WO2012096279A1 - Glass material and method for producing glass material - Google Patents

Abstract

A glass material (G1) is composed of a Pb-free xerogel in the form of a powder, said xerogel containing main components SiO₂ and BaO respectively in amounts of 20-55 wt% and 20-35 wt% and impurities Fe, Cr, Co, Ni, Cu and Pt in an amount of 1 ppm or less in total. The glass material (G1) serves as a starting material for the core glass of a fiber for light guides.

Description

Glass material and method for producing glass material

The present invention relates to a glass material for a light guide fiber for an endoscope and a method for producing the glass material for the fiber.

The light guide that transmits light has a configuration in which a large number of fibers are bundled. As shown in FIG. 1, one fiber 10 includes a core 11 that transmits light, and a cladding 12 that is provided outside the core 11 and reflects light so that the light does not leak outside. The core 11 is made of high refractive index glass, and the cladding 12 is made of glass having a lower refractive index than the core 11.

Lead glass is known as a high refractive index glass, but glass that does not contain lead (hereinafter, also referred to as “lead-free glass”) has been developed for environmental reasons. For example, Japanese Patent Application Laid-Open No. 2004-256389 discloses an aluminosilicate glass that does not contain lead.

Here, both the fiber for endoscope and the optical fiber for optical communication have a function of guiding light, and the basic portions are similar. However, the optical fiber for optical communication is called a single mode fiber, which transmits light of a predetermined narrow wavelength over a long distance of several kilometers or more, whereas the optical fiber for an endoscope is called a multimode fiber, which is a wide visible light. Although light in the wavelength range is a short distance of several meters, it is necessary to guide a large amount of light. For this reason, the structure and manufacturing method of the optical fiber for endoscope are basically similar to the structure and manufacturing method of the optical fiber for optical communication, but the manufacturing conditions and the like are greatly different. For example, the numerical aperture NA of the optical fiber for optical communication is about 0.1 to 0.2, whereas the NA of the optical fiber for endoscope is 0.5 or more. “A to B” means A to B.

In addition, in a medical endoscope, a light guide that transmits light from a light source to the distal end of the endoscope is used for normal light observation by irradiation with white light (for example, a wavelength of 380 nm to 750 nm). However, lead-free glass is more likely to have impurities mixed into the glass material than lead-containing glass. For this reason, it is not easy to obtain a light-gite fiber having a high light transmittance.

Furthermore, in medical endoscopes, not only normal light observation but also various special light observations utilizing the wavelength characteristics of irradiation light are performed. For example, in narrowband light observation (NBI: Narrow Band Imaging), light in two narrow wavelength ranges (390 to 445 nm / 530 to 550 nm) that is easily absorbed by hemoglobin in the blood is irradiated, and Easily distinguish tumor tissue by highlighting capillaries and fine mucosal patterns.

In auto-fluorescence observation (AFI), in order to observe autofluorescence from a fluorescent substance existing in a living tissue such as collagen, the tissue is irradiated with narrow band light having a wavelength of 390 to 470 nm as excitation light. . The autofluorescence observation uses the characteristic that the autofluorescence generated by the excitation light is attenuated in the tumor tissue as compared with the normal tissue. For this reason, in particular, a high light transmittance for blue light (for example, a wavelength of 380 nm to 470 nm) is required for a glass for a light guide fiber for an endoscope.

In the production of the light guide glass, an oxide such as silica or La ₂ O ₃ or a carbonate such as BaCO ₃ is used as a raw material. These raw materials have been highly purified and are commercially available from raw material manufacturers, but the amount of impurities such as Fe, Cr, Co, Ni, and Cu is several ppm to 100 ppm, and few are less than 1 ppm. A raw material having an impurity amount of 0.1 ppm or less is not available at an industrial level. In particular, ZrO ₂ contains a relatively large amount of impurities because it is difficult to purify the raw material.

On the other hand, as disclosed in Japanese Patent Application Laid-Open No. 2009-137836, it is disclosed that a gel produced by a sol-gel method is dried to form xerogel and glass is obtained by sintering xerogel. However, no study has been conducted on the transmittance of impurities and glass.

An object of the present invention is to provide a glass material capable of producing a light-gite fiber having a high light transmittance and a method for producing the glass material. The glass material is a glass precursor called dry gel or xerogel.

The glass material of the embodiment of the present invention is a raw material for the core glass of the light guide fiber, and the main components SiO ₂ and BaO are 20 to 55 wt% and 20 to 35 wt% Fe, respectively, and the impurity Cr. , Co, Ni, Cu, and Pt are made of a powdery xerogel containing 1 ppm or less and containing no Pb.

Moreover, the manufacturing method of the glass material of the core glass of the fiber for light guides of another embodiment of this invention produces the 1st solution containing the metal alkoxide compound which has at least Si, and a nonaqueous solvent. From the first solution preparation step, the second solution preparation step of preparing a second solution containing a plurality of metal element compounds and water, the first solution and the second solution, Fe , Cr, Co, Ni, Cu, and Pt are removed until the total content is 1 ppm or less, the first solution and the second solution are mixed, and a mixed solution containing no Pb is obtained. A solution mixing step to be prepared; and a xerogel preparation step in which the mixed solution is gelled to remove the solvent to prepare a powdery xerogel.

It is a schematic diagram for demonstrating the structure of a light guy fiber.

<Method for producing light-gite fiber>
First, a method for manufacturing a light guide fiber will be briefly described. As already described, the light guide fiber 10 has a cladding 12 made of low refractive index glass that reflects light so that light does not leak out from the side of the core on the outer periphery of the core 11 made of high refractive index glass that transmits light. Have.

An example of a method for manufacturing the light guide fiber 10 is a preform method. In the preform method, first, a preform having a large clad diameter and core diameter is produced by a rod-in-tube method or a double crucible method. The rod-in-tube method is a method of inserting a rod made of core glass into a hollow portion of a tube made of clad glass. A clad glass heated and imparted with flexibility to the outside of the core glass rod may be wound. Then, a part of the preform is drawn, that is, heated and stretched to obtain the light-gite fiber 10 having a desired diameter. In the double crucible method, the core glass is melted in the center of the double crucible, the clad glass is melted around it, and the melted core glass and clad glass are simultaneously extruded from each nozzle and cooled to produce a fiber. is there.

The following conditions are required for the clad glass. (1) The refractive index is lower than that of the core glass. (2) Good chemical durability. (3) The coefficient of thermal expansion (α) is close to that of the core glass. (4) Crystal does not precipitate during fiber drawing. (5) Good fusion with core glass. Etc.

Therefore, the clad glass material is selected from known lead-free glasses in consideration of compatibility with the core glass of the present invention described later. For example, SiO ₂ : 41 to 46 wt%, B ₂ O ₃ <14 wt%, Al ₂ O ₃ <10 wt%, Na ₂ O <11 wt%, K ₂ O <14 wt%, Li ₂ O <1.5 wt%, F <0.2 wt%, and conventional amounts of fining agents. The glass of the composition which contains can be used.

<Measurement method>
Generally, the transmittance of glass is measured based on Japanese Optical Glass Industry Standard JPG 17-1982. In this standard, the transmittance is calculated by measuring the transmittance of two glass samples (3 mm, 10 mm) having different thicknesses and excluding the loss due to surface reflection, and is indicated by the transmittance (%) at 10 mm.

However, in the evaluation of the light guide glass used for the medical endoscope, the above method using a 10 mm thick sample has insufficient measurement accuracy, so it cannot be judged pass / fail. This is because the length of the light guide of the medical endoscope is very long, for example, 3.6 m. For example, the transmittance of a light guide having a length of 3.6 m is 78% (78% / 3.6 m) or more, and the transmittance at a measurement length of 10 mm is 99.93% or more.

However, even with a commercially available high-accuracy spectrometer (for example, model number LAMBDA750, manufactured by PerkinElmer), the transmittance measurement accuracy is only about ± 0.1%. That is, the actual transmittance of a glass having a measured value of 99.93% / 10 mm may be in the range of 99.83 to 100.93% / 10 mm. In order to convert the transmittance of the measurement length of 10 mm into the measurement length of 3.6 m, it is necessary to calculate the transmittance of 10 mm to the 360th power. Then, since the transmittance range is 54.2 to 111.4% / 3.6 m, it is not possible to judge the quality of the glass. Therefore, a more accurate measurement method has been essential to determine whether glass is practically available.

In order to solve this problem, the present inventor made a glass sample having a thickness of about 30 cm and a glass sample having a thickness of 1 cm (10 mm), and used a method of removing surface reflection by calculation. Furthermore, the light path of a normal commercial measuring instrument's focused beam changes depending on the refractive index and thickness, so the size of the image on the photocathode on the detector changes, resulting in a change in the measured value. there were. For this reason, a parallel light flux precisely controlled by a self-made jig was used for the measurement. Note that the glass bar having a length of approximately 30 cm, that is, a thickness of 30 cm, used for the measurement is a semi-finished product that is processed after the measurement and drawn into the fiber 10 by, for example, the rod-in-tube method. That is, in this measurement method, the quality of the glass can be determined during the production.

The transmittance at a measurement length of 30 cm of glass having 78% (78% / 3.6 m), for example, as the transmittance at a wavelength of 400 nm with the light guide having a length of 3.6 m is 97.95%. Even if the measurement accuracy is ± 0.1%, it is only 12 to convert the transmittance with a measurement length of 30 cm into the transmittance with a measurement length of 3.6 m. As a result, the transmittance range is 79.99 to 78.95% / 3.6 m, so that the quality of the glass can be substantially judged.

In the following measurement, the 30 cm long transmittance (T380-750) of light having a wavelength of 380 to 750 nm and the 30 cm long transmittance (T400) of wavelength 400 nm were measured by the above-described methods. The transmittance (T380-750) was the average value of the transmittance of light in the wavelength range of 380 to 750 nm.

The main component composition was measured by EPMA, and the impurity content was measured by ICP-MS. In addition, when a composition etc. are shown, it means that the material which contains "0%" as a range of content is not an essential component but an arbitrary component. In the display of the impurity content, “less than” means that the measurement limit is not exceeded.

The specific surface area of the glass material was calculated as a BET value by a gas adsorption method using nitrogen gas.

<First Embodiment>
Hereinafter, the glass material G1 for light-gite fibers of the first embodiment of the present invention and the method for manufacturing the glass material GG1 will be described.

<First solution preparation process>
The glass material G1 manufactured by the sol-gel method is mixed by mixing a first solution containing a metal alkoxide compound and a non-aqueous solvent and a second solution containing a metal element compound and water. It is manufactured by.

The first solution includes, for example, a metal alkoxide compound having Si such as Si (OC ₂ H ₅ ) ₄ (TEOS), and ethanol as a solvent. The alkoxide compound is controlled so as to be substantially free of water because it is unstable in the presence of water and gels by hydrolysis and polycondensation reactions. Conversely, a state that does not substantially contain water refers to a state in which the gelation reaction does not proceed at a problem rate in production.

For this reason, the non-aqueous solvent of the first solution is used after being sufficiently dehydrated. As the non-aqueous solvent, alcohols such as methanol and propanol, ketones such as methyl ethyl ketone, and other known solvents can be used.

As the metal alkoxide, TEOS having Si that becomes SiO ₂ which is the main component of the glass material G1 is used as an essential component because it is easily available. The metal alkoxide compound having Si may be, for example, butyl silicate in which the carbon number of the alkoxy group is changed, or a compound in which the skeleton of the alkoxy group is changed.

Further, the first solution, which is a component of glass _{GG1, B 2 O 3, Al} 2 O 3, a ZrO _2, B, Al, and Zr, may be mixed with the metal alkoxide compound containing, respectively. That is, the first solution includes a metal alkoxide compound having an element that is a component of the glass GG1.

For example, Zr alkoxide compounds include tetramethoxy zirconium (Zr (OCH ₃ ) ₄ ), tetraethoxy (Et) zirconium (Zr (OC ₂ H ₅ ) ₄ ), tetra-i-propoxy (Pr) zirconium (Zr (O -I-C ₃ H ₇ ) ₄ ), tetra-n-propoxyzirconium (Zr (On-C ₃ H ₇ ) ₄ ), tetra-i-butoxy (Bu) zirconium (Zr (Oi-C ₄ H ₉ ) ₄ ), tetra-n-butoxyzirconium (Zr (On-C ₄ H ₉ ) ₄ ), tetra-sec-butoxyzirconium (Zr (O-sec-C ₄ H ₉ ) ₄ ), or tetra -T-butoxyzirconium (Zr (Ot-C ₄ H ₉ ) ₄ ), etc. can be used.

Further, a compound that is not a metal alkoxide compound may be mixed with the first solution as long as it contains the element of the glass GG1 element, dissolves in the solvent of the first solution, and does not contain moisture. . Here, the phrase “not containing water” includes the case where the metal alkoxide has a minimum water content that does not cause hydrolysis and polycondensation. Moreover, you may add the acid used as the catalyst of a gelatinization reaction, for example, nitric acid containing water, to a 1st solution before mixing with a 2nd solution.

For example, the first solution has a composition having the following group A compounds.

(Group A)
TEOS 11.281kg
B (OEt) ₃ 0.472 kg
Al (OBu) ₃ 0.967 kg
Zr (O-i-Pr) ₄ 1.633 kg
HNO ₃ 0.466kg
Ethanol The first solution having the above composition was transparent and uncolored.

<Second solution preparation step>
The 2nd solution contains the compound used as the component of the glass material G1 which was not added to the 1st solution, and uses water as a solvent. Many elements can be added to the first solution as a metal alkoxide compound, but the alkoxide compound is expensive because it is difficult to alkoxide depending on the element. For this reason, a part of component of glass material G1 is added to a 2nd solution as an inexpensive metal salt. Note that an acid serving as a catalyst for the gelation reaction may be added to the second solution.

For example, the second solution has a composition having the following group B compounds.

(Group B)
_{Zn (NO 3) 2 · 6H} 2 O 3.360kg
_{La (NO 3) 3 · 6H} 2 O 3.707kg
Ba (NO ₃ ) ₂ 5.510 kg
NaNO ₃ 1.180 kg
Water The second solution having the above composition was transparent and uncolored.

Each element that is a component of the glass material G1 may be included in at least one of the first solution and the second solution. For example, aluminum may be contained in the first solution as aluminum alkoxide as described above, or may be contained in the second solution as a metal salt such as aluminum nitrate, It may be included. The metal salt contained in the second solution may be acetate.

<Purification process>
High purity materials are used as the compounds contained in the first solution and the second solution. However, light guide fiber is required to have very high light transmittance. For this reason, the first solution and the second solution are purified until the content of impurities that adversely affect the transmittance is equal to or less than a predetermined amount.

The inventor has found that among the impurities, transition elements such as Fe, Cr, Co, Ni, Cu, and Pt have a great influence on the transmittance of light having a wavelength of 380 nm to 750 nm. Further, the first solution and the second solution are subjected to distillation, column adsorption, or the like until the total content of the six kinds of metals of Fe, Cr, Co, Ni, Cu, and Pt becomes 1 ppm. It has been found that it is possible to obtain a light guide fiber having desired characteristics by purifying by the above method. For example, the first solution is purified to a total value of the metal content of 0.6 ppm or less, and the second solution is purified to a total value of the metal content of 0.4 ppm or less. The total content of the first solution and the second solution, that is, the total content of the mixed solution can be 1 ppm or less. In this specification, platinum (Pt) is one of the transition elements based on the description in the physics and chemistry dictionary.

And since the 1st solution and the 2nd solution are liquid, it is easy to refine. In addition, the compound in a liquid state, for example, a metal alkoxide compound, before the preparation into the first solution or the second solution, may be purified in advance before the preparation.

<Solution mixing process>
While the first solution was stirred, the second solution was dropped to prepare a transparent and non-colored mixed solution. In addition, since neither the 1st solution nor the 2nd solution contains Pb, the mixed solution also does not contain Pb.

In addition, in preparing the first solution and the second solution, mixing and storing the solution, in order to avoid mixing of impurities, not a metal container such as stainless steel or iron or a glass container such as a beaker, but a paper container or plastic A container was used.

Glass GG1 is a lead-free glass having desired characteristics, and thus is a multi-component containing many kinds of elements. Since each element has a different specific gravity and melting point, it is difficult to mix in a solid state. Even when heated and melted, uniform mixing is not easy. However, since the glass material G1 of the present embodiment is mixed in a solution state, it is easy to make uniform.

<Xerogel production process>
The glass material G1 of this embodiment is a powdery xerogel. Here, xerogel is a gel having a network structure and is one type of dry gel, but has a larger specific surface area than a normal dry gel obtained by drying a jelly-like gel. For example, the specific surface area of the glass material G1 is 500 to 1000 m ² / g. The density is 0.05 to 0.5 g / cm ³ . As will be described later, the glass material G1 having a specific surface area within the above range has a low melting temperature and enables energy-saving production, and impurities from the container are hardly mixed at the time of melting.

The mixed solution of the glass material G1 is preferably made into a xerogel by gelling by a spray drying method and removing the solvent. In the spray drying method, the mixed solution is ejected from the nozzle into a fine mist. Then, in the space heated to, for example, 200 ° C., the mist-like mixed solution becomes xerogel after the solvent is removed.

Note that the gelation reaction starts when the first solution and the second solution are mixed. That is, when the mixed solution is allowed to stand for a predetermined time, it becomes a jelly-like gel containing a solvent. For this reason, a mixed solution is spray-dried immediately after preparation.

Even in the spray drying process, it is preferable to use paper or plastic for all containers in order to prevent contamination. For example, the mixed solution in a plastic container is sent to a spray drying device via a plastic tube, and the xerogel is collected in a plastic container. For this reason, the impurity content of the glass material G1 in the xerogel state is substantially the same as that in the mixed solution.

In addition, as a xerogel preparation process, for example, after leaving the mixed solution at room temperature for 30 minutes to form a jelly-like gel, a dry gel dried at 130 ° C. for 48 hours may be used. The dried gel obtained from the jelly-like gel is processed into powder by a pulverizer. The powdery xerogel produced by the above method has a specific surface area as small as 100 to 500 m ² / g and a density as large as 0.5 to 1.0 g / cm ³ as compared with the xerogel produced by the spray drying method.

<Xerogel melting process>
A platinum / zirconia crucible was used to prepare a glass melt in which xerogel was melted, and stirring was performed with a high-purity quartz glass rod. As is clear from the following composition, the composition of the glass GG1 is designed to have a relatively low melting point, and therefore, mixing of impurities from the crucible is also suppressed.

Furthermore, since the glass material G1 is a powdery xerogel having a large specific surface area, when a bulk metal salt having the same composition is melted, the glass material G1 melts at about 1100 ° C. while heating at about 1400 ° C. is required. For this reason, the glass material G1 can suppress the mixing of impurities from the crucible during melting, particularly Pt. That is, the impurity Pt is mainly mixed in the melting step. Further, other impurities may increase in the melting process, but do not decrease. That is, the impurity content of the glass material G1 is smaller than the impurity content of the glass GG1.

The composition of glass GG1 shown below is the glass composition after melting. In general, about 0 to 0.5 wt% of Sb ₂ O ₃ is added as a clarifier to remove bubbles in the glass as necessary. However, since glass GG1 is easy to homogenize, the Sb ₂ O ₃ content is increased. It can be reduced. For example, “low” means 0.0001 wt% to 0.01 wt%. The amount of Sb ₂ O ₃ is not described in the following composition.

The composition of the light GG fiber glass GG1 produced from the glass material G1 of the present embodiment is as follows.

SiO ₂ 31.1 wt%
B ₂ O ₃ 1.3 wt%
Al ₂ O ₃ 2.0 wt%
ZnO 9.1wt%
ZrO ₂ 4.3 wt%
LaO ₃ 13.8 wt%
BaO 32.0wt%
K ₂ O 2.2wt%
Na ₂ O 4.3 wt%
Here, SiO ₂ and B ₂ O ₃ are glass-forming oxides. In order to obtain a stable glass, (A) (SiO ₂ + B ₂ O ₃ ): 20 to 55 wt% or less, (B) SiO ₂ : 20 to 55 wt%, (C) B ₂ O ₃ : 0 to 10 wt% It is. SiO ₂ is an essential component for preventing crystallization of glass and improving X-ray resistance. B ₂ O ₃ is an optional component for preventing crystallization of glass.

BaO is an essential component for obtaining a high refractive index and a high transmittance in the blue region, has an effect on meltability and stability, has an effect, and does not exhibit an adverse effect (hereinafter simply referred to as “effective”). ) Is (D) BaO: 20 to 35 wt%.

ZnO has high refractive index and high transmittance in the blue region, and is effective for melting and stability, but is not an essential component. The effect of ZnO is (E) ZnO: ˜30 wt%.

Al ₂ O ₃ is effective in improving meltability, stability, chemical resistance, heat resistance and hardness, and (G) Al ₂ O ₃ : 0.5 to 10 wt% is effective.

ZrO ₂ is effective in stability, chemical resistance, and heat resistance, and (H) ZrO ₂ : ˜8 wt% is effective. Alkali metal oxides have an effect on meltability, and (I) alkali metal oxides: ˜10 wt% are effective.

La ₂ O ₃ is an important component for obtaining a high refractive index and a high transmittance, and it is effective that (F1) La ₂ O _{3 is} 0.1 to 25 wt%, preferably It is 5 to 20 wt%, and more preferably 9 to 18 wt%. If the content of La ₂ O ₃ is not less than the above range, a desired NA can be obtained with a large refractive index, and if it is not more than the above range, the glass manufacturing difficulty is low, and the glass becomes yellow due to absorption in the blue region. There is no coloring. For this reason, in the composition range of the glass GG1 of the present embodiment, it is more preferable that the La ₂ O ₃ content is 9 to 18 wt%.

In addition, instead of La ₂ O ₃ or mixed, 1 selected from (F) R ₂ O ₃ (R is Gd, Y), or R ₂ O ₅ (R is Ta, Nb) The same effect can be obtained even with more than seeds.

Furthermore, the glass material G1 of the glass GG1 has particularly low impurity content. For this reason, the impurities of glass GG1 were Cr = 0.08 ppm, Fe = 0.4 ppm, Co = 0.05 ppm, Ni = 0.09 ppm, Cu <0.01 pm, and Pt = 0.18 ppm.

<Drawing process>
Using glass GG1 as a core glass and lead-free glass having a refractive index lower than that of glass GG1 as a clad glass, drawing was performed by a rod-in-tube method to produce a fiber 10. In the rod-in-tube method, melt spinning, so-called “drawing” is performed in a state where a core-shaped rod-shaped core glass GG1 is inserted into a tube-shaped glass serving as a clad inside a heating furnace.

The endoscope fiber has a high ratio of the core diameter φC to the fiber diameter φF in order to guide a large amount of light. For example, a desired light quantity cannot be guided unless the core diameter φC of the optical fiber is 80% or more of the fiber diameter φF. For example, when the fiber diameter φF is 30 μm, the core diameter φC is preferably 24 μm (80%) or more, and particularly preferably 27 μm (90%) or more. The upper limit of the core diameter φC is, for example, 95% or less of the fiber diameter φF. If the upper limit is not more than the above range, the clad glass thickness necessary for reflection can be ensured.

The glass GG1 of the present embodiment exhibited excellent characteristics with a transmittance (T1000 @ 380 to 750 nm) of 99% / m and a transmittance (T1000 @ 400 nm) of 98% / m.

From the above results, the transmittance (T1000 @ 380 to 750 nm) of the glass GG1 of this embodiment is 96% / m or more, and the transmittance (T1000 @ 400 nm) is 90% / m or more. Was estimated to be an impurity reduction effect and an R oxide addition effect due to the use of the glass material G1.

In order to achieve a light transmittance of 380 nm to 750 nm of the fiber of 96% / m or more, the glass GG1 has an impurity content of 0.5 ppm or less and a Cr content of 0.5 ppm or less. It is preferable that the content is 0.1 ppm or less, the Co content is 0.01 ppm or less, the Ni content is 0.1 ppm or less, and the Pt content is 0.2 ppm or less.

As already described, the manufacturing process of the fiber 10 is performed with particular attention not to cause contamination of impurities. For this reason, the impurity content of the glass GG1 after melting and the impurity content of the core glass 11 of the fiber 10 are only increased in the Pt content as compared with the glass material G1 in the xerogel state.

Incidentally, it has been found that the glass GG1 has excellent X-ray exposure resistance. In other words, the medical endoscope may be used while irradiating X-rays to confirm the position of the distal end portion of the endoscope after being inserted into the body of the subject. A part of the chemical bond is broken or distorted, resulting in coloring. However, the glass GG1 exhibits high X-ray resistance in an accelerated test in which X-rays corresponding to several hundred doses of irradiation irradiated in one normal operation are performed at a time, and the X-ray resistance is good. It has been confirmed.

As described above, the glass material G1 is less apt to be volatilized at the time of melting because it contains less impurities, easily mixes and easily obtains a homogeneous composition, and has a predetermined chemical bond in the state before melting. It is characterized in that an alkali component or the like is easily retained and a glass having a desired composition is easily obtained, and that a glass having a homogeneous composition is easily obtained by preventing inhomogeneity due to a difference in specific gravity of glass components. For this reason, as shown in the above embodiment, it is easy to manufacture in units of “several tens of kg”.

That is, the glass material G1 of the present embodiment can produce a light-gite fiber having a high light transmittance.

The present invention is not limited to the above-described embodiment, and various changes and modifications can be made without departing from the scope of the present invention.

The present application is filed on the basis of the priority claim of Japanese Patent Application No. 2011-005166 filed in Japan on January 13, 2011, and the above disclosure includes the present specification, claims, It shall be cited in the drawing.

Claims (11)

1. The main components SiO ₂ and BaO are 20 to 55 wt% and 20 to 35 wt%, respectively, and the total content of impurities Fe, Cr, Co, Ni, Cu, and Pt is 1 ppm or less, and does not contain Pb. A glass material comprising a powdered xerogel and being a raw material for a core glass of a light guide fiber.
2. The fiber having the core glass manufactured by melting the xerogel has an average transmittance of light with a wavelength of 380 nm to 750 nm of 96% / m or more, and the transmittance of light with a wavelength of 400 nm of the fiber is 90% / m. It is the above, The glass material of Claim 1 characterized by the above-mentioned.
3. Fe content is 0.5 ppm or less, Cr content is 0.1 ppm or less, Co content is 0.01 ppm or less, Ni content is 0.1 ppm or less, Cu content is 0.01 ppm or less, The glass material according to claim 2, wherein the Pt content is 0.2 ppm or less.
4. The glass material according to claim 3, wherein the specific surface area is 100 to 1000 m ² / g.
5. The glass material according to claim 4, wherein the specific surface area is 500 to 1000 m ² / g.
6. The glass material according to claim 5, wherein the composition is as follows.
   (A) (SiO ₂ + B ₂ O ₃ ): 20 to 55 wt%
   (B) SiO ₂ : 20 to 55 wt%
   (C) B ₂ O ₃ : 0 to 10 wt%
   (D) BaO: 20 to 35 wt%,
   (E) ZnO: 0 to 30 wt%
   (F) one or more selected from R ₂ O ₃ (R is La, Gd, Y) or R ₂ O ₅ (R is Ta, Nb): 0.1 to 20 wt%,
   (G) Al ₂ O ₃ : 0 to 10 wt%
   (H) ZrO ₂ : 0 to 8 wt%
   (I) Alkali metal oxide: 0-10 wt%
   (J) Sb ₂ O ₃ : 0 to 0.15 wt%.
7. A first solution preparation step of preparing a first solution containing a metal alkoxide compound having at least Si and a non-aqueous solvent;
   A second solution production step of producing a second solution containing a plurality of metal element compounds and water;
   A purification step of removing from the first solution and the second solution until the total content of Fe, Cr, Co, Ni, Cu, and Pt is 1 ppm or less;
   A solution mixing step of mixing the first solution and the second solution to produce a mixed solution containing no Pb;
   And a xerogel production step of producing a powdery xerogel by gelling the mixed solution to remove the solvent, and a method for producing a glass material.
8. The xerogel has a Fe content of 0.5 ppm or less, a Cr content of 0.1 ppm or less, a Co content of 0.01 ppm or less, a Cu content of 0.01 ppm or less, and a Ni content of It is 0.1 ppm or less, The manufacturing method of the glass material of Claim 7 characterized by the above-mentioned.
9. The method for producing a glass material according to claim 8, wherein the xerogel preparation step is performed by a spray drying method.
10. The method for producing a glass material according to claim 9, wherein the specific surface area of the xerogel is 500 to 1000 m ² / g.
11. The method for producing a glass material according to claim 10, wherein the composition of the xerogel is as follows.
    (A) (SiO ₂ + B ₂ O ₃ ): 20 to 55 wt%
    (B) SiO ₂ : 20 to 55 wt%
    (C) B ₂ O ₃ : 0 to 10 wt%
    (D) BaO: 20 to 35 wt%,
    (E) ZnO: 0 to 30 wt%
    (F) one or more selected from R ₂ O ₃ (R is La, Gd, Y), or R ₂ O ₅ (R is Ta, Nb): 0.1 to 25 wt%,
    (G) Al ₂ O ₃ : 0 to 10 wt%
    (H) ZrO ₂ : 0 to 8 wt%
    (I) Alkali metal oxide: 0-10 wt%
    (J) Sb ₂ O ₃ : 0 to 0.15 wt%.

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