JP5033386B2 - Method for producing artificial quartz and artificial quartz - Google Patents

Description

  The present invention relates to an artificial quartz having a small foreign matter density and a method for producing the same.

Artificial quartz used as a material for optical elements and crystal units is grown by depositing natural quartz dissolved in a growing solution such as sodium hydroxide in a pressure vessel called an autoclave (metal tower furnace). Manufactured by hydrothermal synthesis. However, while the growth of artificial quartz proceeds in the autoclave, iron (Fe) eluted from the autoclave main body (made of special steel), sodium (Na) in the growth solution, and silicon (Si) as a raw material for artificial quartz A foreign substance such as acumite (NaFeSi ₂ O ₆ ) is also generated by bonding or the like, and a phenomenon that these foreign substances are taken into the artificial quartz crystal being grown is observed.

（表１）異物密度（１ｃｍ^３あたりの個数最大値）の等級とその一般的な用途
Regarding the content of foreign matter in artificial quartz, for example, in JIS C6704 (2005 edition), as shown in (Table 1), the grade of artificial quartz is determined by the size and number of foreign matters contained in 1 cm ³ of artificial quartz. ing.

(Table 1) Grade of foreign matter density (maximum number per 1 cm ³ ) and its general use

  As shown in (Table 1), the artificial quartz grown in the autoclave is properly used for optics such as an optical element and various quartz resonators according to the foreign matter density grade. However, since foreign matter such as alumite is inevitably generated in the autoclave, it is difficult to control the amount of foreign matter generated by adjusting the conditions of hydrothermal synthesis, etc. It was difficult to make them separately.

  For this reason, in the past, artificial quartz crystals were manufactured and then inspected, and artificial quartz crystals were classified into grades based on the density of foreign substances contained therein. It was. In this regard, Patent Document 1 discloses a technique for reducing the density of foreign matter in an artificial quartz crystal by adjusting a seed crystal arrangement method in the autoclave.

Prior to explaining the technique of Patent Document 1, a conventional arrangement method of seed crystals will be briefly described. A plate-shaped (or rod-shaped) seed crystal 1a has a multi-stage configuration installed in an autoclave 2 as shown in FIG. The artificial crystal is grown on the front surface and the back surface toward this figure. Figure 6 is a an enlarged part of the suspension has been the support 23 of the seed crystal 1a shows the state as viewed from the X ₁ direction in FIG. Each seed crystal 1a is fixed on the upper and lower sides of a support frame 23a horizontally mounted between support rods 23b constituting the support 23 by clasps 23c such as a wire, and a surface on which an artificial crystal is grown (hereinafter referred to as a crystal). , a base that growth surface) and the gravitational direction (Y ₁ direction in the drawing) is disposed on the support member 23 so as to be parallel.

In contrast to such a conventional method, in Patent Document 1, as shown in FIG. 7, the basic growth surface of the seed crystal 1 a is tilted in a range of 45 ° to 90 ° with respect to the direction of gravity. The technique of arrangement is described (FIG. 7 (a) shows a state in which the basic growth surface is inclined by 45 °, and FIG. 7 (b) shows a state in which the basic growth surface is inclined by 90 °). By arranging the seed crystal 1a in an inclined state in this way, the foreign matter generated in the autoclave 2 is deposited on the upper basic growth surface of the inclined seed crystal 1a, and the seed crystal 1a is in the lower basic growth surface. As an umbrella. As a result, since the artificial quartz crystal can be grown on the lower basic growth surface without taking in the foreign matter, it is possible to manufacture an artificial quartz with a low foreign matter density.
Japanese Examined Patent Publication No. 57-49520: page 2, column 4, line 41 to page 3, column 5, line 16

  However, when the seed crystal 1a is greatly inclined as described in Patent Document 1, the convection of the growing solution flowing in the autoclave greatly meanders as shown by the broken lines in FIGS. 7 (a) and 7 (b). End up. The artificial quartz grown in such a turbulent convection has a hollow portion called a so-called “su” or is not grown into an artificial quartz having a desired size. It becomes a factor to reduce the yield.

  Further, as shown in the schematic diagram of FIG. 8 (a), when the seed crystals 1a arranged in the autoclave 2 in a row are tilted greatly, the seed crystals 1a at both ends of the row are shown in FIG. 8 (b). Will protrude from the support 23 or come into contact with the autoclave main body 21, so that the seed crystal 1a will not be placed there as shown by the broken line in the figure. Further, as shown in FIG. 8 (a), the distance between the seed crystals 1a is set to L, and an area where the artificial crystal is grown is secured. If the seed crystal 1a is tilted at the same position, the distance between the seed crystals 1a is increased. The distance L ′ (= L cos θ) is shorter than the original distance L. For this reason, in order to secure the growth region of the artificial quartz crystal, it is necessary to reduce the number of seed crystals 1a included in one row and arrange it so that the original distance L can be secured. As described above, when the seed crystal 1a is arranged with a large inclination, there is a problem in that the amount of artificial quartz that can be manufactured in one growth is reduced, resulting in inefficiency.

  The present invention has been made in view of such circumstances, and an artificial quartz crystal manufacturing method capable of efficiently manufacturing a high-quality artificial quartz crystal having a low foreign matter density and an artificial quartz crystal manufactured by this method. It is intended to provide.

The method for producing an artificial quartz crystal according to the present invention is a method for producing an artificial quartz crystal in which an artificial quartz crystal is grown by a hydrothermal synthesis method on a plate-like or rod-like seed quartz placed on a support in an autoclave.
The seed crystal is arranged on the support in a state where its basic growth surface is inclined in a range of 3.5 ° to 16 ° with respect to the direction of gravity.
In particular, the seed crystal is preferably arranged on the support in a state where the basic growth surface is inclined in a range of 5 ° to 16 ° with respect to the direction of gravity.

According to the present invention, since the basic growth surface of the seed crystal is disposed in the autoclave in a state where it is inclined within the range of 3.5 ° to 16 ° with respect to the direction of gravity, the seed crystal grows on the lower side of the inclined seed crystal. It is possible to prevent foreign matter generated in the autoclave from being taken into the artificial quartz crystal. As a result, it is possible to manufacture an artificial quartz with a small foreign matter density.
In addition, since the angle at which the seed crystal is tilted is significantly smaller than the conventional one, it is possible to suppress turbulence in the convection of the growth solution in the autoclave. As a result, it is possible to suppress a product defect (such as formation of a hollow portion formed in an artificial quartz crystal or insufficient size) caused by disturbance of convection, and the yield of products is improved.
Furthermore, since the tilt angle is small, the above-described various effects can be obtained without significantly reducing the number of seed crystals that can be arranged in the autoclave.

First, the configuration of the autoclave 2 used in the present embodiment will be described with reference to FIG. FIG. 1 is a longitudinal sectional view showing an outline of an autoclave 2 for growing an artificial crystal by a hydrothermal synthesis method. The autoclave 2 includes an autoclave main body 21 that is a special steel cylindrical container, a metal lid 25 for sealing the autoclave main body 21, and a heater 24 for heating the autoclave main body 21. Incidentally, the orthogonal axes shown in FIG. _{(X 1, Y 1, Z} 1) indicates the direction which is installed in the autoclave 2. Autoclave 2, the central axis of the autoclave body 21 is disposed so as to be perpendicular (Y ₁ axial direction) with respect to the installation surface having a cylindrical shape.

  The space inside the autoclave main body 21 is partitioned into an upper space 21 a and a lower space 21 b by a baffle plate (convection control plate) 22. In the upper space 21a, a support 23 for placing a large number of seed crystals 1a is installed. The support 23 has, for example, a structure in which flat cylindrical frames are stacked in multiple stages, and has a size that can be accommodated in the upper space 21a. A large number of seed crystals 1a can be arranged on each stage frame based on the rules described later.

  On the other hand, for example, a cylindrical basket-shaped laska container 26 is disposed in the lower space 21b, and the laska (debris crystal) 10 that is a raw material for artificial quartz is stored in the laska container 26. The upper space 21a and the lower space 21b are communicated with each other through a plurality of through holes 22a provided in the baffle plate 22, and fill the space in the autoclave main body 21 (both the upper space 21a and the lower space 21b). The growing solution 11 such as a sodium hydroxide solution thus made can be convected between the upper space 21a and the lower space 21b.

The heater 24 is configured to heat the inside of the upper space 21a from the top to the bottom, for example, at a temperature of 300 to 350 ° C., and similarly to heat the inside of the lower space 21b, for example, at a temperature of 360 to 400 ° C. In addition, the metal lid 25 is provided with a pressure gauge 27 for measuring the pressure in the autoclave main body 21. During the growth of artificial quartz, the autoclave main body 21 has, for example, about 1,000 to 1,500 kgf / cm ^2. It is designed to maintain the pressure of.

Next, the seed crystal 1a will be described. As shown in the perspective view of FIG. 2, for example, the seed crystal 1a is obtained by cutting a quartz crystal along the crystal axes (X, Y, Z axes), the X axis direction is the width direction, the Y axis direction is the longitudinal direction, and the Z axis It is comprised as a flat plate material (or square bar material) which makes a direction the thickness direction. The growth speed of the artificial quartz crystal varies depending on the axial direction, and in the X-axis direction, the Y-axis direction, and the Z-axis direction, the maximum speed is obtained in the Z-axis direction. Artificial quartz is grown relatively quickly on a flat surface (basic growth surface). In addition, in order to distinguish from the installation direction of the autoclave 2 shown in FIG. 1, the X, Y, and Z crystal axis directions of the seed crystal 1a are written as X ₂ , Y ₂ , and Z ₂ , respectively. To explain.

  Next, the support 23 for arranging the seed crystal 1a based on a predetermined rule will be described. As a result of advancing research on the problems described in the background art, the inventors have found that the seed crystal 1a can be obtained even if the inclination of the basic surface of the seed crystal 1a is significantly reduced as compared with the technique described in Patent Document 1. It has been found that the foreign matter density of the artificial quartz grown on the lower side can be reduced. The support 23 according to the present embodiment is configured to reduce the foreign matter density of the artificial quartz grown on the lower side of the seed quartz 1a based on the results of such research. The specific contents will be described below.

3 (a) is a view on an enlarged scale a state of arranging the seed crystal 1a to support 23 for one stage from Z ₁ direction, FIG. 3 (b), also X ₁ direction and the arrangement It is the figure seen from. As shown in FIG. 3A, a large number of support frames 23a are horizontally mounted on the support rods 23b constituting the frame of each stage of the support tool 23. On the other hand, a plurality of through-holes 1b are formed in the upper and lower sides of the XY plane (basic growth surface) of the various quartz crystals 1a. For example, a clasp 23c such as a wire is passed through the through-hole 1b and then the support frame. The seed crystal 1a can be suspended from the support frame 23a above the support 23 by being wound around 23a.

Also, the lower side of the seed crystal 1a is fixed to the support frame 23a on the lower side of the support 23 by a clasp 23c in the same manner as the upper side. In the present embodiment, as shown in FIG. 3B, the seed crystal 1a wraps the clasp 23c around the support frame 23a at a position shifted from the vertically lower side of the support frame 23a on which the seed crystal 1a is suspended. the basic growth surface of the seed crystal 1a is fixed in an inclined state with respect to the direction of gravity (Y ₁ direction). The inclination θ of the basic growth surface with respect to the direction of gravity can be adjusted by changing the position of the support frame 23a around which the lower clasp 23c is wound, the length of the clasp 23c, and the like.

  Here, the relationship between the inclination θ of the basic growth surface of the seed crystal 1a and the foreign substance density of the artificial crystal grown on the lower side of the seed crystal 1a will be described. According to preliminary experiments conducted by the inventors, an artificial quartz having a foreign matter density smaller than that of grade I defined in JIS C6704 (2005 edition) is assumed when the inclination of the basic growth surface is “θ ≧ 3.5 °”. It has been confirmed that it can be trained. Furthermore, when “θ ≧ 5 °” is satisfied, it has been confirmed that an artificial quartz having a foreign substance density smaller than that of class Ia can be grown. Therefore, it has been found that artificial quartz crystals of different grades can be manufactured and switched by switching the inclination of the basic growth surface between “3.5 ° ≦ θ ≦ 5 °” and “θ ≧ 5 °”.

  On the other hand, when the inclination θ of the basic growth surface is further increased by more than 5 °, the number of seed crystals 1a that can be arranged decreases for the reason described with reference to FIG. 8 in the background art. End up. As a result of investigations by the inventors, it has been confirmed that when “θ> 16 °”, the number of seed crystals 1a that can be arranged in the support 23 decreases. Based on the above experiments and examination results, in the present embodiment, when manufacturing a grade I artificial crystal, the inclination θ of the basic growth surface with respect to the direction of gravity is set to, for example, “3.5 ° ≦ θ ≦ 5 °”. For example, “θ = 4 °” within the range, and when it is desired to manufacture a class Ia artificial crystal, for example, “θ = 7 °” within the range of “5 ° ≦ θ ≦ 16 °” can be set. It has become.

Next, the operation of this embodiment will be described. When the growth solution 11 is filled in the autoclave main body 21 in which a large number of seed crystals 1 a are arranged on the support 23 and heated by the heater 24, the Lasca 10 in the Lasca container 26 is dissolved in the growth solution 11. The growing solution 11 in which the laska 10 is dissolved rises to the upper space 21a by generating convection due to the temperature gradient formed in the upper space 21a and the lower space 21b. Since the temperature of the upper space 21a is set lower than that of the lower space 21b, the growth solution 11 becomes supersaturated due to the temperature decrease, and SiO ₂ molecules are precipitated mainly on the basic growth surface of the various quartz crystals 1a. it can. As a result, the artificial quartz crystal is grown in the directions of “+ Z ₂ ” and “−Z ₂ ” shown in FIG.

  On the other hand, fine particles such as alumite produced by the reaction of iron dissolved from the autoclave main body 21 with sodium or silicon in the growth solution 11 are suspended in the growth solution 11. These fine particles ride on the convection of the growing solution 11 and are transported to the vicinity of the seed crystal 1a, and a part thereof is taken into the artificial quartz crystal being grown and becomes a foreign substance (also referred to as inclusion) in the artificial quartz crystal.

Here, in this embodiment, since the basic growth surface of the seed crystal 1a is inclined with respect to the direction of gravity as described above, the fine particles transported in the vicinity of the artificial quartz crystal being grown are not Due to the influence, it is deposited on the basic growth surface on the “−Z ₂ ” side (upper side) shown in FIG. On the other hand, the basic growth surface on the “+ Z ₂ ” side (downward side) is in a state where the seed crystal 1 a itself becomes an umbrella and the above-mentioned fine particles are difficult to adhere. As a result, the artificial quartz manufactured by the manufacturing method according to the present embodiment has a large amount of foreign matter in the upper artificial quartz crystal 12b as shown in FIG. It is an artificial crystal with different foreign substance density depending on the growth direction.

  In addition, since the angle at which the seed crystal 1a is tilted is significantly smaller than that of the prior art, there is no significant disturbance in the convection of the growth solution 11 as shown in FIG. For this reason, there is no formation of a cavity, and an artificial quartz crystal having a desired size is manufactured.

  The artificial quartz manufactured by the above-described method is taken out from the autoclave and then separated into a lower artificial quartz 12a and an upper artificial quartz 12b by dicing or the like. Since the artificial quartz crystal 12a on the lower side is an artificial quartz crystal 12a of a grade corresponding to the magnitude of the inclination of the seed quartz crystal 1a, the foreign matter density can be used according to the grade only by performing a representative inspection for confirmation. It can be shipped as an artificial crystal 12a. On the other hand, with respect to the artificial quartz 12b on the upper side, the foreign matter density is inspected for each artificial quartz crystal 12b as before, sorted to a grade according to the foreign matter density, and shipped according to use.

  According to the present embodiment, there are the following effects. The seed crystal 1a for growing the artificial crystal is arranged in the autoclave main body 21 in a state where the basic growth surface is inclined in the range of 3.5 ° to 16 ° with respect to the direction of gravity. It is possible to prevent foreign matter generated in the autoclave main body 21 from being taken into the artificial quartz crystal 12a growing on the lower side. As a result, it is possible to manufacture the artificial quartz crystal 12a having a small foreign matter density and a grade corresponding to the inclination of the seed crystal 1a.

  In addition, since the angle at which the seed crystal 1a is tilted is significantly smaller than the conventional one, it is possible to suppress the convective disturbance of the growth solution 11 in the autoclave main body 21. As a result, product defects (such as cavities formed in artificial quartz and insufficient size) that are likely to occur due to convective disturbances can be suppressed, and the yield of products is improved. Furthermore, since the angle at which the seed crystal 1a is tilted is small, the above-described various effects can be obtained without dropping the number of seed crystals 1a that can be arranged in the autoclave main body 21.

  In addition, the manufacturing method of the artificial quartz crystal which concerns on this invention is not limited to what was illustrated to embodiment. For example, the seed crystal 1a may be arranged at different angles for each stage of the same support 23, so that different grades of artificial crystal 12a can be made separately by one growth. Further, for example, a metal shielding plate may be attached to the basic growth surface on the upper side of the seed crystal 1a so as to grow only an artificial crystal having a low foreign matter density without growing an artificial crystal having a high foreign matter density. .

  In the present embodiment, the case of using a so-called Z-cut crystal seed 1a for growing an artificial crystal on the XY plane has been described, but the cutting direction of the crystal seed 1a and the direction for growing the artificial crystal are examples of this. It is not limited to. For example, crystal seeds that grow artificial crystals in any direction, such as X-cuts that grow artificial crystals on the Y-Z plane, or r-cuts that rotate the Z-cut 52 degrees clockwise around the X axis The present invention can also be applied.

(Experiment 1)
The artificial quartz crystal was grown by changing the inclination angle of the basic growth surface of the seed crystal 1a, and the foreign matter density of the artificial quartz crystal 12a on the lower side was measured.

A. Experimental Method The seed crystal 1a was placed in an autoclave set under the same conditions as the autoclave 2 shown in the embodiment, and the artificial crystal was grown by changing the inclination of the basic growth surface. The artificial quartz crystal 12a grown on the lower side of the seed crystal 1a was sampled, and the density of foreign matter contained therein was measured.
(Example 1) An artificial quartz crystal was grown with the inclination of the seed crystal 1a set to 3.5 °.
(Example 2) An artificial quartz crystal was grown with the inclination of the seed crystal 1a set to 5 °.
(Example 3) An artificial quartz crystal was grown with the inclination of the seed crystal 1a set to 6.7 °.
(Example 4) An artificial quartz crystal was grown with the inclination of the seed crystal 1a set to 13.5 °.
(Comparative Example) An artificial quartz crystal was grown without tilting the seed crystal 1a (tilt angle 0 °). When the seed crystal 1a is not tilted, the artificial quartz grown has no distinction between the upper side and the lower side, so the artificial quartz grown on an arbitrary basic growth surface was sampled.

（表２）実験により得られた人工水晶の異物密度とその等級
B. The experimental results (Table 2) show the number (foreign material density) for each size of the foreign matter contained in 1 cm ^{3 of} the artificial quartz obtained as a result of the experiment, the total value thereof, and the grade of the grown artificial quartz. Yes. FIG. 5 shows the result of plotting the total value of the foreign substance density of each experimental result on the graph with respect to the inclination of the seed crystal 1a.

(Table 2) Contaminant density and grade of artificial quartz obtained by experiment

  According to the experimental results, in all the experimental results of (Example 1) to (Example 4) in which the basic growth surface of the seed crystal 1a is tilted by 3.5 ° or more with respect to the direction of gravity, JIS C6704 (2005 version) As a result, an artificial quartz having a foreign matter density smaller than that of the grade I defined in the above was obtained. In particular, in the three experimental results (Example 2) to (Example 4) in which the seed crystal 1a is tilted by 5 ° or more, no foreign matter having a size of 10 μm or more was confirmed, and a high-quality artificial quartz exceeding the grade Ia Could get. Moreover, the hollow part like "su" was not observed from the artificial quartz obtained in each Example.

In the case where the seed crystal 1a was not tilted with respect to these results (comparative example), all the experimental results of (Example 1) to (Example 4) were obtained although the obtained artificial quartz satisfied the grade I. The density of foreign matter was the highest compared to
From the above results, it was confirmed that a high-quality artificial quartz having a small foreign substance density and having no hollow portion can be produced simply by tilting the basic growth surface of the seed crystal 1a by at least 3 °, more preferably about 5 °.

(Simulation 1)
The number of seed crystals 1a that can be placed in the autoclave 2 having a predetermined capacity was calculated by changing the inclination angle of the seed crystals 1a.

A. Prerequisites
A seed crystal 1a was placed in an autoclave 2 having a diameter of 65 cm and a depth of 14 m, and the number of crystal seeds 1a that could be arranged therein was calculated.
(Reference example) The number of sheets that can be arranged without tilting the seed crystal 1a was calculated.
(Example 2-1) The number of sheets that can be arranged was calculated by setting the inclination of the seed crystal 1a to 13 °.
(Example 2-2) The number of sheets that can be arranged was calculated by setting the inclination of the seed crystal 1a to 16 °.
(Comparative Example 2-1) The number of sheets that can be arranged was calculated by setting the inclination of the seed crystal 1a to 20 °.

（表３）種子水晶の傾きに応じて配置可能な種子水晶の枚数
B. The simulation results (Table 3) show the number of crystal seeds 1a that can be placed in the autoclave 2 obtained as a result of the simulation.

(Table 3) Number of seed crystals that can be arranged according to the inclination of the seed crystals

  According to the simulation results, 1,350 seed crystals 1a could be arranged in the autoclave 2 without tilting the seed crystals 1a (reference example). In addition, when the seed crystal 1a is tilted by 13 ° (Example 2-1) and when the seed crystal 1a is tilted by 16 ° (Example 2-2), the seed crystal 1a that can be placed in the autoclave 2 having the same capacity is 1 , 200. On the other hand, in the case where the seed crystal 1a is tilted by 20 ° (Comparative Example 2-1), the number becomes 1,050, and the number of sheets that can be placed is reduced by 22.2% compared to the (Reference Example). have done.

It is sectional drawing of the autoclave for growing an artificial quartz by the hydrothermal synthesis method. It is a perspective view of a seed crystal used for cultivation of artificial quartz. It is explanatory drawing which showed the rule which arrange | positions a seed crystal in the said autoclave. It is explanatory drawing which shows the characteristic of the artificial quartz manufactured by the manufacturing method which concerns on embodiment. It is a characteristic view for demonstrating the characteristic of the artificial quartz crystal which concerns on an Example. It is explanatory drawing regarding the general arrangement | positioning method at the time of arrange | positioning a seed crystal in an autoclave. It is explanatory drawing regarding the prior art which improved the said general arrangement | positioning method. It is explanatory drawing which shows the problem at the time of arrange | positioning a seed crystal by the said prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a Seed crystal 1b Through-hole 10 Lasca 11 Growth solution 12a Lower artificial quartz crystal 12b Upper artificial quartz crystal 2 Autoclave 21 Autoclave main body 21a Upper space 21b Lower space 22 Baffle plate 22a Through-hole 23 Support tool 23a Support frame 23b Support rod 23c Clasp 24 Heater 25 Metal lid 26 Lasca container 27 Pressure gauge

Claims (2)

In a method for producing an artificial quartz crystal that grows an artificial quartz crystal by a hydrothermal synthesis method on a plate-like or rod-like seed quartz placed on a support in an autoclave,
The method for producing an artificial quartz crystal, wherein the seed crystal is arranged on the support in a state in which a basic growth surface is inclined in a range of 3.5 ° to 16 ° with respect to a direction of gravity.   2. The artificial quartz crystal according to claim 1, wherein the seed crystal is arranged on the support in a state where a basic growth surface is inclined in a range of 5 ° to 16 ° with respect to a direction of gravity. Production method.

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