JP2008050182A - Glass composition and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a glass composition having high bismuth light emitting efficiency and its manufacturing method. <P>SOLUTION: The glass composition includes 55-75 (exclusive of 75) mol.% of SiO<SB>2</SB>, 5-25 mol.% of Al<SB>2</SB>O<SB>3</SB>, 0.01-5 mol.% of a bismuth oxide (in terms of Bi<SB>2</SB>O<SB>3</SB>) and 0.1-40 mol.% of a divalent metal oxide as essential components, and has a light absorption index at 1,310 nm wavelength of 0.078 cm<SP>-1</SP>or lower. This glass composition can be manufactured by melting a raw material at a temperature of higher than 1,450°C and keeping it for at most 6.5 hours, and then by cooling the molten raw material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a glass composition and a method for producing the same. In particular, it relates to a glass composition containing bismuth as a luminescent species.

  In the field of optical communication, the use of light in the infrared wavelength region, particularly light in the 1310 nm band, is active. As a glass emitting fluorescence in the 1310 nm band, a glass containing silicon oxide as a main component of a glass network former and containing bismuth oxide and aluminum oxide is known (Japanese Patent Laid-Open No. 2003-283028). In this glass, bismuth contained in the bismuth oxide functions as a luminescent species.

In general, a glass having such a composition has been manufactured by melting a raw material batch at about 1600 ° C. for a long time, more specifically, for about 18 hours or more. The reason for melting for a long time is to remove bubbles in the glass melt to increase the clarity of the glass and to increase the homogeneity of the glass.
JP 2003-283028 A

  The conventional glass composition as disclosed in Japanese Patent Application Laid-Open No. 2003-283028 still has room for improvement in light absorption in a wavelength region where fluorescence derived from bismuth is obtained. If the light absorption coefficient in such a wavelength region is lowered, the efficiency of bismuth light emission is increased.

  An object of this invention is to provide the glass composition which contains the bismuth oxide, and can improve the light emission efficiency derived from bismuth, and its manufacturing method.

  The inventor of the present invention has the above object when the melting time of raw materials is set to be significantly shorter than that in the prior art when manufacturing a glass composition containing silicon oxide as a main component of a glass network former and containing bismuth oxide and aluminum oxide. I found it to be achieved.

The present invention is indicated by mol%, SiO _2: 55~75 (but 75 not _{including), Al 2 O 3: 5~25} , Li 2 O: 0~15, Na 2 O: 0~5, K ₂ O: 0 to 5, MgO: 0 to 40, CaO: 0 to 30, SrO: 0 to 20, BaO: 0 to 15, ZnO: 0 to 25, TiO ₂ : 0 to 10, ZrO ₂ : 0 to 5 , B ₂ O ₃ : 0 to 10, P ₂ O ₅ : 0 to 10, GeO ₂ : 0 to 10 and a bismuth oxide, and MgO + CaO + SrO + BaO + ZnO is in the range of 0.1 to 40 mol%. Yes, a glass composition in which the content of the bismuth oxide converted to Bi ₂ O ₃ is in the range of 0.01 to 5 mol%, and the absorption coefficient of light having a wavelength of 1310 nm is in the range of 0.078 cm ⁻¹ or less. I will provide a.

  Another aspect of the present invention is a method for producing the glass composition, comprising: a melting step for melting the raw material of the glass composition; and a cooling step for cooling the molten raw material, Provides a method for producing a glass composition, wherein the raw material is held at a temperature exceeding 1450 ° C. for 6.5 hours or less.

  ADVANTAGE OF THE INVENTION According to this invention, the glass composition which improved the efficiency of bismuth light emission, and its manufacturing method can be provided.

Bismuth oxide is one of the essential components for the glass composition to emit fluorescence in the infrared wavelength region. If the bismuth oxide content (in terms of Bi ₂ O ₃ ) is less than 0.01 mol%, the intensity of fluorescence derived from bismuth (bismuth emission) may be too weak. On the other hand, when the content exceeds 5 mol%, a light absorption peak hardly appears in the excitation wavelength region of bismuth emission, and the emission intensity may decrease instead. For this reason, the range of the bismuth oxide content (in terms of Bi ₂ O ₃ ) is set to 0.01 to 5 mol%.

SiO ₂ is the main component of the glass network former. When the content of SiO ₂ increases, the viscosity of the glass melt increases and it becomes difficult to produce a glass composition. On the other hand, if the SiO ₂ content is too low, the intensity of bismuth light emission is reduced, and devitrification is likely to occur. Thus the scope of the content of SiO ₂ is less than less than 55 mol% 75 mol%.

Al ₂ O ₃ is an essential component for the bismuth oxide to emit bismuth light in the glass composition. If the content is less than 5 mol%, bismuth light emission is less likely to occur. As the content increases, the intensity of bismuth light emission increases. However, if it exceeds 25 mol%, the meltability of the raw material batch tends to deteriorate, and even when completely melted, devitrification easily occurs. Thus the scope of the content of Al ₂ O ₃ is 5 to 25 mol%.

  The divalent metal oxide RO (RO = MgO + CaO + SrO + BaO + ZnO) is an essential component for improving the meltability of the glass. When the content of RO is less than 0.1 mol%, the viscosity of the glass melt increases and it may be difficult to produce the glass composition. As the content increases, homogenization of the glass becomes easier, but when it exceeds 40 mol%, devitrification is likely to occur. For this reason, the range of the content rate of RO shall be 0.1-40 mol%.

  MgO is an optional component that contributes as a glass network modifier. MgO also increases the meltability of the raw material batch. However, if the content of MgO exceeds 40 mol%, a light absorption peak hardly appears in the excitation wavelength region of bismuth emission, and the emission intensity may decrease instead. Further, the viscosity of the glass melt is too low and devitrification is likely to occur. For this reason, the range of the content rate of MgO shall be 0-40 mol%.

  CaO is an optional component that enhances the meltability of the raw material batch. It also increases the devitrification resistance of the glass. In this aspect, CaO is superior to MgO. However, if the content exceeds 30 mol%, the intensity of bismuth emission may decrease on the contrary. For this reason, the range of the content rate of CaO shall be 0-30 mol%. When the glass composition contains MgO and CaO, as shown in Examples described later, it is preferable to adjust the respective addition amounts so that the content ratio of MgO to CaO is in the range of 1.5 or more. .

  SrO is an optional component that enhances the meltability of the raw material batch, like MgO and CaO. Even in a small amount (for example, 0.1 mol%) of SrO, the devitrification resistance of the glass is greatly improved. However, if the SrO content exceeds 20 mol%, the intensity of bismuth emission may decrease rapidly. For this reason, the range of the content rate of SrO shall be 0-20 mol%.

  BaO, as well as MgO, CaO, and SrO, is an optional component that enhances the meltability of the raw material batch. BaO has a higher effect of increasing the refractive index than other divalent metal oxides. As the refractive index increases, the intensity of bismuth emission increases. Therefore, from this viewpoint, BaO may be added in a range of, for example, 0.1 mol% or more. However, if the BaO content exceeds 15 mol%, the intensity of bismuth emission may decrease rapidly. For this reason, the range of the content rate of BaO shall be 0-15 mol%.

  ZnO is also an optional component that enhances the meltability of the raw material batch. ZnO has a higher effect of coloring the glass red or reddish brown than CaO, SrO, or BaO. ZnO is superior in action to increase the refractive index of glass as compared with MgO. Considering this, a small amount (for example, 0.1 mol% or more) of ZnO may be added. However, when the ZnO content exceeds 25 mol%, the intensity of bismuth emission may be reduced. On the other hand, if the content exceeds 25 mol%, the glass may be phase-divided to become milky and a transparent glass may not be obtained. For this reason, the range of the content rate of ZnO shall be 0-25 mol%.

Li ₂ O is an optional component that contributes as a glass network modifier. Li ₂ O lowers the melting temperature to increase the melting property and increase the refractive index of the glass. Addition of an appropriate amount of Li ₂ O (for example, 0.1 mol% or more) enhances light absorption and enhances the intensity of bismuth emission. The higher the content of Li ₂ O, the better. However, if it exceeds 15 mol%, the intensity of bismuth emission may decrease on the contrary. Moreover, when content rate exceeds 15 mol%, the viscosity of a glass melt will fall and it will become easy to produce devitrification. Therefore the range of the content of Li ₂ O is a 15 mol%.

Na ₂ O is an optional component that reduces the liquidus temperature and the devitrification of the glass together with the melting temperature. However, Na ₂ O has the effect of weakening bismuth emission by making the glass dark brown. Thus the scope of the content of Na ₂ O is 0 to 5 mol%.

K ₂ O reduces the liquidus temperature and suppresses the devitrification of the glass. However, K ₂ O has the effect of weakening the emission in the infrared region of the glass, which darkens the bismuth emission by making the glass dark brown. Thus the scope of the content of K ₂ O is 0 to 5 mol%.

As a part of raw materials of divalent metal oxide typified by MgO and alkali metal oxide typified by Li ₂ O, sulfate (eg, MgSO ₄ , Li ₂ SO ₄ ) or nitrate (eg, Mg (NO ₃ ) It is good to use highly oxidizable salts such as ₂ and LiNO ₃ ). This is because a highly oxidizable compound is produced during melting and the reduction of bismuth can be suppressed. When the reducing property is suppressed, erosion of a melting vessel such as a crucible made of platinum or a platinum-based alloy can also be suppressed.

TiO ₂ is an optional component that increases the refractive index of glass and increases the intensity of bismuth emission. TiO ₂ has a stronger effect of increasing the intensity of bismuth light emission than BaO. However, TiO ₂ has the effect of making the glass milky. Thus the scope of the content of TiO ₂ is 0 to 10 mol%.

ZrO ₂ is an optional component that increases the refractive index of glass and increases the intensity of bismuth light emission, like TiO ₂ . However, ZrO ₂ has an action of promoting crystallization of the glass and increasing the density of the glass. Therefore, in order to avoid devitrification and excessive density increase, the content range of ZrO ₂ is set to 0 to 5 mol%.

B ₂ O ₃ is an optional component that lowers the viscosity of the glass melt and homogenizes the glass. However, B ₂ O ₃ has the effect of making the glass milky. Thus the scope of the content of B ₂ O ₃ is 0 to 10 mol%.

The glass composition may further contain P ₂ O ₅ , GeO ₂ or the like. More specifically, P ₂ O ₅ may be contained in a range of 0 to 10% and GeO ₂ may be contained in a range of 0 to 10%.

The glass composition is expressed in mol%, bismuth oxide (in terms of Bi ₂ O ₃ ): 0.01 to 5, SiO ₂ : 55 to 75 (but not including 75), Al ₂ O ₃ : 5 to 25 , Li ₂ O: 0 to 15, Na ₂ O: 0 to 5, K ₂ O: 0 to 5, MgO: 0 to 40, CaO: 0 to 30, SrO: 0 to 20, BaO: 0 to 15, ZnO : 0 to 25, TiO ₂ : 0 to 10, ZrO ₂ : 0 to 5, B ₂ O ₃ : 0 to 10, P ₂ O ₅ : 0 to 10, GeO ₂ : 0 to 10 MgO + CaO + SrO + BaO + ZnO is in the range of 0.1 to 40 mol%.

In addition to these component groups, the glass composition is Y ₂ O ₃ , La ₂ O ₃ , Ta ₂ O ₅ , Nb ₂ for the purpose of controlling the refractive index, controlling the temperature viscosity characteristics, suppressing devitrification, and the like. O ₅ and In ₂ O ₃ may be contained up to 5 mol% in total. Further, the glass composition is a total of As ₂ O ₃ , Sb ₂ O ₃ , SO ₃ , SnO ₂ , Fe ₂ O ₃ , Cl and F for the purpose of fining during melting, prevention of reduction of bismuth oxide, and the like. And 1 mol% may be contained as an upper limit.

  The glass composition is substantially composed of the above component group (component group from bismuth oxide to F listed in the above two paragraphs), in other words, the above component group is a total of 99.9 mol. % Or more of the composition. In this case, as long as the total is less than 0.1 mol%, components other than the above component groups may be contained.

  In the production method of the present invention, the raw material is melted at a temperature exceeding 1450 ° C. Strictly speaking, this “temperature” refers to the ambient temperature. From the viewpoint of preventing reduction of bismuth and suppressing an increase in absorption that does not contribute to light emission, the melting temperature and time of the raw material are preferably as low and short as possible within a range in which the bubble quality and homogeneity of the glass are not extremely lowered. For example, the upper limit of the temperature at which the raw material is melted is preferably 1650 ° C., more preferably 1620 ° C., particularly 1600 ° C. The lower limit of this temperature may be 1500 ° C., further 1550 ° C. Moreover, the upper limit of the time for melting the raw material at a temperature exceeding 1450 ° C. is preferably 6.25 hours, and further 4.5 hours. The lower limit of this time may be 4.0 hours or even 3.5 hours. Even if the melting temperature is lowered to this level and the melting time is shortened, for example, strengthening mixing and stirring of raw materials before melting, increasing the number of raw material additions, strengthening stirring of glass melt, and crucible glass by selecting a crucible shape It is possible to prevent the foam quality and homogeneity of the glass from being lowered by reducing the melt base height.

When the temperature and time in the melting step are controlled in this way, as shown in the examples described later, the absorption coefficient of light having a wavelength of 1310 nm, which is an example of light in the wavelength region where bismuth light emission is obtained, is 0.078 cm ⁻¹ or less. The glass composition which exists in the range of this can be manufactured. Moreover, as shown in the Example mentioned later, the glass composition in which the absorption coefficient of the light of wavelength 1310nm exists in the range of 0.060cm < ^-1 > or less, Furthermore, the absorption coefficient of the light of wavelength 1310nm is 0.040cm < ^-1 > or less. It is also possible to produce a glass composition in the range of

  Details of the reason why the light absorption coefficient of the glass composition decreases when the temperature and time in the melting process are controlled as described above are not clear at this time. However, the present inventors believe that the reduction of bismuth is suppressed.

  The cooling step may be performed, for example, so that the glass obtained by pouring the molten raw material onto the iron plate is annealed in the vicinity of the glass transition temperature, and then the temperature is gradually decreased.

  Hereinafter, the present invention will be described in more detail with reference to examples.

(Example 1)
In terms of mol%, SiO ₂ : 65.3, Al ₂ O ₃ : 14.6, Li ₂ O: 2.5, Na ₂ O: 2.5, MgO: 9.7, CaO: 2.5, Silica, alumina, lithium carbonate, sodium carbonate, magnesium oxide, calcium carbonate, strontium carbonate, and trioxide so that a glass composition of SrO: 2.5 and bismuth oxide (in terms of Bi ₂ O ₃ ): 0.5 is obtained. Bismuth was weighed and a raw material batch was prepared.

  The prepared batch (350 g) was put into a platinum crucible and melted by holding it in an electric furnace heated to an atmospheric temperature of 1550 to 1590 ° C., more specifically 1550 to 1590 ° C. for 6.25 hours. Subsequently, the glass obtained by pouring the glass melt onto the iron plate was held at an atmospheric temperature of 700 ° C., more specifically, in an electric furnace heated to 700 ° C. for 30 minutes. Then, the sample glass was obtained by cooling to 20 degreeC over 18 hours.

(Example 2)
A sample glass was obtained in the same manner as in Example 1 except that the prepared batch was melted by holding it in an electric furnace heated to 1550 to 1590 ° C. for 6.5 hours.

(Comparative Example 1)
A sample glass was obtained in the same manner as in Example 1 except that the prepared batch was melted by holding it in an electric furnace heated to 1600 to 1650 ° C. for 25 hours.

(Comparative Example 2)
A sample glass was obtained in the same manner as in Example 1 except that the prepared batch was melted by holding it in an electric furnace heated to 1600 to 1620 ° C. for 28 hours.

(Comparative Example 3)
A sample glass was obtained in the same manner as in Example 1 except that the prepared batch was melted by holding it in an electric furnace heated to 1550 to 1650 ° C. for 27.5 hours.

(Examples 3 to 29)
Raw material batches were prepared so as to have the compositions shown in Tables 2 to 5. The prepared batch (350 g) was put into a platinum crucible and melted by holding it in an electric furnace heated to an atmospheric temperature of 1620 ° C., more specifically 1620 ° C., for 6.5 hours. The glass obtained by pouring the glass melt onto the iron plate was annealed at an ambient temperature of 700 ° C., and more specifically, held in an electric furnace heated to 700 ° C. for 30 minutes, and then 6.5. A sample glass was obtained by cooling to 50 ° C. over time.

  Using a spectrophotometer (U4100 manufactured by Hitachi), the transmittance of light having a wavelength of 1310 nm in the sample glasses of Examples 1 to 29 and Comparative Examples 1 to 3 was measured. The sample glass was molded to a thickness of 3.0 to 8.0 mm. The light absorption coefficient α was calculated based on the Lambert law from the light transmittance of two sample glasses having different thicknesses.

At this time, the light absorption coefficient α is α = ln (T ₁ / T ₂ ) / (d ₂ −d ₁ ).
However, T ₁ [%]: transmittance at the time of sample thickness d ₁ [cm], T ₂ [%]: transmittance at the time of sample thickness d ₂ [cm], and each unit is as follows. .
α [1 / cm], T ₁ [%], T ₂ [%], d ₁ [cm], d ₂ [cm]

  Similarly, the absorption coefficient of light having a wavelength of 800 nm was also analyzed. The results are shown in Tables 1-5.

As shown in Table 1, in each of the glass compositions of Examples 1 and 2, the absorption coefficient of light having a wavelength of 1310 nm was in the range of 0.078 cm ⁻¹ or less. On the other hand, although the glass compositions of Comparative Examples 1 to 3 had the same glass composition, it was confirmed that the light absorption coefficient was larger than those of Examples 1 and 2.

Further, as shown in Tables 2 to 5, in any of the glass compositions of Examples 3 to 29, similarly to Examples 1 and 2, the absorption coefficient of light having a wavelength of 1310 nm is in a range of 0.078 cm ⁻¹ or less. there were.

In the glass compositions of Examples 1, 3 to 21, and 23 to 29, the absorption coefficient of light having a wavelength of 1310 nm was in the range of 0.060 cm ⁻¹ or less, and the absorption coefficient was even smaller. In particular, Examples 3 to 10, 12 to 15, 17, 20, 23, 24, 26 and 28 have a light absorption coefficient of 1310 nm in the range of 0.040 cm ⁻¹ or less, and the absorption coefficient is particularly small. It was.

  From the comparison between Example 4 and Example 5 and the comparison between Example 8 and Example 9, when the glass composition contains MgO and CaO, the content ratio of MgO to CaO in the glass composition is higher. However, it has been found that the light absorption coefficient can be further reduced. The content ratio is preferably 1.5 or more.

  INDUSTRIAL APPLICABILITY The present invention has a great utility value in each field using bismuth light emission, represented by optical communication, as providing a glass composition with improved bismuth light emission efficiency.

Claims (5)

Expressed in mole%
SiO ₂ 55 to 75 (excluding 75)
Al ₂ O ₃ 5-25
Li ₂ O 0-15
Na ₂ O 0-5
K ₂ O 0-5
MgO 0-40
CaO 0-30
SrO 0-20
BaO 0-15
ZnO 0-25
TiO ₂ 0-10
ZrO ₂ 0-5
B ₂ O ₃ 0-10
P ₂ O ₅ 0-10
GeO ₂ 0-10
And a bismuth oxide,
MgO + CaO + SrO + BaO + ZnO is in the range of 0.1 to 40 mol%, and the content of the bismuth oxide converted to Bi ₂ O ₃ is in the range of 0.01 to 5 mol%.
A glass composition having an absorption coefficient of light having a wavelength of 1310 nm in a range of 0.078 cm ⁻¹ or less. The glass composition according to claim 1, wherein an absorption coefficient of light having a wavelength of 1310 nm is in a range of 0.060 cm ^-1 or less. The glass composition according to claim 2, wherein the absorption coefficient of light having a wavelength of 1310 nm is in the range of 0.040 cm ⁻¹ or less.   The glass composition according to claim 1, comprising MgO and CaO, wherein the content ratio of MgO to CaO is in the range of 1.5 or more. It is a manufacturing method of the glass composition described in Claim 1, Comprising:
A melting step of melting the raw material of the glass composition; and a cooling step of cooling the molten raw material, wherein the melting step is performed by holding the raw material at a temperature exceeding 1450 ° C. for 6.5 hours or less. The manufacturing method of the glass composition implemented.