JP3062031B2 - Method for producing optical component made of rutile single crystal - 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 an optical component made of a rutile single crystal, and more particularly, to a wafer obtained by slicing a rutile single crystal ingot so as to intersect an optical axis <001>. A large number of single crystal chips are cut out from the wafer so that the optical surface becomes the (110) plane, and the (110) plane of each single crystal chip is aligned and polished, so that cutting and polishing can be performed accurately and easily. The technology involved. This technology uses rutile single crystal (Ti
It is useful for manufacturing various optical components such as a polarizer and a retardation plate composed of O ₂ ).

[0002]

2. Description of the Related Art Rutile single crystals have attracted attention as optical components such as polarizers and retardation plates because of their birefringence properties. Currently, single crystal ingots have been grown by the floating zone method or Bernoulli method. I have. When growing a single crystal by the floating zone method, the single crystal grows in the optical axis <001> direction. When processing this rutile single crystal ingot into an optical component, the rutile single crystal ingot is cut and polished into a predetermined shape with reference to the optical axis <001>. Examples of this shape are shown in FIGS.

FIG. 1A shows an example of processing into a parallel plate type. The optical axis <001> is set parallel to the processing surface, and both optical surfaces (light input / output surfaces) 10 are mirror-polished. FIG. 1B shows an example of a birefringent polarizer processed into a wedge shape. Optical axis <001>
Is inclined by 22.5 ° with respect to the vertical line, and the opposing optical surfaces are shifted from the parallel state by an angle α (about 4 °).
In this case, one optical surface (the optical surface 12 located on the front surface in FIG. 1B) is parallel to the optical axis <001>, but both optical surfaces are mirror-polished. In FIG. 1, the optical axis is indicated by a broken arrow.

In the prior art, since the optical axis <001> only needs to be in the optical plane, the orientations of these optical planes are arbitrarily (arbitrarily) selected. In general, optical components having a desired shape are cut from a single crystal ingot so as to be cut as much as possible, and the optical surfaces of the cut single crystal chips are arranged and mirror-polished.

[0005]

When an optical component made of a rutile single crystal is manufactured by a conventional method, a phenomenon that cracks and chipping frequently occur at an edge portion at the time of cutting may occur. In addition, when a large number of single crystal chips are arranged and polished, there is a problem in that the polishing amount becomes uneven, so that processing cannot be performed with high accuracy, and that correction (reworking) requires much time and labor. For this reason, the manufacturing efficiency is poor, and the polishing for repairing may result in a thinner than desired thickness, resulting in a defective product.Although the single crystal ingot is cut out from the single crystal ingot as much as possible, the yield is low. There was a disadvantage that it was bad.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for cutting a single crystal chip from a single crystal ingot, which is unlikely to cause appearance defects such as cracks and chipping, and for mirror polishing a large number of single crystal chips collectively on a lapping machine. Another object of the present invention is to provide a method capable of processing uniformly, accurately, and efficiently.

[0007]

According to the present invention, there is provided an optical system comprising: an optical axis <00;
This is a method for producing a rutile single crystal optical component in which 1> is taken in parallel with a processing surface. Here, the feature of the present invention is that a rutile single crystal ingot is sliced so as to intersect with the optical surface <001> to form a wafer, and the optical surface is (11)
A point is that a large number of single crystal chips are cut out so as to have a (0) plane, all of the cut out single crystal chips are aligned and fixed on a surface plate, and all are polished to a mirror surface. .

When manufacturing a rutile single crystal optical component having the optical axis <001> parallel to the processing surface, processing can be performed in a variety of azimuthal planes. Typical processing surface is (100)
There is a plane or a (110) plane, and of course, a plane inclined between them may be used. However, it has been found that when a single crystal chip is actually cut out from a rutile single crystal ingot at various orientations using an inner peripheral blade (diamond cutter), the occurrence of cracks and chipping greatly differs depending on the orientation. Further, it was also found that the polishing rate was different depending on the orientation plane. The reason that conventional technology cannot perform polishing accurately and efficiently is that a large number of single crystal chips cut out without considering the azimuthal surface are stuck on a surface plate and mirror-polished. It is considered that the robot rotates in a state of being tilted by a difference from the surface. The present invention has been made based on knowledge of such a phenomenon.

[0009]

When the (110) plane is cut out perpendicularly from the (100) plane, the amount of chipping after cutting is very small as compared with the case where the (100) plane is cut out perpendicularly from the (110) plane. . Further, the (110) plane has a lower hardness than the (100) plane and is more easily cut. Therefore, when all of the cut single crystal chips are aligned and fixed on a polishing platen with all (110) planes aligned and polished to a mirror surface at a time, all the single crystal chips are efficiently polished at the same speed and attached. The chips in the surface plate do not tilt, and as a result, processing with high dimensional accuracy can be performed. However, during the polishing process, if the orientations of the arranged single crystal chips are not aligned, the polishing rate is different for each single crystal chip, so that the one that is easy to be polished and the one that is hard to be polished are inclined. It is very difficult to adjust the polishing, for example, the shape is liable to be polished and a shape defect is likely to occur, and a correction is required during the polishing.

[0010]

EXAMPLE A rutile single crystal was grown by the floating zone method. In this method, the single crystal has an optical axis <00
Growing in the 1> direction, a large ingot is obtained. FIG.
2A, the ingot 20 is sliced perpendicular to the optical axis <001> to cut out the wafer 22 (cut surface 1a), as shown in FIG. 2A. ). The single crystal chip 24 is cut out from the wafer 22 such that the (110) plane appears vertically and horizontally to the wafer cut plane, that is, the (001) plane (cut planes 1b and 1).
c). Then, a large number of cut single crystal chips 24 are
All (110) surfaces (cut surface 1b) are aligned and fixed on a platen, and polished to a mirror surface at once. This mirror polishing is performed on both opposing surfaces to obtain a parallel plate type optical component using them as optical surfaces (input / output surfaces).

When manufacturing a wedge-shaped optical component as shown in FIG. 1B, as shown in FIG.
0 is inclined at 22.5 ° with respect to the optical axis <001> to slice the wafer 23 (cut surface 2a). The wafer 23 is cut so that the (110) plane appears perpendicular to the wafer cut plane (cut plane 2b), and further cut perpendicular to the cut planes 2a and 2b to cut out the single crystal chip 25 (cut plane 2).
c). Then, one surface of the (110) plane (cut surface 2b) is polished obliquely (at an angle of about 4 °) and shaped into a wedge shape. Wedge-shaped single crystal chips are all (110) plane (cut plane)
2b) is aligned and attached and fixed on the platen, and polished to a mirror surface all at once. This mirror polishing is performed on both opposing surfaces. As a result, a wedge-shaped optical component having those surfaces as optical surfaces (input / output surfaces) is obtained.

The cutting procedure is performed in the order of the cut surfaces 1a, 1b, and 1c in the case of the parallel plate type optical component, and in the order of 2a, 2b, and 2c in the case of the wedge type optical component. Single crystal chips 24 and 25 without chipping or chipping could be cut out. Such a cutting order is adopted in (10
This is because, since the (0) plane is harder than the (110) plane, if the cut surfaces 1a and 2a are cut later, cracks and chipping frequently occur at the edges. In addition, the mirror polishing of the cut surfaces 1b and 2b could be accurately performed without unevenness in the polishing amount.

The reason why the method of the present invention is effective will be described in more detail based on experimental results. Polishing was performed with a 3 μm wrap, and the hardness of each orientation plane of the rutile single crystal chip was measured. First, a parallel plate type rutile single crystal chip of 5 mm square was cut out so that the (100) plane and the (110) plane were used as optical surfaces, and three chips each were prepared. As shown in FIG. 3, rutile single crystal chips 32 having the same plane orientation were stuck on a ceramic platen 30 having a diameter of 107 mm in a regular triangular shape. And it processed for 10 minutes with a Kemet surface plate. Table 1 shows the measurement results of the scraping amount per minute.

[0014]

[Table 1]

As can be seen from Table 1, the hardness of the rutile single crystal has anisotropy depending on the plane orientation, and the (100) plane is harder to grind than the (110) plane. That is,
The (100) plane is the hardest, from the (100) plane to (110)
As the surface tilts, it becomes softer, and (11
0) The surface is softest. A soft surface is easier to polish, and a hard surface is easier to scratch during polishing. This indicates that it is most preferable that the (110) plane be an optical surface.

Further, as shown in FIG. 4, three (100) faced rutile single crystal chips 32a are provided in a half area of the ceramic platen 30, and a (110) chip is provided in the other half area.
Three rutile single crystal chips 32b with their faces facing upward were attached in a regular hexagonal shape, and polished under the same conditions as described above. Table 2 shows the measurement results of the height after performing the polishing process four times.
Shown in As shown in Table 1, there is anisotropy in hardness depending on the plane orientation, and the (100) plane is harder to be cut than the (110) plane. Therefore, a rutile single crystal chip having a different plane orientation is attached to the same ceramic surface plate. When polishing is performed with the polishing, the height is different and the inclination is large as polishing proceeds.

[0017]

[Table 2]

Therefore, in this state, the dimensional accuracy of all the rutile single crystal chips cannot be obtained. In order to correct this, it is necessary to perform re-polishing with an uneven load. However, it is extremely difficult to rework by applying an eccentric load to obtain an appropriate size, which requires skill. After reworking many times, it may be cut too much than the expected size. By mirror-polishing the soft (110) planes uniformly, the processing can be performed uniformly and efficiently without tilting.

FIG. 5 and Table 3 show the case where the inner peripheral blade (diamond cutter) is cut so that the (100) plane appears perpendicularly from the (110) plane, and the case where the (110) plane appears perpendicularly from the (100) plane. This is the result of observing and measuring the amount of chipping on the (100) cut surface and the (110) cut surface in the case of cutting as described above. In FIG. 5A, the cut surface is (1).
FIG. 5B shows the state of chipping when the cut surface is the (110) plane, respectively.

[0020]

[Table 3]

From Table 3, it can be seen that, when the cut surface is the (110) plane, the amount of chipping is about one-third at the maximum value and about half as the average value when the cut surface is the (100) plane. It can be seen that it can be reduced. It is considered that the reason for this is that, as can be seen from the results in Table 1, since the (100) plane is harder than the (110) plane, cutting or cutting on the hard (100) plane easily causes cracks and chipping at edges. When a single crystal chip is cut out, the optical surface is set to the (110) surface, and the soft (110) surface is cut later, so that a single crystal chip with good chipping and good appearance can be obtained, and the yield is improved accordingly. Also, the amount of polishing is small.

[0022]

According to the present invention, it is possible to cut out a single crystal chip with less cracks and chipping in consideration of the hardness anisotropy of each azimuthal plane of the rutile single crystal. Polishing is facilitated, and thereby, an optical component having a good appearance and high dimensional accuracy can be efficiently manufactured.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an example of the shape of an optical component made of a rutile single crystal.

FIG. 2 is an explanatory view showing an example of a processing order of a rutile single crystal optical component according to the present invention.

FIG. 3 is an explanatory view showing a state of attachment of a rutile single crystal chip used in a polishing test.

FIG. 4 is an explanatory view showing a state of attachment of a rutile single crystal chip used in another polishing test.

FIG. 5 is an explanatory view of a cutting state on the (100) plane and the (110) plane.

[Explanation of symbols]

 10, 12 Optical surface 20 Single crystal ingot 22, 23 Wafer 24, 25 Single crystal chip

Claims (3)

(57) [Claims] 1. A method of manufacturing a rutile single crystal optical component having an optical axis <001> parallel to a processing surface, wherein a single crystal ingot is sliced so as to intersect the optical axis <001> to form a wafer, and A large number of single crystal chips are cut out so that the optical surface becomes the (110) plane, and all the cut out single crystal chips are aligned and fixed on the platen with the (110) planes aligned and polished to a mirror surface at once. A method for producing an optical component comprising a rutile single crystal. 2. The optical axis <001> is set parallel to the processing surface.
In the manufacturing method of parallel plate type rutile single crystal optical components
Te, and a wafer by slicing vertically monocrystalline ingot optical axis with respect to <001>, the cut to appear (110) plane vertically and horizontally perpendicular to the wafer cut surface
Many single-crystal chips were cut out from the wafer and cut out
Each single crystal chip is aligned with the (110) plane to be the optical surface.
The array is fixed on the platen and polished to a mirror surface at once.
A method for producing an optical component comprising a rutile single crystal, characterized in that : 3. The optical axis <001> is set parallel to the processing surface.
In a method for manufacturing a wedge-shaped rutile single crystal optical component, a single crystal ingot is sliced at 22.5 ° with respect to an optical axis <001> to form a wafer, and a (110) plane is perpendicular to the wafer cut surface. Are cut parallel to each other and cut perpendicular to both the wafer cut surface and the (110) cut surface to cut out a large number of single crystal chips from the wafer. After grinding and shaping into a wedge shape, each wedge-shaped single crystal chip is
(110) faces are aligned and fixed on the platen
Single rutile, characterized by being polished to a mirror surface all at once
For manufacturing optical components made of crystals .