JPS6021928B2 - Glass product manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for manufacturing glass products, and in particular,
The present invention relates to a method for manufacturing glass products suitable for forming products or devices used for transmitting light for both video and communication purposes.

The glass compositions of this invention are particularly suitable for forming glass products by drawing into fibers to form glass fibers used as optical fibers for the transmission of electromagnetic energy above 30 z. fiber(
Suitable for forming glassware used to couple electromagnetic energy between optical fibers (or between optical fibers), or between light sources or detectors, or used as part of optical integrated circuits. Suitable for forming or forming glass products used as active elements in lasers or optical amplifiers, or passing through to form glass products used as lenses, or used for relay images Suitable for forming glass products. To embody the above and other similar applications, the term glass waveguide may be used herein. Such a waveguide is 2 none,
It is possible to make one with an attenuation value of 10WB/thing or more from Shigen B/Hiro. For optical integrated circuits, attenuation values on the order of 1 dB/m are used, but for purposes such as remote communications, something less than 1 dB/m is required. The term "glass product" as used in this specification is meant to include products that have some degree of crystallinity. The inventors have already discovered a method of converting phase-separable glasses into porous structures. This porous structure is made mostly of silica, and by adding a refractive index modifying component to this porous structure and further filling the pores, at least one cross section of the sea bream has a uniform or non-uniform refractive index distribution. It can be converted into solid glass products. The present inventors call this method of adding a refractive index modifying component molecular filling. The inventors have demonstrated that such a method can be applied not only to the filling of porous structures produced by the leaching of phase-separated glasses, but also to the filling of other internal structures with a matrix constituting at least one network-forming material. It has been found that this method can also be applied to vented porous structures.

One known method of forming interconnected porous structures other than using phase separation is by CVD. Such methods are described in U.S. Pat.
32605y No. 1 is generally described. Also, in particular, US Pat. No. 3,859,073 describes the formation of porous bodies and the injection of dovants into the porous bodies. Such injection is accomplished by depositing small amounts of material into the pores of the porous body from a relatively dilute solution. In order to achieve a specific refractive index change and a specific refractive index distribution, it is necessary to deposit relatively large amounts of material into the porous matrix.

The inventors have found that, in order to better control the desired refractive index profile, it is essential to carry out the steps in a particular manner and order that has not been shown hitherto. As mentioned above, the main purpose of adding porous substances is to obtain a constant refractive index or refractive index change in the glass product.

According to this method, a product suitable for use as an optical waveguide, for example, can be manufactured. If the refractive index of the entire glass article is constant, this glass article can be suitably used as a core surrounded by a material with a lower different index of refraction as a cladding. This same effect can be produced in the cross section of a clad cylindrical product by creating a graded refractive index profile within the product. The term "parabolic distribution" is used to describe a case where a refractive index gradient exists in any cross section, such that the refractive index decreases progressively or continuously from the center to the periphery. is used. Also,
There are various refractive index profiles created by other means, such as those shown in US Pat. In any method for forming the glass products of this invention, the formation of a porous matrix constitutes a value-adding step, but losses (e.g., destruction) after this step are would reduce economic yield.

Also, it has been difficult to identify factors contributing to losses resulting from fractures, such as the formation of cracks and the appearance of light-scattering sources such as bubbles within the ruptured final product.

In order to obtain increased yields and satisfactory and reliable control of the refractive index, we hereby demonstrate that the previous steps require operating in a special manner and sequence that has not yet been shown. The method was improved.

In terms of yield, as in the production of conventional glass products, changes in methods do not necessarily result in a product without defects, nor do they guarantee that all such products will remain unbroken until subsequent processing steps. It is.

The increased yield means that the inventors have found a way to improve the statistical chance that glass skeins or other glass products will remain unbroken until subsequent processing. However, this means that statistically it cannot be guaranteed that an acceptable product will always be obtained even when all the basic steps of the invention are employed. As already pointed out, the improvements are not only in terms of yield, but also in ensuring that the desired refractive index profile is obtained to a satisfactory degree. There are times when it is difficult. This is mainly based on the following findings. That is, to obtain the best results, it is important that the step of loading the solid material into the pores is carried out in a manner that does not involve evaporation of the solvent, and that the subsequent heating step removes the solvent from the pores of the product. It is essential to increase the temperature of the laminate and, if necessary, the pillow stack should be adjusted so that the desired refractive index profile is achieved. The inventors have also found that certain dopants provide particularly advantageous results due to their physical properties while achieving satisfactory products.

Also, if the porous product to be filled is made by phase separation and leaching of the glass, special care should be taken to reduce losses during processing of the glass rod.
The inventors have discovered that product cracks result from one or more of the following: {a} Inaccurate glass composition; [b} Inaccurate heat treatment conditions for phase separation; Guidance is given below on how to select operating conditions to reduce losses due to cracking that occurs during drying.

This invention relates to a method for producing a desired refractive index profile in a glass article as a function of its dimensions by adding refractive index modifying components (hereinafter referred to as dopants) to a porous matrix having distributed pores. The method consists of the following steps: immersing the porous matrix in a solution of the dopant, separating the dopant within the matrix, removing the solvent (if necessary and decomposition products) from the matrix, and collapsing the porous matrix. In particular, the method is characterized in that part or all of the dopant is deposited by a method that does not involve evaporation of the solvent, and that the removal of the solvent is carried out until substantial formation of the dopant. The rate of heat exchange to remove the solvent (and decomposition products, if necessary) is adjusted to achieve and maintain the desired refractive index profile within the glassware. An outline of a series of steps to obtain a specific refractive index profile is shown below.

The entire process starts from a porous product with pores. That is, the steps are as follows.

{1- The dopant is subsequently deposited in the pores by a non-evaporative process.

This product consists of ta) thermal precipitation, which reduces the solubility of the dopant or dopant compound in the solvent by lowering the temperature to an extent sufficient to cause the dopant or dopant compound to accumulate; to change,
Chemistry, such as replacing the original solvent with a solvent in which the dopant or dopant compound is only slightly soluble, or introducing into solution a chemical that reacts with the dopant or dopant compound to form a less soluble dopant species. It includes the target area. From now on, the term solvent will be used to denote a chemical species that is at some stage a liquid that fills the pores. '21 Final solvent removal begins only after the next product is nearly complete.

The rate at which heat is applied to remove the '31 solvent (and decomposition products if necessary) is adjusted to achieve and/or maintain the desired refractive index profile within the glass article.

Furthermore, an outline of a series of steps for obtaining some specific refractive index distributions is shown below.

The process starts with a porous product and uses thermal deposition of the dopant or dopant compound. Immersing the tabular distribution 'a' porous matrix in a solution of the dopant or dopant compound.

'b' Step of accumulating the dopant by decreasing the temperature.

'c - Evaporation of the solvent present. 'd - The process of heating to a temperature that collapses the pores.

Immersing the step distribution OXa' porous matrix in a solution of the dopant or dopant compound.

{b} Depositing the dopant by lowering the temperature.

'C} Immersion in a solvent for the dopant to partially redissolve and diffuse the dopant from the matrix. (
Only the dopants that have accumulated near the outer surface of the product are removed in this step. ) {d' Step of evaporating the solvent.

[c- Process of heating to a temperature that collapses the pores.

'2'{a' Immersing the porous matrix in a solution of the dopant or dopant compound. {b' Step of settling the dopant by lowering the temperature.

{c- The process of partially drying the porous glass. (
d-Immersion in a solvent for the dopant to partially redissolve and diffuse the dopant from the matrix.

(Only the dopant deposited near the outer surface of the product is removed in this step.)'e} Evaporating the solvent.

'f- Process of heating to a temperature that collapses the pores.

Parabolic distribution [a' Immersing the porous matrix in a solution of the dopant or dopant compound. [b' Step of soaking in a solvent for the dopant at a temperature approximately equal to the temperature at which filling of the dopant into the pores occurs.

The product remains in the solvent for a sufficient time to create a refractive index profile created by diffusion of the dopant within the product such that the dopant concentration decreases as a function of radial distance from the central axis. 'cl The process of depositing the dopant into the pores by decreasing the temperature.

'd) Evaporating the solvent.

'e} Process of heating to a temperature that collapses the pores.

As shown above, the dopant has solubility characteristics that allow a desired dopant concentration in the pores to be achieved by simply diffusing the dopant solution into the pores at a certain temperature and then depositing it by lowering the temperature. It is preferable to use a substance that has Such a method concerns thermal pillowing. Although this method may be adopted, other methods may also be adopted. Therefore, this invention provides a method for manufacturing glass products with a desired refractive index profile using as starting material a suitable porosity matrix such that the refractive index modifying component is separated from the solution by lowering the solution temperature. This includes: As a method other than thermal sinking,
There is a method of decoupling solutes by chemical means without relying on temperature drop. In this method, common ion effects are used to reduce the solubility and solute accumulation (eg, the solubility of CsN03 in water is reduced in the presence of 1N HN03). The reduction in solubility can also be effected by exchanging the solvent, thus allowing subsequent accumulation in a manner that does not involve evaporation of the solvent. These methods include the addition of a suitable precipitating agent that reacts with the dopant or produces an appropriate change in pH. It is also possible to use a method that combines the steps of both thermal and chemical product means. This method is particularly useful when one or more dopants or dopant compounds are introduced into the pores. This invention avoids any subsequent deposition means involving evaporation of the solvent as the sole deposition means. This is because such methods do not yield consistent results. In direct evaporation methods, the solution evaporates from the surface of the product, causing the dopant to migrate from the surface into the interior.

There is also a gravity-driven vertical displacement method that deposits the dopant at the bottom of the product. Both of these effects have the effect of creating an unfavorable refractive index profile. It is fundamental to adjust the heating rate to avoid destroying the initial refractive index profile or damaging the lotus vent structure.

It is possible to create sufficient pressure to destroy the structure of a lock by generating steam or gas in an uncontrolled manner. Therefore, it is better to avoid letting the temperature of the solvent reach the boiling point where a large amount of vapor is likely to be generated. Various heating ranges and methods of controlling the heating to reach the desired results are shown below.

Control of the solvent removal process is necessary to avoid destruction of the pore structure of the moat flaw. i.e., initiating solvent removal at room temperature or below using a lock-proof method, and avoiding rapid changes in temperature that would cause excessively rapid generation of solvent vapor in an enclosed space. It is necessary to take precautions such as: Typical solvent removal methods when the solvent is water include placing the product in a tessicator for about 2 hours at about 2°C, or placing the product in a vacuum for about 4 hours at a temperature just above oo (e.g. 4°C). and then raise the temperature. Also, in some cases, the heating rate is maintained or reduced to a very low rate so that the product remains within a certain temperature range for a sufficient period of time to ensure the continuation of the particular result that occurred before heating. It turned out that this was necessary. In other respects, from one temperature to another,
For example, it may be preferable to rapidly bring the temperature to a point where the pores collapse after removal of the solvent. Later in this specification, guidance is given for aqueous systems, but it is equally applicable when organic solvents or other non-aqueous systems or mixtures of such systems are used. The following criteria can be adopted to select an appropriate dopant from among a large group of index modifying components.

The 'a' dopant must be soluble in the solvent at an appropriate concentration so as not to adversely affect subsequent steps after filling.

'b} The dopant must be capable of coalescing with the matrix either as a pillow pickle or as a subsequent heat-induced decomposition product.

'c) The dopant must be capable of coalescing with the glassy structure at or below the maximum temperature at which the product is subsequently processed.

The wind dopant must not change its physical or chemical state so that it is ejected from the matrix before the pores collapse.

'e} The following conditions exist to obtain low optical loss.
The '1' dopant must be free of iron, copper, and other undesirable transition metal elements.

■ When the pores of the porous matrix collapse, the immiscibility temperature of the composition must be lower than the temperature of the subsequent shaping step required to convert the product into another form.

Known components for modifying the refractive index of glass include:
戊, Pb, AI, P, each in hydrated or unhydrated form
, B, alkali metal, alkaline earth metal and rare metal oxides, nitrates, carbonates, acetates, phosphates, shelf salts, vitreous salts and other suitable salts.

Among these, Cs, Rb, Pb, Ba, AI, Na
, Nd, B and K are preferably used. Other dopants or mixtures of dopants can be used as long as they meet the above criteria. Although it is impossible to list all possible combinations of dopant elements,
The selection of such useful combinations, based on the above-mentioned guidelines, meets the requirements of those practiced in the prior art.
The concentration of dopant or dopant mixture within the final product waveguide will typically vary with location.

However, its concentration is greatest in the optical axis, and the concentration of the dopant or dopant mixture in the total glass composition is from 1 to 20 mol%, preferably from 2 to 15
mol %, more preferably 5 to 10 mol %. As a result, the silica content in the glass is greater than 75 mol%, preferably greater than 80 mol%, and even more preferably greater than 90 mol%, and the error between silica and dopant concentration is typically created by chord 03. ing. When choosing a solvent, it is necessary to consider the following:

[a} A solvent that does not damage the pore matrix.

[b} Solvents that can be purified to low concentrations of undesirable impurities. 'c) Solvents that can be largely removed by substitution with other solvents, evaporation, or decomposition by oxidation (or high temperature reaction with a chemically active atmosphere).

'd} A solvent capable of sufficiently dissolving the dopant compound or combination of dopant compounds to provide the desired level of dopant within the pores carried out by molecular packing.

'e} If a thermal deposition method is used, the dopant solution is such a solvent that has a sufficiently high temperature dependence of solubility to deposit the dopant into the pores when cooled.

'f' When used for deposition by solvent displacement method,
Such solvents have the special solubility properties required by the method. 'g' Economically low cost;
Also a solvent that can be dried at high speed.

Although it is not possible to test all combinations of solvents, water, alcohols, ketones, ethers, mixtures thereof, and salt solutions of these solvents may be used, meeting the above solvent selection criteria well. I understand.

Generally, because of ease and convenience, and because the first step of the post-doping solvent removal step is carried out at or below room temperature, it is usually necessary to cool the pore-filled product. , it is better to adopt thermal deposition method.

Preferably, the dopant used is hydrophilic, and the material is highly soluble at temperatures on the order of 100 qo, such that upon cooling to room temperature or below, a substantial amount of the material separates, thus Preferably, the material has a bond solubility coefficient that is appropriate for the target product.

Also, the dopant must be easily purifiable. That is, it must be such that the iron and transition metal content can be reduced to a negligible amount. More detailed guidance regarding solvent selection is provided by reference to Table 1. Table 1 shows the solubility of dopants in solvents at various temperatures. As already indicated, a number of guidelines need to be taken into account in selecting a scheme to obtain the desired result, and these can therefore be illustrated with reference to Table 1.

First, in order to obtain the desired dopant concentration in the product that gives a significant change in the refractive index, a solution with a sufficiently high concentration of dopant must be found by appropriate selection of dopant compound, solvent, and temperature. No.

To deposit the dopant or dopant compound,
It is necessary to use a solvent with sufficiently low solubility. Also, it is often necessary to remove substantial amounts of dopants from designated areas of the product, such as in glass fiber sheathing, in which case solvents with intermediate solubility are useful. Such dopant removal, as opposed to molecular packing, is called unstuffing. Hereinafter, this will be referred to as de-dopantization. Appropriate control of solubility for precise product formation of dopants or dopant compounds can be achieved in a number of ways. '1} For solvents in which the solubility of the dopant or dopant compound is highly dependent on temperature, thermal deposition methods are most appropriate.

The thermal mirror method has the additional advantage of being able to interrupt diffusion in the shortest time, thus making it possible to fix the desired concentration distribution with high precision. This is shown in Table 1 when the dopant is CSN03. There, the solubility is 4 from the desired loading level at 95oo.
℃ to the desired level of dopant removal. ■ Deposition and thermal pillow deposition due to common ion effects. Deposition occurs or is further enhanced by common ion effects.
For example, when the dopant is nitrate, the concentration of nitrate ions in the solution is increased by adding another source of nitrate ions to the solvent (eg, nitric acid). This reduces the solubility of the nitrate dopant. (Refer to CsNO in Table 1) {31
Deposition by solvent displacement.

Substituting a highly soluble solvent with a less soluble solvent results in a second product. The high solubility of nitrates in water allows water to be used as a solvent for filling operations. Dopant deposition occurred by replacing the water with alcohol, ketone, ether, or a combination thereof. Typical solubility is shown in Table 1. Change in '4' dopant compound.

The solubility range of the dopant compound can be varied by selecting different anions. For example, CSN
The solubility in water can be increased by replacing 03 with Cs2(C03)2. (See row 7 of Table 1) Table 1 As already pointed out, when carrying out the method of the invention on a porous open structure formed by suitable glass phase separation and subsequent leaching, a good In order to consistently and satisfactorily obtain a salable target product with economic yield, it is necessary to optimize the various stages of the method and to find correlations of the various parameters at each stage. It is necessary.

The guidance needed by those skilled in the art is based on the following steps.

'1' Selection of glass composition and heat treatment to obtain proper phase separation.

‘2} Leaching and cleaning.

'3} Filling.

[4} Dopant removal (if necessary).

[5} Drying and solidification.

The guidelines given in steps 3-5 apply to all matrices, not to matrices made from phase-separated glasses.

1. Glass composition and heat treatment time and temperature In order to obtain a satisfactory product, the glass composition must be separated into approximately equal volume ratios when heat treated at a specific temperature, and when maintained at that temperature, the glass composition must have a desired pore size. It is necessary to select a composition that can be phase-separated so that it can be phase-separated.

Much guidance can be given to those skilled in the art in that regard. Thus, the inventors have found it convenient to select such compositions from alkali metal shelf silicate glasses. Further guidance regarding suitable compositions is then provided, as discussed below. A number of compositions suitable for use in the production of porous glasses for various purposes have been reported (U.S. Pat. No. 2,106,744, No. 2).
215036, No. 2 Matsu 170y), but they are usually not for optical applications by methods based on phase separation and leaching of the soluble phase.

The inventors have discovered that only a narrow range of known compositions are suitable for optical waveguide manufacturing.
No. 3,843,341 discloses one such composition.
Although one representative is shown, it is often not preferred for methods where the product produced is wavi-like or elongated in shape, usually with a minimum dimension of four skins or more. For example, a number of known glasses within the preferred range of U.S. Pat. No. 3,843,341, and shown in the table below, were drawn vertically to a diameter of 8 bars at a rate of 1 inch per minute. Although these glasses phase separated, all of the compositions in Table n cracked upon leaching. Table 11 Known compositions that cracked during one lick.Note. The numbers are mol%.In particular, we also found out the following.

{1) As shown in U.S. Pat. No. 3,843,341,
All shelf sodium silicate glass compositions drawn into rods cracked during leaching.

The same was true for the compositions within the composition range indicated as the preferred composition range in the above patent. {21 U.S. Patent No. 3
Many of the shelf alumina silicate glass compositions shown in No. 843,341 cracked when processed as described above.

The compositions within the preferred composition range were also the same. '
Many of the glass compositions in the preferred composition range shown in US Patent No. 3'ZZ170y cracked when processed as described above.

Many of the silica-based glass compositions previously mentioned have proven unsatisfactory due to the need to ensure satisfactory yields of the final product.

However, the inventors have discovered a wide range of useful glass compositions that have not yet been demonstrated. In addition, the inventors have discovered a set of criteria that can be applied to identify other specific ranges of phase-separable glass compositions that give satisfactory yields of product. From a commercial point of view,
Although almost all silicate glass systems exhibit a phase-separated composition range, it is most convenient to use shelf-alkali silicate glasses because they exhibit a wide phase-separated composition range.

In order to obtain a satisfactory product, it is necessary to select the composition as follows.

{1' A composition that separates into two phases, a high silica phase and a low silica phase, upon heat treatment.

Preferably, the low silica phase is dissolved in a suitable solvent. '
21 A composition that separates into phases with approximately equal volume ratios by heat treatment at a specific temperature, and when that temperature is maintained, becomes Liantong Weitenzo.

t3' A composition that melts easily and is easily purified by conventional methods. {A composition that is relatively easily molded into a 4' rod-shaped object or an object with the minimum dimensions (thickness, diameter, etc.) of 4' or less, and hardly undergoes phase separation during the molding process.

Below, a systematic procedure for selecting a suitable composition is presented.

'1' Almost all silicate glass systems exhibit a compositional range of phase separation.

However, shelf-alkali silicate glasses that exhibit a wide phase-separated composition range have commercial value. The low silica phase of glasses in this composition range can be more easily dissolved than in a single acid solution. Also, it is now necessary to add mineral components such as aluminum oxide to improve certain properties of these glasses. However, in phase separation, certain oxides are undesirable because they enter the low silica phase and are difficult to dissolve with a single acid solution. Thus, only those that do not substantially reduce the solubility of the low-silica phase are suitable other components. (2) After determining the glass system (together with the dopant), it is next necessary to determine the compositional immiscibility C and its coexistence temperature Tp.

Tp (C) is a temperature equal to or higher than the temperature at which the glass (C) is uniform. Methods for determining Tp are described in the known literature. (For example, W. Haller, D. Sun. Bl.
ackbum, F. E. Wa bag taffaMR. J. C
harles, "Metastable immiscible surfaces of the Na20-&03-Si02 system," J. Amer. Ceram. Soc. 5
31}, 34-9 (1970)) Legs The inventors have discovered that it is necessary to determine a composition C, which exhibits an equilibrium volume fraction of about 50% at at least some heat treatment temperatures. Let this temperature be To(C,). The method for determining this temperature is as follows. 'a} Three (or more) temperatures (approximately 50 qo apart from each other) T,, T2,
Select T3.

L<T2<T. <T. (C,) The temperature of the glass sample is T,,
At T2 and T3, heat treatment is performed for a long period of time until the color becomes white.

[b} One phase of these heat-treated samples (the same phase was selected for all samples).

) was measured using an electron microscope. '
c) A plot of volume fraction V(T) versus heat treatment temperature T was made.

By interpolation (or extrapolation), the volume fraction is 50 (±5
)% (ie, L(C,)) was determined. (4}
After knowing Tp(C) and To(C,), it is necessary to determine the composition range (C2) within the composition range C, as shown below.

(a} 57500>T.

(C2)>50000(b'75000>Tp(C2)
>60,000 These temperatures are chosen to avoid long heat treatment times. Of course, other ranges can be selected if long-term heat treatment times of one week or more are acceptable. '5- The composition range C2 is further narrowed by the requirement that it must be easily purified during melting.

This requires that the viscosity of the melt at high temperatures must be sufficiently low. In addition,"
"Refining" means removing air bubbles in the glass and dissolving crystals and solids to make it uniform. A narrower range of this C2 is defined as C3. That is, all glasses belonging to C2 are further properly refined. The inventors have found, for example, that a convenient point of view for identifying glasses that can be purified is that glasses containing at least 28% &03 will be satisfactorily purified. ■ Easily purified, 5
Although phase separation occurs at a volume fraction of 0%, not all compositions of C3 are desirable.

That is, there is an additional requirement that the desired composition should exhibit little phase separation during the molding operation. The degree of phase separation during the forming process is influenced by the viscous properties of the glass at and below the coexisting temperature, the dimensions of the product being formed, and the cooling rate. In order to determine the composition C4, which exhibits little phase separation on cooling at and below the coexistence temperature, a product with preform dimensions suitable for use as an optical waveguide that is stretched is subject to the development of large thermal stresses. cooling at a rate low enough to prevent The degree of phase separation that occurs in these products can then be determined. Within the composition range C3 that does not undergo phase separation during the molding process, there is a more limited composition range C4. A composition that satisfies this condition is preferably 7
No 10, 60000, more preferably no 695,
It has a Tp of 640 qo. '71 The final criterion is to ensure that there is sufficient compositional difference between the two separated phases for effective leaching. Therefore, only the composition C* that satisfies the following conditions within the composition range of C4 is selected. Tp(C*)-T.

(C*)27500 Now that the desired composition range C* has been found, any composition Co can be selected within it.

The heat treatment temperature and time for this particular composition of Co is determined by the following procedure. 'a} The heat treatment temperature for Co is set equal to To(Co), ie the temperature at which the volume fractions of the two phases are equal.

If C* is chosen correctly according to the above criteria, this temperature is not so low that the time required to obtain a suitable microstructure for leaching becomes too long and uneconomical. Similarly, this temperature is not too high either. If it is too high, the following can be said. [1] Deformation of the glass occurs during heat treatment.

[2] If the heat treatment temperature is 160℃ or higher than the glass transition point
If it is higher than qC, the phase separation tends to be rapid, and the controllability of the phase separation is poor.

According to these requirements, the preferred heat treatment temperature T days is limited to the following range.

575℃〉TH(C.

)=~(C.)>50000'b} Now that TM(Co) has been determined, the heat treatment is determined by conditions that provide a microstructure suitable for leaching. Heat treatments are carried out at different times. That is, t, (1 hour) < t2 (2 hours) < t
3 (3 hours) etc. The time tmax, beyond which the permeability of the structure begins to be destroyed, can be determined by electron microscopy. The size of the phase that can be leached is determined by micrographs, and the preferred heat treatment time is t
m pine, but the microstructure size at that time is at least 150A, preferably less than 300A. We have applied the above criteria to alkaline shelf silicate systems and identified certain features of the composition range that contribute to good yields of optical fiber preforms of at least two leg diameters, such as phase separation during molding or Problems arising from insufficient phase separation in the phase separation process could be avoided.

Phase separation during molding of glass products from the melt, and insufficient phase separation or destruction of Rentsu horizontal structure during phase separation heat treatment,
Subsequent processes such as the phase-separated glass leaching process and/or the drying process of the leached and filled glass can result in cracking of the glass.
Here, it has become clear that the composition of the composition that provides the best yield falls within the wide range shown below. (All numbers are mol%) In the above table, Q is AI203 concentration (mol%), x is p
And p is the ratio A20/R20 (A20 is K20, RQO
and the sum of the mol% concentration of Cs20, R20 is Li20
, Na20, K20, Rb20 and Cs20 mole%
total concentration), and ^ is the ratio Li20/R20. Since the presence of peaks 203 in the glass affects the results, we will first discuss a glass that does not contain peaks 203.

In the absence of AI203, the ranges shown in the table are appropriate provided K20 is present and p is limited to 0.1-1.0. If the concentration of K20 is zero, then p
The upper limit of the range is 0.8. Lithium glass has a tendency to become opaque, so its chemical substance (Li20)
It is preferable not to use. In this case, R20 is Na20
, K20, Rb20 and Cs20. All other limitations and conditions remain. Rubidium and cesium glasses are more expensive than those made from sodium and potassium. They can be excluded from an economic point of view. At that time, R20 is N
This is the sum of a20 and K20. All other limitations and conditions remain. When more than 0.5 moles of AI203 are present in the glass, a wide range for R20 is between 6 mole% and 9 mole%.

The most economically preferred composition with an AI of 203 is N
It is composed of R20 consisting only of a20 and K20, or R20 consisting only of Na20.

The glass compositions shown in Table m were identified using the above criteria and were found to be satisfactorily used in the molecular packing method of the present invention. That is, these glass compositions provided satisfactory control of the pore structure after phase separation and bleaching, and good yields of the final product. Table m Leaching Composition Another key point of this invention is the leaching of shelf silicate glass which can phase separate.

Before leaching, the product is leached to remove surface contamination or to remove surface layers of the glass that have a significantly different composition than the interior due to volatilization of components such as B03 and Na20 during molding. It is better to perform sand etching with hydrofluoric acid for about 1 hour. Concentration of acid solution, I
Amount of J-Ching Solution and Leaching Temperature Directly Affect the Progress of Leaching In leaching it is fundamental to contact the product with a sufficient amount of leaching solution to dissolve the soluble phase.

Leaching rate is usually controlled by adjusting temperature. The glass should be at a temperature above 80°C, preferably above 9000°C. Also, NH
It is desirable to use an acid solution saturated with 4CI or an equivalent compound that can reduce the concentration of water in the acid leaching solution. Since the thickness of the outer layer swollen by the leaching treatment creates tension in the inner untreated layer, the use of the above compounds reduces loss due to cracking of the product by controlling the swelling field of the treated layer. It has been found that the rate of leaching, and the redeposition of shelf salts into the pores of the glass during leaching, can be regulated by controlling the concentration of shelf salts in the acid leaching solution.

327.3 NH4CI per evening, 33.6' per Wednesday evening
Glass rods (length 10 skin, diameter 8 willow, composition 57% Si02,35
%&03, 4% Na20 and 4% K20), the leaching speed at 95oo was measured.

As a result, it was found that when the amount of B203 in the leaching solution increased, the leaching time became longer. The results are shown in Table W below. Redeposition of shelf salts into the pores is thought to lead to the destruction of the glass rod.

This can be avoided, for example, by replacing the leaching solution with increasing shelf salts. However, this requires large amounts of leaching solution.
For example, in order to avoid a leaching time of no more than 660 minutes, 1550 ml of leaching solution is required per 100 ml of glass. However, this increases costs and also creates pollution. To this end, it has been found convenient to provide a cold trap so that excess material is continuously removed from the solution as it enters the solution from the product being leached. Cold traps are effective at speeding up the process even at temperatures several degrees below the glassware temperature. Preferably, the temperature of the cold trap is an order of magnitude lower than the temperature of the glassware. When NH4CI is present, it is convenient to choose a cold trap temperature such that the acid solution remains saturated with the N ratio CI. Without the presence of NH4CI or equivalent compounds in the leaching solution, glass-like fractures can be suppressed to low levels. However, the amount of NACI should be 1% by weight and preferably 2% by weight since statistically there is an equally low level of glass fin failure when N-ratio CI is present. . The most convenient method for determining the appropriate leaching time is to leaching the glassware and measuring the mass of the product at time intervals until little or no weight loss is observed.

Leached products are usually washed with deionized water.

In some glasses of certain compositions, silica gel buildup is observed within the pores, but this can be removed by cleaning with NaOH. It has also been found that this deposition can be minimized by composition selection. The compositions shown in Table m alleviate this problem, especially those with minimal silica. If the porous matrix has been produced from the already mentioned phase-separable glasses or, for example, by chemical porcelain deposition, the selection of suitable filling and dedopant conditions can be carried out according to the guidelines given below.

With known forms of optical waveguides, the desired physical properties of the optical waveguide (eg, size, closure number, bandpass, etc.) are related to the change in refractive index as a function thereof.

The dependence on the concentration of the dopant or dopant compound can be determined by a literature review or by appropriate experimentation.
These determine the maximum concentration of dopant or dopant compound that the glassware requires. A sufficient amount of dopant or dopant compound must be dissolved in the fill solution to reach the desired concentration at a particular fill temperature and time. These parameters can be determined by the following procedure. (1) Determination of the filling temperature of a porous glass machine {a} Determine the dependence of the solubility of the dopant or dopant compound in a suitable solvent on temperature.

[b} The filling temperature lies between the temperature at which the desired concentration of dopant or dopant compound saturates in the solution of {a-- and the boiling point of the solution.

'21 Determination of filling time of porous glass sill The filling time is
It depends not only on the concentration, temperature and composition of the dopant solution, but also on the size of the microstructure of the porous glass comb.

The procedure given here is for a given set of dopant solution, temperature and microstructure of the porous glass twill. For changes in any of these variables, this procedure should be repeated or modified appropriately according to guidelines. 'a- Measure the diameter of the porous glass strand and soak it in the dopant solution. 'b} Monitor the weight of the porous glass twill as a function of time.

'c) Change in weight of collection with respect to time t y(t) = [M
By plotting (t)-M(〇)] [M(of)-M(0)], the time to beyond which the weight hardly changes is determined.

M(0), M(t), M(target) are the initial weights, respectively.
The weight at time t and the weight at infinite time (an extremely long time). {d} With the same dopant solution and the same temperature, the time t required to fill another porous glass rod of diameter a is given by the following equation:

Example 2 A porous glass rod was filled with a concentrated aqueous solution of CsN03 (120 ml of CSN03 per 100' of solution) at 100°C.

The radius of the glass rod was 0.42 mm. Weight increase as a function of time was measured. The results are shown in Figure 1.
It can be seen that the weight of the glass rod hardly changes after about 200 minutes. Thus, a suitable filling time for this glass rod is about 4 hours. '3' Determination of the dedopant time to create a parabolic distribution of refractive index in a porous glass rod by thermal deposition. In order to create a parabolic distribution of refractive index in a porous glass rod, the filled glass rod made in '2' is immersed in a solvent. This results in partial dedopantization.

This needs to be done at a temperature at which the dopant does not pass. The dedopantation time depends on the temperature as well as on the microstructure of the porous glass comb. The procedure presented here is based on a given filling temperature and microstructure. [a' Dedopantation studies were performed at the temperature at which the glass twill was filled by monitoring the weight change as a function of time while the glass twill was immersed in the solvent.

[b - The characteristic change y(t) of Equation [11] is plotted against time t.

y(t): M-band 3 M-band I1'[c' The eyebrow song o at the time of dedopuntation depends on the desired refractive index distribution.

This is now the next range. 1/3 Mi y (shi) Mi 2
/3 Example A glass rod filled with a porosity of 10,000 with a concentrated solution of CsN03 (120 ml of CsN03 per 100' of solution) was selected.

It was then de-dopantized in water at 100 pm and weight loss was monitored as a function of time. The results are shown in FIG. The dedopant time range can be calculated from the graph. {4'Determination of dedopant temperature and time to create a step-wise distribution of refractive index by thermal product The de-dopant temperature for making step-index type glass fibers depends on the dopant solution.

Since it is better to have as low a refractive index as possible in the armor bag, the dedopant temperature is typically several degrees above the freezing point of the dopant solution. The time required for dedopantation depends on the desired sheath thickness, as well as parameters such as the dedopant temperature, the concentration of the previously used fill solution, and the size of the porosity and microstructures of the glass fins.

The procedure presented here is based on a predetermined set of these variables. If the values of any of these parameters change, the entire procedure will need to be repeated and adjusted according to this guideline. When the desired thickness of the armor bag is d and the radius of the filled glass rod is a (>d), the following equation holds true.

Y = 2 concubines (Hatake) 2 By knowing Y, the correct dedopant time can be determined by the following procedure.

[a} Dedopantation studies were carried out in the desired solution at the desired temperature by monitoring the weight change y(t) of the signature as a function of time.

'b) As shown in FIG. 3, the change in weight of the feature (Equation '1}) with respect to time was blotted.

{c- From the above plot, the time to when y is
I found out.

This is the desired dedopantation time. The practical application of the dedopanation procedure is often to reduce the dopant concentration in the outer layer of the product so as to obtain the desired refractive index profile.

As mentioned above, this means that, for example, when the actual filling is at 95°C
by replacing the dopant solution with a dopant-free solvent at the same temperature, or by replacing the dopant solution with water or dilute nitric acid if the system is water-soluble, when completed with a saturated solution of the dopant. This can be done by

At that time, the dopant tends to diffuse outward, so
The dopant concentration in the cross section of the porous matrix varies. Of course, the time required for dedopantation depends on the volume to be treated, but in the case of a glass casing with a diameter of 8 ribs, about 20 to 30 minutes are required. It is then preferable to stop the dedopantation by substituting the solution surrounding the glass comb with a cold solvent. Alternatively, in the case of water-soluble systems, nitric acid cooled with water or ice at a temperature near the freezing point is used. In the case of water-soluble systems, it has been found that the endpoint can be controlled by measuring changes in the electrical conductivity of the water used for dedopantation. {5) Drying, or removal of solvent, has two effects that affect process economics and product quality.
There are two problems.

These are cracks in the porous glass structure and changes in the dopant concentration distribution. The occurrence of cracks is a statistical problem,
Despite the drying procedure, samples may remain during the process. However, in order to operate the process on a commercial scale, it is necessary to employ procedures that minimize cracking and improve process economics. Such procedures should be such as to prevent dopant from migrating from the interior of the product to the surface resulting in an unfavorable dopant distribution. Due to the movement of the dopant, as shown in Example W, the refractive index at the center decreases and the refractive index at the periphery increases. As mentioned above, the resulting dopant distribution is dependent on dedopantation. Since an appropriate dopant distribution has been obtained in the presence of a solvent in the pore structure, it is essential to dry, that is, remove the solvent, without changing the dopant distribution to an undesirable state. A breakdown of the drying process revealed that there are many factors that influence this process.

They are shown below. [Al Gas generation Gas generation source is solvent, dopant decomposition product substances, and dissolved gases.

If gas evolution is rapid due to rapid heating or insufficient gas removal, the differential pressure created within the pores can destroy the glass and/or transport dopants from inside the glassware. Resulting in. Most of the 'b' size change solvent is removed from the porous glass, but the solvent layer attached to the surface remains chemically bound to the glass.

When they observed this effect using water, they found that this layer persisted up to high temperatures. This phenomenon can also occur with other solvents. The sample shrinks as this layer is removed. If large differential shrinkage occurs in the pore structure, the stresses can increase to the point of cracking. 'C
} Decomposition of Dopant Compound The dopant used in the form of a solution is generally a compound that decomposes thermally.

In this invention, a dopant compound is selected that decomposes before the temperature at which the pores collapse. This decomposition process is generally accompanied by the evolution of large amounts of gas. Generally, it is desirable to control the heating rate during heating to a temperature range in which decomposition occurs to prevent cracking and dopant migration.

(d) Mass transfer may occur at several points in the drying process.

When the product is first dried, the dopant that remains in solution migrates to the surface and is deposited there as the solvent evaporates. If the solvent evaporates violently or boils, even the precipitated dopants can be displaced. After decomposition, if the dopant crystals are small, they are transported in the gas phase. If the dopant has sufficient vapor pressure,
A redistribution of the dopant by the gas phase occurs. If the dopant is a liquid, it will be redistributed by gravity. {e1
Removal of Hydroxyl IonsHydroxyl ions form an absorption band near the infrared, which is even more harmful for use as a waveguide.

If one wishes to remove hydroxyl ions for this or other reasons, a complex problem arises as follows.
That is, a certain amount of hydroxyl ions are trapped in the glass and can only be removed by prolonged heat treatment at high temperatures. However, over the same temperature range, the pores begin to collapse, allowing hydroxyl ions to enter the glass. Below is an outline of a preferred method that appropriately solves these problems. Initial removal of most of the solvent is accomplished by employing conditions where boiling does not occur. In the case of aqueous solutions, two approaches were used. One method is to first dry the porous glass article with the deposited dopants in a desiccator (under 1 atmosphere) for 2 hours at 0.2°C and then place it in a drying oven. Another method is
It consists of placing the product in a vacuum at 100 qo or less and at a temperature above the freezing point of the solution. In this method, when an aqueous solution of CsNQ was used as a dopant, it was found convenient to set the conditions at 4° C. for 2 hours. To further reduce the occurrence of cracks, it has been found convenient, when using an aqueous solvent, to wash the product at the end with a non-aqueous solvent that does not react with the glass. This is believed to help remove hydroxylions. A suitable solvent is, for example, methyl alcohol. It has also been found that it is preferable to warm the glassware maintained below 1000 °C slowly to room temperature under vacuum and usually maintain it for 2 hours before transporting it to the drying oven.

In the case of non-aqueous solutions of the dopant, it has been found appropriate to place the glassware under vacuum at room temperature for a few hours and then transport it to a drying oven.

This speeds up the process compared to methods using aqueous solutions. In the drying oven, the samples are dried at a high drying temperature under vacuum with a heating rate of no more than 3 pC/h, preferably at a heating rate of 15 °C/h, since a low heating range severity can reduce cracking and avoid dopant redistribution. It is desirable to heat it up to

Appropriate low heating Q coverage will determine the economics of the process.

In some cases, it is cost effective to undergo a high rate of destruction in order to increase the rate of product production throughout the process. However, the increase in heating Q severity also needs to be balanced against the increased risk of destroying the desired refractive index distribution of the crack-free product. The example skins show that this problem occurs at a heating rate of 50 oo/hour, at least as far as the dopant used is concerned. High drying temperatures depend on the porous glass matrix.

First, the pores of the unfilled product are crushed, and its glass transition point T
Appropriate value can be found by measuring g. Preferably, the high drying temperature is selected between 50 qo and 150 qo below the glass transition point. More preferably, the temperature is 75 to 1200 below the glass transition point.
A narrow range of 0 is better. The next step in drying is to hold the glass under this high drying temperature for 5 to 20 hours, preferably 40 to 12 hours.

During this period, the glass can be kept under vacuum or at atmospheric pressure under a selected gas. It is desirable to pass gas around the glassware as this assists in the drying process. Also, whatever the drying conditions during the maintenance period, if it is desired to reduce the absorption near the infrared, and if there is residual iron in the glass, the sample should be subjected to oxidizing conditions. Exposure is desirable. At this acidic stage, the Fe20/Fe30 ratio in the glass decreases, and therefore the absorption by Fe20 ions decreases. According to a preferred procedure, a porous glass article having a glass transition temperature of 725q○ is heat treated at 625° C. (10 to 0 below the glass transition temperature) for 9 hours with oxygen gas flowing around the sample. '6} Once the solidification and drying process is completed, the pores of the product are immediately crushed.

The temperature of the product is rapidly raised to a temperature at which solidification occurs.
Solidification is complete when the pores of the product are collapsed and the product is cooled to room temperature. If the product is to be further processed by reheating above the solidification temperature, the solidification step must be carried out at or below atmospheric pressure. If I do not,
Gas generation is likely to occur during reheating, resulting in the formation of bubbles. If the matrix is produced from a glass capable of phase separation, it is desirable to heat the porous glass sample under reduced pressure of oxygen (approximately 1/5 bar) to 82,500 ℃, at which solidification occurs.

Examples of the present invention are shown below, but these are not intended to limit the invention in any way.

Example 1-V Example 1-V illustrates the treatment of a porous matrix with aqueous solutions of dopants at various concentrations and solidification into glasses with different concentrations of dopants.

A general procedure and subsequent processing to produce a porous matrix from a phase-separable glass is provided below. Each example also illustrates the use of different dopants in a range of concentrations, different solidification temperatures, and different final glass compositions. Melting and Forming A glass with a composition of 4 mol% Na20, 4 mol% K20, 36 mol% B203 and 56 mol% Si02 was melted and heated to produce a homogeneous melt, which was drawn. 0.7 in diameter, 0.7 in diameter. & got that glass rod.

Heat Treatment Using a Cooling Coil Glass rods were heat treated at 550 qC for 2 hours to cause phase separation.

Etching before leaching Each glass rod was etched for 1 second in a 5% HF solution and then rinsed with water for three inkstone sand intervals.

Leaching glass rod containing N ratio CI of 2% by weight*M
Leaching was performed at 95oC using CI.

The leaching time was chosen in advance to reach a stage where the rate of weight loss was almost zero.
The trailing time selected in these examples was greater than 3q hours. During leaching, the shelf acid concentration of the leaching agent was maintained below 50°C by providing a precipitation temperature range of 4000°C in the leaching solution. This speeded up the leaching and avoided redeposition of the shelving compounds in the pores of the matrix. 40:00 is chosen so that there is no cross-product of the N ratio CI from the leaching solution. This temperature is above the saturation temperature of the CI so that a suitable amount of N is maintained in solution to greatly reduce sample destruction. Washing The leached material was washed with deionized water.

The washing cycles were conveniently controlled by determining the concentration of iron in the effluent. For convenience, cleaning was carried out at room temperature using 1 portion of water per volume of glass. In discontinuous operation, the water should be changed about 6 to 8 times, giving a wash time of about 3 days. With each water change, the iron concentration is reduced by a factor of 1 when fresh wash water is added, so that washing can produce sufficiently low levels of iron even without iron concentration measurements. It can be considered that this has been achieved. It is better to simply replace the fill wash water with the fill solution, which is an aqueous solution of each dopant, to provide a smooth transition from the last wash step to the fill step.

This is done by draining the water and filling the tube containing the porous glass rod with the filling solution. In Example 1 None, when the sample was removed from the filling solution and cooled to 20°C, the dopant was partially deposited in an amount corresponding to the water solubility of 220 in the residual solution filling the pores. . (e.g. 10% per 100' solution remaining
The evening Ba(N03)2 is dissolved in the water in the pores after thermal deposition at 0. Similarly, 6 Yuhi 3B03 per 100 remaining solutions are dissolved in the water in the pores. ) The remainder of the dopant was subverted during the drying process, which was initiated by placing the porosity product in a desiccator at atmospheric pressure for 2 hours at 2°C. Drying under vacuum was then continued in an oven heated at a heating rate of lyo/h to the high drying temperature (previously defined). This high drying temperature was determined by the method described above, and was 625o0 for the samples used in Example 1 and in the field. Holding time: The glass rod was then maintained at a temperature of 62 mm for 96 hours with oxygen gas flowing around it.

Upon completion of the holding time, the glassware was immediately subjected to a bubble bursting step.

That is, the temperature of the glass product was raised to a temperature at which bubble destruction occurred, and solidified glass twill was produced. This step is carried out in a reduced pressure oxygen atmosphere (approx. 1/F) and the final temperatures are given in the table. Example 1 Example 1.1 Example m Molecularly filled dopant (Pb(N03)2, public B03 aqueous solution) with POO+B203 Glass birch number 7, P(NQ)2 of 40 evenings and 10 evenings per 100 cc of water from 3803 8 total due to the dopant solution ○
Example of filling for 1 hour and breaking bubbles at 82 o
Molecularly filled dopant with N mother ○1 B203 (mother (N03) 2, melon B03 aqueous solution) glass comb number 8, Ba (N03) 2 of 12 minutes per 100cc of water
and 6 Yuhi 3803 for 4 hours of filling at 85 0 and bubble bursting at 83000 Example V The above examples all relate to uniform doping of glass combs.

As mentioned above, the glass rod is left for a sufficient period of time for the dopant solution to diffuse into the pores, and the dopant concentration in the outer layer of the glass rod is adjusted so that a certain refractive index distribution is obtained in the glass rod in which the bubbles have been ruptured. It is possible to reduce the Two porous glass combs were prepared according to the procedure described above and immersed in an aqueous CsN03 solution at a concentration of 95 mm CsN03 for over 4 hours at 100 mm/120 mm CsN03. Next, add 95 glass rods.
qo water and left for 11 minutes and 2 minutes, respectively. After a predetermined period of time, each glass rod is
It was immersed in water at ℃ for 10 minutes to generate a hot pillow of CsNQ. The solvent was then removed and the glass rod was bubble-busted as described above. The obtained refractive index distribution is shown in FIG. Some porous glass shavings produced by the above-mentioned method in Examples were placed in CsN03 and CsC03 solutions as shown in Table V.
It was soaked for more than 4 hours at 5 points.

Next, these glass rods were de-dopantized to obtain a step-like refractive index distribution. (The refractive index profile of glass comb sample 13 is shown in FIG. 5.) The time required for dedopantization was determined using FIG. (In other words, in the case of glass comb sample 13,
y(ra) = 0.50, and according to Figure 3, to = 300
(min)) The filled glass twill was de-dopantized by soaking in ice water for 300 minutes, then the water was removed and the glass twill was bubble-broken as described above. Table V' shows the refractive index at the center of the glass rod. Table V Examples Skin As already mentioned, when using dopant-filled glass rods, it is important to dry at low speeds at temperatures between 0° C. and around 600 qo.

This example illustrates the difference in refractive index distribution due to different heating rates. Some of the filled porous glass rods used in Example V were dedopantized to produce a stepped index profile as shown in Example V. After thermal condensation, the glass twill was dried under vacuum at 4° C. for 24 hours. Next, heating was carried out under vacuum at heating rates of 50, 30, and 15 o0 per hour. The obtained refractive index distribution is shown in FIG. A heating rate of 100° per hour resulted in considerable breakage of the glass rods.

When it is desired not to change the mirrored dopant distribution, the heating rate is preferably 2 pi/hour or less. A comb heated at lyo/hour was selected for fiber processing.

The glass twill piglet molded body was placed between the opposing flames of two gas oxygen torches and the molten end was manually pulled into fibers. The end of the fiber is attached to a rotating drum which draws the fiber to a diameter of 185 mm. This fiber has 0. A white light with a selected spectral range was illuminated by a 100 A wide interference filter whose transmission center was guided by &. The absorbent material was contacted with the armor along a length sufficient to remove any form of armor. Transmission intensity 1(1) was measured on long fibers. At this time, all fibers except one skin were removed and the transmission intensity was measured again. The loss in transmitted intensity (dB/pine) is given by the following equation: Loss (calm/thing) = 1■.

In the weaving formula, 1=12-1, where 12 and 1 are the long and short fibers, respectively, and the length of the fiber (pine).

The loss in transmission intensity was 2&lt;/RTI&gt; less than the 10&lt;/RTI&gt; necessary for many communications applications. EXAMPLE Example 1 The filled porous glass twill after leaching and washing was treated with solution 1 as described in the first part of W.
95oo in CsN03 solution of 120mm per 00cc
Soaked for 4 hours.

The sample was cooled to 20°C, the temperature at which the dopant was partially absorbed. It was then dried in a desiccator for 2 hours at room temperature. Since the obtained sample is uniformly filled,
2 with water at a temperature of 4°C to introduce a certain distribution.
Then washed with Suzu HN03 for 3 minutes. It was then vacuum dried at the same temperature. Once most of the water was removed, the temperature was gradually increased and the sample was slowly dried as indicated in the preferred procedure of this invention. At intermediate temperatures, CsN03 decomposed into Cs20 and various nitrogen oxides. Solidification was complete when the sample turned from white to clear and the sample was removed from the oven. The composition of the final product is 90
．． 6% Si02, 3.4% B203 and 6.0%
of Cs20 (all mol %), and the impurity transition metal was 1 part per million. Example
K As already indicated, wide variations can be made in the selection of dopants, solvents, and loading and dedopant operating conditions, combinations and substitutions of these parameters to obtain desired results, or modifications of operating conditions, etc.

This invention provides guidance to those skilled in the art, and this example illustrates substitutions and combinations of parameters that yielded satisfactory results. All porous glass shavings used were prepared by the general procedure previously described, and solvent removal and heating were performed under favorable conditions. The results obtained are shown in Table 1.

Column and row notes for this table are listed below. 1st column Dopa Soto used.

2nd column 100' dopant concentration per solution.

3rd column Solvent, ie the solvent used in the first filling step. Fourth
Column Temperature (°C) and time required for the first filling process.

Column 5: Solvent A. This solvent is used to reduce the concentration and cause the refractive index change and to produce the dopant order product.

Column 6 Temperature (00) and time required for changes in dopant volume and refractive index distribution.

Column 7 Solvent B is used to properly adjust the dopant concentration in the matrix.

may cause further accumulation before solvent removal. Therefore, the dopant concentration near the glass surface A more complete reduction is possible.

Column 8 Temperature (°C) and time required to adjust dopant distribution by further solvent treatment.

9th column indicates the temperature (00) at which drying starts.

(V) shows drying under vacuum, (A) shows drying at atmospheric pressure in a desiccator in the first stage.

10th column shows the measured value of refractive index.

The first row is the same as the glass ant sample 13 of the example and includes a comparison with the second row.

The second row is further treated with methanol and water. while the same filling solution However, the difference in refractive index increases. There is.

3rd row: CsNQ is replaced with Cs2CQ, which has high solubility.

The filling operation can therefore be carried out at room temperature.

Lines 4 to 9 Different dopant and solvent combinations are used.

Lines 10 and 11 indicate the use of a mixture of dopants.

Line 12 Neodymium nitrate is used as a dopant, and an organic solvent is also used.

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[Brief explanation of the drawing]

Figure 1 is a graph representing the weight fraction obtained by soaking a porous glass rod in a CsN03 solution at 0 p0, and Figure 2 is a graph representing the weight fraction obtained by soaking a porous glass rod in a CsN03 solution at 10 p0. Figure 3 is a graph showing the loss of weight fraction obtained by immersion in water at 100 pm after immersion in porous glass rod.
Graph showing the loss of weight fraction obtained by immersion in water at 4° C. after filling CsN03 with qC. FIG. 4 is a graph showing the refractive index distribution of the glass rod of Example V; 2 shows the cases of 11 minutes and 2 whisker dedopantization, respectively, and FIG.
2 and 3 are heating rates of 15 and 3 according to Example W, respectively.
0 and 50°C. This shows the case where the temperature of the glass stylus is raised. FIGURE I FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5

Claims (1)

[Claims] 1. Adding at least one type of dopant to a porous glass preform having internal communication pores by immersing the porous glass preform in a dopant solution to impregnate the porous glass preform with the solution. and depositing a dopant from the solution into a preform.
In a method for manufacturing glass products that includes the steps of removing the solvent from a porous preform and collapsing the porous preform into a solid body, the temperature of the impregnated porous glass preform is changed to increase the A glass comprising the steps of reducing the solubility of the dopant and depositing the dopant within a porous glass preform prior to substantial evaporation of the solvent, and drying to remove the solvent from the pores to obtain a glass article after collapse. How the product is manufactured. 2. The method of claim 1, wherein a small amount of the solvent is allowed to evaporate before substantially all of the dopant is deposited. 3. The method of claim 2, wherein a second dopant is introduced. 4. Adding the porous glass to a second solvent in which the solubility of the dopant is substantially lower than in the first solvent to reduce the dopant concentration in the outer layer of the porous glass preform prior to heating for solvent removal. 2. The method of claim 1, further comprising dipping the preform. 5. The method of claim 1, wherein the glassware is immersed in a solvent for the dopant so as to change the concentration of the dopant in the pores after immersion in the dopant solution and before deposition of the dopant. 6. The method according to claim 1, wherein the solvent is removed using conditions that do not cause boiling. 7. The method for manufacturing a glass product according to claim 1, wherein the removal of the solvent is started in vacuum at a temperature below room temperature. 8. The method for manufacturing a glass product according to claim 1, wherein the solvent is water, and the removal of the solvent is started in a desiccator at a temperature around room temperature. 9. The method for producing glass products according to claim 1, wherein the solvent is water, and the solvent is replaced with an organic solvent before the start of drying. 10 After most of the solvent has been removed, 1
The method for manufacturing a glass product according to claim 1, wherein the glass product is heated at a slow temperature increase rate of 00° C./hr or less.
11. The method for manufacturing a glass product according to claim 1, wherein the glass product is heated in a vacuum. 12. The method of claim 1, wherein the dopant can change the refractive index. 13 Claims for maintaining the glass product at a high drying temperature of 50 to 150°C, which is below the glass transition temperature of the undoped solidified glass used as a porous glass preform, or heating it at a very low heating rate. A method for manufacturing a glass product according to item 1. 14 High drying temperature is 75 to 1 below the glass transition temperature
14. The method for manufacturing a glass product according to claim 13, wherein the temperature is 25°C. 15 for at least part of the holding time at the high drying temperature;
14. The method of manufacturing a glass product according to claim 13, wherein the product is maintained in an oxidizing atmosphere. 16. The method for producing glass products according to claim 13, wherein the holding time at the high drying temperature is 5 to 200 hours. 17. The method for producing glass products according to claim 15, wherein the high drying temperature is maintained for 40 to 125 hours. 18 After the removal of solvent or decomposition products is nearly complete,
A method for manufacturing a glass product according to claim 1, wherein the temperature of the porous product is increased to a temperature at which collapse occurs. 19. The method for manufacturing a glass product according to claim 18, wherein the final temperature increase is carried out below atmospheric pressure. 20. The method for manufacturing a glass product according to claim 19, wherein the atmosphere in which the final temperature rise to the collapse temperature is carried out is an oxidizing atmosphere. 21 Dopants are oxides, nitrates, carbonates, acetates of Ge, Pb, Al, P, B, alkali metals, alkaline earth metals and rare earth metals, respectively in the form of hydrated or non-hydrated or mixtures thereof; The method for manufacturing a glass product according to claim 1, wherein the material is a substance selected from the group consisting of phosphates, borates, arsenates, and silicates. 22 Dopants are Cs, Rb, Pb, Al, Na, Nd
, B or K or a mixture thereof. 23. The method for manufacturing a glass product according to claim 21, wherein the dopant is a Cs compound. 24. The method for manufacturing a glass product according to claim 21, wherein the dopant is CsNO_3. 25. The method for manufacturing a glass product according to claim 21, wherein the dopant is a Nd compound. 26. The method for manufacturing a glass product according to claim 21, wherein 2 to 15 mol % of dopant is added into the glass. 27. The method for manufacturing a glass product according to claim 26, wherein 5 to 10 mol% of dopant is added to the glass. 28. The method of manufacturing a glass product according to claim 1, wherein the solvent is selected from the group consisting of water, alcohol, ketone, ether, and mixtures thereof. 29. The method for manufacturing a glass product according to claim 28, wherein the solvent is alcohol. 30. The method for manufacturing a glass product according to claim 29, wherein the solvent is water. 31. The method of claim 1, wherein the dopant is substantially completely deposited from the dopant solution within the porous glass preform. 32. The method of claim 1, wherein greater than about 90% of the cesium nitrate is deposited from the dopant solution. 33. The method of claim 1 further comprising the step of collapsing the porous glass preform containing the deposited dopant into a solid body and then drawing the solid body into a fiber. 34. The method of claim 1, wherein the dopant is deposited within the porous glass preform by varying the pH of the solution. 35. The method of claim 4 further comprising the step of immersing the doped porous glass preform in a third solvent in which the dopant has a lower solubility than in the second solvent. 36. The method of claim 4, wherein removal of the second solvent begins only after the deposition is substantially complete. 37. The method of claim 1, wherein the glass article is an optical glass waveguide. 38. The method of claim 1, wherein the rate of heat application is controlled to remove solvent and optionally decomposition products from the pores to provide a desired dopant distribution in the glass product. 39. The method of claim 1, wherein the dopant is deposited by a combination of cooling of the solution within the pores and chemical deposition. 40. The method of claim 1, wherein the dopant comprises a transition metal ion or a rare earth metal ion. 41. The method of claim 1, wherein the dopant comprises cesium, strontium, thorium, uranium or barium. 42. The method of claim 1, wherein the solution includes one or more dopants. 43. The method of claim 1, wherein each solution contains a dopant that is not contained in the other solutions. 44. The method according to claim 1, wherein the removal of the solvent is performed by replacing it with another solvent. 45 The dopants include lithium, sodium, potassium, rubidium, cesium, alkaline earth metals, transition metals, noble metals not included in transition metals, copper, zinc, boron,
Aluminum, thallium, germanium, tin, zinc,
2. The method of claim 1, wherein the metal oxide or salt is selected from the group consisting of phosphorus, arsenic, antimony and bilmuth. 46 The porous glass preform is produced by leaching a glass preform made of alkali borosilicate glass with a leaching solution at the temperature of the preform, and bringing the leaching solution to a precipitation temperature of 20° C. or higher below the temperature of the preform. The method according to claim 1, which is obtained by precipitating boric acid from. 47. The method according to claim 46, wherein the preform is maintained at a temperature of 80° C. or higher. 48. The method according to claim 47, wherein the temperature of the preform is 90° C. or higher. 49 Claim 4, wherein the leaching solution is a mineral acid
The method described in Section 6. 50. The method of claim 49, wherein greater than or equal to 10% by weight of NH_4Cl is present in the leaching solution. 51. The method of claim 49, wherein 20% by weight or more of NH4Cl is in the leaching solution. 52. The method of claim 51, wherein the temperature of the glass preform is 90°C or higher, the precipitation temperature is 35 to 50°C, and the mineral acid is hydrochloric acid.