JP2010189197A - Photoconductive fiber - Google Patents

Abstract

The present invention provides a glass for a photoconductive fiber core that does not contain Pb, has a high refractive index, and is suitable for spinning by a double crucible method, and a photoconductive fiber having the core glass as a core glass.
Pb, As and Ti are substantially not contained, the composition is expressed in mass% as follows, the refractive index nd is in the range of 1.60 to 1.70, and the coloring degree λ80 is 38 or less. And the glass has a liquidus temperature of 1000 ° C. or lower. SiO ₂ ; more than 30% and 45% or less, Al ₂ O ₃ ; 0% or more and less than 3%, B ₂ O ₃ ; 0.1 to 10%, Na ₂ O; 0.1% or more and less than 5%, K ₂ O ; 0% or more and less than 5%, _Li 2 O; 0% or more and less than _{5%, Li 2 O + Na} 2 O + K 2 O = less than 5%, CaO; 0.1~20%, BaO; 20~50%, ZnO; 0 _{.1~25%, ZrO 2; 0.1~10%} .
[Selection figure] None

Description

  The present invention relates to a glass for a core for a photoconductive fiber used for image transfer and a photoconductive fiber using this glass as a core. The photoconductive fiber of the present invention is preferably used particularly for a photoconductive bundle for an endoscope.

  As an optical transmission medium, glass fiber is used in a wide range of fields including the semiconductor industry, medicine and biotechnology. This fiber consists of a core glass in the center and a clad glass surrounding the core glass. Generally, a photoconductive fiber is composed of a high refractive index core glass and a slightly lower refractive index clad glass. With this configuration, the light incident on the core can be totally reflected and conducted through the glass fiber without loss due to light leakage. A higher refractive index of the core glass is preferable because the aperture ratio of the optical element is increased.

  There are two methods for producing photoconductive fibers: a double crucible method and a rod-in-tube method. The former is a method in which glass melted in a crucible having a double structure is adjusted to an appropriate viscosity and spin-molded with a core / cladding structure, and the latter is made up of a core glass processed into a cylindrical shape and a cladding glass processed into a tubular shape. It is a method of drawing and spinning while heating repeatedly.

  Conventionally, glass containing PbO in its composition has been widely used for fibers because it is easy to adjust the refractive index, has high transmittance, is hard to devitrify and is easy to spin. In recent years, however, glass fibers containing no PbO have been demanded in consideration of environmental burdens. Therefore, the present inventors have previously developed a PbO-free glass that does not contain PbO and is suitable for a rod-in tube. (Patent Document 1)

JP2004-010365

  On the other hand, an object of the present invention is to provide a glass for fibers having a high refractive index that does not contain PbO and can be easily formed by a double crucible method. The double crucible method is lower in cost than the rod-in-tube method, but has a greater restriction on the glass used for the core and cladding. The rod-in-tube method is a method in which glass is processed once by processing glass into a cylinder and cladding as a cylinder, and then superimposing them and reheating them to soften them. Then, a fiber using a wide range of glass as a base material can be produced. When glass is heated to a temperature exceeding the transition point, it begins to soften regardless of the composition, so the choice of properties is wide. On the other hand, the double crucible method can shorten the process because the melted glass is fiber-formed during cooling. However, since glass is easily crystallized during cooling, crystal defects are generated in the fiber, and the defects are liable to induce disconnection. Further, if the viscosity of the core and the clad during melting of the glass is not matched, uniform molding becomes difficult. Therefore, in the case of the double crucible method, the thermal stability and viscosity of glass are more restricted than in the rod-in-tube method. This is the reason why the glass for the rod-in-tube method cannot be directly used for the double crucible method.

  If PbO is removed from glass that has been used or is known for conventional fibers, the refractive index decreases and the liquidus temperature rises, making it more difficult to fabricate fibers using the double crucible method. . Further, when PbO is removed, the thermal expansion coefficient also changes, and there is a problem that stress due to the difference in thermal expansion characteristics between the core and the clad remains and problems such as distortion are likely to occur.

  Accordingly, the present invention provides a PbO-free glass that does not contain PbO and is suitable for the production of a core / clad structure photoconductive fiber by the double crucible method, which solves the problem that occurs when PbO is removed from a conventional glass. For the purpose.

The present invention for solving the above problems is as follows.
[1]
Pb, As and Ti are not substantially contained, the refractive index nd is in the range of 1.60 to 1.70, the coloration degree λ80 is 38 or less, the liquidus temperature is 1000 ° C. or less, and the glass composition is Expressed in mass%, SiO ₂ > 30% 45% or less Al ₂ O ₃ 0% or more and less than 3% B ₂ O ₃ 0.1-10%
Na ₂ O 0.1% or more and less than 5% K ₂ O 0% or more and less than 5% Li ₂ O 0% or more and less than 5% Li ₂ O + Na ₂ O + K ₂ O = less than 5% CaO 0-20%
BaO 20-50%
ZnO 0.1-25%
ZrO ₂ 0.1-10%
A glass for a photoconductive fiber core, characterized in that
[2]
Contains at least one component selected from the group consisting of MgO, SrO, La ₂ O ₃ , Nb ₂ O ₅ , Cs ₂ O, Gd ₂ O ₃ , Sb ₂ O ₃ and SnO ₂ as components other than the above. [1] The glass for a photoconductive fiber core according to [1].
[3]
The glass for photoconductive fiber core according to [1] or [2], wherein the linear thermal expansion coefficient at 100 ° C. to 300 ° C. is in the range of 80 × 10 ^{−7 to} 110 × 10 ⁻⁷ .
[4]
The glass for a photoconductive fiber core according to any one of [1] to [3], wherein the glass is spun by a double crucible method.
[5]
A photoconductive fiber comprising a core glass according to any one of [1] to [4].
[6]
The clad glass does not substantially contain Pb, As and Ti, the refractive index nd is in the range of 1.50 to 1.60, the liquidus temperature is 1000 ° C. or less, and the composition of the glass is by mass%. ₂ 40-75%
B ₂ O ₃ 0.1-20%
Na ₂ O 0.1-20%
The photoconductive fiber according to [5], wherein
[7]
The cladding glass is at least one selected from the group consisting of Li ₂ O, K ₂ O, Al ₂ O ₃ , MgO, CaO, SrO, BaO, Cs ₂ O, Sb ₂ O ₃ , and SnO ₂ as components other than the above. Two or more components are contained, The photoconductive fiber as described in [6] characterized by the above-mentioned.

  According to the present invention, there is provided a glass for a fiber core that has a high refractive index and a high thermal stability during spinning molding, and as a result, can produce a high-performance fiber bundle by a double crucible method. Is done.

  Furthermore, according to this invention, the PbO free photoconductive fiber manufactured by the double crucible method using the said glass for fiber cores can be provided.

[Glass for optical transmission fiber core]
The composition of the glass for optical transmission fiber core will be described. Unless otherwise specified, the glass composition is expressed in mass%.

SiO ₂ is a basic component of glass and is an important component that determines the thermal characteristics. If it is 30% or less, the coefficient of thermal expansion becomes high, and the stability and viscosity of the glass become low, so that spin molding becomes difficult. When the content of SiO ₂ exceeds 45%, melting becomes difficult and the refractive index is lowered, so the content of SiO ₂ is set to more than 30% and 45% or less. The content of SiO ₂ is more preferably 31% to 40% by weight, still more preferably 32 to 38%. In the glass of the present invention, as will be described later, instead of setting the content of Al ₂ O ₃ to less than 3%, the content of SiO ₂ is set to more than 30%, so that an alkali metal oxide (Li ₂ O + Na ₂ O + K ₂ O) in combination with less than 5% maintains the chemical durability of the glass.

Al ₂ O ₃ is a component that affects devitrification resistance, flexibility, and chemical durability. If it exceeds 3%, devitrification resistance, flexibility, and chemical durability may be reduced. Therefore, the content of Al ₂ O ₃ is set to a range of 0 to less than 3%. The content of Al ₂ O ₃ is more preferably in the range of 0 to 2%.

B ₂ O ₃ is a basic component of glass, and at the same time, is a component that improves meltability and spinning characteristics. If the content of B ₂ O ₃ is less than 0.1%, there is no effect, and if it exceeds 10%, the refractive index becomes too low. Therefore, the content of B ₂ O ₃ is in the range of 0.1 to 10%. The content of B ₂ O ₃ is more preferably in the range of 3% to 7%.

Na ₂ O is a component that improves the meltability. If the content of Na ₂ O is less than 0.1%, the effect is not obtained, and if it exceeds 5%, the viscosity of the glass is too low, and it becomes difficult to form a double crucible with the clad glass. Therefore, the content of Na ₂ O is in the range of 0.1 to 5%. The content of Na ₂ O is preferably 1 to 5%, more preferably 2 to 4%.

K ₂ O is also a component that improves the meltability of the glass, but if it exceeds 5%, the viscosity of the glass is too low, and it becomes difficult to form a double crucible with the clad glass. Therefore, the content of K ₂ O is in the range of 0 to 5%. The content of K ₂ O is preferably 0 to 4%, more preferably 0 to 3%.

Alkali metal oxide (Li ₂ O + Na ₂ O + K ₂ O) is less than 5%. As described above, in the glass of the present invention, instead of Al ₂ O ₃ content of less than 3%, SiO ₂ content should be more than 30% and alkali metal oxide should be less than 5%. And maintaining the chemical durability of the glass. From the viewpoint of the chemical durability of the glass, the alkali metal oxide (Li ₂ O + Na ₂ O + K ₂ O) is preferably less than 4.5%, more preferably less than 4.0%. Li ₂ O is not an essential component, but is a component that can be added for the purpose of improving the meltability, adjusting the thermal expansion coefficient, adjusting the constant, adjusting the glass transition point, and the like.

  CaO is a component that improves meltability and refractive index. In combination with BaO, the refractive index, glass viscosity and devitrification resistance can be easily adjusted. If the CaO content exceeds 20%, the chemical durability is adversely affected and the devitrification property is also deteriorated. Therefore, the CaO content is in the range of 0 to 20%. The content of CaO is preferably 0.1 to 15%, more preferably 1 to 10%.

  BaO is a component that has a large effect of improving the refractive index. In combination with ZnO, the refractive index, glass viscosity and devitrification resistance can be easily adjusted. However, if the BaO content is less than 20%, the refractive index is low and the devitrification resistance is also poor. On the contrary, when the content of BaO exceeds 50%, the viscosity of the glass is lowered and the devitrification resistance is also deteriorated. Therefore, the BaO content is in the range of 20 to 50%. The content of BaO is preferably 25 to 45%, more preferably 30 to 45%.

  ZnO is also a component that improves meltability and refractive index. If the ZnO content is less than 0.1%, the effect is low, and if it exceeds 25%, the devitrification resistance also deteriorates. Therefore, the ZnO content is in the range of 0.1 to 25%. The content of ZnO is preferably 1 to 15%, more preferably 2 to 10%.

SrO, La ₂ O ₃ , Nb ₂ O ₅ , Cs ₂ O, Gd ₂ O ₃ , Sb ₂ O ₃ and SnO ₂ are not essential components. However, although the purpose (function, effect) varies depending on the component, it is added for one or more purposes such as improvement of meltability, adjustment of thermal expansion coefficient, adjustment of constants, clarification, improvement of chemical durability, etc. be able to.

The fiber core glass of the present invention is substantially free of Pb (PbO), As (As ₂ O ₃ ), and Ti (TiO ₂ ). Pb and As are not included because the load on the environment is large. Since Ti has a large absorption at a short wavelength, the glass for a fiber core of the present invention does not substantially contain Ti because the transmittance is remarkably deteriorated.

  The fiber core glass of the present invention is a glass having a refractive index of 1.60 to 1.70 and a liquidus temperature of 1000 ° C. or lower. The reason for setting the refractive index in the range of 1.60 to 1.70 is to consider the combination of increasing the aperture ratio of the fiber to transmit a bright image and the thermal stability, viscosity, and cladding of the glass. It is. The refractive index is preferably in the range of 1.62 to 1.67. Among the glass compositions, CaO, BaO and ZnO are components that increase the refractive index. Therefore, by adjusting the content of these components within the above range, the above 1.60 to 1.70 Can be adjusted to the range.

Further, the reason why the liquidus temperature is set to 1000 ° C. or less is that, when melt molding is performed by the double crucible method, crystallization does not occur so that defects and disconnection do not occur. The liquidus temperature is preferably 950 ° C. or lower. The liquidus temperature is mainly a component in which Li ₂ O, Na ₂ O, K ₂ O, CaO, and ZnO improve the meltability in the glass composition, so the content of these components is within the above range. It can adjust to the said 1000 degrees C or less by adjusting within.

The glass for a fiber core of the present invention has a coloring degree λ80 of 38 or less. The reason why the coloring degree λ80 is set to 38 or less is to prevent the transmittance of the fiber from deteriorating. The coloring degree of the Japan Optical Glass Industry Association is based on the transmittance measurement result at a thickness of 10 mm. Was found to be almost transparent. This is because if the degree of coloring λ80 exceeds 38, the transmittance of the fiber decreases due to absorption, and it becomes difficult to transmit a bright and high-contrast image. The coloring degree λ80 is preferably 37 or less. Among the glass compositions, mainly SiO ₂ and TiO ₂ are components that affect the coloring degree λ80, so the content of these components is adjusted within the above range (substantially containing TiO ₂ No) can be adjusted to 38 or less.

The glass for a fiber core of the present invention is preferably a glass having a thermal expansion coefficient at 100 to 300 ° C. of 80 × 10 ^{−7 to} 110 × 10 ⁻⁷ . The reason why the coefficient of thermal expansion at 100 to 300 ° C. is within the above range is that, as a multi-component glass having a high refractive index, the coefficient of thermal expansion in this range has a high degree of freedom in composition and is easily matched with the coefficient of thermal expansion of the cladding. Because. The thermal expansion coefficient at 100 to 300 ° C. is preferably in the range of 90 × 10 ^{−7 to} 100 × 10 ⁻⁷ . Thermal expansion coefficient, among the above glass composition, primarily because SiO ₂ is a component that greatly affects the thermal expansion coefficient, by adjusting the content of the component within the above range, the above range Can be adjusted.

[Photoconductive fiber]
The photoconductive fiber of the present invention is formed by combining the following glass for cladding with the above glass for core of the present invention.

As the cladding glass used in the photoconductive fiber of the present invention formed using the core glass of the present invention, for example, the following glass can be used.
Pb, As and Ti are not substantially contained, the refractive index nd is in the range of 1.50 to 1.60, the liquidus temperature is 1000 ° C. or less, and the composition of the glass is mass%. SiO ₂ 40 to 75 %
B ₂ O ₃ 0.1-20%
Na ₂ O 0.1-20%
The cladding glass.

In the cladding glass, SiO ₂ is a basic component of glass and an important component that determines thermal characteristics. If the content of SiO ₂ is less than 40%, the stability and viscosity of the glass are lowered, and spin molding becomes difficult. If it exceeds 75%, melting becomes difficult. Therefore, the content of SiO ₂ is set to a range of 40 to 75%. The content of SiO ₂ is more preferably 45 to 70%, still more preferably 50 to 70%.

B ₂ O ₃ is a basic component of glass, and at the same time improves meltability and spinning characteristics. If the content of B ₂ O ₃ is less than 0.1%, there is no effect, and if it exceeds 20%, spin molding becomes difficult. Therefore, the content of B ₂ O ₃ is in the range of 1 to 15%. The content of B ₂ O ₃ is preferably 5 to 15%.

Na ₂ O is a component that improves the meltability. If the content of Na ₂ O is less than 0.1%, the effect is not obtained, and if it exceeds 20%, the viscosity of the glass is too low, and it becomes difficult to form a double crucible with the core glass. Therefore, the content of Na ₂ O is in the range of 0.1 to 20%. The content of Na ₂ O is preferably 1 to 15%, more preferably 5 to 15%.

Li ₂ O, K ₂ O, Al ₂ O ₃ , MgO, CaO, SrO, BaO, Cs ₂ O, Sb ₂ O ₃ , and SnO ₂ are not essential components. However, although the purpose (function, effect) varies depending on the component, it is added for one or more purposes such as improvement of meltability, adjustment of thermal expansion coefficient, adjustment of constants, clarification, improvement of chemical durability, etc. be able to.

The clad glass is also substantially free of Pb (PbO), As (As ₂ O ₃ ) and Ti (TiO ₂ ). Pb and As are not included because the load on the environment is large. The cladding glass is substantially free of Ti because Ti increases the refractive index too much.

It is appropriate that the clad glass has a refractive index slightly lower than the refractive index of the core glass, for example, a refractive index lower than that of the core glass in the range of 1.50 to less than 1.70. The refractive index difference between the core and the clad is preferably 0.05 or more, more preferably 0.10 or more. If the refractive index difference between the core and the clad is less than 0.05, the difference is small, and the light transmitted through the core may leak without being totally reflected, and the amount of light may be reduced. In consideration of the fact that the amount of light is likely to decrease particularly when the fiber is bent, the difference in the refractive index between the core and the clad is preferably within the above range. From the viewpoint of use in combination with the fiber core glass of the present invention, the clad glass preferably has a refractive index of 1.50 to 1.60. Since the refractive index is mainly a component that lowers the refractive index of SiO ₂ and B ₂ O ₃ in the glass composition, by adjusting the content of these components within the above range, the above 1. It can be adjusted to a range of 50 or more and less than 1.70, preferably 1.50 to 1.60.

The reason why the liquidus temperature is set to 1000 ° C. or lower is to prevent the occurrence of defects and disconnection due to crystallization during melt molding by the double crucible method. The liquidus temperature is preferably 950 ° C. or lower. The liquidus temperature is mainly a component that improves the meltability of B ₂ O ₃ and Na ₂ O in the glass composition. By adjusting the content of these components within the above range, It can adjust to the said 1000 degrees C or less.

In addition, the photoconductive fiber of the present invention is spin-molded using a double crucible method. Therefore, the thermal expansion coefficient of the clad glass is preferably in the range of 80 to 110 × 10 ⁻⁷ / ° C., which is substantially the same thermal expansion coefficient as the core glass of the present invention. Thermal expansion coefficient, among the above glass composition, primarily because SiO ₂ is a component that greatly affects the thermal expansion coefficient, by adjusting the content of the component within the above range, the above range Can be adjusted.

  The glass for photoconductive fiber core and the glass for cladding of the present invention can be produced by a general optical glass manufacturing process. For example, oxides, hydroxides, carbonates, nitrates, chlorides, sulfides, etc. are used as glass raw materials, weighed to the desired composition, mixed and used as raw materials for preparation, A step of preliminarily heating to vitrify, a step of heating the molten glass in a heat-resistant container having a platinum content of 95% or more, and stirring the molten glass with a blade tip rod having a platinum content of at least 95%, It is manufactured through a step of homogenizing and a step of defoaming and clarifying bubbles in the molten glass. The molten glass homogenized in this way is poured out into a frame and molded, and then cooled to room temperature in a furnace heated near the glass cooling point. In the present invention, it is appropriate that all the glass production steps are performed at 1500 ° C. or less.

  The photoconductive fiber is preferably produced by spin molding using a double crucible method. The conditions of the double crucible method used for the production of the photoconductive fiber are not particularly limited and may be known conditions.

EXAMPLES The present invention will be further described below with reference to examples.

  Optical glass grade raw materials are used so as to have the composition shown in Table 1, and raw materials such as oxides, hydroxides, carbonates, nitrates, chlorides and sulfates are weighed so as to have the composition shown in Table 1. The mixed raw materials were put in a platinum crucible, heated and melted at 1400 to 1500 ° C., stirred, homogenized, allowed to stand and clarified, and then poured into a mold. After the glass solidified, it was then transferred to an electric furnace heated near the annealing point of the glass and gradually cooled to room temperature. A test piece necessary for the measurement was cut out from the obtained glass block and subjected to polishing to evaluate the characteristics.

The measuring method of each physical property of glass is as follows.
(1) Refractive index It measured according to Japan Optical Glass Industry Association standard JOGIS-01.
(2) Coloring degree (Coloring degree λ80)
Measurement was performed according to Japan Optical Glass Industry Association Standard JOGIS-02.
(3) Glass transition temperature (Tg) and (4) Linear thermal expansion coefficient of 100 ° C to 300 ° C Measured in accordance with Japan Optical Glass Industry Association Standard JOGIS-08.
(5) The liquidus temperature glass was held at a temperature of 900 ° C. or higher for 2 hours, and the lower limit temperature at which crystals were not precipitated was displayed. In addition, the result of “no crystal recognized” indicates that the liquidus temperature is 900 ° C. or lower.
(6) Young's modulus
Measured by a method according to JIS R1602.

  Next, the glass for core of the present invention (Example 1) and the glass for cladding (Example 7) having the composition shown in Table 2 are combined and spun by the double crucible method to obtain the predetermined photoconductive fiber of the present invention. It was.

  The present invention is useful in the technical field of optical fibers.

Claims (7)

Pb, As and Ti are not substantially contained, the refractive index nd is in the range of 1.60 to 1.70, the coloration degree λ80 is 38 or less, the liquidus temperature is 1000 ° C. or less, and the glass composition is Expressed in mass%, SiO ₂ > 30% 45% or less Al ₂ O ₃ 0% or more and less than 3% B ₂ O ₃ 0.1-10%
Na ₂ O 0.1% or more and less than 5% K ₂ O 0% or more and less than 5% Li ₂ O 0% or more and less than 5% Li ₂ O + Na ₂ O + K ₂ O = less than 5% CaO 0-20%
BaO 20-50%
ZnO 0.1-25%
ZrO ₂ 0.1-10%
A glass for a photoconductive fiber core, characterized in that Contains at least one component selected from the group consisting of MgO, SrO, La ₂ O ₃ , Nb ₂ O ₅ , Cs ₂ O, Gd ₂ O ₃ , Sb ₂ O ₃ and SnO ₂ as components other than the above. The glass for a photoconductive fiber core according to claim 1. 3. The glass for a photoconductive fiber core according to claim 1, wherein the linear thermal expansion coefficient at 100 ° C. to 300 ° C. is in the range of 80 × 10 ^{−7 to} 110 × 10 ⁻⁷ . The glass for a photoconductive fiber core according to any one of claims 1 to 3, wherein the glass is formed by a double crucible method. The photoconductive fiber which a core consists of the glass for cores in any one of Claims 1-4. The clad glass does not substantially contain Pb, As and Ti, the refractive index nd is in the range of 1.50 to 1.60, the liquidus temperature is 1000 ° C. or less, and the composition of the glass is by mass%. ₂ 40-75%
B ₂ O ₃ 0.1-20%
Na ₂ O 0.1-20%
The photoconductive fiber according to claim 5, wherein: The cladding glass is at least one selected from the group consisting of Li ₂ O, K ₂ O, Al ₂ O ₃ , MgO, CaO, SrO, BaO, Cs ₂ O, Sb ₂ O ₃ , and SnO ₂ as components other than the above. 7. The photoconductive fiber according to claim 6, comprising two or more components.