Electric lamp and discharge devices – With luminescent solid or liquid material – Solid-state type
Reexamination Certificate
2001-11-06
2004-01-20
Luebke, Renee (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Solid-state type
C313S512000
Reexamination Certificate
active
06680568
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a light emitting device used for a light source of a liquid crystal display and others. Particularly, the present invention relates to a light emitting device wherein clear and high-luminance emission without a color dapple can be acquired effectively utilizing the light emanating from a semiconductor luminous element for a long term.
A light emitting diode which is a semiconductor luminous element is a small device. Clear luminescent color can be efficiently acquired without anxiety that a light bulb is burnt-out. The light emitting diode has an excellent drive characteristic and is also strong against a vibration and repetitive switching operations. Therefore, the light emitting diode is utilized for a light source of various indicators and a liquid crystal display.
Heretofore, as a light emitting device of a liquid crystal display and others for displaying full color, a light emitting diode (LED) lamp is known. The LED lamp has semiconductor luminous elements emitting colors of red, blue and green, that is, three semiconductor luminous elements of so called RBG. The three semiconductor luminous elements are provided on a board as one unit.
Another type of full color light emitting device is also known. The full color light emitting device has three semiconductor luminous elements emitting colors of red, blue and green provided on a lead frame.
A light emitting diode used for this type of light emitting device has an excellent monochromatic peak wavelength. Therefore, in case that a light emitting device that emits white light is utilizing light emitting diodes that respectively emit red light, green light and blue light, for example, the light emitting diodes that respectively emit each color light are required to be arranged closely to diffuse and mix each color light.
Concretely, to acquire a light emitting device that emits white light, three types of red, green and blue light emitting diodes or two types of bluish green and yellow light emitting diodes are required. That is, to acquire a light emitting device that emits white light, light emitting diodes of plural types different in luminescent colors are required to be used.
In addition, a semiconductor light emitting diode chip has fluctuations in tone and luminance. In case that plural light emitting diodes are made of different materials, the driving power of each light emitting diode chip is different and a power source is required to be individually secured.
Therefore, to acquire the white light, a current supplied to every light emitting diode and others are required to be adjusted. There is a problem that a light emitting diode is different in temperature and aging characteristics, and tone also changes. Further, in case that the emission from each light emitting diode chip is not mixed uniformly, the light may include irregular color and desired white color may not be acquired.
Particularly, in the light emitting device wherein three types of semiconductor luminous elements of red, blue and green luminescent colors are provided on a board and are used as one unit, there is a problem that the light emitting device becomes large. In addition, as there is a distance between the semiconductor luminous elements, there is a problem that it is difficult to acquire uniform mixed color, and the color of the light emitting device becomes coarse.
In the light emitting device in which three types of semiconductor luminous elements of red, blue and green luminescent colors are provided on one lead frame and the like, to acquire the white luminescent color, charge is required to be supplied to all semiconductor luminous elements including red, blue and green. Therefore, there are a problem of large power consumption in view of energy conservation and a problem of a space required for a battery in a portable (mobile) type.
As a light emitting device in which the above-mentioned problems are solved, a light emitting device disclosed in Japanese published unexamined patent applications No. Hei 7-99345, No. Hei 10-190066 and No. Hei 10-242513 is known.
In the light emitting device disclosed in Japanese published unexamined patent application No. Hei 7-99345, an LED chip is mounted at the bottom of a cup. A resin (a color converting member) including a fluorescent material (or a filter material for partially absorbing the emission wavelength of the luminous chip) for converting the emission wavelength of the LED chip to another wavelength is filled inside the cup. Further, another resin is provided for surrounding the above-mentioned resin.
The light emitting device disclosed in Japanese published unexamined patent application No. Hei 10-190066 is provided with an LED chip fixed on a board by a die bonding member and a color converting member provided on the LED chip. The color converting member includes a fluorescent material that absorbs at least a part of light emitted from the LED chip, converts the wavelength and emits the converted light.
In a light emitting device disclosed in Japanese published unexamined patent application No. Hei 10-242513, a pair of mount-leads is provided in the light emitting device. A front edge of one of the mount-leads is in the form of a cup. An LED chip made of a gallium nitride semiconductor is arranged in the cup. The LED chip is electrically connected via an inner lead with the other mount-lead. A transparent resin including a fluorescent material is filled in the cup. In another light emitting device, a gallium nitride semiconductor chip is arranged in the body of the equipment and a transparent resin including a fluorescent material is filled in the body.
The light emitting device disclosed in the above-mentioned each patent application acquires another luminescent color from one type of luminescent color of a semiconductor luminous element itself. Concretely, as a light emitting diode that converts the wavelength of light emitted from an LED chip, white light emission is acquired by mixing light emitted from a blue light emitting diode and light emitted from a fluorescent material that absorbs the above-mentioned light and emits yellow light.
In the light emitting devices disclosed in the above-mentioned patent applications, the color converting member is provided on the LED chip. Therefore, in case that the white light is acquired, the dispersed blue light radiated upward from the LED chip itself and yellow light converted by the color converting member provided on the LED chip are mixed to look white light to a human eye.
To acquire clear and high-luminance white light, scattering and distribution of blue light and yellow light are required to be uniform and constant. However, in the configuration disclosed in the above-mentioned each patent application, the blue light is shielded by the color converting member on the LED chip. Luminance of the light emitting device is determined by a quantity of the light converted by the color converting member and the blue light radiated from the LED chip itself. Therefore, there is a problem that the scattering and the distribution of the color converting member are required to be uniform, and luminance is not satisfactory.
In addition to the color converting member including a fluorescent material for converting the wavelength of the light from the LED chip, a die bonding member (a mounting member) for fixing the luminous chip or the LED chip is required.
Further, the configuration disclosed in Japanese published unexamined patent application No. Hei 7-99345 has a problem that since the semiconductor luminous element is put in the wavelength converting material, it is difficult to acquire mixed color.
Also, in the configuration disclosed in Japanese published unexamined patent application No. Hei 10-242513, the gallium nitride semiconductor is arranged in the cup or the body of equipment. The fluorescent material such as a wavelength converting material is filled above the semiconductor and at the four sides. Hereby, the fluorescent material is uniformly disperse
Fujiwara Tsubasa
Nakano Akio
Kanesaka & Takeuchi
Luebke Renee
McCamey Ann
Nippon Leiz Corporation
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