JP5121165B2 - Manufacturing method of polarizing glass - Google Patents

Description

  The present invention relates to a manufacturing method of a polarizing glass used as a polarizer for a small optical isolator used for optical communication or the like, or an optical switch or an electromagnetic sensor composed of a combination of a liquid crystal, an electro-optic crystal, and a Faraday rotator. .

  Glass that contains finely dispersed metal particles with oriented and dispersed shape anisotropy, such as silver particles and copper particles, becomes a polarizer because the light absorption wavelength band of the metal differs depending on the incident polarization direction. It has been known. It is also known that such polarizing glass can be produced by reducing the stretched glass containing copper halide particles or glass containing silver halide particles.

For example, Patent Document 1 discloses a method for producing polarizing glass from glass containing copper halide particles. In this method, the copper halide particles are elongated at a temperature at which the viscosity of the glass is in the range of 10 ⁷ to 10 ¹⁰ Pa · S, and then the copper halide particles are reduced by heat treatment in a reducing atmosphere. A polarizing glass containing metallic copper particles having a shape anisotropy is produced.

  Further, Patent Document 2 proposes a method of drawing a metal halide particle-containing glass as an improved method of producing a polarizing glass containing metal copper particles having shape anisotropy. In this method, when drawing a glass preform in which metal halide particles are dispersed, the stretched glass is cooled (natural cooling) at the same time as stretching, and the stretched glass is naturally cooled efficiently. This prevents the re-spheroidization of the metal halide particles thus produced and produces a polarizing glass having excellent polarization characteristics.

  By the way, the conventional polarizing glass used as a component of a high performance trunk optical isolator requiring about 35 dB of isolation has a plane size of 1.0 to 1.2 mm square. And this non-reciprocal element for optical isolators was manufactured by aligning and adhere | attaching this polarizing glass on the crystal | crystallization of the same Faraday element individually. Parts having a size smaller than this are difficult to handle. For example, it is not easy to bond the polarizing glass and the crystal of the Faraday element, and it is difficult to put it into practical use.

  On the other hand, recently, small parts having a plane size of about 0.5 to 0.6 mm square have been used for metro type optical isolators. In the manufacturing method, first, a Faraday element crystal of about 10 mm square and a polarizing glass having the same size are aligned and pasted. Next, it is cut into a large number of parts of about 0.5 to 0.6 mm square. According to this method, it is possible to easily produce a large number of parts that require a plane area of about 1/4 as compared with the conventional product.

  However, there was no problem when polarizing glasses with small plane dimensions were individually aligned and bonded to the same size Faraday element crystal, but when a relatively large size polarizing glass of about 10 mm square was used. The problem of polarization axis misalignment in the glass plane cannot be ignored. That is, if there is a portion where the polarization axis is shifted in the glass surface, the portion is bonded to the Faraday element in a state where the polarization axis is shifted, and the polarization characteristics as an optical isolator are impaired.

  Conventionally, a method described in Patent Document 3 is known as a method for reducing polarization axis deviation in polarizing glass. In this method, the temperature distribution of the heating furnace used for stretching is set so that the temperature at both ends in the direction perpendicular to the stretching direction is lower than the central portion, and the glass thickness of the preform is increased to 4 mm or more. At the time of stretching, the cooling rate of the glass at both ends in the width direction is made relatively faster than the center, and the freezing of the structure at both ends is accelerated, thereby opening the half-shaped opening of the halide metal stretching axis at both ends. It is to suppress.

Japanese Patent No. 2740601 Japanese Patent No. 2849358 JP 2004-224660 A

  However, as described in Patent Document 3, when the temperature of both ends of the heating furnace is set low and the preform glass is stretched, both ends in the width direction of the stretched glass are higher in viscosity than the center portion. Since it is stretched, both ends are subjected to greater tension than the center, so that the halide metal fine particles at both ends are stretched more than the center, resulting in variations and distribution in the in-plane extinction ratio characteristics. There's a problem.

  Further, when the preform glass is increased in thickness and stretched, both end portions are cooled relatively faster than the center portion in the width direction, and as a result, the temperature at the end portion of the heating furnace is lowered. Thus, there is a problem that variation and distribution occur in the extinction ratio characteristic in the surface. In addition, when the thickness of the preform glass is increased, the volume of the preform increases, and it is necessary to apply a larger tension during stretching. Therefore, it is necessary to make the stretching apparatus large enough to withstand the tension. Come out. Further, since the volume of the preform increases, a large amount of glass as a base material is consumed, resulting in a problem that the cost increases.

  Accordingly, an object of the present invention is to reduce the in-plane polarization axis deviation of the polarizing glass, improve the in-plane extinction ratio characteristic, and manufacture a polarizing glass that is homogeneous and inexpensive to manufacture. It is to provide a method.

The invention of claim 1 is a method for producing a polarizing glass in which metal particles having shape anisotropy are oriented and dispersed in glass, and the glass preform in which metal halide particles are dispersed is heated. A stretching step of stretching, and a reduction step of reducing a part or all of the metal halide particles to a metal particle by reducing the glass sheet obtained by the step. In the stretching step, The glass sheet is forcibly cooled by forced cooling means, and the forced cooling is performed on a central portion in the width direction of the glass sheet being stretched .

Invention of Claim 2 is a manufacturing method of the polarizing glass of Claim 1 , Comprising: As the said forced cooling means, the spray nozzle of gas is provided, The said forced cooling is from the said nozzle with respect to the said glass sheet in the process of extending | stretching. It is characterized in that it is performed by spraying a gas.

Invention of Claim 3 is a manufacturing method of the polarizing glass of Claim 2 , Comprising: The gas of temperature lower than room temperature is used as said gas, It is characterized by the above-mentioned.

Invention of Claim 4 is the manufacturing method of the polarizing glass of Claim 1 , Comprising: As the forced cooling means, the cooling member which controlled temperature lower than the circumference | surroundings is provided, the said forced cooling is made into the said cooling member, It carries out by making it adjoin to the surface of the glass sheet in the middle of extending | stretching.

  According to the first aspect of the present invention, the glass sheet in the middle of stretching is not naturally cooled (cooled) at room temperature as in the prior art, but is forcedly cooled by forced cooling means. By increasing the speed at which the stretching axis freezes as a whole, the inclination of the halide metal fine particles to the center side of the upper part of the stretching axis at the widthwise end of the stretched glass sheet (the stretching axis c) Character inclination) can be kept small. Then, by reducing the glass sheet, it is possible to obtain a polarizing glass having a small polarization axis deviation in the width direction in the stretched plane.

  Moreover, when the cooling rate of the glass sheet is increased, it is possible to prevent the stretched shape of the stretched metal halide particles from returning, and after reduction, a polarizing glass having a high extinction ratio can be obtained in the entire width direction. In addition, since it is not necessary to prepare a particularly thick preform, the number of preforms collected from the base glass can be increased, and the manufacturing cost can be reduced. In addition, since the cross-sectional area of the preform can be reduced, the load applied to the take-up device can be reduced, and a large take-up device is not required, so that the manufacturing cost can be kept low.

According to invention of Claim 1 , since the center part of the width direction of the glass sheet in the middle of extending | stretching is forcedly cooled, by making the glass structure of a center part freeze earlier than an edge part, the extended halide metal particle upper part in an edge part The force toward the center side of the film can be reduced, and the inclination of the cross-section of the stretching axis can be kept small. Also, with natural cooling (cooling) of stretched glass sheets as in the past, the central part in the width direction is difficult to cool and the end part is easy to cool, resulting in a difference in tension between the central part and the end part due to the difference in glass viscosity. As a result, the phenomenon that the extinction ratio characteristic is different between the center part and the end part has occurred, but by forcedly cooling the center part of the stretched glass sheet by the forced cooling means, at the center part and the end part in the width direction. The difference in cooling rate can be reduced. Therefore, the difference in tension between the central portion and the end portion of the halide metal fine particles becomes small, the stretched state of the halide metal fine particles becomes uniform in the width direction, and after reduction, the variation in the width direction of the extinction ratio characteristic of the polarizing glass The distribution can be reduced.

According to the invention of claim 2 , since the glass sheet is forcibly cooled by blowing gas from the nozzle, the temperature of the glass sheet can be easily controlled with simple equipment.

According to invention of Claim 3 , since the gas of temperature lower than room temperature is sprayed, a glass sheet can be cooled rapidly.

According to the invention of claim 4 , since the glass sheet is forcibly cooled by bringing the cooling member whose temperature is controlled lower than the surroundings close to the surface of the glass sheet, the temperature of the glass sheet can be easily controlled by simple equipment. can do.

Embodiments of the present invention will be described below with reference to the drawings.
The method for producing a polarizing glass according to the first embodiment comprises heating a polarizing glass in which metal particles having shape anisotropy are oriented and dispersed in the glass, and a glass preform in which metal halide particles are dispersed. A stretching process for stretching and a reduction process in which the obtained glass sheet is subjected to a reduction treatment to form a part or all of the metal halide particles as metal particles. The glass sheet being stretched is forcibly cooled by forced cooling means.

  FIG. 1 is an explanatory view of a polarizing glass manufacturing method according to the first embodiment, in which 1 is a glass preform, 2 is a preform feeding device, 3 is a heating furnace, 4 is a pulling roller, 1A is a glass sheet, 5 Is a gas spray nozzle, and 6 is a windproof cover. This manufacturing method is characterized in that a gas blowing nozzle 5 is provided as a forced cooling means, and forced cooling is performed by blowing gas from the nozzle 5 to the glass sheet 1A being stretched.

  Here, having shape anisotropy means having an aspect ratio exceeding 1. Examples of the metal of the metal particles 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 light absorption wavelength, and is preferably in the range of 2: 1 to 100: 1, for example. In particular, in order to make the absorption wavelength near the optical communication wavelength (1.31 to 1.55 μm), the range of 10: 1 to 30: 1 is preferable.

  The metal particles having shape anisotropy in the polarizing glass are oriented and dispersed substantially in one direction in the glass. Examples of the type of glass that is a base material include silicate glass, borosilicate glass, borate glass, and the like in which the glass softening temperature is higher than the melting point of the halide.

  As a raw material, glass in which metal halide particles are dispersed is used. Examples of the halogen of 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. Etc. Glass in which metal halide particles are dispersed can be easily produced by a known method.

  Such metal halide particles preferably have a particle size in the range of 50 to 200 nm, particularly in the range of 70 to 170 nm. 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 a light absorption wavelength at a wavelength for optical communication. When the particle size is larger than the above range, when a polarizing glass is used, the influence of transmission loss due to metal halide remaining in the glass tends to increase. In addition, the content of the metal halide is sufficiently affected by transmission loss due to the metal halide remaining in the glass when a sufficient extinction ratio is obtained by the metal particles obtained by the predetermined reduction treatment and the glass is made into a polarizing glass. It is preferably adjusted to such an extent that it does not become necessary, and can be changed by appropriately adjusting the amount of metal and halogen forming the halide in the glass composition.

  By the way, it is considered that the polarization axis deviation in the plane of a polarizing glass having a plate size of about 10 mm square occurs in the stretching process. When a plate-like preform is heated and stretched, the halide metal fine particles present in the preform are stretched into a rod shape near the glass softening temperature (above the melting point of the halide metal), and the glass structure freezes (around Tg) ), The stretching axis is fixed. At that time, the polarization axis shift occurs. Therefore, the generation principle will be described.

  FIG. 2 is a view as seen from the front in the width direction (in the direction of arrow II in FIG. 1) at the stage of extending the plate-like preform 1 to the glass sheet 1A. The plate-like preform 1 gradually decreases in width due to heat stretching. At this time, at the point A where the reduction rate of the width of the preform 1 is large, the stretching axis of the halide metal fine particles P at the end of the preform 1 is in the shape of a reverse C-shape opened upward with respect to the central portion. It is greatly inclined. This inclination corresponds to a change in the outer shape of the preform 1.

  At the point B where the decrease in the width of the preform 1 is gentle, the inclination of the inverted letter C opened above becomes smaller as the change in the outer shape decreases. At a point C just before the width of the preform 1 becomes constant, the inclination of the stretching axis at the end of the preform 1 is parallel to the center portion.

  Immediately before the glass structure freezes (between points C and D), as shown in FIG. 3, the halide metal particles P are subjected to a large downward tension at the center in the width direction within the stretched surface and are equal to the left and right. Since it receives tension, its stretching axis is parallel to the stretching direction. However, at the end in the width direction in the stretched surface, for example, the right end, a large downward tension and a slight downward tension are applied, and the reaction force is a large upward reaction force and a slight upper left tension. A reaction force acts on the drawn fine particles P. As a result, at the right end in the width direction within the stretched surface, the stretched halide fine particles are inclined slightly to the left (center side) on the upper side. Similarly, at the left end in the width direction within the stretched surface, the stretched halide fine particles are inclined slightly upward on the right side due to a slight reaction force to the upper right.

  And, at the point D where the width of the preform 1 is minimized and the glass structure is frozen, the influence of the reaction force toward the center of the end portion of the preform 1 described above is opposite to the points A and B. The stretching axis is slightly inclined to the shape of the letter C opened in the middle. At point E, where the glass structure is frozen and the width of the preform is the same as that at point D, the stretching axis is inclined in the shape of the letter C, which opens downward, at the same inclination as point D. Since this continues, the polarization axis is shifted in the plane of the polarizing glass cut to about 10 mm square after the reduction treatment.

  In that respect, the method of this embodiment is characterized in that, in the step of heating and stretching the glass preform in which the metal halide particles are dispersed, the stretched glass sheet is continuously cooled by a cooling means. Cooling here does not mean that the glass sheet is naturally cooled (cooled) at room temperature, but rather means that cooling gas is forcedly blown onto the glass sheet to promote heat dissipation.

  As described in Patent Document 2, the glass sheet 1A drawn out from the heating furnace 3 is cooled by moving it from the deformation start position of the glass preform 1 to a position where the ambient temperature becomes 100 ° C. within 120 seconds. Although the speed can be adjusted so that the stretched halogenated fine particles do not re-sphericalize, the cooling speed can be increased by further forced cooling. Further, by increasing the cooling rate, it is possible to prevent the stretched shape of the further stretched metal halide fine particles from returning, and a polarizing glass having a high extinction ratio can be obtained after the reduction.

  In addition, by the forced cooling by blowing the cooling gas, the cooling rate in the entire width direction of the stretched glass is increased, and the rate at which the stretching axis freezes as a whole increases, so that the halide at the end of the stretched glass sheet described above. It is possible to suppress the metal fine particle stretching axis from being inclined toward the center (the inclination of the C of the stretching axis). That is, by performing forced cooling from point B, the distance (BD) to point D where the glass structure freezes is shortened, and at the same time, the stretching axis at the preform end opens downward. The inclination angle can be kept small. Then, by reducing the glass sheet, a polarizing glass having a small deviation of the polarization axis in the width direction in the stretched plane can be obtained.

  In this case, in particular, in the step of heating and stretching the glass preform 1, it is effective to cool the central portion in the width direction of the stretched glass sheet 1A. Here, the center portion in the width direction refers to a range of 2% to 60%, preferably 10 to 50% of the sheet half width from the center point of the width of the stretched glass sheet 1A toward both ends. By cooling the central portion of the stretched glass in the width direction, the reaction force toward the center of the upper portion of the stretched halide metal particles at the width direction end portion is reduced, and the inclination of the stretch direction due to the reaction force is reduced. The inclination of the C shape of the stretching axis can be kept small.

  In addition, since the difference in cooling rate between the center portion and the end portion in the width direction of the stretched glass sheet is small, the difference in tension applied to the halide metal fine particles is small between the center portion and the end portion, and the stretched state Becomes uniform in the width direction, and after reduction, the variation and distribution in the width direction of the extinction ratio characteristic of the polarizing glass can be reduced.

The glass sheet obtained by stretching is then subjected to a reduction treatment so that part or all of the metal halide particles in the glass are converted into metal particles. This reduction treatment can be performed, for example, by heat-treating sheet-like glass in a reducing gas atmosphere. Examples of the reducing gas include hydrogen gas and CO—CO ₂ gas. The reduction conditions vary depending on the type of metal halide to be reduced. However, if the reduction temperature is too high, the reduction temperature is determined in consideration of the re-sphericalization of the metal particles obtained by reduction. For example, in the case of copper halide, it is appropriate that the temperature is about 350 to 550 ° C. The reduction time can be appropriately determined in consideration of the reduction temperature and the degree of reduction. Usually, it can be performed in a range of 30 minutes to 10 hours.

  In this method, since it is not necessary to prepare a particularly thick preform, the number of preforms collected from the base glass can be increased, and the manufacturing cost can be reduced. In addition, since the cross-sectional area of the preform can be reduced, the load applied to the take-up device can be reduced, and a large take-up device is not required, so that the manufacturing cost can be kept low.

As the cooling gas, any gas such as Air, Ar, N ₂ , O ₂ , H ₂ , or a mixed gas may be used. Moreover, the cooling rate can be further increased by passing the cooling gas through a cold trap or the like to remove moisture in the gas and lowering the temperature of the gas sprayed onto the glass below room temperature.

  Further, when the cooling gas is sprayed on the stretched glass, it is preferable to spray the gas at an angle downward so that there is no influence of a temperature drop on the heating furnace 3. Further, a windproof cover 6 as shown in FIG. 1 may be attached between the heating furnace 3 and the stretched glass so that the cooling gas does not flow into the heating furnace 3.

  The shape of the nozzle 5 may be, for example, a circular tube with an inner diameter of about 0.5 to 20 mmΦ or a rectangular tube with a size of about 20 × 2 mm. Further, the spraying effect can be changed by appropriately adjusting the shape and size of the nozzle 5 according to the width, thickness, stretching speed, and the like of the glass to be stretched.

  Also, the flow rate when the gas is blown is preferably set at a level at which a weak blow of, for example, about 0.01 to 5.0 liters / minute is possible, and the flow rate is also the distance between the nozzle 5 and the glass, and the angle of the blow. The temperature of the gas to be blown, the shape of the nozzle, the area of the opening, the stretching speed, etc. may be adjusted as appropriate. If it is blown too strongly, the temperature of the upper heating furnace 3 may be disturbed, or the glass that has been stretched and subjected to strong strain will be rapidly cooled, so care must be taken.

FIG. 4 is an explanatory diagram of the second embodiment of the present invention.
In the first embodiment, the stretched glass sheet is forcibly cooled by blowing gas from the nozzle. However, in this embodiment, the stretched glass sheet 1A is cooled at a temperature lower than that of the surroundings. The controlled cooling member 7 is inserted close to the surface of the glass sheet 1A to absorb the heat of the glass sheet 1A.

  The cooling member 7 has a structure in which the cooling medium can be circulated therein. When the cooling medium is sent from the temperature control device 8 connected to the outside, the temperature is kept lower than that of the surroundings. Thus, the heat of the glass sheet 1A is absorbed. In addition, if the heat generated by the glass sheet 1A is absorbed by the cooling member 7 and the heat transmitted to the circulating cooling medium is released by the temperature control device 8, the cooling member 7 and the cooling medium to be used are used. The type and the like can be selected as appropriate.

  Thus, the glass sheet 1 </ b> A can be forcibly cooled also by using the cooling member 7. Therefore, the same effect as that of the first embodiment described above can be obtained. Further, by disposing the cooling member 7 so as to correspond to the central portion in the width direction of the glass sheet 1A, it is possible to obtain the same effect as forcing the central portion by blowing gas.

FIG. 5 is an explanatory diagram of the third embodiment of the present invention.
In the first and second embodiments, the case where the glass sheet 1 </ b> A coming out of the heating furnace 3 is forcibly cooled by spraying gas from the nozzle 5 or the proximity of the cooling member 7 is shown. In the embodiment, a heat shield member 9 that blocks heat radiation from the heating element 3a to the central portion in the width direction of the glass sheet 1A is inserted between the heating element 3a in the heating furnace 3 and the glass sheet 1A being stretched. . By doing in this way, the amount of heat received at the central portion in the width direction of the glass sheet 1A can be limited, and the glass sheet 1A at the stage of exiting the heating furnace 3 has a temperature distribution similar to that for forcedly cooling the central portion. Can be given to. Therefore, the same effects as those of the first and second embodiments can be obtained.

  The heat shield member 9 that blocks heat radiation from the heating furnace 3 may be any material that has heat resistance and heat insulation, such as ceramics such as alumina, zirconia, and quartz, or a cooled metal such as SUS. In particular, ceramics such as alumina, zirconia, and quartz are particularly preferable as a heat shielding material because they are particularly excellent in heat insulation and have good shape workability and heat resistance.

  Moreover, it is also possible to efficiently use the radiant heat of the heating furnace 3 by using a material obtained by applying a ceramic powder such as quartz, zirconia, alumina or the like on a SUS plate having a thickness of about 0.3 to 3 mm and baking it. It is preferable as a shielding method.

  As the shape of the heat shield member 9, for example, a rectangular shape of 20 × 5 mm, a trapezoidal shape such as an upper surface 6 × lower surface 4 × height 5 mm, a rectangular shape or a trapezoidal shape with a chamfer of about R several mm, etc. Can do. Further, the shape and size are suitably adjusted depending on the width, thickness, stretching speed, etc. of the glass to be stretched.

  Next, examples will be described.

In Example 1, a polarizing glass was prepared as follows.
(1) Creating a preform:
Composition composed of SiO ₂ 59.6%, AlF ₃ 2%, Al ₂ O ₃ 6.8%, B ₂ O ₃ 20%, Na ₂ O 9.7%, NaCl 1%, CuCl 0.8%, SnO 0.1% The glass was melted at 1410 ° C. in a 5 liter platinum crucible, poured into a mold, and cooled at 470 ° C. to prepare a glass block. The glass block was cut into an appropriate size and heat-treated at 750 ° C. for 90 minutes to obtain a glass containing copper chloride particles having an average particle diameter of about 100 nm in the glass block. This glass was processed to obtain a plate-like glass preform in which both sides of a 110 × 250 × 3 mmt surface were optically polished.

(2) Stretching process:
The above preform was heated and stretched with a drawing apparatus. As shown in FIG. 1, the preform 1 was attached to the feeding device 2, and the position was set so that the lower end portion of the preform 1 was substantially at the center of the heating furnace 3. The temperature in the heating furnace 3 was raised to 710 ° C. by a temperature control device (not shown). A wire is wound around the lower end of the preform 1. After the temperature of the furnace 3 is stabilized, the wire is applied with a load, the glass starts to stretch, and the stretched glass reaches the roller portion of the pulling device 4. Later, the weight of the wire was removed.

  The stretched sheet-shaped glass was sandwiched between drive rollers as the pulling device 4, and the temperature in the heating furnace 3 was reset to 690 ° C. After the temperature is stabilized, nitrogen gas at room temperature is blown at an angle of about 45 ° with respect to the glass sheet 1A at a flow rate of 0.5 liter / min from a blowing nozzle 5 having an opening shape of 30 mm in the horizontal direction and 5 mm in the vertical direction. However, the preform was fed at 15 mm / min by the preform feeding device 2, and at the same time, tension was applied by the roller to continuously pull the glass sheet 1A. At this time, the distance between the glass and the spray nozzle 5 was 5 mm, and the pulling speed was 40 cm / min. The obtained glass sheet had a width of 18 mm, a thickness of 0.6 mm, and a tensile stress of 20.5 MPa.

(3) Reduction:
The obtained glass sheet 1A was heat-treated at 425 ° C. for 8 hours in a hydrogen gas atmosphere at 1 atm to produce a polarizing glass. Table 1 shows the measurement result of the extinction ratio at 1.31 μm at the center point in the width direction, the point 5 mm away from both ends in the width direction, and the deviation of the polarization axis with the polarization axis at the center point as the reference angle. Shown in

  In Example 2, preform preparation and heat stretching similar to Example 1 were performed. However, dry air of 0 ° C. was used as the cooling gas, and the nozzle 5 was a circular tube having an inner diameter of 2 mmφ. The spray angle of the nozzle 5 was set to about 60 ° with respect to the glass surface to be cooled, and the gas flow rate was set to 2.0 liters / minute. The obtained glass sheet 1A was subjected to the same reduction as in Example 1. Table 1 shows the results of the measured extinction ratio and polarization axis deviation.

  In Example 3, the same preform production and heat stretching as in Example 1 were performed. However, a rectangular copper cooling member 7 having a horizontal direction of 30 mm and a vertical direction of 10 mm is placed 5 mm away from the glass sheet 1A and opposed to the glass sheet 1A as shown in FIG. 4 to cool the glass sheet 1A. went. The rectangular copper cooling member 7 has a structure in which cooling water circulates inside, and each cooling member 7 sandwiching the glass sheet 1A is connected to two pipes that circulate cooling water. Water is guided to an external chiller (cooling water temperature control device 8), and cooling water at 15 ° C. circulates. The obtained glass sheet was subjected to the same reduction as in Example 1. Table 1 shows the results of the measured extinction ratio and polarization axis deviation.

  In Example 4, the same preform production and heat stretching as in Example 1 were performed. However, as shown in FIG. 5, two ZrO 2 heat shield members 9 having a horizontal direction of 30 mm, a vertical direction of 20 mm, and a thickness of 3 mm were inserted between the stretched glass sheet 1 A and the heating element 3 a of the heating furnace 3. . Then, the two heat shielding members 9 were opposed to each other with a distance of 5 mm from the glass surface, and the lower end thereof was installed in accordance with the lower end of the heating furnace 3 to extend the radiation heat from the heating furnace 3. The central portion of the glass sheet 1A in the width direction was cooled. The obtained glass sheet was subjected to the same reduction as in Example 1. Table 1 shows the results of the measured extinction ratio and polarization axis deviation.

  In Example 5, the same preform production and heat stretching as in Example 1 were performed. However, as shown in FIG. 5, between the stretched glass sheet 1A and the heating element 3a of the heating furnace 3, ZrO2 powder is applied to both sides of a SUS plate having a horizontal direction of 5 mm, a vertical direction of 30 mm, and a thickness of 2 mm and dried. Two heat shield members 9 were inserted. Then, the two heat shielding members 9 were opposed to each other with a distance of 5 mm from the glass surface, and the lower end thereof was installed in accordance with the lower end of the heating furnace 3 to extend the radiation heat from the heating furnace 3. The central portion of the glass sheet 1A in the width direction was cooled. The obtained glass sheet 1A was subjected to the same reduction as in Example 1. Table 1 shows the results of the measured extinction ratio and polarization axis deviation.

  In Example 6 (Comparative Example 1), the same preform production and heat stretching as in Example 1 were performed. However, the means of Example 1 to Example 5 (cooling and heat receiving adjustment by a nozzle, a cooling member, and a heat shielding member) were not taken on the stretched glass. The obtained glass sheet was subjected to the same reduction as in Example 1. Table 1 shows the results of the measured extinction ratio and polarization axis deviation.

  As can be seen from Table 1, in Examples 1 to 5, the variation in extinction ratio between the end portion and the center portion was smaller than in Example 6 (Comparative Example 1). Also, the polarization axis misalignment angle at the end was reduced.

It is explanatory drawing of 1st Embodiment of this invention. It is explanatory drawing of the generation | occurrence | production mechanism of the inclination of the extending | stretching axis | shaft used as the origin of a polarization axis shift. It is an explanatory view of the mechanism of occurrence of the tilt of the stretching axis that causes the polarization axis deviation. It is explanatory drawing of 2nd Embodiment of this invention. It is explanatory drawing of 3rd Embodiment of this invention.

Explanation of symbols

1: Preform 1A: Glass sheet 3: Heating furnace 5: Gas spray nozzle 7: Cooling member 9: Heat shield member

Claims (4)

A method for producing a polarizing glass in which metal particles having shape anisotropy are oriented and dispersed in glass,
A stretching step of heating and stretching the glass preform in which the metal halide particles are dispersed;
Reducing the glass sheet obtained by the step to have a metal particle as a part or all of the metal halide particles,
In the stretching step, the glass sheet in the middle of stretching is forcibly cooled by a forced cooling means, and the forced cooling is performed on the central portion in the width direction of the glass sheet in the middle of stretching. Method. It is a manufacturing method of polarizing glass according to claim 1 ,
A method for producing a polarizing glass, wherein a gas blowing nozzle is provided as the forced cooling means, and the forced cooling is performed by blowing gas from the nozzle to the glass sheet being stretched. It is a manufacturing method of polarizing glass according to claim 2 ,
A method for producing a polarizing glass, wherein a gas having a temperature lower than room temperature is used as the gas. It is a manufacturing method of polarizing glass according to claim 1 ,
As the forced cooling means, a cooling member whose temperature is controlled to be lower than the surroundings is provided, and the forced cooling is performed by bringing the cooling member close to the surface of the glass sheet that is being stretched. Method.

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