JP2580406B2 - Method for manufacturing reflector base - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a reflector which is useful for astronomical observation, beam focusing or space industry.
In particular, the present invention relates to a method for manufacturing a reflector base that is lightweight, has excellent operability, and has high structural strength and optical characteristics.

[0002]

2. Description of the Related Art Conventionally, astronomical reflectors and high energy beams have been used.
For example, a reflector used for optical condensing such as a film is formed by depositing a metal vapor-deposited film of aluminum or the like as an optical reflecting layer on the surface of a bubble-free reflecting mirror plate made of quartz glass, high silicate glass, or the like. It is formed, and it is supported on the operation support base and freely rotated. Such a reflecting mirror base is required to maintain accuracy without being affected by the temperature of the reflecting surface or an internal force change. Such reflectors have hitherto been 5 mm in diameter.
The small size of about 20 cm was the mainstream, but in recent years, a large one with a diameter of 30 cm to 1 m or more has been required in order to obtain a high light collection rate. became. However, since such a large one becomes extremely heavy, deformation due to its own weight is likely to occur due to a change in the supporting posture such as the supporting angle of the reflecting mirror, and a swelling phenomenon occurs on the mirror surface, thereby reducing the optical performance of the reflecting mirror. There were problems such as lowering.

As described above, as the size increases, mirror surface undulations and the like change due to subtle volume change and deformation of the reflector base due to radiation of the condensing beam and changes in environmental temperature. Since the performance of the mirror is deteriorated, quartz glass or high silicate glass having a small thermal expansion change has been used as a material for the reflecting mirror. However, these glasses make the reflector base heavy and reduce the operability of the reflector. Therefore, in order to improve the operability, it is required to reduce the base as much as possible. In line with such practical demands, many proposals have been made for supporting a large reflector plate, particularly, for maintaining sufficient supporting strength and achieving weight reduction.

For example, Japanese Patent Publication No. 63-57761 discloses a light-weight reflector material for a celestial body, which has a support grid made of several rows of tubes, such as quartz glass, between a transparent reflector plate (front plate) and a rear plate. Each tube of the tube row is staggered so as to have a contact line or contact zone with two tubes of an adjacent row, and the thickness of the tube wall in the area of the contact line or the like is such that the remainder of the wall A special tube structure is disclosed in which the tubes are welded together along contact lines and the like. However, the astronomical reflector material having such a special configuration is not only complicated in configuration but also complicated to manufacture, and is extremely disadvantageous industrially. Further, such a reflector material has a remarkably low strength in the surface direction of the reflector, and cannot be said to be a satisfactory support member for polishing a flat surface or a curved surface of an integrated reflector plate.

Furthermore, it is difficult for the reflector material to make the effective height of the tube material, which is a support grid, strictly constant in the strict sense at the time of manufacture. The unevenness remains as a distortion, which causes a temporal change such as swelling of the mirror surface at a later date, which is a major factor in lowering the performance of the reflector. Also, due to its structure, when the mirror surface is horizontal and vertical with respect to gravity, the rigidity against its own weight changes and the surface accuracy changes slightly depending on the mirror surface, so the posture is movable. However, it is difficult to use for applications that require operability.

The technology disclosed in Japanese Patent Publication No. Sho 61-26041 relates to a lightweight mirror. In particular, a support grid made of quartz glass is moved between a front plate (reflecting mirror plate) and a rear plate made of quartz glass. It describes a celestial lightweight mirror that is fused and integrated so as not to be. This support grid is composed of a quartz glass plate-like member and / or a tubular member placed on a support plate, each of which has a plate shape of 2 mm.
The space remaining between the individual parts is filled with the substance to be sintered, consisting of granules, small pieces of tubules, small particles, small pieces of platelets or mixtures thereof, and this arrangement is combined by graphite rings. Then, they are heated to a sintering temperature in a non-oxidizing atmosphere in a furnace, and the support grid thus formed is heated and fused to the front plate and the rear plate so as not to move. It is also disclosed to be linked.

However, in this method, a large number of plate-like members or tubular members having an appropriate shape are prepared in advance, and a predetermined space arranged in parallel is filled with a sintering material, or a reinforcing tubular member filled with a sintering material is filled. This is a serious industrial disadvantage because it requires cumbersome operations, labor, and time, which must be properly arranged to fuse the front plate and the rear plate. In addition, the method using this tubular member is insufficient in weight reduction, and the flat plate is difficult to polish because the portion of the front plate for the reflector to which the tubular support member is fused is distorted, and optical precision is impaired. Problem.

[0008]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a light-weight reflector base having excellent operability in which the reflection mirror surface is not distorted by a change in temperature or deformed by its own weight. Another object is to provide a highly practical foamable porous support member that is lightweight and has excellent three-dimensional strength in a direction orthogonal to the support direction of the reflector plate as a support member for the reflector plate. Still another object is to provide a practically extremely useful reflector base which is substantially airtightly sealed without being contaminated by mirror polishing or other processing or handling.

[0009]

SUMMARY OF THE INVENTION The gist of the present invention is to provide a method of manufacturing a lightweight reflector base comprising the constituent elements described in claim 1 of the specification.

The reflecting mirror is a reflecting mirror that collects and scatters light, for example, sunlight and beams, and is particularly useful for astronomical objects and the space industry. The reflecting mirror can be used for utilizing light or solar heat, and the reflecting surface of the silicon oxide transparent bubble-free plate forming the mirror surface is formed into a flat surface or a predetermined curved surface according to the purpose of use. Further, a metal deposition film suitable for the type of light to be used is formed on the surface. Regardless of the method of use, the reflecting mirror is required to have high optical reflection accuracy and easy operability. Therefore, it is important that the reflecting surface is made of a material that does not substantially deform in response to temperature changes.As a reflecting plate, high-purity high-silicic acid is a transparent material that does not contain bubbles made of lath or quartz glass. A plate is used.

In the method of the present invention, the member supporting such a reflector plate is preferably a quartz glass or a high silicate glass made of at least 99% by weight of silicon oxide and has an apparent density of 0.1 to 1 g. / Cm ³ is used. When the apparent density of the porous foam is less than 0.1 g / cm ³ , the supporting strength for supporting the reflector plate is weak, and when it exceeds 1 g / cm ³ , the weight reduction is insufficient,
The tendency to deform due to its own weight increases, and satisfactory operability cannot be obtained.

Such foams are mainly closed cells.
ConstitutionBecauseFormed by such closed cells,
Network with three-dimensional lattice structureFoam layer
Is guaranteed higher compressive strength in all directions.
Such foamlayerThe reflector plate evenly over the entire surface
supportDoFrom the pressing applied to the surface of the reflector plate during polishing.
Not only has excellent resistance to pressure,Thatsurface
It provides excellent resistance strength in the direction parallel to
It is extremely desirable as a holding member for a work plate.

[0013] Such a foam is produced, for example, by subjecting a hydroxyl group-containing quartz glass powder made of silicon oxide to an ammonification reaction under heating in an ammonia atmosphere, and molding and sintering it into a desired shape. The resulting product is heated and reacted in an ammonia atmosphere to produce an ammoniated glass sintered body.Then, the sintered body is heated and melted at a temperature of, for example, 1500 to 1800 ° C., and a gas is easily generated from the glass. It is manufactured in. At that time, by preventing the burst of gas bubbles generated in the molten glass, a foam mainly composed of closed cells can be effectively obtained. A foam can also be produced by mixing a powder component that reacts and sublimates at the melting temperature of glass into silica powder and heat-fusing the mixture. In this production, it is necessary to form bubbles having an appropriate desired diameter. Foaming conditions are selected so as to secure and prevent the formation of open cells due to overheating.

The porous foam produced in this manner is appropriately cut into a desired shape, for example, a disk or a square plate, according to the size and shape of the reflector, and one surface thereof is used for the reflector. A transparent non-bubble quartz glass plate or a high silicate glass plate is fused to the other surface, and a quartz glass plate or a high silicate glass plate of a relatively low purity is fused and integrated as a rear plate. In this integration operation, a silica powder having a softening point lower than the softening point of the porous foam layer is provided between the joining surface between the upper surface of the porous foam layer and the back surface of the reflecting mirror disk. Spread thinly on the entire surface, for example, form a layer of about 1 mm over the entire surface, hold it in a joined state through it, and heat it to a temperature above the softening point of the silica powder for about 1 to 4 hours, which is effective. Can be integrated by fusion.

When the softening point of the silica powder is equal to or higher than the softening point of the support member, the porous support member softens and melts during the heating and integration, so that the closed cells may burst or the surface of the substrate may be deformed. This is inconvenient because there is no phenomenon. In general, those obtained by the sol-gel method or the thermochemical vapor phase method have a relatively low melting point, and thus the pulverized product can be suitably used as the silica powder. The finer the silica powder, the more uniform the fused bonding layer is formed. For example, a silica powder having a particle size of 10 μm or less is extremely desirable in practical use. According to this integration method, the fusion bonding area is greatly increased, and the reflector plate is more stably fixed to the foam layer. In this bonding, the back surface of the reflector plate and the surface of the porous body to be bonded are formed in advance in the same surface shape so as to substantially substantially contact the entire surface.

The reflecting mirror plate which is fused and integrated on one side of the foam layer is a transparent plate made of quartz glass or high silicate glass having the highest possible purity and substantially containing no bubbles. Body. Even if fine air bubbles are contained in the reflector, the reflection surface may cause an undesired state such as distortion or distortion, so that it is not possible to produce a highly accurate reflecting mirror. Also, the plate that is melt-integrated on the other surface does not need high purity and transparency like a reflector plate, and it may contain some air bubbles or lose transparency, It is important that the plate is made of quartz glass or high silicate glass which does not substantially affect the change.

In the method of the present invention, after both plates are integrally joined to the foam layer, a seal layer of quartz glass or high silicate glass is fusion-formed on the peripheral side surface of the laminate. The seal layer does not necessarily need to be completely airtight, but it is preferable to smooth finish the peripheral side surfaces, particularly all side surfaces of the foam layer, prior to the formation of the seal layer.
The smooth finishing treatment can be performed by a generally known method such as, for example, smooth polishing with a grinder or baking with a fire such as a hydrogen-oxygen combustion flame.

Next, the formation of a fused layer of quartz glass or high silicate glass on the peripheral side surface of the smooth-finished laminate is performed by fusion bonding.
The glass powder may be adhered to the surface to be sealed and heated and melted to form a glass seal layer.However, a glass plate corresponding to the width and length of the peripheral side surface is burned by a combustion flame. It is practical to fuse and integrate the peripheral side surfaces sequentially.
The reflecting mirror substrate having such a glass seal layer formed thereon is:
For example, in mirror polishing with an aqueous abrasive, not only can the side surface contamination of the substrate by the finely powdered aqueous abrasive be substantially completely prevented, but also the physical strength of the reflecting mirror substrate is greatly improved, and the polishing is performed precisely. The mirror surface can be kept stable for a long time.

As described above, the surface of the transparent reflector plate of the laminated body whose peripheral side surface is glass-sealed as described above is, for example, flat or flat by a generally known precision polishing method using an aqueous abrasive. A predetermined curved surface is precisely polished, and a metal for a reflecting mirror, for example, a metal thin film such as aluminum or silver is formed on the polished surface by vapor deposition or other means, thereby completing a lightweight large reflecting mirror. In addition, when the metal thin film is formed on the mirror surface, it is exposed to a high temperature, and the peripheral side seal is expanded due to the expansion of the gas inside the base.
If there is a concern that the metal layer may be damaged, it is desirable to provide one or a plurality of small through holes on the peripheral side surface.

The method of the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 is a partially cutaway perspective view of an example of a disk-shaped base for a lightweight large-sized reflector manufactured by the method of the present invention. In the figure, a transparent, bubble-free, high-purity quartz glass reflecting mirror plate 2 is provided on one surface of a quartz glass disc-shaped porous foam layer 1, and a translucent quartz glass plate is provided on the other surface. The plate 3 is fused and integrated, and then an elongated plate 4 of quartz glass is sequentially fused and integrated from one end to the peripheral side surface of the integrated laminate to form a seal layer. The thus-obtained lightweight and large-sized reflector base of the present invention is precisely mirror-polished to form a flat high-precision reflecting mirror surface 2 ', and the polished surface is polished by metal deposition or the like. A reflective film is formed to provide an optically excellent reflecting mirror.

[0021]

According to the method of the present invention, a light-weight base body on which a flat or curved mirror having a stable and excellent optical surface accuracy is formed on a reflecting mirror surface can be effectively provided. In addition, the large reflecting mirror obtained by the method of the present invention has excellent structural strength despite its light weight, and its high-precision mirror surface is stably maintained over a long period of time. Availability is extremely high.

[0022]

Now, the present invention will be described in further detail with reference to specific examples. Example 1 Silicon tetrachloride was supplied to an oxyhydrogen flame burner and flame-hydrolyzed to produce a quartz glass soot body, which was reacted with ammonia gas at a temperature of 1000 ° C. for 2 hours, and then an ammonia atmosphere was produced. The gas was expelled and heated to a temperature of 1600 ° C. to form a foam, and a quartz glass porous foam having an apparent density of about 0.3 g / cm ³ was obtained. This foam was cut into a disk with a diameter of 350 mm and a thickness of 25 mm.

A transparent and bubble-free quartz glass disk having a diameter of 350 mm and a thickness of 3 mm is placed on the front surface of the porous disk.
Heat fusion was performed at a temperature of 00 ° C. At that time, a silica glass disk with a diameter of 350 mm and a thickness of 3 mm is placed on the lower surface of the porous disk as a back plate, and similarly, a thin layer of silica fine powder is spread as a fusing agent. And a laminate was obtained. Next, an elongated quartz glass plate having a thickness of 1 mm and a size of 30 mm × 1100 mm was fused and integrated on the peripheral side surface of the laminate with an oxygen-hydrogen burner to form a seal layer.

The flat surface of the transparent non-bubble quartz glass plate of the large reflecting mirror substrate thus obtained was precisely polished using an aqueous polishing liquid. When the flatness of the surface due to optical interference fringes was examined for this surface, the interference fringes were parallel,
It was confirmed that the entire surface had a very high degree of flatness. By depositing a thin film of aluminum on the precision polished surface, a highly accurate flat reflecting surface suitably used for laser light or the like was obtained. A large-sized reflector having a vapor-deposited film formed thereon is extremely desirable because it is much lighter and has better optical characteristics than a conventionally known lightweight reflector.

[0025]

As described above, the large-sized reflector base formed by surrounding the porous foam layer obtained by the method of the present invention with a quartz glass plate has a porous foam layer having no bubble and a transparent quartz glass reflector plate. Has a very high structural strength despite its light weight and excellent operability, since the rear plate facing and is fused and integrated over the entire surface and the glass seal layer on the peripheral side is fused and integrated. For example, there is no risk of deformation or breakage even when stress such as pressing during polishing is applied, and there is no inconvenience that the quartz glass reflecting mirror plate is distorted and the light reflection characteristic is reduced, so that it is highly practical. Have a value.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view of an example of a disk-shaped lightweight large-sized reflector base made by the method of the present invention.

[Description of sign]

 DESCRIPTION OF SYMBOLS 1 ... Disc-shaped porous foam layer made of quartz glass 2 ... Reflector plate made of transparent and bubble-free high-purity quartz glass 2 '... Precision polished surface of 2 3 ... Made of quartz glass Plate 4 ... Quartz glass seal layer

Continuation of the front page (72) Inventor Yoshiaki Okamoto 8-34, Haramachi, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Limited Okamoto Optical Co., Ltd. (56) References JP-A-52-40349 (JP, A) JP-A-61- 151501 (JP, A) JP-B 61-26041 (JP, B2)

Claims (2)

(57) [Claims] 1. Substantially closed cells made of quartz glass or high silicate glass having an apparent density of 0.1 to 1 g / cm ^3.
A transparent foam-free quartz glass or high silicate glass reflector plate on one surface of the porous foam layer composed of, and a quartz glass or high silicate glass plate on the other surface , respectively.
Softening point lower than the softening point of the porous foam layer between the joining surfaces
Held in a bonded state via a layer of silica powder having
Manufacturing a reflecting mirror base body by heating to a temperature higher than the softening point of silica powder and fusing and integrating, and then fusing and forming a sealing layer of quartz glass or high silicate glass on the peripheral surface thereof; Method. 2. The method according to claim 1, wherein the sealing layer on the peripheral side is formed of a long quartz gas.
Lath or high silicate glass plate is fused and formed
The process according to claim 1, wherein that.