JPH08220301A - Method for manufacturing optical component made of rutile single crystal - Google Patents

Abstract

(57) [Summary] [Purpose] When cutting a single crystal chip from a single crystal ingot, it is difficult for defects in appearance such as cracks and chipping to occur, and when a large number of single crystal chips are collectively mirror-polished on a lapping machine. In addition, it is possible to uniformly and accurately and efficiently process. [Structure] A method for producing a rutile single crystal optical component having an optical axis <001> parallel to a processed surface. The rutile single crystal ingot 20 is sliced so as to intersect the optical surface <001> into wafers 22 and 23, and a large number of single crystal chips 24 and 25 are formed from the wafers so that the optical surface becomes the (110) plane. All the single crystal chips that have been cut out are stuck together with their (110) faces aligned and fixed on a surface plate, and are collectively polished to a mirror surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an optical component made of rutile single crystal, and more specifically, it slices a rutile single crystal ingot so as to intersect with an optical axis <001> to obtain a wafer. By cutting a large number of single crystal chips from the wafer so that the optical surface becomes the (110) surface and aligning the (110) surface of each single crystal chip for polishing, cutting and polishing can be performed accurately and easily. It is about the technology to do. This technology uses rutile single crystal (Ti
It is useful for manufacturing various optical components such as a polarizer and a retardation plate made of O ₂ ).

[0002]

2. Description of the Related Art Since rutile single crystals exhibit birefringence, they are attracting attention as optical components such as polarizers and retarders. Currently, single crystal ingots are grown by the floating zone method or Bernoulli method. There is. When a single crystal is grown by the floating zone method, the single crystal grows in the optical axis <001> direction. Then, when this rutile single crystal ingot is processed into an optical component, the rutile single crystal ingot is cut into a predetermined shape and polished based on the optical axis <001>. An example of this shape is shown in FIGS.

FIG. 1A shows an example of processing into a parallel plate type. The optical axis <001> is set parallel to the processed surface, and both optical surfaces (light input / output surfaces) 10 are mirror-polished. 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 optical surfaces facing each other are deviated 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. Note that, in FIG. 1, the optical axis is shown by a dashed arrow.

In the prior art, since the optical axis <001> only needs to be in the optical surface, the azimuths of these optical surfaces have been selected arbitrarily (freely). In general, a single crystal ingot was cut so that as many optical components as desired could be cut out, and the optical surfaces of the cut single crystal chips were lined up 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 chippings frequently occur at an edge portion at the time of cutting may occur. Further, when a large number of single crystal chips are arrayed and polished, there is a problem in that the amount of polishing becomes uneven and processing cannot be performed accurately, and that correction (reprocessing) takes a lot of time and labor. Therefore, the manufacturing efficiency is low, and it may become a defective product because it becomes thinner than the desired thickness due to polishing for correction, and the yield is high even though as many single crystal chips as possible are cut from the single crystal ingot. It had the drawback of being bad.

An object of the present invention is to prevent the appearance of defects such as cracks and chippings from occurring when a single crystal chip is cut out from a single crystal ingot, and when a large number of single crystal chips are collectively mirror-polished on a lapping machine. In addition, it is to provide a method capable of uniformly and accurately and efficiently processing.

[0007]

The present invention provides an optical axis <00.
1> is a method of manufacturing a rutile single crystal optical component in which the surface 1> is parallel to the processed surface. Here, a feature of the present invention is that a rutile single crystal ingot is sliced so as to intersect the optical surface <001> to form a wafer, and the optical surface from the wafer is (11
A large number of single crystal chips are cut out so as to form the (0) plane, and all the cut single crystal chips are attached with the (110) planes aligned and fixed on a surface plate, and are collectively polished to a mirror surface. .

When manufacturing a rutile single crystal optical component whose optical axis <001> is parallel to the machined surface, it is possible to machine in various azimuth planes. A typical machined surface is (100)
The surface may be a surface or a (110) surface, but it may be a surface inclined between them. However, when a single crystal chip was actually cut out from an ingot of a rutile single crystal with various azimuth planes by using an inner peripheral blade (diamond cutter), it was found that cracks and chippings were significantly different depending on the azimuth planes. Further, it was also found that the polishing rate differs depending on the azimuth plane. The reason why the conventional technique cannot perform polishing accurately and efficiently is that the single crystal chips cut out without considering the azimuth plane are attached to a surface plate and mirror-polished. It is thought that this is because it rotates in an inclined state due to the difference from the surface. The present invention has been made based on the 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 suppressed to be much smaller than when 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 easily scraped. Therefore, if all the cut single crystal chips are aligned and fixed on the polishing surface plate with all (110) faces aligned and polished to a mirror surface in a batch, 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, machining with high dimensional accuracy can be performed. Incidentally, in the polishing process, when the orientations of the arrayed single crystal chips are not uniform, the polishing rate is different for each single crystal chip, so that some are easily polished and some are difficult to be polished and tilt. The polishing adjustment is extremely difficult because, for example, a defective shape 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
It grows in the 1> direction and a large ingot is obtained. FIG.
When manufacturing a parallel plate type optical component as shown in A of FIG. 2, as shown in A of FIG. 2, the ingot 20 is sliced perpendicularly to the optical axis <001> to cut out the wafer 22 (cut surface 1a). ). A single crystal chip 24 is cut out from the wafer 22 so that a (110) plane appears vertically and horizontally with respect to a wafer cutting plane, that is, a (001) plane (cutting planes 1b, 1
c). Then, a large number of the cut single crystal chips 24 are
All (110) faces (cutting faces 1b) are aligned and attached, arrayed and fixed on a surface plate, and collectively polished to a mirror surface. This mirror-polishing is performed on both surfaces facing each other, and a parallel plate type optical component having them as optical surfaces (incoming / outgoing surfaces) is obtained.

When manufacturing a wedge type optical component as shown in FIG. 1B, as shown in FIG. 2B, an ingot 2 is produced.
The wafer 23 is cut out by slicing 0 at an angle of 22.5 ° with respect to the optical axis <001> (cutting surface 2a). The wafer 23 is cut so that a (110) plane appears perpendicular to the wafer cut surface (cut surface 2b), and further cut perpendicularly to the cut surfaces 2a and 2b to cut out a single crystal chip 25 (cut surface 2
c). Then, one surface of the (110) surface (cut surface 2b) is obliquely polished (angle of about 4 °) to be shaped like a wedge. All of the wedge-shaped single crystal chips are (110) planes (cut planes)
2b) are aligned and attached, fixed in an array on a surface plate, and polished to a mirror surface all together. This mirror-polishing is performed on both opposite surfaces. As a result, a wedge-shaped optical component having those surfaces as optical surfaces (entrance / emission surfaces) can be obtained.

The cutting process 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. It was possible to cut out the single crystal chips 24 and 25 without chipping. Adopting such a cutting order is (10
This is because the (0) plane is harder than the (110) plane, and if the cut surfaces 1a and 2a are later cut, cracks and chippings frequently occur at the edges. In addition, the mirror-polishing of the cut surfaces 1b and 2b allowed the polishing amount to be uniform and the polishing to be performed accurately.

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

[0014]

[Table 1]

As can be seen from Table 1, the rutile single crystal has anisotropy in hardness depending on the plane orientation, and it is understood that the (100) plane is harder to grind than the (110) plane. That is,
The (100) plane is the hardest, and from the (100) plane to (110)
It becomes softer as it is tilted in the plane direction, (11
0) The surface becomes the softest. A softer surface is easier to polish, and a harder surface is more likely to be scratched during polishing. From this, it is understood that it is most preferable to use the (110) surface as the optical surface.

Further, as shown in FIG. 4, three rutile single crystal chips 32a having the (100) face up are provided in a half region of the ceramic surface plate 30, and the remaining half region is (110).
Three rutile single crystal chips 32b with their faces up were attached in a regular hexagonal shape and polished under the same conditions as above. Table 2 shows the measurement results of the height after performing the polishing process four times.
Shown in As shown in Table 1, hardness is anisotropic depending on the plane orientation, and the (100) plane is harder to grind than the (110) plane. Therefore, rutile single crystal chips with different plane orientations are attached to the same ceramic surface plate. If it is attached and polished, the height will be different and it will be greatly inclined as the polishing progresses.

[0017]

[Table 2]

Therefore, in this state, the dimensional accuracy of all rutile single crystal chips cannot be obtained. In order to correct this, it becomes necessary to apply an unbalanced load and perform re-polishing. However, it is very difficult and extremely difficult to rework by applying an unbalanced load to obtain an appropriate size. Over the course of re-machining many times, too much of the planned size may occur. By aligning the soft (110) faces and performing mirror polishing, it is possible to perform processing uniformly and efficiently without tilting.

FIG. 5 and Table 3 show the case where the inner peripheral blade (diamond cutter) cuts so that the (100) plane appears perpendicularly from the (110) plane and the case where the (110) plane appears perpendicularly from the (100) plane. The results are obtained by observing and measuring the chipping amount for the (100) cut surface and the (110) cut surface in the case of cutting in this way. In FIG. 5A, the cut surface is (1
FIG. 5B shows the chipping state in the case of the (00) plane, and FIG. 5B shows the chipping state in the case of the cut plane being the (110) plane.

[0020]

[Table 3]

From Table 3, when the cut surface is the (100) surface, the chipping amount is about 1/3 at the maximum value and about half the average value when the cut surface is the (110) surface. It can be seen that it can be reduced. It is considered that this is because, as can be seen from the results in Table 1, the (100) plane is harder than the (110) plane, and thus when the hard (100) plane is cut, cracks and chippings are likely to occur at the edges. When the single crystal chip is cut out, the optical surface is the (110) plane, and the soft (110) plane is cut later to obtain a single crystal chip with good appearance and less chipping, and the yield is improved accordingly. Also, the amount of polishing is small.

[0022]

INDUSTRIAL APPLICABILITY According to the present invention, in consideration of the hardness anisotropy of each azimuth plane of rutile single crystal, single crystal chips with few cracks and chippings can be cut out, and when a large number of them are mirror-polished at one time, It becomes easy to polish, and by doing so, it is possible to efficiently manufacture an optical component having a good appearance and high dimensional accuracy.

[Brief description of drawings]

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

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

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

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

FIG. 5 is an explanatory view of a cut 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)

[Claims] 1. A method for manufacturing a rutile single crystal optical component in which an optical axis <001> is parallel to a processed surface, a single crystal ingot is sliced so as to intersect with the optical axis <001>, and a wafer is prepared from the wafer. A large number of single crystal chips are cut out so that the optical surface becomes the (110) plane, and all the cut single crystal chips are attached with the (110) plane aligned and fixed on a surface plate, and polished into a mirror surface at once. A method of manufacturing an optical component made of a rutile single crystal, comprising: 2. A method for manufacturing a parallel plate type rutile single crystal optical component, wherein a single crystal ingot is provided with an optical axis <001>.
2. The manufacturing method according to claim 1, wherein a single crystal chip is cut by slicing perpendicularly to a wafer to obtain a wafer, and cutting so that (110) planes appear vertically and horizontally with respect to the wafer cut surface. 3. A method for manufacturing a wedge-shaped rutile single crystal optical component, wherein a single crystal ingot is 22.5 mm with respect to an optical axis.
A wafer is obtained by slicing with a tilt, and cut so that the (110) plane appears parallel to the wafer cut surface and also cut perpendicularly to both the wafer cut surface and the (110) cut surface. The manufacturing method according to claim 1, wherein a single crystal chip is cut out by cutting, and one (110) cut surface is obliquely ground to form a wedge shape.