CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims priority to Japanese Patent Application No. 2018-184045, filed on Sep. 28, 2018, and Japanese Patent Application No. 2019-166348, filed on Sep. 12, 2019, the entire disclosures of which are incorporated herein by references in their entirety.

BACKGROUND

Technical Field

The present invention relates to a light emitting device.

Description of Related Art

Light emitting devices using a light emitting element, such as a light emitting diode (which may be hereinafter referred to as “LED”) or a laser diode (which may be hereinafter referred to as “LD”), have been used for various kinds of light sources. A light emitting device using a light emitting element, such as LED or LD, is a light source having a high conversion efficiency, has small electric power consumption and a long lifetime, and allows reduction in size, and thus is used for a light source in place of an incandescent lamp and a fluorescent lamp. In particular, a surface-mount light emitting device has such characteristics as small size, emission of light with a bright color, good initial driving characteristics, and durability against vibration and repeated turning-on and off. Increase in the output power of the light emitting element is also rapidly progressing. The light emitting device using LED or LD is used in various fields including a light emitting device of automobile use and indoor lighting, a backlight source for a liquid crystal display device, an illuminating device, a light source device for a projector.

In the light emitting device, a sealing member covering the light emitting element is used for protecting the light emitting element from moisture, dusts, and the like. For the sealing member, a composite containing an epoxy resin is used, as described, for example, in Japanese Unexamined Patent Publication No. 2001-234032, Japanese Unexamined Patent Publication No. 2002-145993 or Japanese Unexamined Patent Publication No. 2002-302533. Furthermore, a silicone resin is also used as the sealing member along with the increase of the output power of the light emitting element as described in Japanese Unexamined Patent Publication (Translation PCT Application) No. 2015-505329.

SUMMARY

However, the sealing member made of a composite containing an epoxy resin tends to discolor to yellow due to light and heat emitted from the light emitting element with an increased output power, which may cause change in the color of the light emitted from the light emitting device, so that the desired long lifetime may not be achieved. Furthermore, the sealing member a composite containing a silicone resin has high gas permeability and tends to transmit air, so that the silver plating used in the light emitting device discolors over time due to sulfides in air, which may result in reduction of the luminous flux of the light emitting device.

One object of certain embodiments of the present invention is to provide a light emitting device in which sulfurization resistance is improved and lumen maintenance is increased.

A light emitting device according to a first embodiment of the present disclosure includes a light emitting element configured to emit light having a peak wavelength of 320 nm or more, a substrate which includes a conductive member on which the light emitting element is mounted, and a sealing member which covers the light emitting element, in which the conductive member contains silver, and

the sealing member made of a cured silicone composite containing the following components (A), (B), (C), and (D):

(A) an organopolysiloxane containing at least two alkenyl groups that are each bonded to a silicon atom per one molecule;

(B) an organohydrogenpolysiloxane containing at least two hydrogen atoms that are each bonded to a silicon atom per one molecule;

(C) a hydrosilylation catalyst; and

(D) a zinc silanolate represented by the following formula (1):



In the formula (1), R1to R7each independently represent a linear, branched, or cyclic monovalent hydrocarbon group having 1 to 10 carbon atoms, which may be substituted by a fluorine atom, or each independently represent a hydroxy group or an alkoxy group; and m represents an integer of 1 or greater.

According to one embodiment of the present disclosure, a light emitting device that is improved in sulfurization resistance and has a high lumen maintenance can be provided.

