of light emitted from the large phosphor particles and light emitted from the light emitting element and for emitting light having a longer peak wavelength than that of said at least one of the light emitted from the large phosphor particles and the light emitted from the light emitting element;causing the large phosphor particles to be absorbed on the surface of the light emitting element to form a layer of the large phosphor particles thereon; andsealing the light emitting element and the large phosphor particles by means of a sealing member containing the small phosphor particles.

9. A method for producing a light emitting device as set forth in claim 8, wherein said large phosphor particles are absorbed by electrostatic absorption.

10. A method for producing a light emitting device as set forth in claim 8, wherein said large phosphor particles have a particle diameter of not less than 10 μm and of less than 50 μm, and said small phosphor particles have a particle diameter of not less than 1 μm and of less than 10 μm.

11. A method for producing a light emitting device as set forth in claim 8, wherein said light emitting element is a light emitting element for emitting light having a peak wavelength in the wavelength range of from 420 nm to less than 490 nm, said large phosphor particles are phosphor particles for emitting light having a peak wavelength in the wavelength range of from 490 nm to less than 590 nm, andsaid small phosphor particles are phosphor particles for emitting light having a peak wavelength in the wavelength range of from 590 nm to 780 nm.

12. A method for producing a light emitting device as set forth in claim 8, wherein said small phosphor particles are dispersed in said sealing member.

13. A light emitting device comprising: a mounting portion having a recessed portion;a light emitting element, mounted on a bottom face of the recessed portion of the mounting portion, for emitting light having a predetermined peak wavelength;a layer of large phosphor particles, formed on the light emitting element, for absorbing light emitted from the light emitting element and for emitting light having a longer peak wavelength than that of the light emitted from the light emitting element;small phosphor particles, which have a smaller particle diameter than that of the large phosphor particles, for absorbing at least one of light emitted from the large phosphor particles and light emitted from the light emitting element and for emitting light having a longer peak wavelength than that of said at least one of the light emitted from the large phosphor particles and the light emitted from the light emitting element; anda sealing member, in which said small phosphor particles are dispersed, for sealing the light emitting element and the layer of large phosphor particles in the recessed portion of the mounting portion,wherein a difference between the maximum and minimum values of correlated color temperatures is not greater than 500K when the correlated color temperatures of light emitted from the surface of the sealing member are measured every 10° in the range of from 10° to 170° with respect to the tangent plane at the center of the surface of the sealing member.

14. A light emitting device as set forth in claim 13, wherein said large phosphor particles have a particle diameter of not less than 10 μm and of less than 50 μm, and said small phosphor particles have a particle diameter of not less than 1 μm and of less than 10 μm.

15. A light emitting device as set forth in claim 13, wherein said light emitting element is a light emitting element for emitting light having a peak wavelength in the wavelength range of from 420 nm to less than 490 nm, said large phosphor particles are phosphor particles for emitting light having a peak wavelength in the wavelength range of from 490 nm to less than 590 nm, andsaid small phosphor particles are phosphor particles for emitting light having a peak wavelength in the wavelength range of from 590 nm to 780 nm.

16. A light emitting device as set forth in claim 13, which has a general color rendering index Ra of not less than 90.