JP2005029401A - Reflecting mirror for light source, and light source unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflecting mirror which is excellent in heat resistance, secures a sufficient surface accuracy, has a reflective surface with a surface roughness small enough to be coated with a vapor deposition film without being polished, can have a larger effective reflective surface, can be made small-sized and lightweight, and is excellent in mechanical strength. <P>SOLUTION: The reflecting mirror for a light source in a high-voltage discharge lamp unit is manufactured as follows: minutely rugged parts present on the inside reflective surface of a reflecting mirror mainly comprising SiO<SB>2</SB>are filled and coated with polysilazane, which is a high-molecular inorganic polymer convertible into the same substance as the reflecting mirror; and the polysilazane is converted into SiO<SB>2</SB>to change the minutely rugged surface into a smooth mirror surface. A light source unit having the reflecting mirror mounted thereon is also provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
It belongs to a light source device used in a projection type light source device such as a liquid crystal projector, which is a combination of a short arc discharge lamp and a reflecting mirror, and in particular, various problems that occur with downsizing of the device are used together with the lamp. The present invention relates to a light source device that is mainly a reflecting mirror.
[0002]
[Prior art]
Conventionally, the reflector used in this type of light source device is made of borosilicate glass, and by applying a cold mirror to its inner surface, the heat rays radiated from the lamp escape from the back of the reflector and reflect visible light to the front. To function.
[0003]
However, at present, in the downsizing of devices required for these projection type light source devices, the shortest distance between the lamp light emitting part and the reflecting surface of the reflecting mirror is 2 mm or less because of the large thermal expansion coefficient of borosilicate glass. In the case of such a design, that is, when it is used in a state where the temperature of the reflecting surface exceeds 500 ° C., the reflecting mirror may be cracked or damaged in extreme cases due to thermal stress due to repeated lighting and extinguishing. The fragments were scattered in the projector, causing a big problem.
[0004]
In order to improve the heat resistance of the reflector, borosilicate glass is used as a starting material. After press molding with a pressing die, the crystallized glass obtained by reheating to near the melting temperature is crystallized. There are also examples used for this material, but after glass molding, it is shrunk or deformed when crystallizing during reheating, so it is not sufficient in terms of dimensional accuracy, especially surface accuracy, and smoothness of the reflective surface However, the reflective surface was smoothed by chemical mechanical polishing of the reflective surface as a step after molding.
[0005]
The reflector made of the above borosilicate glass has an average thickness of about 4 mm in order to ensure mechanical strength in preparation for lamp rupture. It is unsuitable for discharge lamp devices for projectors of ultra mobile type and mobile type that are frequently carried.
[0006]
Also, recently, has begun to use more highly heat-resistant quartz glass, as is well known technology, the spherical silica as a raw material, this was slurried adding an additive is molded by slip casting method using the mold, 10 ^- There is a method of sintering under a vacuum condition of ⁴ Pa. (For example, see Non-Patent Document 1 and Non-Patent Document 2)
[0007]
However, as a characteristic drawback of this slip cast molding method, the surface roughness of the reflecting surface requiring smoothness becomes very large. Therefore, chemical mechanical polishing of the reflecting surface in the subsequent process is required as in the case of the crystallized glass reflector.
Further, by performing chemical mechanical polishing, a smoothing of the reflecting surface can be obtained, but there is also a secondary problem that the surface accuracy is lost.
[0008]
FIG. 2 shows a conventional example of a light source unit of a projection projector light source device. The rotating paraboloid reflecting mirror 3 whose inner surface is a cold mirror has a focal length (f) of 6.5 mm and an outer dimension of 52 × 56 mm. Further, the maximum diameter of the central bulge 2 is 10.0 mm, the average wall thickness is 2.5 mm, the distance between the electrodes is 1.1 mm in a discharge vessel having an internal volume of about 0.08 ml, and argon gas as a starting auxiliary gas In addition, the short arc high-pressure mercury vapor discharge lamp 1 in which hydrogen bromide used for preventing flickering and preventing blackening during the lifetime is sealed, and in addition, 16 mg of mercury as a luminescent substance having a buffer effect is sealed, It is an example of the light source part of the light source device for liquid crystal projectors which arrange | positions in the vicinity of the focal distance of a reflective mirror and whose rated power consumption is 150W.
[0009]
The reflecting mirror is manufactured by melting borosilicate glass, embossing, crystallizing it, and smoothing the irregularities on the inner surface of the reflecting portion by chemical mechanical polishing, and the thermal expansion coefficient is about 16 × 10. ^-7 / K, weighs about 80 g, thickens the bottom near the focal point, and has an average glass thickness of about 4 mm so that it can mechanically withstand the impact when the lamp bursts. The structure is housed inside, and a translucent glass plate having a thickness of about 4 mm is provided on the front surface of the reflecting mirror so that the fragments of the lamp are not scattered to the outside as a structure that can withstand the burst that occurs during the lifetime. When there is no forced air cooling means such as a fan in the projector to be used, the surface temperature of the reflector inner surface closest to the lamp is 580 ° C. to 640 ° C.
[0010]
In a reflector made of ordinary borosilicate glass (thermal expansion coefficient = about 36 × 10 ⁻⁷ / K), the heat resistance temperature (strain temperature) is at most about 480 ° C. Since it is scarce, the present situation is that only crystallized glass with inferior dimensional accuracy is used, ensuring only heat resistance and corresponding to miniaturization.
[0011]
In addition, including a simple borosilicate glass reflector, it is made by stamping in consideration of mass production, so the stamping mold (mold) has sufficient transferability of the stamping part having a paraboloid of revolution. Even if it is secured, the taper angle is set to 5 degrees or more so that it can be easily released from the molded product. If this angle is 4 degrees or less, a part of the glass is firmly fixed to the mold during molding, the mold is not released from the mold, and a part of the glass remains on the mold surface. This may cause defective products during the process or damage the mold itself. Therefore, setting the taper angle to 5 degrees or more must be protected even if you want to increase the effective reflection area on the inner surface. It was a necessary condition. Therefore, even when the outer dimension is large, the effective reflection area on the inner surface is unexpectedly small due to the large taper angle. In addition, an example in which the glass thickness is set to 4 mm on average and the pressure at the time of stable operation of the short arc discharge lamp used together with the reflector is 200 atm is also introduced. When borosilicate glass was used as crystallized glass, the thickness was necessary to obtain mechanical strength.
[0012]
[Non-Patent Document 1]
"Development of energy-saving manufacturing technology for high-purity and transparent quartz glass", New Energy and Industrial Technology Development Organization (Kyushu Industrial Technology Center), March 2000, P40-49
[Non-Patent Document 2]
"Development of energy-saving manufacturing technology for high-purity and transparent quartz glass", New Energy and Industrial Technology Development Organization (Kyushu Industrial Technology Center), March 2001, P48-54
[0013]
[Problems to be solved by the invention]
In view of the problems described above, heat resistance is excellent, sufficient surface accuracy is ensured, the surface is made sufficiently small so that a vapor deposition film can be applied without polishing the reflection surface, and a larger effective reflection surface is taken. An object of the present invention is to obtain a reflector that can be reduced in size and weight, and has excellent mechanical strength, and a light source unit using the same.
[0014]
[Means for Solving the Problems]
The present invention has the following configuration in order to solve the above problems.
The main component is a reflecting mirror made of SiO _{2. The} micro uneven surface present on the reflecting surface of the inner surface is filled with a polysilazarane, which is a polymer inorganic polymer that is the same material as the reflecting mirror, and then converted to SiO ₂ . A light source reflecting mirror and a light source unit including the reflecting mirror are provided.
[0015]
In the reflecting mirror, the coating layer of the reflecting surface of the reflecting mirror is a multi-layer coating of one or more layers, and a light source reflecting mirror and a light source unit equipped with the reflecting mirror are provided.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described below with reference to FIGS.
FIG. 1 is a part of an embodiment of the present invention, and shows an example in which the rated power consumption is 150 W as in the conventional example. The reflector used together is made of quartz glass.
In the short arc high pressure discharge lamp unit, the short arc high pressure discharge lamp 21 having a pair of electrodes 27 and 27 'and having an arc length of 2 mm or less has a bulging portion 22 (light emitting portion) of the reflecting mirror 23 used together with the lamp. The reflecting mirror is arranged near the focal point, and the reflecting mirror has at least a portion obtained by cold stamping spherical SiO ₂ and is made of quartz glass containing 90% or more of silicon dioxide, and the light emitting portion of the discharge lamp and the reflecting The shortest distance from the reflecting surface of the mirror is 2 mm or less. Moreover, it has a part with a draft taper angle of at least 3 degrees or less.
[0017]
In FIG. 1, 24 is a reflecting surface of the concave reflecting mirror 23, 26 is a cap of the discharge lamp 21, 28 and 29 are molybdenum foil and molybdenum wire of the discharge lamp 21, and 30 is a sealing portion. Reference numeral 31 denotes a terminal of the base 26, 32 denotes a cylindrical portion of the reflecting mirror 23, and the discharge lamp 21 is fixed to the cylindrical portion 32 of the reflecting mirror 23 via a cement 33.
[0018]
The production method of the quartz glass reflecting mirror is described as follows. For example, at least one of spherical silica having an average particle diameter of 0.6 μm (average particle diameter of 0.3 μm, 0.6 μm, and 3 μm). At least one of them was press-molded and fired, and although each of them had a slight difference in shrinkage, it became a sintered quartz molded body), water-soluble resins such as polyvinyl alcohol and polyvinyl acetal as binders, and A mixture of 2 to 5% by weight of a wax or stearic acid hydrocarbon or fatty acid emulsion to form an aqueous solution (slurry), and then granulated with a spray dryer to improve the moldability and dispersibility Is transferred to a second mold (called “body mold” or “bottom”) of the mold at room temperature (cold), and the mold is pressed with a press pressure of about 7 MPa. The first mold (referred to as “arrow” or “plunger”) is press-molded for about 10 seconds with respect to the second mold, and after the press-molding, the first mold and the second mold After taking out the press-formed product made in this way, the binder is burned in an oven having an oxidizing atmosphere of about 1000 ° C., and the temperature is reduced to 1320 ° C. below the softening temperature of quartz glass in an oxidizing atmosphere or neutral / reducing atmosphere. It is produced by holding for several hours and sintering. At this time, although it can be similarly produced in a vacuum heating furnace, since the manufacturing cost can be reduced by heating in the air industrially, it was produced using a heating furnace that is not vacuum.
[0019]
Here, in the process from press forming up to after sintering, there is a certain shrinkage (about 80%) in the dimension, so that the size of the stamping die is set larger so that it becomes the dimension you want to obtain after sintering Needless to say.
[0020]
It has been found that the mold used for the press molding has a phenomenon that the mold surface slides well because it forms spherical silica, and the taper taper angle of the mold can be set sufficiently smaller than that of the mold molding of molten glass. In view of this, in this example, the draft taper angle was assumed to be 1 °. However, when producing a cloth to be a reflecting mirror, no chipping, large wear, material residue, etc. were generated at all.
[0021]
In addition, since conventional molten borosilicate glass is hot-molded, the glass component evaporates and seizes on the first mold surface, and after several hours of use, the mold surface must be polished to repeat polishing. Although the mold surface gradually deviates from the design value and the reflection direction characteristics change, this manufacturing method does not occur because it is cold-molded and no polishing of the mold surface is required. The surface accuracy error from the design value of the concave mirror was within 0.05 mm without damaging the surface of the pressing die, and the surface accuracy was sufficiently maintained.
[0022]
Next, regarding the surface roughness of the inner surface of the reflecting mirror, as shown in FIG. 3, when the spherical silica powder is pressed by a mirror mold, the surface is sufficiently mirrored due to the influence of the binder 41 and the like that have been raised on the surface. Here, in the figure, 42 indicates spherical silica having an average particle diameter of 0.6 μm, and 45 indicates a press surface (reflecting mirror reflecting surface).
[0023]
However, on the inner surface of the reflecting mirror that has undergone preliminary firing and main firing, minute irregularities of about 0.1 μm to 1 μm as shown in FIG. 4 and FIG. found. In the figure, reference numeral 43 denotes sintered silica glass. This minute unevenness causes the reflection mirror surface to be in a state of irregular reflection as if the reflecting mirror surface is thin and cloudy when the reflecting film is deposited, which causes a decrease in reflectance.
[0024]
In the present embodiment, in order to smooth the minute irregularities, the problem was solved by filling the minute irregularities with a filling material. As the filling material, SiO ₂ which is the same material as the base material and has translucency was used, and as a filling method of SiO ₂ , a method of applying polysilazane to the reflecting mirror surface and using baking or hydrolysis was used. Polysilazane is — (SiH ₂ NH) —
It is a material that is converted into dense high-purity silica by heating and reacting with moisture and oxygen with an inorganic polymer soluble in an organic solvent having a basic unit. For example, polysilazane used in this embodiment is NP-110 and NP-140 manufactured by Clariant Japan.
[0025]
The application method could be spray, hand coating, or flow coating. Although the film thickness varies depending on the concentration, a transparent silica film of about 0.1 μm to 0.3 μm was obtained as a result of baking for 30 minutes in a 150 ° C. electric furnace with a 1% solution. This film thickness can sufficiently improve the current surface roughness to some extent, but as shown in FIG. 6, this film is multi-layered into two or more layers and coated to form a more sufficient smooth reflecting surface as a reflector. I was able to. In the figure, 44 indicates a polysilazarane-converted SiO ₂ multilayer film.
[0026]
In addition, it is said that a concentration of 2% or less is good for normal application, but a 20% concentration liquid is prepared with xylene to 5%, 10%, 15%, and 20%, applied, and similarly an electric furnace at 150 ° C. As a result of baking for 30 minutes, it was possible to form a film on all of the base materials because the base material was the same. Especially, in the case of a 20% solution flow coat, the effect of sufficiently reflecting the reflective surface with a single coating was obtained. At a concentration of 10% or more, some SiO ₂ crystals were precipitated during coating. In conclusion, with a 15 to 20% solution, if the coating atmosphere was properly controlled, a film that could withstand practical use could be formed by each coating method. Even in an ambient atmosphere, a 3% to 10% solution can be easily applied without cracking, clouding, or crystallization of the silica film if a single layer film or multilayer film is formed by hand coating, spraying, or flow coating. It was found that the film could be used practically and the coating efficiency was improved from 1% to 2% solution.
[0027]
7 and 8 show a sample of the present invention in which one layer of 5% solution was actually applied by flow coating, left to stand in a nitrogen atmosphere, dried and then baked in an electric furnace at 150 ° C. for 30 minutes. It is the image which observed the surface roughness state of a 10 micrometer square of the sample before performing the process of this with AFM (atomic force microscope).
Before coating, the average surface roughness Ra was 50 nm and the maximum height difference P-V was 800 nm, but after coating, the average surface roughness Ra was 1 nm and the maximum height difference P-V was greatly improved to 30 nm. I found out.
As can be seen from the above results, a smooth surface sufficiently practical as a reflector could be produced by this technique.
[0028]
On the other hand, with respect to the effective reflection surface, if the outer diameter is the same as that of borosilicate glass, the extraction angle can be set small in the reflection mirror made of quartz glass, so that the effective reflection surface can be made sufficiently large. Things turned out. And, the mechanical strength of quartz glass is about 1.5 times larger than that of borosilicate glass, and the thermal expansion coefficient of quartz glass is 6 × 10 ⁻⁷ / K sufficiently strong against thermal stress. Because there is something, the glass thickness can be reduced, so it was made as thin as 3 mm, the lamp was forcibly ruptured, and the mechanical strength was evaluated, but there was no crack in the reflector, so no damage was seen, Confirmed that it does not cause problems. Therefore, there is an advantage that the short arc discharge lamp 21 can be designed to be sufficiently close to the reflecting surface 24 of the reflecting mirror to improve the optical efficiency.
[0029]
In this embodiment, when the focal length of the rotating paraboloid of the reflecting surface 24 in the concave reflecting mirror 23 is set to 5.5 mm and the shortest distance between the lamp light emitting portion and the reflecting surface of the reflecting mirror is designed to be 1.0 mm, Optical efficiency was improved compared to borosilicate glass.
[0030]
Even in the case of the combination, no abnormality was found in the reflecting mirror throughout the lifetime, and it was found that the apparatus can be made smaller than before.
[0031]
The effective reflecting surface was also improved because the punching taper angle of the pressing die was set to 1 degree.
[0032]
Since the press molding can take a sufficient amount of time during the press molding, the dimensional accuracy is good, and the weight can be made to be a very light reflecting mirror of about 45 g. As a reflector for mobile projectors and a light source device combined therewith, it showed excellent characteristics.
[0033]
When using a quartz glass reflector whose effective reflection area is set to be the same as that of borosilicate glass, the outer dimension is about 49.5 mm × 53.5 mm, which can be further reduced, and the weight is about 40 g. It has also been found that half the weight is required compared to that made of silicate glass. A light source device that combines a parabolic reflector (focal length f = 5.5 mm) made in this way with a short arc discharge lamp with a rated power consumption of 150 W and an arc length of 1.0 mm is manufactured and tested for life. However, no problem was caused even when the rated life exceeded 2000 hours.
[0034]
【The invention's effect】
As explained above, by using quartz glass instead of the conventional borosilicate glass for the reflecting mirror, it has excellent heat resistance, and since the focal length of the reflecting mirror can be selected small, characteristics excellent in optical efficiency can be obtained, It is possible to provide a reflector for a short arc discharge lamp and a light source unit that are suitable for miniaturization and weight reduction required for projectors mainly called ultra mobile systems and mobile systems.
[0035]
In addition, there is no hassle of polishing the mold (mold) each time, and since the polishing is not frequently performed, the inner surface shape of the mold can be maintained without deviating from the design value, so that the mold life is improved. Has the accompanying effect of being superior.
[0036]
In the present invention, since the reflecting mirror is formed of spherical silica, it is excellent in releasability between the mold and the molded product, so that the draft taper angle can be selected to be small, so that the reflection area is sufficiently large and the effective reflection surface is Since a large reflecting mirror can be obtained, it is possible to meet the demand for further miniaturization. At the same time, since the mechanical strength is excellent, the reflector can be thinned.
[0037]
In the present invention, since the reflecting mirror is formed of spherical silica, the surface roughness of the reflecting mirror is smaller than that of the conventional reflecting mirror, but even if surface processing is performed to further reduce the roughness, it does not deviate greatly from the design value. Since a reflecting mirror is obtained, a highly efficient reflecting mirror with excellent reflection characteristics can be obtained.
[0038]
In addition, in the present invention, the minute irregularities on the inner surface of the reflecting mirror are coated with the same material to make a smooth mirror surface, and the surface accuracy of the molded product made according to the design value by polishing that has been conventionally performed is high heat resistance, high without breaking the surface accuracy A reflector as designed with high efficiency can be obtained.
[0039]
Furthermore, the coating smoothing relating to the reflecting mirror of the present invention can be used not only for the reflecting mirror made of quartz glass but also for a reflecting mirror made mainly of SiO ₂ such as crystallized glass.
[0040]
A light source unit as a short arc discharge lamp combined with such a reflection mirror made of quartz glass sufficiently satisfies the demand for miniaturization of a projection light source device.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a light source unit of a light source unit showing an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a light source unit of a conventional typical light source device. Schematic diagram of the state of spherical SiO ₂ [FIG. 4] Schematic diagram of the state of spherical SiO ₂ immediately after preliminary firing of the reflector of the present invention [FIG. 5] Schematic diagram of state of spherical SiO ₂ immediately after the final firing of the reflector of the present invention [FIG. FIG. 7 is a schematic view of a mirror-coated polysilazane coated on the enlarged surface of FIG. 5. FIG. 7 is a surface roughness measurement result (bird's eye view) of the reflecting mirror of the present invention by AFM.
FIG. 8 shows a surface roughness measurement result (bird's eye view) of an AFM of a reflecting mirror before performing the processing of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1, 21 ... Short arc discharge lamp 2, 22 ... Expanding part 3, 23 ... Concave mirror 4, 24 ... Reflecting surface 5, ... Front cover glass 6, 26 ... Base 7, 27 ... Electrode 8, 28 ... Molybdenum foil 9, 29 ... Molybdenum wire 10, 30 ... Sealing part 11, 31 ... Terminal 12, 32 ... Tube part 13, 33 ... Cement 41 ... Binder 42 ... Average particle size 0.6 µm Spherical silica 43 ... Sintered silica glass 44 ... Polysilazane converted SiO ₂ multilayer film 45 ... Press surface (reflecting mirror reflecting surface) )

Claims (3)

The main component is converted to SiO ₂ after polysilazane was filled coating is a polymeric inorganic polymer as a reflector and the material in the minute uneven portion present in the reflective surface of the inner surface of a reflective mirror composed of SiO _2, fine uneven surface A reflecting mirror for a light source, characterized by having a smooth mirror surface. 2. The light source reflecting mirror according to claim 1, wherein the coating layer of the reflecting part on the inner surface of the reflecting mirror is one or more layers. A light source unit comprising the reflecting mirror according to claim 1.

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