JPH07335376A - Infrared light source - Google Patents

Abstract

PURPOSE:To realize a high luminance with no unevenness with low power consumption, and downsize a device by combining an infrared light emitting boy consisting of a silicon carbide sintered body having prescribed physical properties, a leg part consisting of a heat resisting material having low heat conductivity, and a conductive member together. CONSTITUTION:A silicon carbide sintered body having a sintered body density of 2.8g/cm<3> or more and an electric specific resistance value at room temperature lower than 1OMEGAcm is thinned in the top end part, and superposed to form a flat infrared light emitting body 1. A heat resisting material of ceramic such as alumina having low heat conductivity is used for the leg part 2 between the light emitting body 1 and a electrode part 2, whereby the flow of heat from the light emitting body 1 is interrupted. A metal having high electric conductivity is used for a conductive member 4 between the electrode part 2 and the light emitting body 1. The light emitting body 1 and the leg part 3 are separately bonded to one side surface of the member 4 molded into a plate, and integrated thereto. The member 4 may consist of a thin film by evaporation. Thus, oxidation resistance, heat resistance, and thermal impact resistance are excellent, and S/N ratio is also enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared light source which is excellent in oxidation resistance, heat resistance and thermal shock resistance and which is preferably used in an oxidizing atmosphere.

[0002]

2. Description of the Related Art For example, as an infrared light source used in an infrared spectroscopic device, a coiled nichrome line light source has been conventionally used.
There are metal ribbon filament light sources, molybdenum silicide light sources, Nernst lamps, wound ceramic lamps, and global light sources.

[0003]

Here, in order to improve the S / N ratio of the infrared spectrophotometer, a light source with high brightness is required. Since the radiant energy of the light source is proportional to the fourth power of the absolute temperature, it is necessary to raise the temperature of the heating element to obtain a high-luminance light source. However, the conventional techniques have the following disadvantages.

Coiled nichrome wire and metal ribbon filament light sources are oxidized at 1000 ° C. or higher in the atmosphere,
There is a problem that the life is shortened. Therefore, in order to prevent such oxidation of the light source, it is necessary to fill it with an inert gas, which has a problem that the structure is complicated and the cost becomes high. Also, molybdenum silicide has a relatively low emissivity and can be used even at 1700 ° C.
It is very fragile and difficult to micromachine, and it cannot be thinned, so
The light emitting part cannot be concentrated, and the specific resistance is 0.0003.
Since it is small, a certain amount of large current is required to generate heat.

Further, the Nernst lamp and the wound-ceramic lamp cannot be self-started because the ceramics used have a high room temperature specific resistance, and an auxiliary heater is required, which complicates the light source structure. Further, since it is difficult to perform fine processing, the resistance cannot be concentrated, the connection at the electrode portion becomes relatively long, the light emitting source cannot be downsized, and the power efficiency becomes poor. Moreover, zirconia and alumina used as ceramics have relatively low emissivity.
The average is 0.75 at ˜20 μm and 0.15 at 3 μm.
~ 0.30.

Since the global light source uses silicon carbide as a light source material, it has a very excellent emissivity, but it has the same drawbacks as the above-mentioned Nernst lamp and wound ceramic lamp. Also, it is necessary to cool the electrode part with water,
There is a problem that the structure is complicated and the power efficiency becomes worse. In order to improve the S / N ratio of the infrared spectrophotometer, the light source must have high brightness, high emissivity in a wide wavelength range, and that the light emitting section has no temperature unevenness and is concentrated. Will be needed. In order to obtain the high brightness light source of
Since it is proportional to the power, it is necessary to raise the temperature of the heating element. It is necessary to select a heating element material that has a high emissivity in a wide wavelength range. What is more important is that there is no temperature unevenness in the light emitting part and the light is concentrated. Usually, the light emitting source is an infrared light emitting body and an optical system (reflector and lens) that collects light emitted from the light emitting body and closes it.
Consists of. After the parallel light flux is passed through the gas measuring cell, the infrared detector partially detects the infrared rays partially absorbed by the gas. Therefore, if the parallel luminous flux of the infrared rays is not good, the infrared rays are attenuated because they collide with the inner wall of the measurement cell and repeat reflection, so that the S / N ratio of the infrared spectrophotometer is extremely deteriorated. In order to obtain a strong parallel light flux of infrared rays, there is no temperature unevenness,
It is desirable to have a centralized point-shaped or planar light-emitting source. Further, by concentrating the light emitting portions, the temperature of the electrode portion is lowered and the power consumption is reduced, so that the deviation of the parallel light flux due to the mechanical distortion of the optical system due to the influence of heat can be prevented. However, the conventional technique has the disadvantages described above, and such an ideal light source does not exist.

At the same time as the present application, the present inventors filed a patent application “Red
Outer line light source and its manufacturing method "
Focusing on the existing silicon carbide material, the density of the sintered body is 2.8 g /
cm ³Above, electrical resistivity at room temperature is less than 1 Ω · cm
, Which consists of a dense and electric discharge machineable silicon carbide sintered body
We have developed an external light source. Of course, even with silicon carbide alone,
Even as an infrared light source, it does not exist conventionally as described above.
It is an ideal light source, but silicon carbide has good thermal conductivity.
In addition, if the electrode portion is made of silicon carbide as it is, the electrode portion
It had the drawback that the temperature of the product would rise.

[0008]

In the present invention, as a result of earnestly studying this inconvenience, as a result, a compact having a sintered body density of 2.8 g / cm ³ or more and an electrical resistivity value of 1 Ω · cm or less at room temperature is obtained. Infrared light source light emitter made of silicon carbide sintered body that can be electric discharge machined, and to prevent heat conduction to the electrodes, the legs are made of a heat-resistant material such as ceramics with low thermal conductivity to allow heat flow. On the other hand, the above-mentioned problem was solved by using a composite body in which a conductive member made of a member having good electric conductivity such as a metal and carbon for conducting electricity is combined to form an infrared light source.

The first means for solving the above problems in the present invention is carbonization in which the density of the sintered body is 2.8 g / cm ³ or more and the electrical resistivity at room temperature is 1 Ω · cm or less. Infrared light emitter 1 made of a silicon sintered body, the infrared light emitter 1 and an electrode section 2 for supplying power to the infrared light emitter 1.
And a leg portion 3 made of a heat-resistant material which is interposed between the leg portion 3 and the electrode portion 2 to block heat conduction from the infrared light emitting body 1 to the electrode portion 2.
Conductive member 4 for energizing the infrared light emitter 1 from the
It is an infrared light source equipped with.

In the second means of the present invention, the conductive member 4 of the first means is formed into a plate-like body, and the infrared light emitting body 1 is joined to a part of one side surface of the conductive member 4 so that the conductive material 4 is electrically conductive. By joining the leg portions 3 to other portions on the same side surface of the member 4, the infrared light emitting body 1, the leg portion 3, and the conductive member 4 are integrated. Third of the present invention
Means for joining and integrating the infrared light emitter 1 and the leg portion 3 of the first means, and by vapor deposition or the like so as to straddle the infrared light emitter 1 and the leg portion 3. That is, the formed thin film is provided as the conductive member 4.

A fourth means of the present invention is to provide the above first to third means.
The infrared light emitter of the above means has a centralized planar light emitting portion in which fine resistance circuits are densely formed. A fifth means of the present invention is that the heat-resistant material leg portions of the first to fourth means are formed of a low heat conductive material made of ceramics. The details of the infrared light source containing silicon carbide of the present invention will be described below.

A silicon carbide sintered body having a sintered body density of 2.8 g / cm ³ or more and an electric resistivity value of 1 Ω · cm or less at room temperature was thinned by electric discharge machining and superposed. The structure is flat and each thinned wire receives radiant heat from each other. In order to block the flow of heat in the legs, it is desirable to use a heat-resistant material made of ceramics such as alumina, zirconia, forsterite, and steatite, which has a low thermal conductivity. For this, it is possible to use a material whose thermal conductivity is lowered by making the structure of the material have a high porosity.

As the conductive member, nickel, copper, platinum, gold, silver, carbon or the like having high electric conductivity can be used. Then, the infrared light emitter made of the silicon carbide sintered body, the heat-resistant material leg portion, and the conductive member are combined and integrated to obtain an infrared light source. Here, as an example of the method of composite integration, the conductive member is a plate-shaped member, the infrared emitter is provided at a part of one side surface of the plate-shaped member, and the infrared emitter is provided at another portion on the same side surface. By joining the light emitting bodies, the infrared light emitting body, the heat-resistant material leg portion, and the conductive member are integrated. It should be noted that an appropriate space may be provided between the infrared light emitter and the heat-resistant material leg portion, or both may be simply in contact with each other without providing a space. good.

As another method of integration, the infrared light emitter and the heat-resistant material leg portion are joined and integrated, and vapor deposition is performed so as to straddle the infrared light emitter and the heat-resistant material leg portion. By disposing a thin film formed of, for example, the conductive member, the infrared light emitter, the heat-resistant material leg portion, and the conductive member are integrated. For joining, a conventionally known joining method can be used. For example, the silicon carbide luminescent material and the leg are preliminarily metallized at the joint. The metallization material may be a commonly used material, but a material having heat resistance to some extent is desirable. For example, silver-copper-titanium, silver-
Titanium, nickel-titanium, gold-titanium, platinum-titanium and the like are suitable. In the metallization method, an appropriately selected metal powder is placed in an agate mortar, mixed well, made into a paste using screen oil, and applied to the joint portion. Next, the coated silicon carbide luminescent material and the legs are dried by a vacuum dryer at about 100 to 150 ° C. for about 30 minutes, then placed in a vacuum furnace and heat-treated at a necessary temperature.

Next, the joining portion between the silicon carbide luminescent material and the leg portion and the metal thin film having high electric conductivity are set in a vacuum furnace with a brazing agent sandwiched between them and heat-treated at a necessary temperature. As a brazing material for joining, it is preferable to use a brazing material having high heat resistance such as silver brazing material, nickel brazing material, gold brazing material, palladium brazing material, and platinum brazing material. The composite thus bonded is metallized and brazed including the alumina insulating plate and the nickel electrode to manufacture an infrared light source.

[0016]

According to the present invention, the power consumption is significantly reduced,
Since the temperature of the electrode part has also decreased, it is now possible to realize a high-intensity infrared light source that is flat and has no unevenness of light with extremely low power consumption. It has become possible to significantly reduce the size of peripheral devices, including the device. In addition, the heat from the light emitting source causes a phenomenon that occurs because the temperature of the peripheral device is increased.

Further, since the impurities existing in the grain boundaries are small, a high thermal conductivity of 150 W / m · K or more can be obtained.
Therefore, the thermal response is very fast, and thermal equilibrium is reached in a short time, so that it can be used as a pulsed light source for infrared rays.

[0018]

EXAMPLES Examples of the present invention will be described in detail below, but the present invention is not limited thereto. 5% by weight of amorphous silicon carbide ultra-day powder having an average particle size of 0.01 μm and a specific surface area of 96 m ² / g, obtained by gas phase synthesis by plasma CVD using silicon tetrachloride and ethylene as raw material gases,
95% by weight of β-type silicon carbide powder having an average particle diameter of 0.7 μm and a BET specific surface area of 13 m ² / g as silicon carbide powder
Dispersed in methanol, and then 1 with a ball mill.
Mix for 2 hours.

The mixture is then dried to an inner diameter of 100.
mm graphite mold and filled with a hot press machine under an argon atmosphere at a press pressure of 400 kg / cm ³ ,
Sintering was carried out for 90 minutes at a sintering temperature of 2200 ° C. When the density of the obtained silicon carbide sintered body was examined, it was 3.1 g / c
It was m ³ . Further, the three-point bending strength of this sintered body at room temperature was 64.3 kg / mm ³ when measured according to JIS R-1601, and the three-point bending strength at 1500 ° C. was 68. 0.5 kg /
It was mm. When the electrical resistivity at room temperature was measured by the four-terminal method, a result of 0.05 Ω · cm was obtained, and when the thermal conductivity at room temperature was measured by the laser flash method, it was 197 W / m. It was K. The surface of the sintered body was etched with potassium ferrocyanide having a concentration of 10%, and the microstructure of the sintered body was examined by a scanning electron microscope (SEM). As a result, the pore size was 1 μm.
It was found to be a very homogeneous and dense structure with the number of m or less and the number thereof being small.

Next, the diameter is 100 mm and the thickness is 5 mm.
The disc-shaped silicon carbide sintered body of Fig.
As shown in (1), (2) to FIGS. 4 (1), (2), the light emitting bodies 11, 21, 31 of the infrared light source were cut out. The structure of the luminous body of this infrared light source is such that the thinned portions (width 0.4 mm) are overlapped as flatly as possible so that each thinned wire receives radiant heat from each other. The resistance circuit is densely formed and has a centralized planar shape.

In these examples, the tip portions 12, 2 of the light emitter are
As shown in FIGS. 2 to 4, the line widths of 2 and 32 are set to about 0.4 to 1.0 mm in view of the specific resistance and thermal conductivity of silicon carbide. Originally, there is no restriction due to the improvement in chemical resistance and heat resistance. Also,
The width of the wire at the tip is 0.3 mm because the width of the wire for electrical discharge machining is at least 0.2 mm, but it is not limited in principle.

In this way, the line width of the tip is 0.4 m.
An infrared light source having an exemplary shape was prepared in which the distance between the lines was 0.3 mm and the line was folded back to have a thickness of 1.0 mm and a thickness of 1.0 mm. Detailed dimensions of the infrared light source are shown in FIGS. The wire electric discharge machining was performed using a transistor pulse circuit type electric discharge machine. A brass wire with an outer diameter of 2 mm was used as the discharge wire, and the processing conditions were a processing voltage of 50 V and a pulse width of 1.2 μse.
c, the rest time was 20 μsec.

After the electric discharge machining, the surface roughness of the electric discharge machined surface was measured and found that Rmax was 2.5 μm.
It was confirmed that the above-mentioned silicon carbide sintered body had good electric discharge machinability. Then, as shown in FIG. 1, a leg 42, an insulating plate 45, and a plate-shaped or semi-circular disk-shaped member made of alumina are used, and a conductive member 43 made of a nickel plate and a nickel for voltage application are used. The light source for infrared rays was assembled by the electrode 44 made.

In order to metallize the joint portion, a mixed powder of silver-copper (27 wt%)-titanium (5 wt%) was mixed with a screen oil in an agate mortar and applied as a slurry, which was then applied in a vacuum atmosphere (5 × 10 ^{− 5} Torr or less), 87
It heat-processed at 0 degreeC and metallized. Next, silver-copper (28
(wt%) thin film was used to heat braze silicon carbide, alumina, and nickel thin plates at 850 ° C. in a vacuum atmosphere (5 × 10 ⁻⁵ Torr or less). Further, the alumina insulating plate 45 and the nickel electrode were similarly metallized and brazed and assembled as an infrared light source as shown in FIG.

Table 1 shows the results of the heating experiment of the infrared light source according to this embodiment. A direct current voltage was applied to the infrared light source to stabilize the temperature at the tip temperature of 1000 ° C. or higher. The temperature at the tip was measured with a thermoviewer at an emissivity of 0.8, and the temperature at the electrode was measured using a K thermocouple.

[0026]

[Table 1]

After this heating experiment, heating was continued for another 5 hours, but almost no wear was observed on the tip of any shape of the silicon carbide luminescent material, and after the heating test was repeated 10 times, the tip and No abnormality was found at the joint between silicon carbide and alumina. Also, although it takes about 3 minutes to initially heat at 1000 ° C, it takes about 2 minutes when the voltage is turned off.
At 0 seconds, the temperature of the tip portion decreased to 400 ° C., and when the voltage was applied again at that time, the temperature reached 1000 ° C. in about 5 seconds. This ON / OFF operation was repeated 1000 times, but it was desired that almost no abnormality was recognized in the tip portion of silicon carbide and the joint portion of silicon carbide and alumina.

Further, the temperature rise of the electrode portion could be effectively prevented.

[0029]

As described above, according to the infrared light source of the present invention, it has excellent oxidation resistance, heat resistance, and thermal shock resistance, is preferably used in an oxidizing atmosphere, and has high emissivity and high emissivity. High, flat, with no uneven light, and low power consumption,
It is possible to reduce the heat conduction to the small electrode portion, that is, the temperature rise of the electrode portion is small.

Therefore, it becomes possible to realize an infrared planar light source with high brightness and high emissivity with very low power consumption,
Since it is possible to extract a strong parallel light flux with little loss, the S / N ratio of the infrared spectrometer can be significantly improved. Further, the water cooling of the electrode portion, which was necessary in the past, is not necessary, and the infrared light emitting source and its peripheral devices can be greatly downsized.

Since the thermal response is very fast and thermal equilibrium is reached in a short time, it can be used as a pulsed light source for infrared rays. Thus, as an infrared light emitting source, it has a high S / N ratio, high durability, long life,
Since the size of the infrared emission spectrometer is extremely small, the range of applications of the infrared emission spectrometer is expanded in a wide range from industrial use to research use, resulting in great industrial effects.

[Brief description of drawings]

FIG. 1 is a front view, a plan view and a side view showing an infrared light source according to the present invention.

FIG. 2 is a plan view and a side view showing a configuration example of a light emitting body of an infrared light source according to the present invention.

FIG. 3 is a plan view and a side view showing a configuration example of a light emitting body of an infrared light source according to the present invention.

FIG. 4 is a plan view and a side view showing a configuration example of a light emitting body of an infrared light source according to the present invention.

[Explanation of symbols]

 1 Light emitter 2 Electrode part 3 Leg part 4 Conductive member

Claims (5)

[Claims] 1. An infrared emitter (1) made of a silicon carbide sintered body having a sintered body density of 2.8 g / cm ³ or more and an electrical resistivity value of 1 Ω · cm or less at room temperature, The heat from the infrared light emitter (1) to the electrode portion (2) is interposed between the infrared light emitter (1) and the electrode portion (2) for supplying power to the infrared light emitter (1). An infrared light source comprising a leg portion (3) made of a heat-resistant material that blocks conduction, and a conductive member (4) for conducting electricity from the electrode portion (2) to the infrared light emitter (1). 2. The conductive member (4) is a plate-like member, and the infrared light emitter (1) is joined to a part of one side surface of the conductive member (4) to form the same conductive member (4). The infrared light emitter (1), the leg portion (3), and the conductive member (4) are integrated by joining the leg portions (3) to other portions on the side surface. The infrared light source according to claim 1, wherein 3. The infrared light emitter (1) and the leg portion (3) are joined and integrated with each other, and straddle the infrared light emitter (1) and the leg portion (3). The infrared light source according to claim 1, wherein a thin film formed by vapor deposition or the like is provided as the conductive member (4). 4. The infrared light emitter according to claim 1, wherein the infrared light emitter has a centralized planar light emitting portion in which fine resistance circuits are densely formed. Light source. 5. The infrared light source according to claim 1, wherein the heat-resistant material leg portion is formed of a low heat conductive material made of ceramics.