JPH09263413A - Production of glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove water remaining in an org. solvent contained in a treating liq. by immersing gel in the treating liq. while dehydrating the liq. with a desiccating agent at the time of immersion before drying when glass is produced by a sol-gel method. SOLUTION: Gel formed from a sol is immersed in a treating liq. contg. an org. solvent while dehydrating the liq. with a desiccating agent. This method is very effective in the production of distributed index glass having distribution in the compsn. The immersion is effectively carried out in a process immediately before drying. When the gel is dried without passing through the immersion process, a desiccating agent is added to a liq. holding the gel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing glass by the sol-gel method applicable to optical elements such as cameras and microscopes.

[0002]

2. Description of the Related Art Generally, when a glass is produced by a sol-gel method, a sol is prepared by subjecting a silicon alkoxide, which is a skeleton of the glass, to a hydrolysis reaction in a solvent such as ethanol with a catalyst such as hydrochloric acid. The sol becomes a wet gel by the polycondensation reaction. The solvent contained in the pores in the wet gel body is removed by drying and then baked to densify and produce glass.

In particular, when producing optical glass by the sol-gel method, various metal components are added to the sol in order to change the refractive index. As a method of introducing the metal component, there is a method of adding an alcohol solution of a metal alkoxide or a derivative thereof or a solution in which a metal salt is dissolved. Among them, the method using a metal salt is that the raw material is inexpensive, it can be handled in air, and a large amount of metal component can be easily introduced into the sol due to its high solubility in various solvents. Have such advantages.

A wet gel containing a metal component is dipped in an organic solvent, and the metal ion introduced in the form of a water-soluble salt is
It is disclosed in Japanese Patent Publication No. 27575/1993 that the phenomenon in which the gel body is moved to the surface of the gel body at the same time as the moisture is dried is prevented. This method is carried out by immersing the gel body in an organic solvent which has a low solubility in metal salts and is miscible with water.

On the other hand, the gradient index optical element is one in which the medium itself has a power (refractive power) by imparting a refractive index distribution to the medium, and has an excellent aberration correction capability. It is attracting attention as an optical element that can reduce the number of lens system components and is essential to next-generation optical systems. As a method of manufacturing the gradient index optical element, a sol-gel method, an ion exchange method, a molecular stuffing method or the like is used. In particular, the sol-gel method can obtain a glass body having a large diameter, and can give a distribution to a polyvalent metal oxide that contributes to optical characteristics, and thus can obtain various gradient index optical elements. This is a possible manufacturing method.

A method of manufacturing a gradient index optical element by the sol-gel method is described in JP-A-60-142239, JP-B-6.
No. 8179, for example. JP 6
According to the method disclosed in 0-42239,
A wet gel is prepared from silicon alkoxide and germanium alkoxide or titanium alkoxide, and this gel body is immersed in water or dilute hydrochloric acid. Germanium or titanium, which is a component that gives a high refractive index, is partially eluted by the water or diluted hydrochloric acid, but silicon is hardly eluted, so only the germanium or titanium component in the gel body is eluted by water or diluted hydrochloric acid. Thereby, it is possible to give a concentration distribution to germanium or titanium. The gel body having the concentration distribution thus formed is subsequently immersed in an organic solvent for the purpose of stopping the formation of the concentration distribution, and the solvent in the gel body is replaced to stop the concentration distribution. By drying and firing this gel body, a gradient index optical element in which the refractive index decreases from the center toward the outer peripheral portion is obtained.

Further, the method described in Japanese Patent Publication No. 6-8179 makes a sol obtained by hydrolyzing a solution mainly containing a silicon alkoxide and a metal salt into a gel so that the solution has a low solubility in the metal salt. After precipitating fine crystals of the metal salt in the gel by immersing the gel body, by immersing the resulting gel body in a solution containing a metal salt different from the metal salt, the metal salt contained in the gel Crystallites gradually elute from the surface into the external solution. At this time, the metal component contained in the gel has a large contribution to the refractive index, and the metal component contained in the solution has a small contribution to the refractive index. In the gel,
Concentration distributions of convex and concave are formed on the two types of metal components, but since the metal component that greatly contributes to the refractive index has a strong influence, drying and firing this gel body makes it possible to move from the center to the outer periphery. Thus, a gradient index optical element whose refractive index is reduced is obtained.

In these methods, even if the gel body is immersed in an organic solvent and the solvent containing water in the gel pores is replaced with an organic solvent containing no water, the water content in the system is completely removed. Therefore, it is difficult to completely prevent the concentration distribution from being disturbed, and it is difficult to manufacture a gradient index optical element whose refractive index is precisely controlled.

That is, when a gel body containing a metal salt is produced for the purpose of producing a homogeneous glass, it is desirable to disperse the metal salt uniformly in the gel, but the metal salt generally has high solubility in water. For this reason, it is easy to concentrate on the gel surface due to the influence of the water that moves in the skeleton during drying,
Since the composition distribution is disturbed, it was difficult to produce a homogeneous glass body having a metal component having a desired composition with a gel body having a slight amount of water. Similarly, when a composition distribution is imparted to a metal component to a gel body using a metal salt as a raw material to produce a gradient index optical element, the composition-controlled metal component migrates in the gel body for the same reason. Therefore, as shown in FIG. 1, since the relationship between the refractive index and the distance from the center portion tends to have a distribution in which the unevenness of the refractive index is reversed in the peripheral portion, the reproducibility is poor and the refractive index distribution It has been difficult to manufacture a glass body whose temperature is precisely controlled.
When a lens system is manufactured using a gradient index optical element having such a distribution shape, the refractive index difference (Δn) between the central portion and the peripheral portion is small, so the power of the medium itself is weak. In addition, since there is an inflection point in the lens peripheral portion, the light ray cannot be condensed well, and the aberration correction effect peculiar to the gradient index optical element cannot be obtained. Further, there is a problem that the effective diameter of the lens is limited if it is attempted to avoid the inflection point in the peripheral portion.

In the process of producing a dry gel, the surface tension of the solvent in the pores causes a significant volume contraction. At this time, the gel body containing water in the gel has a large surface tension of water. Therefore, stress is likely to be generated in the pores, the force for contracting the skeleton of the gel is excessively generated, and the gel body is easily cracked. For the purpose of preventing cracking of the gel body, the gel body is dipped in a liquid of an organic compound such as alcohol, dioxane, or acetone.
As disclosed in Japanese Patent Laid-Open No. 4), the water content in the system is not completely removed by this method, so that the generation of cracks cannot be completely prevented.

As described above, the water content remaining in the gel body is
It has an adverse effect on the gel body. In addition to this, the water contained in the gel body includes the following. Unreacted component of hydrolyzed water added during sol preparation Water produced by dehydration condensation reaction after metal alkoxide of sol raw material is hydrolyzed, or water mixed in metal alkoxide Crystal of metal salt used for sol raw material Moisture released from water-bearing compounds, or deliquescent metal salts taken up from the air.When an aqueous solution is used as the immersion treatment solvent, the residual water content is an impurity when an organic solvent is used as the immersion treatment solvent. Water contained in the air, or water taken in from the air during processing. As described above, since water enters the gel body in various steps before drying the gel body, when the gel body is finally transferred to the drying step, the water remains in the gel body. . As described above, the gel body immersed in the organic solvent still causes the occurrence of cracks or causes the composition to change. The method of simply immersing the gel body in the organic solvent is the water content in the gel body. This is because it cannot be completely removed. It is considered that this is due not only to the water contained as impurities during the dipping treatment but also to the water remaining in the gel body.

That is, when the gel body is subjected to the immersion treatment, the gel body that has been subjected to the immersion treatment in a certain solvent is transferred to the next immersion treatment step. At this time, the skeleton of the gel body is impregnated. The solvent will be carried over to the solvent in the next step. At this time, if the system originally contains water, the water will be carried over to the next step together with the solvent, so that the amount of water in the solvent in the next step cannot be substantially eliminated. As described above, the gel body produced by the sol-gel method tends to have residual water in the step of the immersion treatment before the drying treatment, which adversely affects the gel body after the drying step. It is preferable to remove water as much as possible.

[0013]

DISCLOSURE OF THE INVENTION It is an object of the present invention to provide a method for preventing glass from remaining in a dipping treatment in an organic solvent before a drying treatment in a method for producing glass by a sol-gel method. In particular, it is an object of the present invention to provide a method for removing water remaining in the immersion solvent particularly in the immersion treatment of the gel body.

[0014]

The method of the present invention is a method for producing glass by a sol-gel method, in which a gel is formed from a sol with a desiccant when immersed in a treatment solution containing an organic solvent. It is a method for producing glass in which the treatment liquid is subjected to immersion treatment while dehydrating. Further, it is a method for producing glass, which is a gradient index glass having a distribution in the composition. In the method for producing a glass body by the sol-gel method, the gel body is produced by dehydrating the syneresis liquid generated from the gel body with a desiccant.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION That is, according to the present invention, in the gel body produced by the sol-gel method, water is likely to remain during the dipping treatment step before the drying treatment, which adversely affects the gel body after the subsequent drying step. Therefore, it has been found that it is desirable to remove water as much as possible by a desiccant when the gel body is dipped. The method of the present invention, in the immersion treatment solvent, in the syneresis fluid from the gel body, or in the step of immersing the gel body in an organic solvent having a small surface tension such as alcohols and ketones which is an immersion treatment immediately before drying,
This is a method in which the amount of water in the treatment liquid is reduced by a desiccant to greatly reduce the amount of water remaining in the gel body during the drying step.

For example, in the case of producing a silica single-component gel body, when the gel body is prepared without immersion treatment, the gel body is immersed in the syneresis fluid generated from the gel body. However, it is possible to move to the drying step, but it is possible to remove the water present in the syneresis solution by adding a desiccant.

Further, when a gel body containing a metal salt as a raw material is prepared and the gel body is immersed in an organic solvent for the purpose of precipitating and fixing the metal component as fine crystals in the pores of the gel,
By adding a desiccant to an organic solvent that is an immersion solvent, it is possible to remove water in the system. The method of the present invention, for the purpose of forming a composition distribution in the metal component, etc., such as immersion treatment in water or a solvent system of a mixture of water and an organic solvent, such as various cases other than when water is effectively used Applicable to immersion treatment solvent.

The step in which the present invention is particularly effective is a step immediately before the drying treatment, and when the gel body is produced and then the drying step is carried out without passing through the dipping treatment, the gel body is held. It is effective to add a desiccant to the synergic fluid, and when the gel body is immersed in a solvent, the final step, and when the immersion treatment is repeated several times, all the steps, especially the immersion step. It is preferably carried out in the final step of the treatment.

When a concentration-imparted gel body containing a metal salt is used as a raw material for producing a gradient index optical element, it is added to the treatment liquid for imparting the concentration distribution. The present invention is very effective for forming a metal salt concentration distribution with good reproducibility, since a small amount of water greatly changes the solubility or the diffusion rate.
In this case, it is very effective to apply the present invention to the step of giving the concentration distribution. Similarly, the application to the processing steps before and after the step of giving the concentration distribution is also effective. That is, the application to the step immediately before the concentration distribution application can more completely prevent the influence of moisture at the time of the concentration distribution application, and the application to the next step of the concentration distribution application,
It is possible to effectively prevent re-diffusion of the metal component, and to reliably fix the applied concentration distribution shape.

On the other hand, in the step of removing water from the gel body by immersing the gel body in the organic solvent, water is mixed in the organic solvent once used for the dipping treatment, so that the solvent is used every time. Had been replaced with a new one. Therefore, when treating a large amount of gel body, a large amount of organic solvent was required, but according to the present invention, by adding a desiccant to the solvent, water in the immersion solvent is removed. Therefore, it is not necessary to replace the solvent with a new one each time the gel body is immersed, and the amount of solvent used can be greatly reduced. Such a process can be applied when the effluent from the gel is mainly water. For example, when the metal salt flows out from the gel as in the step of giving the concentration distribution, the concentration of the metal component in the solution must be taken into consideration, but a gel body containing the metal salt as a raw material is substantially used as the metal salt. It is very effective when immersed in a solution that does not dissolve.

The desiccant used in the present invention can be applied by appropriately setting the amount of desiccant according to the amount of moisture to be removed, and by exchanging the desiccant having adsorbed moisture. The water content in the organic solvent can be kept below a certain level. The desiccant is removed by removing the desiccant from the organic solvent by placing the desiccant in an exchangeable container that does not prevent the passage of liquid and immersing it in an organic solvent, or by filtering the solvent to which the desiccant is added. A new desiccant may be added. Alternatively, the organic solvent may be dried by circulating it between a container containing a desiccant.

In the method of the present invention, since the water that has migrated into the solvent by the immersion of the gel body can be quickly removed, there is no change in the state of the organic solvent in which the gel body is immersed, and a large amount of gel body is treated. Even in this case, it is possible to perform the treatment in which there is little change in the treatment between the gel bodies. Therefore, it is possible to obtain a glass of constant quality, and it is possible to obtain a glass of excellent quality regardless of whether the treatment is carried out by a batch system or a continuous system. Furthermore, in order to relatively reduce the amount of water carried over during the dipping treatment,
Conventionally, a large amount of solvent was used as compared with the gel volume, but since the residual amount of water is small in the method of the present invention, a sufficient effect can be obtained if the amount of gel does not come out of the liquid surface. You can

As the desiccant that can be used in the present invention, any desiccant can be used as long as it does not undergo a chemical reaction with an organic solvent or the like serving as a treatment liquid and does not deteriorate.
Specifically, metal salts such as calcium chloride, magnesium sulfate, calcium sulfate, sodium sulfate, sodium,
Alkali metals such as potassium, lithium aluminum hydride, hydrides such as calcium hydride, calcium oxide,
Examples thereof include oxides such as phosphorous pentoxide, activated alumina, molecular sieves, and porous materials such as silica gel. As the desiccant, it is preferable to use an appropriate desiccant in consideration of the kind of the solvent to be treated, the residual water content, the moisture absorption rate, the moisture absorption capacity, etc., according to each purpose. For example, when removing water in an organic solvent, calcium chloride is not preferable because it easily forms an adduct with alcohols and ketones, and metallic sodium reacts with certain halides, alcohols and ketones. It is not preferable because it causes Sodium sulphate, magnesium sulphate, calcium sulphate and calcium oxide are suitable for alcohols such as ethanol and ketones such as acetone which are often used for the immersion treatment of the gel. In particular, since these sulfates take in water as water of crystallization, they can be easily regenerated and repeatedly used by heating after filtering and separating.

Although the gel body produced by the sol-gel method is generally silica gel containing silica as a main component, since the gel body itself already contains a large amount of solvent in the pores in the wet gel stage, The water in the system is not selectively adsorbed, and the water dissolved in the solvent can be effectively removed by a newly added desiccant. Therefore, when the wet gel of silica is immersed in a solvent, if the dried silica gel is added thereto, the newly added silica gel will selectively absorb water. As described above, it is possible to effectively remove the water remaining in the solvent by adding the desiccant to the solvent, to suppress the occurrence of cracks when subsequently drying the gel body, and to prevent the metal due to water. It is possible to prevent the movement of the components, and it becomes possible to manufacture high-quality glass with high yield.

[0025]

EXAMPLES The present invention will be further described below by showing Examples of the present invention. Example 1 Silicon tetramethoxide (Si (OCH ₃ ) ₄ ) 209
To 350 g of ethanol, 350 ml of ethanol and 48 ml of 2N hydrochloric acid were added, and the mixture was stirred at room temperature for 1 hour. To the solution was added a solution of 77 g of titanium tetra-n-butoxide (Ti (OnC ₄ H ₉ ) ₄ ) and 350 ml of ethanol. Stir for 1 hour. 1 mol / l barium acetate aqueous solution 4 was added to this solution.
00 ml and 160 ml of acetic acid were added and stirred for 1 hour to obtain a sol. This sol was poured into 100 fluororesin containers having a diameter of 18 mm, allowed to stand in a constant temperature bath at 50 ° C. for gelation, and further aged. The obtained gel body is 0.2mo
1 / l barium acetate isopropanol: water = 6: 4
Mixed solution of ethanol: methanol = 8: 2,
Immersion treatment was carried out in the order of ethanol to deposit fine crystals of barium acetate in the gel pores. Further, the barium component was given a composition distribution by being immersed in a mixed solution of 0.3 mol / l potassium acetate in methanol: water for 5 hours. The 50 gels were immersed in 3200 ml of acetone containing 50 g of magnesium sulfate.
This gel body was dried in a constant temperature bath at 30 ° C, and a dry gel without cracks was obtained. By continuously raising the temperature to 690 ° C to make a non-porous glass, glass without cracks was obtained. I got a body. Also, when the refractive index distributions of 10 out of 50 glasses were measured, all of them had a parabolic distribution as shown in FIG. The difference (Δn) is 0.
It was 0284. Moreover, almost no variation in the refractive index distribution was confirmed.

Comparative Example 1 Of the gel bodies prepared in Example 1, the remaining 50 were 32
Immersion in 00 ml of acetone, followed by 30 ° C
Drying was carried out in the same temperature bath. However, 18 of the 50 gel bodies had cracks. Similarly, 32 gel bodies which were not cracked were continuously heated to 690 ° C. to obtain a glass body, but further 5 glass bodies were cracked. The refractive index distribution of 10 of the remaining 27 glass bodies was measured, and the distribution shape was such that unevenness was reversed in the peripheral portion as shown in FIG. 3 showing the distance from the center and the refractive index. The shape of the refractive index distribution of the glass body of the present invention had large variations, and Δn was smaller than that of Example 1 and was 0.016 on average.

Example 2 50 ml of silicon tetramethoxide and 50 ml of silicon tetraethoxide were mixed, 42 ml of 0.01N hydrochloric acid was added thereto, and the mixture was stirred at room temperature for 1 hour to carry out a partial hydrolysis reaction. Here, 1.25 mol / l lead acetate aqueous solution 1
A mixture obtained by previously mixing 80 ml and 26 ml of acetic acid was added. The solution was stirred until the solution was completely and uniformly mixed, and then 80 ml was dispensed into four cylindrical containers each having an inner diameter of 35 mm to obtain a gel body. The obtained gel body was aged for 7 days in a constant temperature bath at 30 ° C., and then isopropanol: water =
Prepare a saturated solution of lead acetate at a mixing ratio of 8: 2 and
The gel body was immersed at a temperature of ° C. Subsequently, the gel was immersed in the order of isopropanol, isopropanol: acetone = 8: 2 (volume ratio) and 5: 5 mixed solvent, and acetone. Here, from the isopropanol immersion treatment, sodium sulfate was added to each of the treatment solutions of isopropanol: acetone = 5: 5, and lithium aluminum hydride was added in the final step of acetone immersion until hydrogen gas was not generated.

This gel body was moved into a drying container, a lid having a pinhole was installed, and the gel was dried in a constant temperature bath at 30 ° C. After the completion of drying, firing was performed by subsequently raising the temperature to 570 ° C. However, firing was possible without cracking all four. The compositional distribution of the obtained glass body in the radial direction was measured, and as shown in FIG. 4 showing the distance from the center and the composition ratio, it was constant regardless of the position in the radial direction.
The composition ratios of the other three glass bodies were almost the same.

Comparative Example 2 A gel body similar to that of Example 2 was prepared and immersed in a solvent without adding a desiccant. Subsequently, when it was dried by the same method, two of the four gel bodies had cracks. The remaining two gel bodies were fired to obtain glass bodies without cracks. When the composition of the obtained glass bodies in the radial direction was analyzed, the relationship between the distance from the center and the lead concentration composition was shown. As shown in FIG. 5, the lead concentration was high in the peripheral portion, and the degree of compositional variation was different between the two samples.

Example 3 Silicon tetramethoxide (Si (OCH ₃ ) ₄ ) 440
ml and dimethylformamide (312 ml) were mixed and stirred, and then 240 ml of methanol, 540 ml of water and 14.4 ml of 1N aqueous ammonia were premixed and then added. After stirring for 10 minutes, put it in a cylindrical container with an inner diameter of 50 mm.
Dispense into a book to a height of about 10 cm, and add a cylindrical gel to
This was produced. After gelation, it was aged for 1 week in a constant temperature bath at 60 ° C. The synovial fluid leached from the gel body during aging, and the gel body was in a state of being immersed in the synergic fluid. Of the six gels, sodium sulfate was added as a desiccant to the synergic solution of three gel bodies. After further aging for 1 day, the process proceeded to the drying step.
The remaining three gel bodies were aged for one day without adding anything, and the gel bodies that had been subjected to the drying step were taken out of the container and transferred into a container having a pinhole, and then kept in a constant temperature bath at 60 ° C. Dried in. At this time, the gel body to which the sodium sulfate was added to the syneresis could be dried without cracking, but all the gel bodies to which the sodium sulfate was not added to the syneresis were cracked at the time of contraction, and finally It broke apart.

Example 4 A gel body having the same composition and shape as in Example 2 was prepared. After aging this gel body for 7 days in a constant temperature bath at 30 ° C.,
A saturated lead acetate solution having a mixing ratio of isopropanol: water = 8: 2 was prepared, and the gel body was immersed at a temperature of 60 ° C.
Subsequently, the gel body was subjected to immersion treatment in the order of isopropanol, isopropanol: acetone = 8: 2 (volume ratio) and a mixed solvent of 5: 5, and acetone. As the immersion treatment liquid at this time, sodium sulfate was added to the immersion treatment liquid of isopropanol: acetone = 5: 5 from the isopropanol immersion treatment as in Example 2, and lithium aluminum hydride was added to the final acetone. did. Furthermore, this gel body was added with calcium oxide as a desiccant to obtain 0.3 m.
Immersion in an ethanolic solution of potassium acetate of ol / l for 8 hours formed a distribution in the composition. The gel body was immersed in acetone containing lithium aluminum hydride,
After a lapse of time, a glass body obtained by shifting to a drying step, drying in a constant temperature bath at 30 ° C., and then firing is Δn = 0.0.0 as shown in FIG. 6 showing the relationship between the distance from the center and the refractive index. It was 082, and the disorder of the refractive index in the peripheral portion could not be confirmed.

Comparative Example 3 A gel body was prepared in the same manner as in Example 2. This was immersed in the same manner as in Example 4 to form a distribution in the composition, and then immersed in acetone for 24 hours. Further, two of them were replaced with fresh acetone and subjected to further immersion treatment for 24 hours. After drying this gel body under the same conditions as in Example 4,
The glass body obtained by firing shows the relationship between the distance from the center and the refractive index. As shown in FIG. 7, when the acetone immersion treatment is performed once, Δn = 0.061, as shown by the solid line,
In the case of two times of acetone immersion, Δn =
It was as small as 0.075, and disorder of the refractive index was confirmed in the peripheral portion. Even when the number of times of immersion in acetone was increased to remove more water, the disorder of the refractive index distribution was large as compared with the gradient index optical element produced by the method of the present invention.

Example 5 100 gel bodies having the same composition as in Example 2 were prepared and continuously treated with the same treatment liquid. For the lead acetate saturated solution of isopropanol: water = 8: 2 (volume ratio), prepare a separate container for the gel body, start dipping treatment one by one every 3 minutes, and maintain a constant volume ratio for the gel body. Immersion treatment was performed in the liquid volume. From the gel body that has been subjected to the immersion treatment in a saturated solution of lead acetate, the immersion treatment apparatus shown in FIG. 8 is prepared for each type of solvent, and isopropanol, isopropanol,
A mixed solution of isopropanol: acetone = 8: 2 (volume ratio) and 5: 5 was continuously immersed in acetone, and after immersion for a certain period of time, a process of shifting to the next step was performed. FIG.
In the processing apparatus, the processing tank 1 mounts the gel body 3 on the gel body mounting apparatus 2 and performs processing while moving in the processing liquid 4. A desiccant is added to the treatment liquid from the desiccant addition nozzle 5 to remove water in the treatment liquid. The desiccant in the treatment liquid is filtered by the filtration device 7 of the treatment liquid circulation unit 6 and circulated to the treatment tank by the treatment liquid circulation pump 8. From the isopropanol immersion at this time, isopropanol: water = 5: 5 Magnesium sulfate was added to the immersion treatment liquid of, and lithium aluminum hydride was added to acetone. Immersion treatment was sequentially started from the gel body after the treatment in an ethanol solution of 0.3 mol / l potassium acetate to which magnesium sulfate was added, and a distribution was formed in the composition by the immersion treatment for 8 hours. The gel body, which had been subjected to the concentration distribution treatment, was sequentially immersed in a solution prepared by adding calcium hydride to ether. A desiccant was further added to each liquid to which the desiccant was added according to its water adsorption capacity. By such a method, the gel bodies that had undergone the immersion treatment were sequentially transferred to the drying step at regular intervals. After drying,
By raising the temperature to 570 ° C., the material became non-porous and a gradient index optical element was produced. The gel body produced in this example did not break even before it became glass. Further, among the desiccants used here, magnesium sulfate was able to be reused by recovering the hydrate filtered through a filter and subjecting it to heat treatment.

Further, the refractive index distribution shapes in the radial direction of the 1st, 50th and 100th glass bodies were measured and evaluated in the processing order of the manufactured gradient index optical element, but the distribution shape has no practical problem. It was only a difference in level, and it was not possible to confirm the disorder of the refractive index in the peripheral portion.

[0035]

As described above, according to the method for producing a glass body of the present invention, a glass body having a stable quality such as a refractive index can be produced with good yield and good reproducibility.
Also, it is possible to repeatedly use the immersion solvent,
It is very advantageous for cost reduction.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the relationship between the refractive index of glass manufactured by a conventional method and the distance from the center.

FIG. 2 is a diagram illustrating the relationship between the distance from the center of the glass manufactured by the method of the present invention and the refractive index distribution.

FIG. 3 is a diagram illustrating the relationship between the distance from the center of the glass manufactured by the method of the comparative example and the refractive index.

FIG. 4 is a diagram illustrating the relationship between the distance from the center of the glass produced by the method of the present invention and the composition ratio.

FIG. 5 is a diagram illustrating the relationship between the distance from the center of the glass manufactured by the method of the comparative example and the composition of lead concentration.

FIG. 6 is a diagram illustrating the relationship between the distance from the center of the glass manufactured by the method of the present invention and the refractive index distribution.

FIG. 7 is a diagram illustrating the relationship between the distance from the center of the glass manufactured by the method of the comparative example and the refractive index.

FIG. 8 is a diagram illustrating an immersion treatment apparatus used in the method of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Processing tank, 2 ... Gel body mounting apparatus, 3 ... Gel body, 4 ... Processing liquid, 5 ... Desiccant addition nozzle, 6 ... Processing liquid circulation part, 7 ...
Filtration device, 8 ... Pump for circulating treatment liquid

Claims (3)

[Claims] 1. In a method for producing glass by a sol-gel method, when a gel body formed from a sol is immersed in a treatment liquid containing an organic solvent, the treatment liquid is dehydrated by a desiccant while the treatment liquid is immersed. A method for producing glass, which comprises: 2. The method for producing glass according to claim 1, wherein the glass is a gradient index glass having a distribution in composition. 3. The method for producing glass according to the method for producing glass by the sol-gel method, wherein the gel body is produced while dehydrating the synovial fluid generated in the gel body with a desiccant.