JP2750229B2 - Large and lightweight reflector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly practical reflector used for astronomical observation, beam condensing, diffusing, or the space industry. The present invention relates to a light-weight large-sized reflector base that does not need to be made.

[0002]

2. Description of the Related Art Conventionally, astronomical reflectors and high energy beams have been used.
The reflector used for optical condensing, diffusing, or changing the optical path of a mirror or the like, polishes the surface of a plate made of quartz glass, high silicate glass, etc. to a flat surface or a predetermined curvature surface. As a reflective layer, a conventionally known method, for example, a vapor deposition film of a metal such as aluminum is formed under heating conditions of 400 ° C. to 800 ° C. by a CVD method, and this is supported on a lightweight operation support. And can be freely operated in a desired direction. Since such a vapor deposition operation is required, the material for the reflecting mirror is required to maintain accuracy that is not affected by the temperature of the reflecting surface or an internal force change.

[0003] In the past, such reflectors were mainly small ones having a diameter of about 5 to 20 cm.
In order to reflect a large diameter beam and obtain a high light collection rate,
Large-sized ones of 30 cm to 1 m or more are required, and such large-sized ones have been put into practical use. The mirror surface undulation due to the delicate volume change of the mirror surface and the thermal deformation due to the high temperature heat treatment when depositing the metal reflective film on the mirror surface lowers the performance of the reflecting mirror. High silicate glass has come to be mainly used. However, as the size of the reflector increases, the weight of the reflector itself becomes extremely large, and deformation of the reflector due to its own weight is caused by changes in the support posture, such as the support angle of the reflector, and as a result, the mirror surface swells and the performance decreases. Has become.

[0004] On the other hand, to solve these problems, many proposals have been made on reflectors that reduce the weight of the reflector material and provide high holding strength. 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 between a transparent reflector plate and a rear plate, such as quartz glass. The tubes are staggered to have a contact line or contact zone with two tubes in an adjacent row, reducing the wall thickness of the tube in the area of the contact line or the like as compared to the rest of the wall; A special pipe structure in which the pipes are welded to each other along a contact line or the like is disclosed. However, such a specially constructed astronomical reflector material is not only complicated in construction, but also difficult to manufacture, and is extremely disadvantageous industrially.In addition, the supporting portion and the non-supporting portion of the support grid are subject to polishing pressure from the vertical direction of the mirror surface. Thus, the degree of deformation of the mirror surface is different, and it cannot be said that the material is satisfactory for polishing the curved surface of the integrated reflector plate.

In addition, it is difficult to make the effective height of the tube material, which is a support grid, strictly constant in the strict sense during the production of the reflector material. Such irregularities remain as distortions and cause changes over time, such as swelling of the mirror surface, at a later date, which is a 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.

Japanese Patent Publication No. Sho 61-26041 relates to a lightweight mirror, and more particularly, to a lightweight mirror made of quartz glass which is connected between these front and rear plates so as not to move. A lightweight mirror for a celestial body in which a support grid is fused and integrated. The support grid is formed by placing a plate-shaped member and / or a tubular member made of quartz glass on a supporting plate, and in each of the spaces left between the two members, a granular material, a small tube piece, and the like. , Filled with the material to be sintered, consisting of small particles, platelets or mixtures thereof, the arrangement being held together by graphite rings, which are then heated in a furnace under a non-oxidizing atmosphere under a non-oxidizing atmosphere. It is disclosed that the supporting grid thus formed is connected to the front plate and the rear plate by heat fusion so as not to move.

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 the sintering material is used. Since it requires troublesome operation, labor, and time for appropriately arranging the front plate and the rear plate and fusing the front plate and the rear plate, it is difficult to industrially adopt the method. Moreover, in this method, the front plate where the support grid is fused often forms a strain, or the sintered material itself is a porous body having low-density continuous pores, so that it shrinks or collapses. The disadvantage that the shape changes and the concave surface accuracy of the front plate surface is impaired cannot be avoided.

[0008]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a practical large reflector which is lightweight and excellent in operability such as adjusting the direction of the reflector surface. Another challenge is
Provided is a large-sized reflector having excellent strength that is easy to manufacture, has excellent front plate (reflection mirror plate) support strength, and has an integrated base layer that does not cause deformation or undulation even when the reflection mirror surface is polished. It is in. Still another object is to provide a reflecting mirror having a uniform and excellent reflecting surface in which a plate forming the reflecting mirror surface can be distorted due to a change in temperature and does not undergo thermal deformation upon deposition of the reflecting film.

[0009]

Means for Solving the Problems The present inventors have conducted many trial production studies to solve the above problems, and as a result, have developed a practically excellent large lightweight reflector. That is, the present invention provides a large reflector having a reflective film deposited on a flat surface or a surface formed with a predetermined curvature, wherein the reflector is made of bubble-free transparent quartz glass or high silicate glass having a mirror surface on the surface. A multilayer structure comprising a mirror surface forming layer and a base layer composed of a silicon dioxide porous foam layer integrated thereunder, wherein the mirror surface forming layer is located at the center of the multilayer structure reflecting mirror. A layer thickness in the range of 2 to 20% of the thickness of the part,
The porous substrate layer has a total pore volume contained therein.
The gist of the present invention is a large-sized light-weight reflector having at least 15% closed cells and an apparent density of 0.1 to 1 g / cm ³ . Further, a large-sized and lightweight reflector in which a reinforcing layer is integrally formed below the porous base layer of the reflector is more preferable.

The large and light reflecting mirror of the present invention collects and scatters light, for example, sunlight and laser beams, and is useful mainly for celestial bodies, laser condensing, and solar heat. It is a reflecting mirror, and a film suitable for reflected light is formed on the mirror forming surface, and is used as a reflecting mirror for various uses. Such large-sized lightweight reflectors are required to have particularly high reflector accuracy and high operability due to weight reduction. This weight reduction requires a weight reduction of 50% or more, preferably 70% or more, in the case of a weight-reducing reflector in comparison with a mirror body of the same type having a more practical structure.

Accordingly, the mirror-forming layer is made of a substantially bubble-free transparent high silicate glass or quartz glass which is not deformed by a change in temperature, and the base layer holding the mirror-forming layer is also formed of a mirror-forming layer. A silicon dioxide-based member that does not generate distortion due to a difference in thermal expansion between the layer and a thermal expansion during deposition of the reflective film is used. Such a silicon dioxide member can be suitably used as long as it contains 90% or more of silicon dioxide. Thus, the silicon dioxide-based member integrally formed as a base layer below the mirror-forming layer to support the mirror-reflecting mirror plate contains a large number of closed cells in its pores in order to obtain weight reduction and strength, and 0.1%. It is important that the porous foam has an apparent density of 密度 1 g / cm ³ .

When the proportion of closed cells in the pores of the porous foam is increased, a network having a three-dimensional lattice structure is formed, and the strength is remarkably improved. However, when the apparent density of the foam is less than 0.1 g / cm ³ , the wall thickness of the closed cells forming the three-dimensional lattice structure is thin, and the strength for supporting the mirror surface forming layer is insufficient. The polishing pressure causes the porous portion to be easily crushed partially, and the surface of the mirror-forming layer corresponding to the portion is extremely slightly depressed and deformed, which causes a great decrease in the accuracy of the reflecting mirror surface, which is inconvenient. It is. The apparent density is 1 g / cm
^If it exceeds ³ , the weight of the reflector is not sufficiently reduced, so that it is likely to be deformed by its own weight, and depending on the holding posture of the reflector, a warp in the direction of gravity is generated, and the accuracy of the reflector surface is significantly impaired. It is not practical because the operability is greatly reduced as the size increases.

Further, the porous substrate layer contains 3
In order for a network having a three-dimensional lattice structure to be sufficiently formed, it is necessary to have closed cells of 15% or more of the total pore volume. If the total volume of closed cells is less than 15%,
It is not preferable because cracks may occur along the continuous ventilation holes in the porous base layer due to surface pressing due to finish polishing of the reflecting mirror surface or bending deflection due to its own weight. The smaller the diameter of the closed cell is better to form the lattice structure,
Normally, a size of about 0.1 mm to 3 mm is desirable.

The large reflector according to the present invention has an appropriate size in consideration of the weight reduction of the reflector surface forming layer in consideration of the strength condition of the base layer comprising the silicon dioxide porous foam layer as described above. It is important to give strength. The strength of the mirror forming layer is
Although it depends on the thickness of the transparent quartz glass plate, many prototype experiments have shown that the mirror-forming layer plate has a thickness in the range of 2 to 20% of the total thickness at the center of the reflecting mirror composed of the mirror-forming layer and the base layer. It has been found that it is practically very desirable to prepare a plate. If the thickness is less than 2%, it is difficult to obtain high reflection accuracy due to insufficient strength of the reflecting mirror layer and to maintain a long-term stability. If the thickness is more than 20%, the weight of the reflecting mirror is not sufficiently reduced. In connection with this, the strength of the base layer must be increased, so that the weight of the reflector is further increased,
Its operability is significantly impaired.

The base layer constituting the reflecting mirror of the present invention is formed into a desired shape after heating and reacting a silica powder containing silicon dioxide, preferably, for example, 90% or more silicon dioxide and containing a hydroxyl group in an ammonia atmosphere. After molding and sintering, or molding and sintering silica powder, the compact is heated and reacted in an ammonia atmosphere to heat the ammoniated porous body to a temperature of 1500 to 1800 ° C to melt the powder. At the same time as releasing the gas from the silica. Alternatively, a powder which reacts and sublimates at a silicon dioxide melting temperature may be mixed into silica powder and heated and fused to obtain a porous foamed member.

In the preparation of these molten foams, the ammoniating reaction conditions, for example, ammonia atmosphere concentration,
The apparent density of the foam can be controlled by selecting the reaction temperature, the reaction time, the degree of pulverization of the silica powder, or the amount of the sublimable powder to be added. However, in this method, it is important to carefully perform foaming so as not to form open cells, and a careful temperature control is required. In the melt foaming process, for example, two disk-shaped
Ammonia powder can be filled between the bon plates, or heated and melted by sandwiching the ammoniated disc-shaped sintered body to obtain a porous lightweight member having a desired shape.

Further, in the large-sized and lightweight reflecting mirror of the present invention, it is preferable to provide a reinforcing layer on the lower surface of the base layer in order to supplement the strength, and to use a silicon dioxide plate similar to the porous base layer. Then, it is fused and integrated with the lower surface of the base layer. As the reinforcing layer plate, a sintered body of silicon dioxide powder or a closed-cell-containing glass body is advantageously used in order to reduce the weight of the reflector and to enhance the reinforcing effect. The reinforcing layer preferably employed practically has, for example, an apparent density of 0.8 to 2.5 g / cm ³ . In the case of the glass body reinforcing layer, those containing 60% or more of closed cells are preferable. The thickness of the reinforcing layer is related to the apparent density, but is 2% to 20% of the central thickness of the reflecting mirror, similarly to the reflecting mirror surface forming layer.
% Is preferable.

The integration of the porous foam base layer with the mirror surface forming layer plate and the reinforcing layer plate is performed by heat fusion. In order to increase the fusion area as much as possible, the interface to be fused and integrated is formed. In addition, a silica powder having a softening point lower than the softening point of the base layer, for example, fine powder silica powder having a particle size of 10 μm or less is interposed, and the softening point of the silica powder is maintained while keeping the layers joined. Heating to the above temperature for about 1 to 4 hours can be performed effectively. Such a low-melting-point silica powder can be generally obtained by a sol-gel method before vitrification or a thermochemical vapor phase method. In the above-mentioned application for forming the bonding layer, the powder is desirably as fine as possible. For example, the powder is used after being crushed and adjusted to 10 μm or less.

According to this integration method, a stable multi-layered reflecting mirror having an excellent bonding strength without greatly increasing the fusion bonding area and without causing the transparent mirror surface forming layer to peel off during polishing of the reflecting mirror surface. can get. To prevent such peeling, the total cross-sectional area ratio of the substantial connection wall thickness and the total cross-sectional area ratio of the pore portion occupying the entire area of the boundary layer between the porous base layer and the mirror surface forming layer is determined by the ratio of the substantial connection wall thickness. The total cross-sectional area should be at least 5% of the total cross-sectional area.

In the multilayer structure thus integrated, the surface of the mirror forming layer is then polished to a mirror surface having a predetermined curvature. In the mirror finishing, a frictional force parallel to the surface and a pressure perpendicular to the surface (approximately 0.5 N / cm ² ) are applied. However, according to the present invention, the base layer mainly contains closed cells and has a mirror forming layer having a predetermined thickness. As a result, a large-sized lightweight reflector having the required composite strength has substantially the same resistance strength in all directions, and furthermore, the mirror surface forming layer and the base layer which is its supporting layer are firmly bonded. In addition, safe and high-precision processing is possible even during polishing at the material stage, and as a result, a large-sized high-precision reflecting mirror having a reflecting film formed on a mirror surface is obtained. On the high-precision mirror-polished surface, finally, a vapor deposition film as a metal reflecting mirror suitable for the use thereof is formed according to the reflected light, and this is attached to an operation device for use.

The present invention will be described with reference to the drawings. FIGS. 1 and 2 are a perspective view and a schematic cross-sectional view of an example of a large-sized lightweight reflecting mirror of the present invention, wherein a disc-shaped mirror surface forming layer 1 of a bubble-free and transparent quartz glass or high silicate glass plate and a lower side are shown. A substrate layer 2 comprising a layer of silicon dioxide porous foam is fused and integrated;
On the surface of the mirror surface forming layer 1, a metal deposited reflective film 3 is formed. FIG. 3 is a schematic cross-sectional view of an example in which a disk-shaped reinforcing layer 4 of a silicon dioxide sintered body is fused and integrated on the lower surface of the base layer to reinforce the reflecting mirror. FIG. 4 is a schematic cross-sectional view of an example of a large-sized and lightweight concave reflecting mirror of the present invention having a mirror surface forming layer 1 ′ having a concavely curved surface, and the surface of the mirror surface forming layer 1 ′ is likewise metal-deposited. A reflective film 3 is formed, a disc-shaped reinforcing layer 4 is fused and integrated on the bottom surface of the base layer 2, and a thin silicon dioxide peripheral side reinforcing layer 5 is substantially airtightly formed on the entire peripheral surface. And further reinforcement.

[0022]

The large and light reflecting mirror of the present invention is lightweight in itself, has almost no deformation of the mirror surface due to the temperature and operating posture of the use environment, and has excellent operability. Compared with a large-sized reflector having a lattice structure, it has a simple configuration, is easy to manufacture, and is provided at low cost, which is extremely advantageous industrially.

[0023]

Next, the reflecting mirror of the present invention will be described in more detail with reference to specific examples. Example 1 About 98% of silicon dioxide powder containing about 300 ppm of hydroxyl groups was
Formed and sintered into a large disk at a temperature of 00 ° C and heated and reacted in an ammonia atmosphere.
The mixture was heated and melted and foamed for 1 minute to form a porous foam having an apparent density of 0.1 g / cm ³ , and the foam was cut out to form a disc-shaped substrate layer. The ratio of closed cells to all pores in the base layer was about 15%. The content of the closed cells is determined by measuring the apparent density of the base layer and the density of the silicon dioxide matrix itself constituting the base layer, and measuring the density of the open pores obtained by immersing the base layer, which is the original porous foam, in a liquid. Calculated easily from volume.

On the other hand, a flat, mirror-free layer of a transparent, bubble-free disk made of high-purity quartz glass was formed, and this layer was placed on the upper surface of a base layer obtained by thinly spreading silica powder having an average diameter of about 8 μm over the entire surface. The layers were overlapped and fused together at a temperature of about 1600 ° C. in the joined state. Next, the circumference of this laminate was cut to a diameter of 1000
After making a disk of mm, the surface of the mirror surface forming layer is finished to a flat surface with a thickness of 1 mm through diamond grinding, abrasive polishing, and polishing, and furthermore, aluminum metal is vapor-deposited by the CVD method (vapor phase growth method). A light reflecting mirror with a diameter of 1000 mm and a thickness of 50 mm was manufactured by forming a glossy reflecting mirror film.

Example 2 A reflector having the same dimensions and shape as in Example 1 was prepared in the same manner as in Example 1 except that the foaming temperature was slightly lowered and a base layer having an apparent density of 1.0 g / cm ³ was prepared. did.

Example 3 In Example 1, sintering of a silicon dioxide powder compact as a raw material of a base layer was performed using a somewhat thick mirror-forming layer.
The temperature was set at 1300 ° C., and the foaming temperature was set at an intermediate temperature between Example 1 and Example 2. In this way, a reflector having the same overall thickness and diameter as in Example 1, a mirror surface forming layer thickness of 10 mm, and an apparent density of the base layer of 0.8 g / cm ³ was produced.
The ratio of closed cells in the substrate layer was about 60%.

Example 4 In Example 1, the thickness of the base layer was reduced by about 1 mm, and opaque quartz glass having a specific gravity of 2.2 was welded as a reinforcing layer instead. Was manufactured.

Comparative Examples 1 to 3 The same manufacturing method as in Example 1 was used, but the sintering temperature of the silicon dioxide powder to be the base layer was lower than that in Example 1 (1000
° C), and the foaming temperature during the production of the substrate layer is set in the intermediate region between Example 2 and Example 1, so that the overall thickness and diameter are the same as in Example 1, the mirror-surface-forming layer thickness is 10 mm, and the substrate layer density A reflector having a low closed cell density of 0.8 g / cm ³ and a closed cell ratio of about 10% in the substrate layer was prepared (Comparative Example 1). In addition, by the control of the same manufacturing method as in the above Examples and Comparative Examples,
A low-density base layer having the same overall thickness and diameter as in Example 1, a mirror-forming layer having a thickness of 1 mm, an apparent density of the base layer of 0.05 g / cm ³ , and a closed cell ratio of about 15% in the base layer. A reflector was prepared (Comparative Example 2). Furthermore, the thickness of the mirror surface forming layer is 0.5 m
m, a base layer density of 0.1 g / cm ³ , and a thin mirror having a mirror surface forming layer having a closed cell ratio of about 15% in the base layer was prepared (Comparative Example 3). Table 1 summarizes the multilayer structures of the above examples.

[0029]

[Table 1]

Comparative Examples 4 and 5 For reference, as a conventional reflecting mirror, a reflecting mirror composed of one layer of quartz glass (Comparative Example 4) and a short tube of 40 mm in diameter and 2 mm in thickness were mounted on two 2 mm quartz glass disks. Were laid out without gaps, welded together, polished on one side, and provided with a reflective film to produce a lightweight reflector having a conventional lattice structure (honeycomb structure) base layer (Comparative Example 5). .

The following tests were performed on the obtained lightweight reflectors, and each reflector was evaluated. Test 1: The bonding state between the base layer and the mirror surface forming layer was observed from the polishing surface side and the side surface before depositing the reflective film, and the presence or absence of abnormalities was examined. As a result, no abnormalities were observed in both Examples 1 and 2, but in Comparative Examples 1 and 2, when viewed from the side surface and the polishing surface side, a small peeling crack was formed in the joint portion between the base layer and the mirror surface forming layer. Was observed. Further, in Comparative Example 3, a plurality of cracks were observed in the mirror surface forming layer.

Test 2: The outer periphery of the reflector was supported at three points, and the surface accuracy of the reflector was measured. The surface accuracy was measured for each of the vertical and horizontal root mean square roughness (RMS) and the maximum height (Rt) of the roughness curve. Table 2 shows the results.
Shown in

[0033]

[Table 2]

From Table 2, it can be seen that, in the comparative example, the difference between RMS and Rt in the vertical state and the horizontal state is large, whereas in the example, there is no significant change in RMS and Rt both in the horizontal and vertical states, and especially in the reinforcement. It can be seen that in Example 4 in which the layer was provided, the change in precision was extremely small and the operability was good. Further, compared to the comparative example 5 which is a conventional lightweight reflector, both the surface accuracy and the difference between the horizontal and vertical directions showed better results in the example.

Test 3: The weight of each reflector was reduced with respect to the weight of a reflector having the same dimensions, except that the reflection film was made of transparent quartz glass. Measurements were made for Examples 1 and 4 and Comparative Examples 4 and 5. went. As a result, the weight reduction rate is
94%, Example 4 92%, Comparative Example 4 0%, Comparative Example 5 78%
%Met. From this, it can be understood that the reflector of the present invention achieves a higher weight reduction rate than the conventional reflector.

[0036]

The thickness of the mirror surface forming layer is 2 to 20% of the thickness of the central portion of the reflecting mirror, and the apparent density of the base layer is 0.1 to 1 g / cm.
³ , the large and lightweight reflecting mirror of the present invention, in which 15% or more of the total pore volume of the porous substrate layer is constituted by closed cells, has no risk of being damaged when the mirror surface is polished, and has a highly accurate reflecting surface. Can be formed, and the surface accuracy can be maintained regardless of the posture such as horizontal or vertical, and the operability and the accuracy of the reflecting surface are far superior to those of the conventional lightweight reflecting mirror. Further, the one in which the reinforcing layer is provided on the lower surface of the porous substrate layer can obtain higher operability.

[Brief description of the drawings]

FIG. 1 is a perspective view of an example of a large lightweight reflector according to the present invention.

FIG. 2 is a schematic sectional view of FIG.

FIG. 3 is a schematic cross-sectional view of a reflector in which a reinforcing layer is integrated with a lower surface of the base layer.

FIG. 4 is a schematic cross-sectional view of an example of the large-sized and lightweight concave reflecting mirror of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Mirror surface forming layer 1 '... Concave mirror surface forming layer 2 ... Base layer 3 ... Metal deposition reflection film 4 ... Reinforcement layer 5 ... Peripheral side surface reinforcement layer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-52-40349 (JP, A) JP-A-57-136604 (JP, A) JP-A-61-151501 (JP, A) 41802 (JP, A) JP-A-4-323601 (JP, A) JP-B-61-26041 (JP, B2) JP-B-63-57761 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02B 5/08 G02B 5/10

Claims (2)

(57) [Claims] 1. A large reflecting mirror having a reflecting film deposited on a flat surface or a surface having a predetermined curvature, wherein the reflecting mirror is made of bubble-free and transparent quartz glass or high silicate glass having a mirror surface on the surface. A multilayer structure comprising a mirror surface forming layer and a base layer composed of a silicon dioxide porous foam layer integrated thereunder, wherein the mirror surface forming layer is located at the center of the multilayer structure reflecting mirror. Part of the porous substrate layer contains at least 15% of the total pore volume contained therein as closed cells, and has a thickness of 0.1 to 20%.
A large, lightweight reflector with an apparent density of 1 g / cm ³ . 2. The large-sized structure according to claim 1, wherein a silicon dioxide reinforcing layer having an apparent density of 0.8 to 2.5 g / cm ³ is further integrally formed under the porous base layer of the multilayer structure. Lightweight reflector.