JPH1027926A - Photo-semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the photo-semiconductor device to be applicable for a long time at high output by containing a low melting point solid material at a normal temperature thermally coupled with a light emitting element arranged on a substrate. SOLUTION: A substrate 203 is used for fixing a light emitting element 101 so as to arrange said element 101 in various shapes. A heat accumulating means efficiently accumulates heat emitted from the light emitting element 101 to avert any unfavorable effect on the light emitted element itself and the driving action of the same. The heat accumulating means using the latent heat contains a low melting point member solid at normal temperature, The low melting point member 205 accumulates the heat by melting down the heat generated by the light emitting element 101 to suppress the temperature rise of the light emitting element 101. Through these processors, the safe and light photo-semiconductor device in long life and high efficiency to a specific wavelength generating on heat at all.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-output optical semiconductor device which can be used for curing a photocurable composite for dental use, an image output device, and the like. The present invention also relates to an optical semiconductor device which has very little adverse effect on thermal destruction and life of a light emitting element even when used.

[0002]

2. Description of the Related Art Light emitting diodes (hereinafter, also referred to as LEDs) have advanced from low power and low luminance light sources to high luminance and ultra high luminance. In addition, the emission wavelength has recently expanded from infrared to yellow-green to blue, green, and UV regions, and the emission luminous efficiency is about to reach a light bulb or more. Under such circumstances, there has been a movement to utilize light emitting elements such as LEDs not only as point light sources or signal sources but also as highly efficient wavelength selectable light sources. In particular, it can be said that the use of light in a short wavelength range is far more reasonable than the use of a tungsten lamp.

[0003] For example, a halogen bulb is used for curing a light-curable composite for dental use. FIG. 4 shows an example of the curable composite device. As a light source for curing the composite, a filter transmitting near 470 nm and a halogen bulb are used. Light is emitted by supplying electric power supplied from a battery power supply to a halogen bulb.
The light from the halogen bulb is focused by a lens through a filter for selecting a wavelength. Such a device is large in size, and condensed light is guided into the oral cavity via an optical fiber. Thereby, it is possible to cure the composite by irradiating only the desired composite arrangement site.

A composite curing device is used for curing a resin in a short time with a high-output light source. If a cordless dental photocurable composite curing device using a halogen bulb is operated with a battery power source such as a Ni-Cd battery, the limit is 30 to 50 W. In this case, the heat generation is large and the light conversion efficiency of the halogen bulb is about 10%.
%. The light of the halogen lamp is white light having a very wide wavelength range, and the effective light passing through a blue filter for selecting a wavelength is attenuated to about 10%. Therefore, the utilization factor with respect to the original power is very low, being close to 1% as a whole. In addition, since the power consumption is large, the weight and the volume of the battery power supply must be large, and the advantage of the cordless is reduced by half. Further, since a condensing part for a halogen bulb is required and the temperature of the lamp itself becomes high, there is a limit to downsizing.

[0005] For such applications, the narrow spectrum, high efficiency, low power consumption and miniaturization of LED chips are just the perfect thing. For example, assuming a halogen lamp of 30 W, the effective light output is 300 mW. If this is simply substituted for an LED chip with an output of 5 mW, 60 chips are required. In such an application, it is necessary that the light amount is high and the density is high so that it can be used as an integrated light source. Therefore, the light emitting elements must also be mounted at a high density. Each LED chip can be configured as an LED chip having a size of about 350 μm square. Therefore, a maximum of about 3 mm square is sufficient even for 8 × 8 pieces, and the size can be reduced for handy use.

[0006]

However, although the amount of heat generated by each light emitting element is smaller than that of a halogen lamp, an optical semiconductor device in which light emitting elements are arranged at a high density has a problem.
When driven at high output, the temperature of the light emitting element itself rises rapidly.
Semiconductors are generally vulnerable to heat, and the heat generated by the light emitting element itself may cause a shift in emission wavelength, a decrease in luminance, and an unstable light intensity. Further, the light emitting element itself may be damaged. Therefore, if the device is used for a long time or is used repeatedly, its characteristics change between the early stage and the late stage of light emission, and the device may not function as desired. For this reason, it is conceivable to release the heat generated by the light emission of the light emitting elements to the outside using a heat sink or heat pipe, which is a good thermal conductor having high thermal conductivity. In the case of driving by means of, it is not sufficient that the temperature is raised instantaneously and the heat is radiated and diffused into the air through a radiator or the like. In addition, in the case of reducing the size and weight, dissipating heat to the outside only by the heat radiating portion does not allow a member or the like affected by heat to be arranged near the heat radiating portion. Further, using a new driving means such as a blowing fan as a cooling device consumes extra power.
In addition, a DC motor that generates high-frequency noise for cooling is not preferable because it is considered as a factor that causes malfunction of other communication devices and medical devices.

[0007] In general, in consideration of cordless use, light weight, small size, and high output are contradictory, so that it cannot be used continuously for a long time. Semiconductors are thermally weak and excessive power input will extremely shorten the life of the semiconductor. The present invention has been made to solve these problems, and provides an optical semiconductor device which can be used for a long time with high output, can be reduced in size and weight, and further has excellent optical characteristics and semiconductor characteristics. Is to do.

[0008]

According to the present invention, there is provided an optical semiconductor device in which a semiconductor light emitting element disposed on a substrate emits light by electric power from a power supply, wherein the semiconductor light emitting element is thermally coupled to the light emitting element disposed on the substrate. An optical semiconductor device having heat storage means containing a low-melting substance that is solid at normal temperature.

[0009] Further, the substrate is an optical semiconductor device in which the substrate is a metal, ceramic, glass or a plastic composite containing them, and the optical coupling between the light emitting element and the heat storage means is connected by a heat pipe. Device.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides a light-weight and small-size light-emitting device having excellent optical characteristics and semiconductor characteristics by storing heat generated by a light-emitting element by utilizing a member having a very large heat of fusion compared with specific heat. It has been found that the optical semiconductor device can be a simple optical semiconductor device.

That is, it is not enough to release the heat generated by the light emitting element with a rapid and large amount of heat only to the outside.
By temporarily storing the heat generated by the light emitting element in the heat storage means containing the low melting point member, it is possible to suppress the temperature rise of the light emitting element and maintain the optical characteristics and the semiconductor characteristics while maintaining excellent optical characteristics and semiconductor characteristics. It is possible to reduce the size and weight.

Hereinafter, the present invention will be described in detail. FIG. 1 is a schematic diagram of the present invention, in which an LED chip as a highly efficient wavelength-selectable light emitting element is fixed on a film-like substrate or a copper plate. LED chip has 4 light output
A total of 64 blue LEDs using a gallium nitride-based compound are mounted in a matrix of 8 × 8 to obtain 500 mW with an emission wavelength of 70 nm. The heat storage means is constituted by a copper frame containing a substance having a low melting point such as metallic gallium which is solid at normal temperature. LE
The substrate to which the D-chip is fixed is attached on an extension of the heat storage means extending from the copper frame for thermal coupling with the heat storage means. The LED chip is configured to be drivable by being electrically connected to a battery power supply, a control circuit, and the like. With this configuration, heat emitted from the light emitting element when the optical semiconductor device is driven is thermally conducted by the copper frame to the heat storage means containing a low-melting substance that is solid at room temperature, and solid at room temperature. Is heated. At first, the temperature rises in inverse proportion to the specific heat due to the conducted heat, but when the melting point of the filling is reached, the temperature does not rise any more. Normally, the heat of fusion is significantly higher than the specific heat, so that even a small amount of filling can withstand the input of large power for a considerable amount of time. Can be. A light-emitting element in which a rise in temperature is suppressed can exhibit stable optical characteristics and semiconductor characteristics. Hereinafter, the configuration of the present invention will be described in detail.

(Light Emitting Element 101) As the light emitting element 101 used in the present invention, GaAlN, ZnS, ZnSe, SiC, Ga
P, GaAlAs, AlInGaP, InGaN, Ga
A light emitting layer formed of a semiconductor such as N or AlInGaN is used. Examples of the semiconductor structure include a homostructure having a MIS junction, a PIN junction, and a PN junction, a heterostructure, and a double heterostructure. The emission wavelength can be selected from ultraviolet light to infrared light depending on the material of the semiconductor layer and its degree of mixed crystal. Further, the light emitting layer may have a single quantum well structure or a multiple quantum well structure in order to have a quantum effect. In order to obtain a dental optical semiconductor device, a gallium nitride-based compound semiconductor having a high output peak from 470 nm to 480 nm, which is considered to be most effective for polymerization in a dental composite range, is used.
It is particularly preferable to use an ED chip.

A desired electrode is formed on the semiconductor thus formed by using a vacuum evaporation method, sputtering, or various CVD methods utilizing heat, light, discharge energy, or the like. The semiconductor electrode may be provided on one surface side of the semiconductor, or may be provided on both surfaces. After directly cutting the semiconductor wafer on which the electrodes are formed by a dicing saw in which a blade having a diamond cutting edge is rotated, or after cutting a groove having a width wider than the cutting edge width (half cut),
The semiconductor wafer is broken by external force. Alternatively, a very thin scribe line (meridian) is formed on a semiconductor wafer by a scriber in which a diamond needle at the tip reciprocates linearly.
Are drawn in a grid pattern or the like, and then the wafer is split by an external force and cut from the semiconductor wafer to form LED chips.

As a light emitting element, the L
The ED chip itself may be directly fixed to the substrate and used, or an LED chip may be arranged on a lead frame, and after electrical continuity is obtained, a resin protective body or the like may be used. In order to electrically connect the LED chip to the conductive pattern of the substrate, it may be performed by a conductive adhesive, solder, or the like, or by wire bonding a conductive wire using a gold wire, an aluminum wire, or the like. Is also good.

In order to configure the optical semiconductor device so that each of the emission wavelengths of RGB can be selected, a light emitting element that emits RGB light can be used. A light emitting element capable of emitting RGB can use various semiconductors, but it is preferable to use a gallium nitride-based compound semiconductor in green and blue wavelength regions as a high-luminance semiconductor material, and in a red wavelength region. It is preferable to use a gallium-aluminum-arsenic-based semiconductor or an aluminum-indium-gallium-phosphorus-based semiconductor. This makes it possible to selectively perform exposure processing by light irradiation or the like.

The total irradiation time and the total irradiation amount of the light emitting element can be selected depending on the type and amount of the composite used. Therefore, the irradiation time of the light emitting element can be reduced by increasing the output of the light emitting element and increasing the number of light emitting elements. The light emitting element can be controlled via various drive control circuits as drive means. By providing this drive control circuit, it is possible to control the intermittent light emission and the light emission output of the light emitting element, and also to control the light emission amount and time according to the remaining amount of the battery power source and the temperature of the heat storage means. In an optical semiconductor device used for photopolymerization, the photopolymerization type composite range can improve the light emission intensity etc. in proportion to the light emission time in order to prevent the polymerization reaction from being promoted only on the surface and the inside from being unreacted. it can. Such a control of the light emitting element can be easily formed by various control means provided in the optical semiconductor.

After the light emitting elements are integrated, the light may be further converged and used through a lens, or the light may be converged using a lens for each light emitting element and protected from the external environment. The emission wavelength can be further selected by including a dye and / or a pigment in the lens to have a filter effect.

(Substrate 203) The substrate 203 is a light-emitting element 1
The light emitting element 101 is used to fix the light emitting element 101 in various desired shapes depending on the pattern of the substrate. In order to conduct heat generated from the light emitting element 101 to the heat storage means, the substrate itself may be formed as a member having good heat conductivity, or may be combined with another member having good heat conductivity. Specifically, as the substrate, metal, ceramic, glass, a plastic composite obtained by laminating them, or the like can be suitably used. In the case of an insulating substrate, a conductive pattern is formed by plating or the like in order to establish electrical conduction with the light emitting element. In the case of a metal substrate, a conductive pattern can be formed again after forming SiO ₂ , SiN or the like by various CVD methods or the like. Various materials such as copper, iron, aluminum, and alloys thereof can be given as metal members having good heat conductivity. Further, heat from the light emitting element may be transferred to the heat storage means using a heat pipe. In any case, any material can be used as long as it can efficiently conduct heat from the substrate on which the light emitting elements are arranged to the heat storage means. Note that when the light-emitting element is to be driven by a pulse, an alternating current, or the like, it is more preferable to use a metal substrate for the purpose of absorbing electromagnetic waves generated from the light-emitting element or the like. The shape of the substrate is
Although various shapes can be used, the light from the light emitting element can be easily collected by using the concave shape.

(Heat Storage Means) The heat storage means of the present invention is for efficiently storing heat from the light emitting element 101 therein so that the light emitting element itself and the driving of the light emitting element are not adversely affected. Therefore, various types and amounts are used depending on the heat generation amount of the light emitting element. As the heat storage means, a means utilizing the renewed heat can efficiently absorb the heat from the light-emitting element, so that the room temperature (about 25
(° C.), it is preferable to use one containing a solid low melting point member. Such a low-melting member 205 accumulates heat by melting the heat generated by the light emitting element 101 and suppresses the temperature rise of the light emitting element 101. When the heat storage means is heated, the temperature rises in proportion to the specific heat until it reaches the melting point of the low melting point member. Therefore, it is necessary that the light-emitting element be a member that melts at a temperature at which the light-emitting element can be driven stably. Therefore, the melting point is preferably 80 ° C. or lower, more preferably 50 ° C. or lower, depending on the type of the light emitting element. The heat once stored is radiated when the driving of the light emitting element is stopped and / or the heat storage means is forcibly cooled by liquid cooling, air cooling, or the like, so that the low melting point member solidifies again and can store heat. In the case of a dental composite curing device in which the LED chips 101 are arranged at a high density, the irradiation time of the light emitting element is about 10 to 40 seconds, but the temperature rises rapidly. Therefore, the light emitting element cannot be sufficiently cooled by ordinary heat radiation by air cooling or the like, and the present invention is particularly effective.

The heat radiation of the heat stored in the heat storage means can be promoted by liquid cooling such as air cooling, forced air cooling, water cooling or oil cooling in addition to returning to room temperature, but they are separated from the optical semiconductor device. It does not hinder the convenience of use. Specific heat storage means can be formed by hermetically sealing metal gallium, paraffin, or the like in a container made of copper, aluminum, or the like having good heat conductivity. The amount of the low melting point member in the heat storage means can be easily calculated from one power input to the light emitting element. In addition, by making the inside of the heat storage means pleated or the like, the surface area can be increased and the heat transfer efficiency can be improved. Note that at least a part of the heat storage means may be used by covering it with a heat insulating material such as a ceramic or various resin cases, if desired, so that the heat of the heat storage means is not restricted during use.

(Power Source 206) The power source 206 only needs to drive at least the light emitting element 101 of the optical semiconductor device. Therefore, various things such as those using commercial power, primary batteries and secondary batteries can be used,
A battery power supply is preferred for cordless operation. Various batteries such as a lithium battery and a manganese battery can be used as a primary battery, and a lithium ion battery and a nickel cadmium battery can be used as a secondary battery. These can be connected in series and / or in parallel as desired to provide a battery power source. The battery power supply can be driven independently or can be used jointly with a power supply from a system power supply or the like.

(Heat Pipe) The heat pipe is used to efficiently conduct heat generated by light emission of the light emitting element to the heat storage means. Such a heat pipe evacuates the inside of a metal pipe with a capillary structure on the inner wall of the pipe,
It can be formed by sealing a small amount of water, alternative chlorofluorocarbon, etc. as the working fluid. The heat of the light emitting element heats one end of the heat pipe, and the working fluid in that portion evaporates. The working fluid that has become a vapor flow moves at a high speed to a low-temperature portion that is in contact with the heat storage means. When the vapor stream contacts the tube wall of the low temperature section and is cooled and condensed, it returns to the heating section that is in thermal contact with the light emitting element by capillary action or gravity, and repeatedly transports heat continuously. Thus, heat generated by the LED chip can be efficiently conducted to the heat storage means. The heat pipe can be more efficiently conducted by inserting the heat pipe into the heat storage means filled with a substance having a low melting point. Hereinafter, specific embodiments of the present invention will be described, but it goes without saying that the present invention is not limited to only the embodiments.

[0024]

【Example】

(Example 1) A gallium nitride-based compound semiconductor was used as a blue LED (emission wavelength: 450 nm). On the cleaned sapphire substrate, a TMG gas, a nitrogen gas and a dopant gas were flowed together with a carrier gas, and a gallium nitride-based compound semiconductor was formed by MOCVD. By switching the dopant gas, a gallium nitride semiconductor having N-type conductivity and a gallium nitride semiconductor having P-type conductivity were formed to form a PN junction. (It is annealed at 400 ° C. or higher to make it a P-type semiconductor.)

After exposing the surface of each PN semiconductor by etching, an electrode was formed by sputtering. The semiconductor wafer thus completed was divided to form LED chips as light emitting elements. LED using epoxy resin on flexible board with copper pattern formed
Fix the tip. In addition, each electrode of the LED chip and the copper pattern are wire-bonded using an Au wire as a conductive wire to be electrically connected to each other. Thus, a total of 64 blue LED chips were mounted in a 30 mm square, 8 × 8 in series and parallel. This substrate was used as a heat storage means and attached to the tip of a copper frame filled with about 15 g of metal gallium (m.p. 29.7 ° C.). In addition, a substrate on which LED chips are arranged for dental use is arranged perpendicularly to the apparatus to facilitate use. Figure 2
It is connected like. The forward voltage of each LED chip was adjusted to within 0.1 V at 60 mA, and individual limiting resistors could be omitted. Four Ni-Cd secondary batteries are connected in series at about 5 V as a battery power supply, and are electrically connected to a substrate on which the light emitting elements are arranged. A current of 4 A was passed in total, and an optical output of about 500 mW was obtained. 200m at 1.3A
W output was obtained. The optical semiconductor device was used as a dental composite, and a composite range (Silux Plus manufactured by 3M) was irradiated with light for 30 seconds. Even after 0.1 g of the composite was completely cured, the temperature of the flame did not exceed 33 ° C. In addition, even if it was repeatedly used 100 times or more, it could be used as it was at the initial stage by immersing it in a glass of water (20 ° C.) for 3 minutes.

(Comparative Example 1) A configuration was made in the same manner as in Example 1 except that metal copper bulk was used instead of metal gallium. As a result of using the device in the same manner as in Example 1, the temperature around the LED chip was increased, the emission wavelength was shifted compared to the initial characteristics, and in some cases, the device did not emit light at last.

Example 2 About 10 g of paraffin (m.p. 42-44 ° C.) was used in place of metal gallium, which is a low-melting member that is solid at room temperature and contained in heat storage means, and metal gallium was included. The configuration was the same as in Example 1 except that the inside of the heat storage means and the substrate of the light emitting element were connected by a heat pipe. As in the case of the first embodiment, even when used repeatedly, the drive could be carried out without any change from the initial stage. Further, the flame temperature could be more stable than in Example 1.

[0028]

As described above, the optical semiconductor device according to the present invention can irradiate intense light having a specific wavelength, and can be used as a light source for photo-curing of a composite resin, exposure of various photosensitive materials, and a measuring instrument. A small irradiation device that can be used from the outside to the infrared region can be obtained.

Further, the size of the device can be reduced as compared with a halogen lamp or the like, and an optical semiconductor device having much higher efficiency for a specific wavelength can be obtained. An optical semiconductor device which is safe, light and has a long life without heat can be obtained.

By adopting the structure of claim 2 of the present invention, an optical semiconductor device with a further reduced temperature rise can be obtained.

According to the third aspect of the present invention, an optical semiconductor device in which the heat from the light emitting elements is efficiently conducted to the heat storage means so that the light emitting elements are densely packed and heat is stored even when the temperature rises rapidly. It can be.

According to the configuration of the fourth aspect of the present invention, a stable optical semiconductor device can be obtained because the light emitting element is melted within a temperature at which the light emitting element can be driven stably.

[0033]

[Brief description of the drawings]

FIG. 1 is a schematic view of an optical semiconductor device of the present invention used for a dental composite curing device.

FIG. 2 is a schematic top view of the light emitting device of the present invention, and is a cross-sectional view taken along line AA of FIG.

FIG. 3 is an example of a circuit diagram of the present invention.

FIG. 4 is a schematic sectional view of a dental composite curing device using a halogen lamp shown for comparison with the present invention.

[Explanation of symbols]

 101: LED chip disposed on a substrate 102: Battery power accommodating case 203: Substrate on which a light emitting element is disposed 204: Tip of thermal storage means 205: Low melting point member in thermal storage means 206: Battery power supply 401: Halogen lamp 402: Composite curing equipment body 403: Reflecting mirror 404: Lens 405: Optical fiber 406: Battery power supply 407: Filter

Claims (3)

[Claims] 1. An optical semiconductor device for emitting light from a semiconductor light emitting element disposed on a substrate by power from a power supply, the optical semiconductor device having a low melting point that is thermally coupled to the light emitting element disposed on the substrate and is solid at room temperature. An optical semiconductor device comprising heat storage means containing a substance. 2. The optical semiconductor device according to claim 1, wherein the substrate is a metal, ceramic, glass, or a plastic composite obtained by laminating at least one of them. 3. The optical semiconductor device according to claim 1, wherein said light emitting element and said heat storage means are thermally coupled by a heat pipe.