JPS6086053A - Glass product - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a new glass product, and more particularly to a new glass product suitable for forming products or devices used in the transmission of light for both video and communications purposes. In particular, the glass composition according to the invention can be made into a fiber with a
It is suitable for forming glass products such as glass fibers used as optical fibers for transmitting electromagnetic energy exceeding OGHZ i, or for forming two or more optical fibers (
Glassware suitable for forming glassware used to couple electromagnetic energy between optical fibers (or bundles of optical fibers) or between light sources or detectors, or used as part of optical integrated circuits Suitable for forming glass products used as active elements in lasers or optical amplifiers, or suitable for forming glass products used as lenses, or for relaying images. Suitable for forming all glass products used. To embody the above and other similar applications, the term glass waveguide may be used herein. Moreover, such waveguides can be made with attenuation values ranging from 2 to 5 dB/km to over 100 dB/km. For optical concentrator circuits, 1dB/
Attenuation values on the order of cIn are used, but for purposes such as telecommunications, less than 5 dB/km is required. . As used herein, the term "glass product" 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 formed almost entirely from silica, and by adding a refractive index modifying component gold to this porous structure and further crushing the pores, the porous structure has a uniform or non-uniform refractive index distribution along the axis of at least one cross section. can be converted into other 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 leaching of phase-separated glasses, but also to the filling of other internal structures having at least one network-forming material throughout the matrix. It has been found that this method can also be applied to a continuous porous structure. One known method of forming an interconnected porous structure other than using phase fraction m' is by CVD. Such methods are generally described in US Pat. Nos. 2,272,342 and 2,326,059. Also, in particular, U.S. Pat.
No. 9073 describes the formation of a porous body and the injection of a dopant into the porous body. Such injection is carried out by the deposition of small amounts of material into the pores from a relatively dilute solution into the porous matrix (IJ) 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.

The present inventors have discovered that in order to better control the desired refractive index distribution, it is essential to carry out the entire process in a special manner and order that has not been demonstrated so far. .

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 product is constant,
This glass article can suitably be used as a core surrounded by a material with a low differential refractive index as a cladding. This same effect can be produced in the cross section of the product without cladding by creating a graded refractive index profile within the product. In cases where there is a refractive index gradient in any cross section, such that the refractive index decreases progressively or continuously from the center to the periphery, it is called a "parabolic distribution". words are used. There are also various refractive index profiles created by other means, such as those shown in US Pat. No. 3,830,640.

In any method for forming the glass articles of this invention, the formation of a porous matrix constitutes a value-adding step, but losses (e.g. breakage) after this step
would reduce economic yield in large-scale production operations.

Also, it has been difficult to identify factors that result in losses resulting from fractures, such as the formation of cracks or 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 means of improving the subsequent chances of glass rods or other glass products remaining 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 mentioned, the improvement lies not only in terms of yield, but also in ensuring that the desired refractive index profile is obtained to a satisfactory extent. .

This is mainly based on the following findings. That is, to obtain the best results, it is important that the step of depositing 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. It is essential to increase the temperature of the product and, if necessary, the deposit 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) incorrect glass composition; (b) incorrect 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 a porous matrix having interconnected pores (hereinafter referred to as a dopant). . The method includes the steps of 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 crushing and peeling the porous matrix. The method is particularly characterized in that a portion or all of the dopant is deposited by a method that does not involve evaporation of the solvent, and removal of the solvent does not substantially result in deposition. and that the rate of heat supply to remove the solvent (and decomposition products, if necessary) is adjusted to achieve and/or maintain the desired refractive index profile within the glassware. It is in.

An outline of a series of steps to obtain a specific refractive index distribution is shown below. The entire process starts from a porous product with communicating pores.

That is, the process is as follows.

(The lidopant is deposited into the pores of the body by a non-evaporative process.) This deposition is done by lowering the temperature and the solubility of the dopant or dopant compound in the solvent. (b) changing the pH of the solution to the point of precipitation, replacing the original solvent with a solvent in which the dopant or dopant compound is only slightly soluble; chemical precipitation, such as introducing into solution a chemical that reacts with the dopant compound to form a less soluble dopant compound.

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.

(2) Final solvent removal is initiated only after the deposition is completed.

(3) The rate at which heat is supplied to remove the 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 a tono9t or dopant compound.

Tabular distribution (,) The process of immersing a porous matrix in a solution of a dopant or dopant compound.

(b) Step of depositing cytopan) by temperature drop.

(c) Evaporating the solvent present.

(d) A step of heating to a temperature that collapses the pores.

Step distribution (1) (a) Immersing the porous matrix in a solution of the total dopant or dopant compound.

(b) Step of depositing carbonate due to temperature drop.

(c) immersion in a solvent to partially redissolve the dopant and diffuse it out of the matrix. (Only the dopant deposited near the outer surface of the product is removed in this step.) (d) Evaporating the solvent.

(,) The process of heating to a temperature that collapses the pores.

(2) (,) Immersing the porous matrix in a solution of a dopant or dopant compound.

(b) Step of depositing the dopant by decreasing the temperature.

(c) partially drying the porous glass rod; (d) immersing it in a solvent for the dopant to partially redissolve the dopant and diffuse it from the matrix. (
Only the particles deposited near the outer surface of the product are removed in this step. ) (e) Evaporating the solvent.

(f) A step of heating to a temperature that collapses the pores.

Parabolic distribution (,) The process of immersing a porous matrix in a solution of tonocent or tonoyant compounds.

(b) Immersion in a solvent for the dopant at a temperature approximately equal to the temperature at which dopant filling 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.

(c) A step in which 4 tons are deposited in the pores due to temperature drop.

(d) Evaporating the solvent.

(e) A step of heating to a temperature that collapses the pores.

As mentioned above, the dopant has a solubility property that allows the desired dopant concentration in the pores to be achieved by completely dispersing the dopant solution into the pores at a certain temperature and then simply lowering the temperature and depositing it. It is preferable to use a substance having Such methods involve thermal deposition. Although this method is likely to be adopted, other methods may also be adopted.Therefore, the present invention uses a suitable porous material as a starting material such that the refractive index modifying component can be separated from the solution by lowering the solution temperature. The present invention includes a method of manufacturing a force glass product having a desired refractive index profile using a matrix.

As a method other than thermal deposition means, there is a method of depositing solutes by chemical means without relying on temperature drop. In this method, common ion effects are used to precipitate solutes through a total solubility reduction equation (e.g., the solubility of CsNo3 in water decreases in the presence of IIO3).
. Reduction in solubility can also be achieved by exchanging the solvent, thus allowing deposition to occur in a manner that does not involve evaporation of the solvent. These methods include the addition of a suitable precipitant that reacts with the tonoQant or produces an appropriate change in pH. It is also possible to use a method that combines the steps of both thermal deposition and chemical deposition means. This method is particularly useful when one or more dopant or doient compounds are introduced into the pores.

This invention avoids any deposition method that involves evaporation of a solvent as the sole deposition method.

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 tend to create an undesirable refractive index profile.

It is essential to adjust the heating rate in order to avoid destroying the initial refractive index profile or damaging the interconnected pore structure. Creating sufficient pressure to destroy the structure of a vacuum is possible 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 vessel heating to achieve the desired results are provided below. Control of the solvent removal process is necessary to avoid destruction of the pore structure of the waste. i.e., starting solvent removal at room temperature or below by non-boiling methods, and avoiding rapid changes in temperature that would result in excessively rapid generation of solvent vapor in a confined space. It is necessary to take precautions. Typical solvent removal methods when the solvent is water include placing the product in a desiccator for about 24 hours at about 22°C, or placing the product in a vacuum for about 4 hours at a slightly higher temperature (e.g. 4°C). and then raise the temperature. In other cases, the heating rate may be maintained or reduced to a very low rate so that the product remains within a specified temperature range for a sufficient period of time to ensure the continuation of the specified result that occurred prior to heating. It turned out to be necessary. In other respects, it may be preferable to transition rapidly from one temperature to another, such as a temperature at which the pores collapse once solvent removal is complete. 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.

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

(b) The tonocent must be capable of coalescing with the matrix either as a deposit or as a subsequent thermally induced decomposition product.

(c) The material must be capable of coalescing with the vitreous structure at or below the maximum temperature at which the product is subsequently processed.

(d) The physical or chemical state of the y band must not change so that the IJ wax is lost before the pores collapse.

(e) In order to obtain low optical loss, VC has the following conditions.

(1) Topants must not contain iron, copper, hexagrams, or other unwanted transition metal elements.

(2) Porous Ma) When the IJ wax pores collapse, the immiscibility temperature of the composition must be lower than the temperature of the subsequent molding step required to convert the product into another form.

Known ingredients for modifying the refractive index of glass include:
Ge + Pb r, each in hydrated or unhydrated form
Aj*P+B% There are oxides, nitrates, carbonates, acetates, phosphates, borates, arsenates and other suitable salts of alkali metals, alkaline earth metals and rare earth metals. Among these, Cs.

Rb, Pb, Ba, At, 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 not possible to enumerate all possible combinations of dopant elements, the selection of such useful combinations based on the above-mentioned guidelines is in accordance with what is known in the art.

The concentration of the Do Yant or Do/Gunt mixture in the final product waveguide will typically vary depending on location. However, its concentration is at its maximum in the optical axis, and the concentration of the dopant-spreading mixture in the entire glass composition is between 1 and 20 molar, preferably between 2 and 15 molar, more preferably between 5 and 10 molar. be. As a result, the silica content in the glass is greater than 75 mole, preferably greater than 80 mole, and even more preferably 9
The error between silica and dopant concentrations is typically created by B2O3.

When selecting a solvent, it is necessary to consider the following:

(a) A solvent that does not damage the porous matrix.

(b) Solvents that can be purified to low concentrations of undesirable impurities.

(C) Solvents that can be substantially removed by substitution with other solvents, evaporation, or decomposition with acids (or high temperature reactions with chemically active atmospheres).

(d) Do-yant compounds or P
A solvent that can sufficiently dissolve the combination of panto compounds.

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

(f) when used for precipitation (by solvent displacement method);
Such solvents have the special solubility properties required by the process.

(g) A solvent that is economically low cost and 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, for reasons of ease and convenience, it is better to carry out the first step of the solvent removal step after deep doping at room temperature or below, which usually requires cooling the pore-filled product. Therefore, it is better to adopt the thermal deposition method.

Preferably, the dopant used is water-soluble, yet the substance is highly soluble at temperatures on the order of 100°C, and on cooling to room temperature or below a substantial amount of the substance separates, thus Those having immersion solubility coefficients that are suitable for target deposition are preferred.

Also, the dopant must be easily purifiable. The material 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 I. Table ■ shows the solubility of dopants in solvents at various temperatures.

As already indicated, a number of guidelines need to be considered in selecting a scheme to obtain the desired result, and these can therefore be illustrated with reference to Table I.

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. In order to deposit the dopant compound, it is necessary to use a solvent of 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 filling, is called unstuffing. Hereinafter, this will be referred to as de-dopantization. Appropriate control of the solubility of the dopant or dopant compound in the precise deposition reservoir can be accomplished in a number of ways.

(1) The thermal deposition method is most appropriate for solvents in which the solubility of docent or dopant compounds is highly dependent on temperature. The thermal deposition method has the additional advantage of being able to block diffusion in the shortest time.
In this way, a desired concentration distribution can be fixed with high accuracy.

This is shown in Table 1 when the catalyst is CsNO3. There, the solubility varies from the desired level of loading at 95°C to the level of desired dopa/t removal at 4°C.

(2) Deposition due to common ion effects and thermal deposition. 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 nitrates. (See CsNO5 in Table I) (3)
Deposition by solvent displacement. By replacing a solvent with high solubility with a solvent with low solubility, precipitation occurs. Due to the high solubility of nitrates in water, water can be used as a solvent for the filling operation. Replacing the water with alcohol, ketone, ether, or a combination thereof resulted in the deposition of KJ: 9 tons. Typical solubility is shown in Table I.0 (4) Variation of dopant compounds. The solubility range of the tono9ant compounds can be varied by selecting different anions. For example, CsNo. 3 is CB□(C
The solubility in water can be increased by substitution with O3)2. (See row 7 of Table 1) to to to to to to to to to to to to to to to to to to to. fart . Hehe
To 0 to 0. As already pointed out, when carrying out the method of the present invention on a porous interconnected structure formed by phase separation and subsequent gluing of a suitable glass, it is possible to obtain a salable product with good economic yield. It is necessary to optimize the various steps of the method in order to consistently and satisfactorily obtain the desired product.
It is also necessary to find correlations between various gloss parameters at each stage.

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) Desiccation and assimilation.

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, have the desired pore size. It is necessary to select a phase-separable composition that forms a continuous structure. Much guidance can be given to those skilled in the art in that regard. That is, the tree inventors
We have found it convenient to select from such compositions and alkali metal borosilicate glasses. Further guidance regarding suitable compositions is then provided as described below.

A number of compositions suitable for use in the production of porous glasses for various purposes have been reported (US Pat. Nos. 2,106,744, 2,215,036, 22,217).
09), 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 two representative examples are shown, it is often preferred for methods where the product produced is rod-shaped or elongated, usually with a minimum dimension of 4 cm or more. . For example, a number of known glasses within the preferred range of U.S. Pat. No. 3,843,341 and shown in Table H below were drawn vertically into an 8-diameter bar at a rate of 1 inch per minute. Although these glasses phase separated, Table ■
All of the compositions cracked during leaching.

Table ■ Known compositions that cracked during leaching 8 30 62
0 8 35 57 0 8 40 52 0 10 30 60 0 10 35 55 0 10 40 50 0 10 30 59 1 10 35 54 1 10 40 49 1 Note: The numbers are based on Morch.In particular, we also found the following.

(1) As shown in U.S. Patent No. 384334.1,
All sodium borosilicate 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.

(2) Many of the sodium alumina borosilicate glass compositions shown in US Pat. No. 3,843,341 cracked when processed as described above. The same was true for compositions within the preferred composition range.

(3) Many of the glass compositions in the preferred composition range shown in US Pat. No. 2,221,709 cracked when processed as described above.

Many of the borosilicate-based glass compositions previously mentioned have proven unsatisfactory due to the need to ensure satisfactory yields of the final product. but,
The inventors have now discovered a wide range of useful glass compositions that have not yet been demonstrated. In addition, the inventors have discovered a series of criteria that can be applied to identify other specific ranges of phase-separable glass compositions that provide satisfactory yields of product.

From a commercial standpoint, although almost all silicate glass systems exhibit a phase-separated composition range, it is most convenient to use borosilicate alkali 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.

(2) A composition that separates into phases with approximately equal volume ratios upon heat treatment at a specific temperature, and forms a continuous microstructure when maintained at that temperature.

(3) Compositions that are easily melted and easily purified by conventional methods.

(4) A composition that is relatively easily molded into a rod-shaped object or an object with a minimum dimension (thickness, diameter, etc.) of 4+++n or less, and which hardly undergoes phase separation during the forming 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, borosilicate alkali glasses that exhibit a wide phase-separated composition range have commercial value. The low silica phase of glasses in this composition range can be easily dissolved in a single acid solution. It is also often necessary to add other ingredients, 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 (along with the dopant),
Next, it is necessary to determine the immiscible region C of the composition and its coexistence temperature T. T and (C) are kept at a temperature higher than the temperature at which the glass (C) is uniform. Methods for determining T are described in the known literature.

(For example, W, Haller * D, H, Black
kburn +F, E, Wagstaff and R
, J. Charles [Na2O-B 20 s −
Metastable immiscible surfaces of the 8102 system j J, Amer.

C@ram, Sac, j4 (1), 34-9 (1
970)) (3) The inventors have discovered that it is necessary to determine a composition c1 that exhibits an equilibrium volume fraction of about 50% at least at certain heat treatment temperatures. This temperature fo
(C1). The method for determining this temperature is as follows.

(a) Three (or more) temperatures (approximately 50' from each other)
C away) select T+, Tx+T3.

Ts < T2 < TI < To (Ct) A long-term heat treatment is carried out until the glass sample becomes white at temperature 'I'+ + 72 and T3.

(b) Volume fraction V(
T) was measured using an electron microscope.

(c) A plot of volume fraction V(T) versus heat treatment temperature T was created. Using the interpolation method (or extrapolation method), the temperature at which the volume fraction becomes 50 (±5)% (ie, To(C1)) was determined.

(4) After knowing T, (C) and To (C1), it is necessary to determine the composition range (C2) within the composition range CI as shown below.

(a) 575℃≧To(Cz)≧500℃ (b) 750
°C≧Tp (Cz)2600 °C These temperatures are chosen so as not to result in long heat treatment times. of course,
Other ranges are possible 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, "refinement"
This means removing air bubbles and dissolving crystals and solids to make them homogeneous. Let C3 be a narrower range of C2. 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% B2O3 will be satisfactorily purified.

(6) Although easily purified and phase separated at a volume fraction of 50%, the composition of C3 is not entirely desirable. That is, there is an additional requirement that the desired composition should not phase separate at any time 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. 1 to determine the composition C4, which exhibits almost no phase separation on cooling at coexistence temperatures and below temperatures.Products with preform dimensions suitable for use as optical waveguides are subject to the development of large thermal stresses. The gas is cooled at a slow enough rate 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, a more limited composition range C
There are 4. The composition that satisfies this outside prefecture is preferably 71
0 to 600°C, more preferably 695 to 640°C
It has a T of °C.

(7) 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.

T (Co) To (Co)≧75°C Having found the desired composition range C*, any composition co can be selected therein. The heat treatment temperature and time for this particular composition co is claimed by the following procedure.

(a) The heat treatment temperature for Co is set equal to To (C'o), ie the temperature at which the volume fractions of the two phases are equal. if,
If C is chosen correctly according to the above criteria, this temperature will not be so low that the time required to obtain the appropriate 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.

B1] Deformation of the glass occurs during heat treatment.

[2] If the heat treatment temperature is 160℃ or higher than the glass transition point
If the temperature is above ℃, phase separation tends to be rapid;
Controllability of phase separation deteriorates.

According to these requirements, the preferred heat treatment temperature TI is limited to the following range:

575℃>TH(Co)=To(Co))500℃(b
) Since TH(co) was determined, the heat treatment is determined by the conditions to obtain a microstructure suitable for leaching.

Heat treatments are carried out at different times. i.e. tl (1 hour)
<12 (2 hours) <tS (3 hours), etc. The time tmax, beyond which the continuity of the structure begins to be broken, can be determined by electron microscopy. The size of the phases that can be leached is determined by micrographs, and the preferred heat treatment time is less than tmlLX, but the microstructure size at that time is at least 150X, preferably less than 300X.

We applied the above criteria to borosilicate alkaline systems and identified certain features of the composition range that contribute to a good yield t of optical fiber preforms of at least 2 gourd diameters, such as phase separation during molding. Alternatively, problems arising from insufficient phase separation in the phase separation process could be avoided. Phase separation during forming of glass products from the melt, and insufficient phase separation or disruption of communicating structures during phase separation heat treatments, such as in the leaching process of phase-separated glass and the drying process of leached and filled glass. This can lead to cracking of the glass in subsequent steps or both.

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%) Wide range Preferred range 5102 48 -64 49.5-59B,,05
28 -42 33 -37R204-96,5-8 At2030-3 0-2.0 ρ 0-1.0 . 0.20-0.8 α O-30-2,4 λ O-0,50 χ 0.1- 1.0 0.2- 0.8 In the above table, α is At20. Concentration (mol Llb), χ is ρ+(1
/3) α-λ, and ρ is the ratio A20/R20 (A20 is the sum of the mol% concentrations of Rb2O and C820,
R20 is the total concentration of L120, Na20, R20, Rb2O and C1120), and λ is the ratio L
It is 120/R20.

Since the presence of At203 in the glass influences the results, we will first discuss glasses that do not contain At203. When At203 is not included, the range shown in the table is 20. It is appropriate if ρ exists and ρ is limited to 0.1 to 1.0. If the concentration of 20 is zero, the upper limit of the range of ρ is 0.8.

Lithium glass tends to be opaque, so it is preferable not to use that chemical (L120). In this case, R20 is NazO1K20, Rb2O and Ca
This is a total of 20 concentrations. All other limitations and conditions remain.

Rubidium and cesium glasses are more expensive than those made from sodium and potassium.

Those Pi can be excluded from an economical point of view.

At that time, R20 is the sum of Na20 and 20.

All other limitations and conditions remain.

When more than 0.5 moles of At203 are present in the glass, a wide range for R20 is between 6 and 9 moles.

The most economically preferred composition with At203 is N
A 20 and only 20 R20, or Na 2
It is composed of R20 consisting of only 0.

The glass compositions shown in Table 1 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 leaching, and good yields of the final product.

Leechin 16330520 It 63.7 29.4 6.3 0.6 0DI
61.2 34 2 2.8 ON 60.7 35.
1 2 2.2 0V 59.7 33 5.4 1.
9 0Vl 59.3 34.3 1.6 4゜80■
58.4 34 5.6 0 2 ■ 59.1 34 4.9 0 0 D(57,7355,700
．． 10 0 0 0.10 --0 0 0.58 0
0 0.58 6460 0 0.52 0 0 0
．． 52 --0 0 0.26 0 0 0.26 6
780 0 0.75 0 0. 75 6330 0
0.26 0 0 0.26 6872 0 0.2
9 0 0 0.29 6870 1.6 0 1.6
0 0.53 --0 0 0.50 0 0 . 5
0 6700 0. 250 0. 25710 0 1.0 0 1.0 0 . 33 681 Another key feature of this invention is the borosilicate glass paste which is capable of phase separation. Before leaching, leaching is carried out to remove surface contamination or to remove the surface layer of the glass which has a different composition due to the volatilization of components such as B2O3 and Na20 during molding. It is recommended that the product be etched with hydrofluoric acid for about 10 seconds.

The concentration of the acid solution, the amount of leaching solution and the leaching temperature directly affect the progress of leaching. In leaching, it is essential to contact the product with a sufficient amount of leaching solution to dissolve the soluble phase. The leaching rate is usually controlled by adjusting the temperature. The glass is heated to a temperature above 80°C, preferably 90°C.
The temperature should be above °C. Also, NI (4C4
It is desirable to use an acid solution saturated with a compound capable of reducing the concentration of water in the acid leaching solution. Since the thickness of the swollen outer layer caused by the leaching process creates tension in the inner untreated layer, the use of the above compounds reduces the loss due to cracking of the product by controlling the swelling of the treated layer. It is.

It has been found that the rate of leaching, and redeposition of borate into the pores of the glass during leaching, can be adjusted by controlling the concentration of borate in the acid leaching solution.

33.6ml per 327.3g of NH4Cl1 water
Glass rods (length 10 cT++, diameter 8 mi, composition 57% sI
O□, 35% B2O3, 4%Na 20 and 4%
The ching speed at 95° C. was measured when leaching 20).Results It was found that as the amount of B2O3 in the leaching solution increased, the ching time became longer. The results are shown in Table ■ below.

Table ■ 0425±50 41.2 625±50 61.5 642±50 84.7 725±50 106.1 1670±50 Redeposition of borate 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 amounts of borate. However, this requires large amounts of leaching solution.

For example, since the leaching time is not longer than 660 minutes, a leaching solution of 1550+nl per 100 ml of N is required. However, this increases costs and also creates pollution.

It has therefore been found convenient to provide K with 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 in speeding up the process, even at temperatures several degrees below the temperature of the glassware. Preferably, the temperature of the cold trap is 20°C lower than the temperature of the glassware. NH4C
It is convenient to choose a cold trap temperature at which the acid solution remains saturated with NH4Cl when 1 is present.

Without the presence of NH4C4 or an equivalent compound in the leaching solution, glass rod breakage can be suppressed to a low level. However, since statistically there is an equally low level of glass rod failure when NH4Cl is present, the amount of NH4C4 should be greater than 10% by weight, preferably 20% by weight.
Preferably, it is expressed in weight percent.

The most convenient way to determine the appropriate leaching time is to leaching the glassware and measuring the mass of the product at intervals until a significant or no weight loss is observed.

Leached products are usually washed with deionized water. Certain compositions of glass exhibit silica gel deposits within the pores, which can be removed by cleaning with NaOH. It has also been found that compositional selection can minimize this deposition. The compositions shown in Table 1 alleviate this problem, especially those with minimal silica.

When porous IJ waxes are produced from the already mentioned phase-separable glasses or by, for example, chemical vapor deposition, the selection of suitable filling and dedopant conditions can be carried out according to the guidelines given below.

If an optical waveguide of known shape is used, the desired physical properties of the optical waveguide (e.g. size, numerical aperture, bandpass, etc.)
is related to the change in refractive index as a function. 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 do-yount or dopant compound that the glassware requires. Sufficient amount of de-
The Yant or Donoyant compound must be dissolved in the filling solution to reach the desired concentration at a particular filling temperature and filling time. These parameters can be determined in the following steps.

(1) Determination of the filling temperature of the porous glass rod (,) Determine the dependence of the solubility of the dopant or doant compound in a suitable solvent on the temperature.

(b) The filling temperature is determined by the desired concentration of dopant or dopant.
The temperature is between the temperature at which the solvent compound saturates the solution of (a) and the boiling point of the solution.

(2) Determining the filling time of a porous glass rod 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 rod. The procedure given here is for a given set of dopant solutions, temperatures and porous brass rod microstructures. For changes in any of these variables, this procedure should be repeated or modified appropriately according to guidelines.

(a) Measure the diameter (ao) of a porous rod and immerse it in the dopant solution.

(b) Monitoring the weight of the porous glass rod as a function of time.

(c) Slight weight change over time t y(t) = [#
(t) −#(0) ) / CMCω) −Af(0
) ) to determine the time to beyond which the weight hardly changes.

M(0), #(1), and M(o:I) are the initial weight, the weight at time t, and the weight at infinite time (very long time), respectively.

(a) At the same dopant solution and the same temperature, the time t required for another porous material of diameter a to fill the lath rod is given by the following equation.

t=toC-! -]2 &6 Drifting porous glass rods are heated to 100℃ in a concentrated aqueous solution of CllNO3 (
It was filled with 120 g of CsN05 per 100 WL of solution. The radius of the glass rod was 0.42c+++.

Weight increase as a function of time was measured. The results are shown in FIG. 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 dedopant time to create a parabolic distribution of refractive index in a porous glass rod by thermal deposition. Partially dedopantized by soaking. This needs to be done at a temperature that does not allow de Yant to precipitate. The dedopantation time depends on the microstructure of the porous glass rod as well as on the temperature. The procedure presented here is based on a given filling temperature and microstructure.

(,) The weight i! as a function of time while the glass rod is immersed in the solvent. A study of dedopantation was carried out at the temperature at which the glass rods were filled by monitoring f.

(b) The minute change y(t) in equation (1) was plotted against time t.

y(t)=Modanji'' (1) #(oO) -AI (0) (c) The dedopantation time to depends on the desired refractive index profile. It often ranges from:

1/3≦y(to)<2/3 A porous glass rod filled with 100 ml of concentrated CsNO3 solution (120 g of CsNOs per room ml of solution) was selected. It was then de-dopantized in water at 100°C and the weight loss was monitored as a function of time. The results are shown in FIG. The range of decent times can be divided from the graph.

(4) Determination of the dedopant temperature and time for creating a stepwise distribution of refractive index by thermal deposition. dependent on the solvent solution. Since it is better to have as low a refractive index as possible in the armor, 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 matrix parameters such as the concentration of the fill solution used before the dedopantation temperature and the size of the microstructure of the porous glass rod. The procedure presented here is based on a predetermined set of these variables. If the value of any of these parameters changes, the entire procedure will need to be repeated and adjusted according to this guideline.

If the desired thickness of the sheath is d and the radius of the filled glass rod is a (>d), then the following equation holds.

Y=2! ! --(u)2 By knowing Y, the correct dedopant time can be determined by the following procedure.

(a) Trace weight change as a function of time y (t)
(b) The trace weight change with respect to time (equation ( 1)) was plotted.

(c) From the above plot, we found the time to where y(to)=Y. This is the desired dedopantation time.

Practical applications of dedonoyantization procedures are often
In order to obtain the desired refractive index profile, the dopant concentration in the outer layer of the product must not be reduced.

As mentioned above, this means that, for example, when the actual filling is at 95°C
When the saturated solution of the dopant is completed, the dopant solution can be replaced with a dopant-free solvent at the same temperature, or if the system is water soluble, the dopant solution can be replaced with water or dilute nitric acid. - This can be done by substituting the solution with a dent solution. At that time, the dopant concentration in the cross section of the porous matrix is changing since the dopant tends to diffuse outward. Of course, the time required for dedopantation depends on the volume being treated, but the diameter 811
For a 1M glass rod, approximately 20 to 30 minutes are required. It is then preferable to stop the desorption by replacing the solution surrounding the glass rod with 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 desorption.

(5) Drying or removal of solventDrying has two
There are two problems. These are cracks in the porous glass structure and changes in the de Mentes concentration distribution. Cracking is a statistical problem in that the sample can remain in the process despite the drying procedure. 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 the dopant from migrating from the interior of the product to the surface resulting in the desired mixed dopant distribution. The refractive index in the center decreases, while the refractive index in the periphery increases.As mentioned above, the resulting dopant distribution is dependent on de-centration.In the presence of solvent in the pore structure, Now that a suitable dopant distribution has been achieved, it is essential to dry, ie, remove the solvent, without changing the dopant distribution to an undesirable state.

Analysis of the drying process revealed that there are many factors that influence this process. They are shown below.

(,) The sources of gas generation are solvents, docent decomposition products, and dissolved gases. If the gas evolution is rapid due to rapid heating or insufficient gas removal, the differential pressure created within the pores can break the glass and/or transport tonnoyants from inside the glassware. (b) Most of the size change solvent is removed from the porous glass, but the solvent layer on 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 shrinkages occur in the porous structure, the stresses can become large to the point of cracking.

(c) Decomposition of De-Zont Compounds De-Zonto used in solution form is generally a compound that decomposes thermally. In this invention, a de Youngt compound is selected that decomposes before the temperature at which the pores collapse. This decomposition process is generally accompanied by the production 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 de-gund migration.

(d) Mass transfer may occur at several points in the drying process. When the product is first dried, any dehydration that remains in the solution
The solvent 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 replaced. After decomposition, if the de Gundt crystals are small, they are transported in the gas phase. If the dopant has sufficient vapor pressure, redistribution of the dopant through the gas phase will occur. If the do/cent is a liquid, it will be redistributed by gravity.

(,) Removal of Hydroxyl Ions Hydroxyl ions form absorption bands near the infrared that are often harmful for use as waveguides. 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, within the same temperature range, the stomata begin to collapse,
Hydroxyl ions penetrate into 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 a non-boiling regime. In the case of aqueous solutions, two approaches were used. One of them is
The porous glass article with deposited dopants is first dried in a desiccator (under 1 atmosphere) at 22 DEG C. for 24 hours and then placed in a drying oven.

Another method consists in placing the product in vacuum at a temperature below 100° C. and above the freezing point of the solution. In this method, when an aqueous solution of CaNO3 is used as a
I found it convenient to be outside the prefecture for 24 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 hydroxyl ions. A suitable solvent is, for example, methyl alcohol.

In addition, before transporting glassware maintained below 10°C to the drying oven, it is warmed slowly to room temperature under vacuum, and usually for 24 hours.
It has been found preferable to maintain time.

In the case of non-aqueous solutions of dopants, it has been found suitable to place the glassware under vacuum at room temperature for 24 hours and then to transport it to a drying oven. This speeds up the process compared to methods using aqueous solutions.

In the drying oven, the sample is dried under vacuum for 30 minutes, as a low heating rate reduces the occurrence of cracks and avoids dopant redistribution.
It is desirable to heat to the high drying temperature at a heating rate of 0°C/hour or less, preferably 15°C/hour.

A suitably low heating rate will determine the economics of Zorothes. 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 rate must also be balanced against the increased risk of destroying the desired refractive index profile of the crack-free product. Example 2 shows that, at least as far as the dopant used is concerned, this problem occurs at a heating rate of 50° C./hour.

The high drying temperature depends on the porous glass material (IJ wax). An appropriate value can be found by first crushing the pores of an unfilled product and measuring its glass transition temperature Tg. and preferably 50° below the glass transition point.
It is advisable to choose a high drying temperature between 150°C and 150°C. Further, more preferably 75 to 120 below the glass transition point.
A narrow range of degrees Celsius is better.

The next stage of drying is to maintain the glass under this high drying temperature for 5 to 200 hours, preferably 40 to 125 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 one wishes to reduce near-infrared absorption, and if residual iron is present in the glass, the sample can be exposed to oxidizing conditions. This is desirable. At this oxidation stage, Fe”/Fe3 in the glass
+ ratio decreases and therefore absorption by Fe2+ ions decreases. According to a preferred procedure, a porous glass article having a glass transition temperature of 725°C is heat treated at 625°C (100°C below the glass transition temperature) for 96 hours with oxygen gas flowing around the sample.

(6) Assimilation Once the drying process is completed, the pores of the product are immediately crushed.

The temperature of the product is rapidly raised in the temperature range where 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 assimilation temperature, the solidification step must be carried out at or below atmospheric pressure. If I do not,
Gas is likely to be generated during reheating, resulting in the formation of bubbles.

If the matrix is produced from a glass that is capable of phase separation, it is desirable to heat the porous glass sample under reduced pressure of oxygen (approximately 115 °C) to 825°C, where 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 dopant concentration ranges, different solidification temperatures, and different final glass compositions.

Melting and molding 4 mol-〇Na2O, 20.36 mol/L for 4 mol.

A glass having a composition of 100% B2O3 and 56% SiO□ was melted and stirred to produce a homogeneous melt, which was drawn into glass rods with a diameter of 0.7 to 0.8 cm.

Heat treatment using a cooling coil The glass rod was heat treated at 550° C. for 2 hours to cause phase separation.

Each glass rod was etched in 5 g of HF solution for 10 seconds, and then washed with water for 30 seconds.

Leaching glass rod with 3N-HCt containing 20 parts by weight of NH2Cl
Leaching was carried out at 95°C. The leeching time is set to reach a stage where the rate of weight loss is almost zero.
Selected after previous trials. The leaching time selected in these examples was over 30 hours. During leaching, the boric acid concentration of the leaching agent was maintained at 509/l or less by providing a precipitation temperature range of 40°C. This speeded up the leaching and avoided redeposition of boron compounds within the pores of the matrix. The temperature of 40° C. was chosen to avoid precipitation of NH2Cl from the leaching agent solution. This temperature is above the saturation temperature of NI (4Ct) so that a suitable amount is maintained in solution to greatly reduce sample destruction.

Washing The leached material was washed with deionized water. Washing cycles were conveniently controlled by adjusting the iron concentration in the effluent. Washing was conveniently carried out at room temperature using 10 volumes 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 ten when fresh wash water is added, so that the iron concentration is low enough for cleaning even without iron concentration measurements. can be considered to have been achieved.

It is better to simply replace the fill wash water with the fill solution, which is an aqueous solution of each do/cent, 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 Examples ■ to ■, when the sample was removed from the filling solution and cooled to 22°C, the dopant was partially deposited in an amount corresponding to the 22°C water solubility in the residual solution filling the pores.

(For example, Bt6I per remaining 100 mJ of solution
a(NO3)2 is dissolved in the water in the pores after thermal deposition at 22°C. Similarly, the remaining g of H5BO per 100 ml of solution is dissolved in the water in the pores.

) Residues of doant were deposited during the drying process, which was initiated by placing the porous product in a desiccator at atmospheric pressure for 24 hours at 22°C. Drying was then continued under vacuum in an oven heated at a heating rate of 15° C./hour to the high drying temperature (previously defined). This high drying temperature was determined by the method described above, and was 625°C for the samples used in Examples 1 to 2.

Maintenance time Next, the glass rod was held for 96 hours while oxygen was flowing around it.
A temperature of 25°C was maintained.

Upon completion of the assimilation hold time, the glassware was immediately subjected to a bubble breaking step. That is, the temperature of the glass product was raised to a temperature at which bubble destruction occurred to produce a solidified glass rod. This process is carried out in a reduced pressure oxygen atmosphere (approximately 115 bar),
Final temperatures are given in the table.

Example■ Glass rod number 7, 40g of P per 100cc of water (No.
3') Filling at 85 °C for 12 hours with a toner solution consisting of H2PO4 of 2 and Ill and bubble bursting at 825 °C Example ■8 Glass rod number 8, 12 g of Ba(N) per 100 cc of water.
Example V: Filling for 4 hours at 85° C. and Pore Destruction at 830° C. with a Dopant Solution Consisting of H5PO3 of O3)2 and 6I All of the above examples concern uniform doping of a lath rod. 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 to obtain a refractive index distribution that corresponds to a glass rod with broken bubbles. It is possible to reduce the

Two porous glass rods were prepared according to the procedure already described and immersed in an aqueous CsNos solution with a concentration of 120 g of CsN0 in 100 m of solution at 95° C. for more than 4 hours. The glass rods were then transferred to 95°C water and left for 11 and 20 minutes, respectively. After a predetermined period of time had elapsed, each glass rod was immersed in water at 0° C. for 10 minutes to cause thermal precipitation of C3No3. The solvent was then removed and the glass rod was bubble-busted as described above. The obtained refractive index distribution is shown in FIG.

Example (2) Several porous glass rods produced by the above method were immersed in CsNos and C82CO3 solutions as shown in Table (1) at 95°C for over 4 hours. Next, these glass rods were dedopantized to obtain a stepwise refractive index distribution. (The refractive index profile of glass rod sample 13 is shown in FIG. 5.) The time required for de-dumping was determined using FIG.

(i.e., end of glass rod sample 13, y(to)=0.5
0 = 300 (min) as shown in Figure 3) The filled glass rod was de-dotted by immersing it in ice water for 300 minutes, then the water was removed, and the The bubbles were destroyed in a glass rod using this method. The refractive index at the center of the lath rod is shown in Table ■.

Table ■ 9 20,! il 0M2Co3/100 penalty H201,
4621030, 9℃g2Co3/100aH201,
4751175gCm2Co3/1OOrnlH20]
,,48812 60,ji' CmN0s7100m
1 aqueous solution 1.47513 120gC8NOs710
0m/! Aqueous solution 1.486 Example ■ As already mentioned, when using a glass rod filled with a doant, it is important to dry at a low speed at a temperature between 0°C and around 600°C.

This example illustrates the difference in refractive index distribution due to different heating rates. Some of the filled cellular glass rods used in Example V were dedopanted to produce a stepped index profile as shown in Example 2. After thermal deposition, the glass rods were dried under vacuum at 4° C. for 24 hours. Next, the mixture was heated under vacuum at a heating rate of 50.degree. C., 30.degree. C., and 15.degree. C. per hour. The obtained refractive index distribution is shown in FIG.

At a temperature increase rate of 100° C. per hour, considerable breakage of the glass rod occurred. When it is desired not to change the deposited dopant distribution, the temperature increase rate is preferably 20° C./hour or less.

A rod heated at 15° C./hour was selected for fiber processing. The glass rod preform was fed between the opposing flames of two gas oxygen torches and its molten end was manually pulled into a fiber. The end of the fiber is attached to a rotating drum which draws the fiber to a diameter of 185μ. The fiber was illuminated with white light having a spectral range selected by a 100X wide interference filter centered on transmission at 0.85μ. The absorbent material was contacted with the armor along a length sufficient to remove the form of the armor. Transmission intensity I (4
was measured on long fibers. At this time, all fibers except 1rrL were removed and the transmitted intensity was measured again.

The transmission intensity loss (dB/km) is given by the following equation.

In the formula, 1=12-1. t2 and t11 have long and short fiber lengths (km), respectively. The transmission power loss was 25 dB/km, which is less than the 100 dB/km required for many communications applications.

EXAMPLE ■ A filled porous glass rod after leaching and washing was soaked in 100 g of C3NO5 solution as described in the first part of Example 1-IV.
It was immersed for 4 hours at 5°C. The sample was cooled to 22° C., the temperature at which Donoyant partially precipitated. Next, it was dried in a desiccator at room temperature for 24 hours. The obtained sample is uniformly packed, so in order to introduce a certain distribution, 4
in water for 92 hours, then in 3N HNO3 at a temperature of
Washed for 0 minutes. It was then vacuum dried at the same temperature. Once this portion of water was removed, the sample was slowly dried by increasing the temperature as indicated in the preferred procedure of this invention. At intermediate temperatures, CsNo 5 is C
It decomposed into a2O 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% 5I02.3.
The composition was 4% B2O3 and 6.0% Ctr20 (both molti), and the transition metal impurity was 10 parts per million parts.

Examples ■ As already indicated, selection of dopants, solvents, and operating conditions for loading and unloading, combinations and substitutions of these parameters, or modification of operating conditions to obtain desired results, etc. can vary widely. This invention provides guidance to those skilled in the art, and this example illustrates permutations and combinations of lamators that have yielded satisfactory results. All porous glass rods used were prepared according to 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 row: Do Zonto used.

2nd column: concentration of 100ml solution.

3rd column: Solvent, i.e. the solvent used in the first filling step.

Column 4: Temperature (°C) and time required for the first filling step.

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

Column 6: Temperature (°C) and time required for de cent deposition and change in refractive index profile.

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

Further deposition may occur before solvent removal. and the dopant near the glass surface. This allows for a more complete reduction in the concentration.

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

Column 9: Shows the temperature (°C) at which drying starts.

(V) is drying under vacuum, (A) is drying under vacuum. In the desiccator at the first stage Indicates drying under atmospheric pressure.

10th column shows the measured values of refractive index.

The first row is the same as the glass rod sample 13 of Example ① and includes a comparison with the second row.

Row 2 includes further treatment with methanol and water, while using the same filling solution but increasing the refractive index difference. Row 3 replacing 08NO3 with the more soluble C82CO3. There is. 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 De Youngt uses neodymium nitrate and also uses an organic solvent.

[Brief explanation of drawings]

Figure 1 is a graph representing the weight fraction obtained by immersing a porous glass rod in a CsNo3 solution at 100°C;
Figure 3 is a graph showing the weight fraction loss obtained by immersion in water at 100 °C after filling a porous glass rod with 10
A graph showing the loss of weight fraction obtained by filling CaNO3 at 0°C and immersing it in water at 4°C. Figure 4 is a graph showing the refractive index distribution of the glass rod of Example ②, and the curve is 1 and 2 show the cases of de-dotting for 11 minutes and 20 minutes, respectively, and FIG. 5 is a graph showing the refractive index distribution of the filled glass rod sample J3 of Table V of Example 1.2 and 3 are respectively heating rate 1 according to Example 1
The case where the glass rod was heated at 5.30 and 50°C/hr is shown. Applicant's representative Patent attorney Takehiko Suzue Figure 1: between sections (direction) Figure 2: Unexamined patent application (through) Figure 3: Clear Vl (through) Figure 4: Kano-n-ka-Unoga-iro-to (mm) ) Figure 5

Claims (1)

[Claims] Consists of a composition consisting of 1,48 to 64 moles of C5102, 28 to 42 moles of B2O3, and 4 to 9 moles of R20, where R20 is Na2O and R20°Rb O
and at least one selected from the group consisting of Cs□0
A glass product comprising seeds, wherein the composition has a content of 0.2 to
ρ of 0.8, ρ is defined by the ratio of [A20]/[R20], where [A20] is 20, Rb2
O and C820, [R20) is the sum of Na2O, R20, Rb2O and C820, and the composition has an equilibrium volume fraction of about 50 at a temperature of 500-575°C. Therefore, glass products can withstand acid leaching without cracking. 2. The composition contains θ~3 mol of At203', and α is O~3. χ is 0.2 to 1.0, α is A
The glass product according to claim 1, wherein χ is expressed by the formula χ=ρ0('/3)α and has a coexistence temperature Tp of 640 to 695°C. 3, S102 is 49.5-59 molti, B2O3 is 2
The glass product according to claim 1, wherein R20 is 8 to 42 molts, and R20 is 6.5 to 8 molts. 4. The glass product according to any one of claims 1 to 3, wherein the amount of R20 is 6.5 to 8 mol. 5. The glass product according to any one of claims 1 to 3, wherein R20 consists of only Na 20 and 20. 6, B20. A glass product according to any one of claims 1 to 3, wherein the amount is 33 to 37 mol. 7. The glass product according to any one of claims 1 to 3, wherein 5t()z is 56 mol%, B2O3 is 36 mol%, R20 is 4 mol%, and Na20 is 4 mol%. The glass product according to any one of claims 1 to 3, wherein the amount of s,5to2 is 49.5 to 59 molti. 9. The glass product according to claim 1 or 2, wherein the coexistence temperature Tp is 640 to 695°C. 10. The glass product according to any one of claims 1 to 3, which is an unleached optical waveguide preform. 11. The glass product according to claim 2, wherein α is greater than 0.5 p and [R20] is 6 to 9 mol.