JP3881391B2 - Manufacturing method of polarizing glass - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a polarizing glass used in a small optical isolator used in optical communication using a semiconductor laser and an optical fiber.
[0002]
[Prior art]
As a polarizer used for a small optical isolator, a small extinction ratio, a high extinction ratio and a low insertion loss are required at a wavelength of 1.31 μm or 1.55 μm, and polarizing glass is frequently used. As an example of such a polarizing glass, there is a copper-containing polarizing glass disclosed in JP-A-5-208844. This glass is prepared by (1) melting a copper halide-containing glass by a normal melting method, (2) heat treating the copper halide-containing glass to precipitate copper halide fine particles in the glass, and (3) By pulling or extruding the glass at a high temperature, the copper halide fine particles are elongated and (4) heat-treated in a reducing atmosphere. By this method, a polarizing glass containing metallic copper particles having an aspect ratio of 2: 1 to 15: 1 can be formed on the surface layer of the glass. This is a condition such that the absorption peak wavelength in the extinction direction of the glass is about 1.3 to 1.7 μm, and a high extinction ratio can be expected at a wavelength of 1.31 μm or 1.55 μm.
[0003]
[Problems to be solved by the invention]
In the field of such a small optical isolator, it is strongly desired to reduce the insertion loss of the polarizer. In order to reduce the insertion loss in the copper-containing polarizing glass, it is effective to reduce the scattering loss of the copper halide particles and the metal copper particles. It is desirable that the particle diameters of the copper halide particles and the metal copper particles contained in the polarizing glass are small. However, if the particle diameters of the copper halide particles and the metal copper particles are reduced, it is necessary to elongate smaller copper halide fine particles to make anisotropic particles during the production of polarizing glass. The insertion loss of the polarizing glass is desirably 0.06 dB or less, and for that purpose, the copper halide particles before elongation must have an average particle diameter of, for example, 100 nm or less. However, when the copper halide fine particles are made small, a large stress is required for elongation.
[0004]
The actual maximum stress that can be applied during the glass elongation process to obtain anisotropic particles is within the range where the glass is not damaged by the pulling and drawing methods, and the die (made of carbon or boron nitride) is worn by the extrusion method.・ Determine within the extent that damage occurs and is hated. For example, Japanese Patent Laid-Open No. 5-208844 describes an example (Example 6) in which a glass containing copper halide fine particles having a diameter of about 70 nm is stretched by a pulling method. However, stretching of the glass requires a load of 39.2 MPa ( 400 kgf / cm ² ) , and requires a load 1.5 to 2 times that of glass containing copper halide fine particles having a diameter exceeding 100 nm. Under such conditions, the glass is easily broken during stretching, and even if polarizing glass is obtained at the laboratory level, it is difficult to shift to actual production from the viewpoint of stable operation. That is, in order to reduce the insertion loss of the polarizer, it is desirable that the copper halide particles and / or metal copper particles contained in the polarizing glass have a smaller particle size. However, it has been difficult to stretch without causing problems such as breakage of glass containing copper halide fine particles having a particle diameter of 100 nm or less.
[0005]
Therefore, an object of the present invention is a method for stably producing a copper-containing polarizing glass with low insertion loss, and even glass containing copper halide fine particles having a smaller (100 nm or less) particle diameter does not damage the glass. It is providing the said manufacturing method including the process which can be extended | stretched.
[0006]
[Means for Solving the Problems]
The present inventors have made various studies in order to solve the above problems. As a result, as long as the concentration of copper halide contained in the glass is within a certain low range, even if the particle diameter of the copper halide fine particles contained in the glass is 100 nm or less, the glass can be easily broken. The present invention was completed by finding that a polarizing glass that can be stretched and has polarization characteristics equivalent to those of the conventional one and low insertion loss can be obtained. According to this method, it is possible to produce a polarizing glass without substantially causing breakage of the glass during stretching and abrasion / breakage of the extrusion die.
[0007]
That is, the present invention is a method for producing a polarizing glass in which metallic copper particles having shape anisotropy are oriented and dispersed in the glass, wherein the content of copper halide is expressed in wt%, A step of heat-treating a borosilicate glass having a SnO content of 0.01 to 0.12% that is 0.3 or more and less than 0.5% to precipitate copper halide in the glass was obtained. A step of heating the glass at a temperature corresponding to a viscosity of 1 × 10 ⁶ to 1 × 10 ¹¹ poise to elongate the copper halide particles in the glass, and one of the obtained copper halide particles in the glass The present invention relates to the above production method comprising a step of reducing a part or all of the metal and depositing metallic copper particles.
[0008]
The present invention will be described below. In the method for producing a polarizing glass of the present invention, a borosilicate glass having a copper halide content expressed by weight% of 0.3 or more and less than 0.5% is used. A borosilicate glass is suitable because it easily contains copper monovalently and easily precipitates copper halide particles by heat treatment. If the content of copper halide is less than 0.3%, copper halide particles cannot be precipitated by heat treatment. On the other hand, when the copper halide content is 0.5% or more, a larger force is required to stretch the glass containing the copper halide particles, which causes problems such as glass breakage and die wear.
[0009]
Said borosilicate glass, for example, and in _{weight%, SiO 2; 48~65%,} B 2 O 3; 13~33%, Al 2 O 3; 6~13%, AlF 3; 0~ 5%, R ₂ O (where R is an alkali metal); 0 to 5%, RCl; 0 to 5%, alkaline earth oxide; 0 to 5%, copper halide ; It may be a glass having a composition of less than 5%, SnO; 0.01 to 0.12%, As ₂ O ₃ ; 0 to 5%. Here, SnO is a reducing agent and has a function of making divalent copper monovalent. The amount obtaining pressurized in the range of 0.01 to 0.12% depending on the copper amount and dissolution schedule.
[0010]
In order to make a glass having the above composition, oxides, carbonates, hydroxides and halides can be used as raw materials. A glass batch based on the above composition is prepared, melted and cast, and then cooled to room temperature to obtain a desired glass. Next, the glass is cut into an appropriate size and subjected to heat treatment, whereby fine particles of copper halide particles can be precipitated in the glass. The heating temperature is suitably in the range of 650 ° C. to 750 ° C., for example. When the temperature is lower than 650 ° C., the precipitation time tends to be too long. When the temperature is higher than 750 ° C., the particles grow in a short time and the particle diameter tends to be difficult to control. By controlling the particle size to be small, the scattering loss of the obtained polarizing glass can be reduced. In order to make the insertion loss of the polarizing glass 0.06 dB or less, it is appropriate that the average particle diameter of the copper halide particles is 100 nm or less.
[0011]
Next, the glass is heated to a temperature corresponding to 1 × 10 ⁶ to 1 × 10 ¹¹ poise to stretch the copper halide particle-containing glass, and the copper halide particles in the glass are stretched. Although there is no restriction | limiting in particular in the extending | stretching method of glass, For example, the drawing method, the drawing method, and the extrusion method can be used. If the temperature at which the glass is stretched is too high, the elongated particles are liable to return to a spherical shape or split. If the temperature is too low, the glass tends to break. Moreover, since there exists the viscosity of the glass suitable according to the extending | stretching method of glass, it can extend | stretch in an appropriate viscosity range in consideration of these. For example, in the drawing method that can be stretched at high speed to thin glass, the low viscosity region (1 × 10 ⁶ to 1 × 10 ⁸ poise), and in the extrusion method that is not suitable for high speed molding, the high viscosity region (1 × 10 ^8). ~ 1 × 10 ¹¹ poise) is suitable.
[0012]
It is appropriate to stretch the glass so that the aspect ratio of the elongated copper halide particles in the glass is 3: 1 to 60: 1. Thereby, metallic copper particles having an aspect ratio of 2: 1 to 16: 1 can be deposited in the reduction step. In order to give polarization characteristics in the near infrared, it is preferable to contain metallic copper particles having an aspect ratio in the above range.
[0013]
Next, some or all of the copper halide particles in the obtained glass are reduced to precipitate metal copper particles. In order to provide sufficient polarization characteristics, at least a part of the copper halide particles is reduced to metallic copper. The reduction of the copper halide particles can be performed using a known method. For example, it is appropriate to perform the reduction for 30 minutes to 10 hours at a temperature in the range of 350 to 550 ° C., preferably 375 to 475 ° C. under the same conditions as described in JP-A-5-208844. If the temperature of the heat treatment is too low, it takes a long time to obtain sufficient polarization characteristics, and if it is too high, the elongated particles may return to a spherical shape or split. For the reduction, a reducing gas such as hydrogen gas can be appropriately used.
[0014]
【The invention's effect】
According to the production method of the present invention, even when a glass containing copper halide particles having a particle diameter of 100 nm or less is stretched, the absorption peak wavelength of the copper halide particles corresponds to 1.3 to 1.7 μm with a small stress. It can be stretched to a certain aspect ratio and can be stably stretched without glass breakage or die wear / breakage. Thereby, a copper-containing polarizing glass having a high extinction ratio and a low insertion loss can be stably provided at a low cost.
[0015]
【Example】
Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples.
Example 1
In _{wt%, SiO 2; 59.9%} , B 2 O 3; 20.5%, Al 2 O 3; 6.8%, AlF 3; 2.0%, Na 2 O; 9.8%, NaCl 1.0%, CuCl; 0.45%, SnO; 0.077%. SiO ₂ , H ₃ BO ₃ , Al (OH), AlF ₃ , Na ₂ CO ₃ , NaCl, CuCl, SnO, etc. were used as raw materials. These raw materials were put in a 5-liter platinum crucible and melted at about 1400 ° C., then poured into a mold and cooled to room temperature to obtain the glass. This glass was cut into an appropriate size, placed in an electric furnace, started to be heated, held at 735 ° C. for 1 hour, and then cut off and cooled. As a result of observation with a transmission electron microscope, it was confirmed that copper chloride particles having an average of about 93 nm were precipitated in the glass by this heat treatment. From this glass block, a plate glass of 2 × 20 × 220 mm was obtained by cutting and polishing, and this was used as a preform for drawing.
[0016]
FIG. 1 shows a schematic diagram of a drawing apparatus. In the figure, 1 is a preform, and the preform 1 is held by a feeding device 2 via a wire and is movable downward. The vicinity of the tip of the preform 1 is softened in the heating furnace 3 and drawn by the tension device 4 downward from the lower end of the preform 1. By drawing, a linear glass 5 in which elongated metal halide particles are dispersed is formed. The linear glass 5 drawn out of the heating furnace 3 is rapidly cooled by the outside air. A cylindrical hood 6 with a lid 7 is provided on the heating furnace 3.
[0017]
Next, the drawing procedure will be described. Attach the preform to the feeder and set it so that its tip is located slightly below the center of the furnace. The temperature rise is started and the temperature is maintained at 720 ° C. (corresponding to a viscosity of 5.9 × 10 ⁶ poise) and the preform tip is necked down. The necked-down glass is sandwiched between take-up rollers driven by a motor, and the take-up is started by rotating the rollers. By drawing at a feed speed of 10 mm / min and a take-up speed of 1 m / min, a glass having a cross section of about 0.2 × 2.0 mm was continuously obtained. From the value indicated by the load cell attached to the drawing device, the tension at this time was about 750 g. Therefore, by dividing the cross-sectional area of 0.2 × 2.0 mm, it is calculated to have been drawn in stress ^{18.4MPa (188kg f / cm 2)} .
[0018]
The tension was lower than that of Comparative Example 1 described later, and the drawing was performed stably without breakage of the glass. The drawn glass was cut to an appropriate length and heat-treated at 425 ° C. for 4 hours in a hydrogen atmosphere. The transmittance curve of the obtained glass is shown in FIG. A solid line indicates a case where polarized light in the transmission direction of the polarizing glass is incident, and a broken line indicates a case where polarized light in the extinction direction is incident. The absorption peak wavelength of this glass is. The extinction ratio was 1.5 dB and the insertion loss was 0.04 dB. However, the insertion loss is a value measured when AR coating for 1.55 μ is applied.
[0019]
Comparative Example 1
A glass having the same composition as the glass of Example 1 was used except that CuCl was 0.85% and SnO was 0.11%. The heat treatment for copper chloride precipitation was performed at 720 ° C. for 1 hour. As a result of observation with a transmission electron microscope, the average particle shape of the copper chloride particles in the glass by this heat treatment was about 91 nm. Drawing and hydrogen reduction were performed under the same conditions as in Example 1. As a result, the absorption peak wavelength of the obtained glass was 0.90 μ, the extinction ratio of 1.55 μ was less than 2 dB, and it was not practical as a polarizing glass.
[0020]
Comparative Example 2 The same glass composition, melting conditions, heat treatment conditions and reducing conditions as in Comparative Example 1 were used. In order to make the absorption peak wavelength near 1.5 μm, it is necessary to increase the stress, and the drawing conditions are as follows. That is, the wire was drawn at a temperature of 704 ° C. (corresponding to a viscosity of 1.1 × 10 ⁷ poise) at a feed speed of 10 mm / min and a take-up speed of 1 m / min. Tension at that time was 1.8kg (about in terms of stress ^{44.1MPa (450kg f / cm 2)} ). In this drawing, the glass broke in the middle and the drawing was interrupted. The breakage point was in the furnace, where the glass width was reduced to about 2 mm. The resulting glass was hydrogen reduced. As a result, the absorption peak wavelength was 1.54 μ, and the extinction ratio of 1.55 μ was 60 dB. Although the performance is sufficient, it was difficult to draw the wire over a long length without breakage under these conditions.
[0021]
Example 2
A glass having the same composition as that of the glass used in Example 1 was cut and placed in a mold having an inner diameter of 50 mm, followed by heat treatment at 735 ° C. for 1 hour. By this heat treatment, 93 nm copper chloride having a grain shape was precipitated. This is put into a portion sandwiched between a die and a punch of an extrusion device, held at 620 ° C. (equivalent to a viscosity of 7.2 × 10 ⁸ poise), and a load of 20 ton is applied to the glass through a punch (metal rod) with a hydraulic cylinder. The product was extruded from a die extrusion port to a 5 mm diameter rod. In order to prevent fusion with the glass at high temperature and high pressure, carbon with poor wettability was used for the die, but there was no damage although there was some wear due to this extrusion. The bar was cut to an appropriate length, and then the side surface was polished to obtain a 0.5 × 60 mm plate. This plate was subjected to hydrogen reduction under the same conditions as in Example 1. The transmittance curve of the obtained glass is shown in FIG. The absorption peak wavelength was 1.55 μ, and the extinction ratio of 1.55 μ was 56 dB. The insertion loss of the sample with the AR coat was 0.06 dB.
[0022]
Comparative Example 3
Using glass having the same composition as that used in Comparative Example 1, heat treatment was performed at 730 ° C. for 1 hour. The average particle size of the precipitated copper chloride was 100 nm. Next, the extrusion was performed according to the procedure shown in Example 2. The condition was a temperature of 620 ° C. and a load of 25 ton. Using this glass, cutting polishing and hydrogen reduction were performed under the same conditions as in Example 2. As a result, the absorption peak wavelength was 1.18 μm, and the extinction ratio of 1.55 μm was 10 dB. Despite increasing the extrusion load, the absorption peak wavelength was as short as 1.18 μm, and the performance was insufficient. On the other hand, the dies were worn very often, and after several runs, the dies often cracked.
As described above, in order to obtain a polarizing glass having the same performance as that of the present invention using a glass having a high copper chloride concentration, it is necessary to stretch with a larger stress. As a result, glass breakage in the wire drawing process and die wear / breakage in the extrusion process are inevitable.
[0023]
Example 3
wt%, SiO ₂ ; 56.0%, B ₂ O ₃ ; 17.5%, Al ₂ O ₃ ; 6.0%, AlF ₃ ; 4.0%, Na ₂ O; 10.0%, NaCl 2.0%, MgO; 3.0%, CuCl; 0.40%, SnO; 0.070%. SiO ₂ , H ₃ BO ₃ , Al (OH) ₃ , AlF ₃ , Na ₂ CO ₃ , NaCl, MgCl, MgCO ₃ , CuCl, SnO, etc. were used as raw materials. These raw materials were put in a 5-liter platinum crucible and melted at about 1400 ° C., then poured into a mold and cooled to room temperature to obtain the glass. The glass was cut into an appropriate size, held at 730 ° C. for 1 hour, then cut off and cooled.
[0024]
As a result of observation with a transmission electron microscope, the average particle diameter of the copper chloride particles in the glass by this heat treatment was about 85 nm. From this glass block, a plate glass of 2 × 20 × 220 mm was obtained by cutting and polishing, and this was used as a preform for drawing. Drawing was performed by the same drawing procedure as in Example 1. Holding at 725 ° C. (corresponding to a viscosity of 6.3 × 10 ⁶ poise) and drawing at a feeding speed of 10 mm / min and a take-up speed of 1 m / min, a glass having a cross-section of about 0.2 × 2.0 mm is obtained. Obtained continuously. Subsequently, hydrogen reduction was performed under the same conditions as in Example 1. The absorption peak wavelength of this glass was 1.45 μm, and the extinction ratio of 1.55 μm was 52 dB. The insertion loss of the sample with the AR coat was 0.04 dB.
[0025]
Example 4
_{59.9%, B 2 O 3;} ; SiO 2 in _{wt% 20.5%, Al 2 O} 3; 6.8%, AlF 3; 2.0%, Na 2 O; 9.8%, NaCl; A glass having a composition of 1.0%, CuCl; 0.34%, SnO; 0.058% was produced. As raw materials, SiO ₂ , H ₃ BO ₃ , Al (OH) ₃ , AlF ₃ , Na ₂ CO ₃ , NaCl, CuCl, SnO, etc. were used. These raw materials were placed in a 5-liter platinum crucible and dissolved at about 1400 ° C., then poured into a mold and cooled to room temperature. This glass was cut into an appropriate size, placed in an electric furnace, started to rise in temperature, held at 740 ° C. for 4 hours, then cut off and cooled. As a result of observation with a transmission electron microscope, it was confirmed that copper chloride particles having an average of about 86 nm were precipitated in the glass by this heat treatment. From this glass block, a plate glass of 2 × 20 × 220 mm was obtained by cutting and polishing, and this was used as a preform for drawing.
Drawing was performed by the same drawing procedure as in Example 1. A glass having a cross-section of about 0.2 × 2.0 mm by holding at 725 ° C. (corresponding to a viscosity of 6.3 × 10 ⁶ poise) and drawing at a take-up speed of 6 mm / min and a feed rate of 0.6 m / min. Was obtained continuously. Subsequently, hydrogen reduction was performed under the same conditions as in Example 1. However, the reduction time is 24 hours. The aspect ratio of the metal particles was about 4: 1. The absorption peak wavelength of this glass was 1.40 μm, and the extinction ratio of 1.55 μm was 50 dB. The insertion loss of the sample with the AR coat was 0.04 dB.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a drawing apparatus used in Examples. FIG. 2 is a spectral transmittance curve of a polarizing glass obtained in Example 1.
3 is a spectral transmittance curve of the polarizing glass obtained in Example 2. FIG.

Claims (5)

A method for producing a polarizing glass in which metallic copper particles having shape anisotropy are oriented and dispersed in glass, wherein the content of copper halide is expressed in terms of% by weight and is 0.3 or more and 0.00. The step of heat-treating a borosilicate glass having a SnO content of 0.01 to 0.12% and precipitating copper halide in the glass, and the resulting glass has a glass viscosity of less than 5% Heating at a temperature corresponding to 1 × 10 ⁶ to 1 × 10 ¹¹ poise to elongate the copper halide particles in the glass, and reducing part or all of the copper halide particles in the obtained glass And the step of depositing metallic copper particles. Salt-based borosilicate glass, and in _{weight%, SiO 2; 48~65%,} B 2 O 3; 13~33%, Al 2 O 3; 6~13%, AlF 3; 0~5%, R ₂ O (where R is an alkali metal); 0 to 5%, RCl; 0 to 5%, alkaline earth oxide; 0 to 5%, copper halide; 0.3 to less than 0.5% _{, SnO; 0.01~0.12%, As 2} O 3; the process of claim 1, further comprising 0-5% of the composition.  The production method according to claim 1 or 2, wherein copper halide particles having an average particle diameter of 50 to 100 nm are precipitated.  The manufacturing method according to any one of claims 1 to 3, wherein the copper halide particles are stretched by drawing, drawing, or extruding the glass. The manufacturing method according to claim 1, wherein the copper halide is copper chloride.

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