JP3260131B2 - Manufacturing method of polarizing glass - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a polarizing glass. More specifically, the present invention relates to a method for producing a polarizing glass having a small extinction ratio distribution in a plane. The polarizing glass is used as a polarizer for a small optical isolator used for optical communication and the like, an optical switch composed of a combination of a liquid crystal, an electro-optic crystal, a Faraday rotator, and the like, and an electromagnetic sensor.

[0002]

2. Description of the Related Art Glass containing dispersed and anisotropically fine metal particles having shape anisotropy, for example, silver particles and copper particles, has a resonance absorption peak wavelength of the metal which differs depending on the incident polarization direction. It is known to be a polarizer. It is also known that such a polarizing glass can be produced by reducing elongated glass containing copper halide particles or glass containing silver halide particles. For example,
A method for producing a polarizing glass from a glass containing copper halide particles is disclosed in JP-A-5-208844.
This method involves elongating the copper halide particles in the glass by pulling or extruding the glass containing the copper halide particles at a temperature at which the viscosity of the glass is in the range of 10 ⁸ to 10 ¹¹ poise, and then reducing the temperature in a reducing atmosphere. To reduce the copper halide particles by heat treatment to produce a polarizing glass containing elongated shape-anisotropic metallic copper particles.

Further, as an improved method of producing a polarizing glass containing the above-described shape-anisotropic metallic copper particles, there has been proposed a method of drawing glass containing metal halide particles (Japanese Patent Laid-Open No. 8-231241). Gazette). This method can prevent destruction or breakage of glass at the time of elongation and re-spheroidization of the elongated metal halide particles, and can obtain a high yield from the metal halide particle-containing glass as a raw material and a polarized light having high surface accuracy. It is for producing glass.

[0004]

The polarizing glass used as a component of the conventional optical isolator has a plane size of 1.4 to 1.7 mm square. By bonding such a polarizing glass to the crystal of the Faraday element, a non-reciprocal element for an optical isolator has been manufactured. Therefore, in the method for manufacturing a polarizing glass using the above-described drawing method, a preform (usually having a width of 20 mm) made of glass containing metal halide particles is drawn so as to have a width of 2 mm, and then a predetermined size is formed. To produce a polarizing glass. However, parts having the above dimensions are difficult to handle, and, for example, the work of bonding the polarizing glass and the crystal of the Faraday element is not easy.

On the other hand, recently, it has become possible to produce a relatively large crystal for a Faraday element.
It has become possible to obtain crystals for Faraday elements having a size of about mm square. A non-reciprocal element for an optical isolator can be manufactured by adhering a polarizing glass having the same size as a crystal for a Faraday element having a size of about 10 mm square and cutting the glass to a desired size, thereby improving work efficiency.
However, it has been found that when a polarizing glass having a width of 10 mm is to be manufactured by a conventional drawing method, a distribution occurs in the extinction ratio in a plane (in the width direction), and a new problem occurs in that the product yield is reduced.

Accordingly, an object of the present invention is to provide a method for manufacturing a polarizing glass by a drawing method, which manufactures a polarizing glass having a relatively wide width and a relatively constant extinction ratio distribution in a plane (width direction). It is to provide a method.

[0007]

SUMMARY OF THE INVENTION The present invention is a method for producing a polarizing glass in which metal particles having shape anisotropy are oriented and dispersed in glass, wherein the metal halide particles are dispersed. Process of drawing glass preform
(However, the drawing is performed so that the ratio of the width of the glass preform to the width of the glass obtained by drawing is in the range of 5: 1 to 2: 1), and the glass obtained by drawing is performed. The present invention relates to a method for producing a polarizing glass, which comprises a step of reducing some or all of the metal halide particles into metal particles by a reduction treatment. Hereinafter, the present invention will be described.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is a method for producing a polarizing glass in which metal particles having shape anisotropy are oriented and dispersed in the glass. Here, having shape anisotropy means that
Has an aspect ratio of more than Examples of the metal include copper, silver, gold, and platinum. The aspect ratio of the metal particles can be appropriately determined according to the physical properties required for the polarizing glass, particularly the absorption peak wavelength, and can be, for example, in the range of 2: 1 to 100: 1. However, the aspect ratio of the metal particles is preferably in the range of 10: 1 to 30: 1 in order to make the absorption peak wavelength around the communication wavelength (1.3 to 1.55 μm). The anisotropically shaped metal particles in the polarizing glass of the present invention are substantially oriented in one direction and dispersed in the glass. Examples of the type of glass as the base material include silicate glass, borosilicate glass, and borate glass.

In the present invention, a glass in which metal halide particles are dispersed is used as a raw material. Examples of the halogen in the metal halide include chlorine, bromine and iodine. Examples of the metal halide include silver chloride, silver bromide, silver iodide, copper chloride, copper bromide, copper iodide, gold chloride, gold bromide, gold iodide, platinum chloride, platinum bromide,
Platinum iodide and the like can be mentioned. Glass in which metal halide particles are dispersed can be easily produced by a known method.

[0010] Such metal halide particles have a particle size of 50 to 200 nm, more preferably 80 to 170 nm.
Is preferably within the range. When the particle size is smaller than the above range, it is difficult to obtain a predetermined aspect ratio when drawing, and as a result, it tends to be difficult to obtain an absorption peak wavelength in an infrared region. If the particle size is larger than the above range, the influence of the transmission loss due to the metal halide remaining inside the glass when the polarizing glass is formed tends to increase. In addition, the content of the metal halide is such that the metal particles obtained by the predetermined reduction treatment have a sufficient extinction ratio, and when a polarizing glass is used, the effect of transmission loss due to the metal halide remaining inside the glass is large. It is preferable that the amount is adjusted to the extent that it does not become too small, and it can be changed by appropriately adjusting the amounts of the metal forming the halide and the halogen in the glass composition.

In the production method of the present invention, a drawing method is employed as a method for drawing glass. By employing the drawing method, a glass having uniform dimensions can be obtained over a long length, and a polarizing glass having high polarization characteristics can be manufactured. It is known that a drawing furnace usually has a Gaussian temperature distribution in the drawing direction. The Gaussian temperature distribution is
T = T a ₀ exp temperature distribution similar to the curve shown by (-aH ^2). In the equation, T ₀ is the peak temperature, a is a constant, and H is the position in the drawing direction with the peak temperature position as the origin.
(J. Appl. Phys. Vol. 49 No. 8 p4419 (1978)) A drawing furnace having such a Gaussian temperature distribution is described in, for example, JP-A-8-231241.
At the peak temperature position of the drawing furnace having such a temperature distribution, the glass preform is drawn and largely deformed,
The glass that has been deformed into a tape shape moves in the drawing furnace, and the temperature decreases as the glass moves in the drawing direction.

The drawing step in the method of the present invention is performed so that the ratio of the width of the glass preform to the width of the glass obtained by drawing is in the range of 5: 1 to 2: 1. By doing so, it is possible to obtain a polarizing glass in which the distribution of the extinction ratio in the plane (width direction) is relatively constant. More preferably,
The width ratio is in the range of 4.5: 1 to 3: 1. As described above, when manufacturing a polarizing glass having a relatively large width (for example, about 10 mm), a glass base material used for drawing and a glass base material used for drawing are considered in consideration of the width of the polarizing glass as a final product. The width reduction ratio can be determined.

The ratio of the width of the glass obtained by drawing can be controlled by the ratio of the feeding speed of the glass preform to the drawing speed of the stretched glass. That is, when the ratio of the width of the glass obtained by drawing and the width of the glass preform is, for example, 4: 1, the ratio between the feeding speed of the glass preform and the drawing speed of the stretched glass is 1:16.
(Corresponding to the ratio of the cross-sectional area of the glass preform to the cross-sectional area of the glass obtained by drawing).

Further, the above-mentioned drawing shows that the stress on the glass in which the metal halide particles are dispersed is 50 kg /
cm ^{2 to} 300 kg / cm ² , preferably 150 k
It is preferable to carry out the treatment so as to be in the range of g / cm ^{2 to} 250 kg / cm ² . By drawing in this range, breakage of the glass and the like can be prevented, and the metal halide particles can be appropriately elongated. By controlling the stress, the aspect ratio of the particles can be controlled, and the absorption peak wavelength of the polarizing glass can be controlled. The stress is 50 kg / cm
^{When it is} less than ² , the metal halide particles cannot be elongated to a desired aspect ratio, and it is difficult to obtain a polarizing glass having an absorption peak wavelength in an infrared region. Also, if the stress is 30
If it exceeds 0 kg / cm ² , a force higher than a practical breaking value is applied to the glass, and the glass tends to be easily broken. The stress can be controlled by the temperature (viscosity of the glass) at the time of drawing and the drawing speed.

The above glass has a viscosity of 3 × 10 ⁷ poise to
It is preferable that the line is drawn in a state of 2 × 10 ⁹ poise. By drawing the glass in the above range, the glass can be stretched while preventing the glass from being broken. If the viscosity is 3 × 10 ⁷ poise or less, the viscosity is too low to apply the stress necessary to elongate the metal halide particles, and the temperature reaches the temperature range of the heat treatment for precipitation of the metal particles. The size (particle diameter) of the halide particles may change. The viscosity of the glass is 2 ×
If it exceeds 10 ⁹ poise, a large tension is required for drawing even if the drawing speed is reduced, so that the probability of breaking during drawing tends to increase. The viscosity of the glass at the time of drawing is
Preferably, it is in the range of 1 × 10 ⁸ poise to 1 × 10 ⁹ poise. Since the viscosity of the glass changes depending on the type and temperature of the glass, the temperature at which the viscosity is reached is appropriately set according to the type of the glass.

Further, by reducing the thickness of the glass preform obtained by drawing, the temperature distribution in the drawing direction of the glass immediately after the deformation can be quickly brought close to the temperature distribution of the furnace. It is advantageous for prevention of the formation of a carbon black. The thickness of the glass preform obtained by drawing is appropriately 2 mm or less, preferably 1 mm or less, from the viewpoint of preventing re-spheroidization. When the thickness of the glass obtained by drawing is 1 mm or less, the glass obtained by drawing can be cooled particularly efficiently, and re-spheroidization of the elongated metal halide particles can be prevented. More preferably the thickness of the glass after drawing,
0.2 to 0.5 mm. However, as described above, in the method of the present invention, since the reduction ratio of the width at the time of drawing is set to a constant value, the dimensions of the glass base material are determined by the reduction ratio of the width at the time of drawing and the size of the glass after drawing. The thickness is determined in consideration of the thickness.

Further, the drawn metal preform moves from the deformation start position of the drawn glass preform in the drawing to a position where the ambient temperature becomes 100 ° C. within 120 seconds, preferably within 60 seconds. It is preferable from the viewpoint of preventing the particles from re-spheroidizing.
However, this time can be appropriately changed depending on the thickness of the drawn glass preform, and it is preferable that the thicker the glass preform, the shorter the time it is moved and the faster the cooling.

By performing drawing under the above conditions, a glass containing metal halide particles having a desired aspect ratio in a dispersed state can be obtained. The metal halide particles are reduced to metal particles in a later step, but the volume may be reduced when the metal halide particles are reduced to metal particles. Therefore, the aspect ratio of the metal halide particles is preferably determined in consideration of the aspect ratio of the metal particles obtained by reduction.

As the glass preform in which the metal halide particles are dispersed, it is preferable to use a glass preform having a rectangular or substantially rectangular cross section from the viewpoint of using a polarizing glass as an end product for an optical isolator.
Here, the substantially rectangular shape includes an elliptical shape. In addition, the cross-sectional shape can be appropriately determined according to the shape required for the polarizing glass as the final product. However, the rectangle is generally a square or a rectangle.

FIG. 1 shows an example of an apparatus used for drawing according to the present invention. In FIG. 1, reference numeral 1 denotes a preform. The preform 1 is held by a feeder 2 via a fixing jig 3 and a stainless steel rod, and is movable downward. The vicinity of the front end of the preform 1 is softened by a heating unit 8 in a heating furnace (drawing furnace) 4 and drawn from a lower end of the preform 1 downward by a tension device 5. By drawing, a linear glass 6 in which elongated metal halide particles are dispersed is formed. The linear glass 6 drawn out of the heating furnace 4 is rapidly cooled by outside air.

A lid 7 having a hole through which a stainless steel rod for connecting the feeder 2 and the fixing jig 3 passes is mounted at the center of the heating furnace 3. The lid 7 prevents the glass from being broken due to a rapid temperature rise when the preform 1 is inserted into the heating furnace 4, and the heating furnace 4
It has the effect of preventing the release of heat inside. The temperature of the heating furnace 4 is controlled by a temperature control device (not shown), so that the viscosity of the preform 1 in the heating furnace 4 can be adjusted appropriately. In the preform 1, a linear glass 6 in which metal halide particles having a desired aspect ratio are dispersed can be obtained by adjusting the feeding speed by the feeding device 2, the pulling speed by the pulling device 5, and the tension. .

In the present invention, in order to prevent breakage of the glass at the time of drawing and to enhance the smoothness of the glass, the preform before drawing is subjected to polishing treatment and etching (for example, etching with an acid solution). After the drawing, a polishing treatment can be performed to further improve the surface smoothness of the substrate.

The linear glass obtained by drawing is then subjected to a reduction treatment to convert some or all of the metal halide particles in the glass into metal particles. This reduction treatment can be performed, for example, by performing a heat treatment on the linear glass in a reducing gas atmosphere. Examples of the reducing gas include a hydrogen gas and a CO—CO ₂ gas. The conditions for reduction differ depending on the type of metal halide to be reduced. However, the reduction temperature is determined in consideration of the fact that the metal particles obtained by reduction if the reduction temperature is too high will be re-spheroidized. For example, in the case of copper halide, about 3
Suitably, it is 50-550 ° C. Further, the time for the reduction can be appropriately determined in consideration of the reduction temperature and the degree of the reduction. Usually, the reaction can be performed for 30 minutes to 10 hours.

The method for producing a polarizing glass of the present invention is a composite comprising a glass layer containing shape-anisotropic metal particles and a glass substrate containing no metal particles, metal halide particles or the like and substantially not causing light scattering. The present invention can also be applied to a method of manufacturing a mold type polarizing glass.

[0025]

The present invention will be further described below with reference to examples. Example 1 (1) Preparation of preform 59.9% of SiO ₂ , 2.0% of AlF ₃ , Al ₂ O
₃ 6.8%, B ₂ O ₃ 20.5%, Na ₂ O 9.7%,
NaCl 1.0%, CuCl 0.8%, SnO0.
A glass having a composition of 1% is melted at 1410 ° C. in a 5 liter platinum crucible, and then poured into a mold at 470 ° C.
, To produce a glass block. The glass block was cut into an appropriate size and heat-treated at 735 ° C. for 60 minutes to obtain a glass containing copper chloride particles having an average particle size of about 95 nm in the glass block. This glass was polished to produce a plate-shaped glass preform having a width of 20 mm, a thickness of 2 mm and a length of 200 mm.

(2) Etching of the preform The preform was immersed in an etching solution containing 100 ml of hydrofluoric acid, 400 ml of sulfuric acid and 500 ml of water for 10 minutes to etch the surface, then washed with water and dried. (3) Drawing The etched preform was drawn by the drawing apparatus shown in FIG. The preform 1 was attached to the feeding device 2 (the position was set by wire so that the lower end of the preform 1 was almost at the center of the heating furnace 3. The temperature in the heating furnace 3 was set to 675 by a temperature control device (not shown). A wire was wound around the lower end of the preform 1. After the temperature in the furnace 3 was stabilized, a load was applied to the wire to start elongation of the glass. The resulting glass is sandwiched between driving rollers, which are tensioning devices 4, and the temperature in the heating furnace 3 is increased to 675 ° C. (glass viscosity ν = 4).
(× 10 ⁷ poise). After the temperature was stabilized, the tape-shaped glass was continuously pulled by applying tension to the lower end of the glass with a roller. At this time, the feeding speed of the feeding device 2 is 25 mm / min, and the feeding speed of the pulling device 4 is 0.4 mm.
m / min.

The tensile stress was about 200 kg / cm ² . The width of the pulled glass is 5mm and the thickness is 0.5m
m and the width ratio to the preform was 4: 1.

(3) Reduction The obtained linear glass was subjected to 425 in a hydrogen gas atmosphere.
C. for 4 hours to produce a polarizing glass. FIG. 2 shows the result of measuring the extinction ratio in the width direction of the polarizing glass.
The portion where the extinction ratio was constant was about 3 mm.

Comparative Example 1 50 mm wide × 2 mm thick containing copper chloride particles having an average particle size of about 95 nm
× A plate-shaped glass preform having a length of 200 mm was drawn under the same conditions as in Example 1. However, if the temperature in the heating furnace 3 is 64
The temperature was 5 ° C. (viscosity of glass ν = 2 × 10 ⁸ poises), the feed rate was 10 mm / min, and the take-off rate was 1 m / min. The width of the obtained glass is 5 mm, the thickness is 0.2 mm,
The ratio to the width of the preform was 10: 1. This glass was treated under the same conditions as in Example 1 (42% in a hydrogen gas atmosphere).
FIG. 3 shows the result of measurement of the extinction ratio in the width direction of the obtained polarizing glass after reduction treatment at 5 ° C. for 4 hours. The portion where the extinction ratio was constant was about 2 mm.

Example 2 50 mm wide × 2 mm thick containing copper chloride particles having an average particle size of about 95 nm
× A plate-shaped glass preform having a length of 200 mm was drawn under the same conditions as in Example 1. However, the temperature in the heating furnace 3 is set to 61
The temperature was set at 0 ° C. (viscosity of glass ν = 1 × 10 ⁹ poise), the feed speed was 25 mm / min, and the take-off speed was 0.4 m / min. The obtained glass has a width of 12.5 mm and a thickness of 0.5.
mm, and the ratio to the width of the base material was 4: 1. This glass was treated under the same conditions as in Example 1 (4 times in a hydrogen gas atmosphere).
FIG. 4 shows the result of measuring the extinction ratio in the width direction of the obtained polarizing glass after reduction treatment at 25 ° C. for 4 hours. The portion where the extinction ratio was constant was about 10 mm.

[0031]

According to the present invention, there is provided a method for producing a polarizing glass by the drawing method, wherein the width of the polarizing glass is relatively wide and the distribution of the extinction ratio in the plane (width direction) is relatively constant. A manufacturing method can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a drawing apparatus used in the method of the present invention.

FIG. 2 shows an in-plane (width direction) distribution of the extinction ratio of the polarizing glass obtained in Example 1.

FIG. 3 shows the distribution of the extinction ratio in the plane (width direction) of the polarizing glass obtained in Comparative Example 1.

FIG. 4 shows the distribution of the extinction ratio in the plane (width direction) of the polarizing glass obtained in Example 2.

Claims (2)

(57) [Claims] 1. A method for producing a polarizing glass in which metal particles having shape anisotropy are oriented and dispersed in glass, comprising the steps of: drawing a glass preform in which metal halide particles are dispersed. However, the drawing is performed such that the ratio of the width of the glass preform to the width of the glass obtained by drawing is in the range of 4.5: 1 to 3: 1 ), and the glass obtained by drawing. A process for reducing the metal halide particles to convert a part or all of the metal halide particles into metal particles. 2. The glass preform has a viscosity of 3 × 10 ^7.
2. The production method according to claim 1, wherein the wire is drawn in a state of poise to 2 × 10 ⁹ poise.