JP5488865B2 - Glass melting furnace and glass melting method - Google Patents

Description

  The present invention relates to a glass melting furnace and a glass melting method suitable for melting a cover glass for a solid-state imaging device package.

  A solid-state image pickup device package used in an image pickup apparatus such as a digital camera or a video camera has a cover glass provided in an airtight manner on the front surface of the solid-state image pickup device arranged in the package body. As high-quality, high-definition images are required for imaging devices, the density of solid-state image sensors has increased, and the glass used for the cover glass that covers the front of the solid-state image sensor is also high-quality glass with few optical defects. It is necessary to be.

  In order to obtain high-quality glass with few optical defects, it is necessary to increase the purity of the glass raw material and to minimize the contamination in the glass melting process, specifically, the contamination from the glass melting furnace materials. In addition, it is necessary to reduce as many striae and bubbles as possible, which are foreign matter defects and inherent characteristic defects of glass.

  On the other hand, as a glass melting furnace for continuously obtaining molten glass, a raw material melting tank (a glass raw material inlet, a molten glass outlet is shown in FIG. 5 and FIG. (Not shown) 51 and 61, for example, tank bodies 53 and 63 for melting a glass raw material using a refractory 52 such as an electroformed brick as a tank material are formed, and the inner wall surface of the tank is a refractory surface 52a. There is a thing (FIG. 5) and a thing (FIG. 6) which further provided the platinum member 62 on the surface of the refractory and made the inner wall surface of the tank a platinum surface 62a.

  In the case where the inner wall surface of the tank is constituted by the refractory surface 52a, the durability of the tank material is low because the refractory 52 is eroded by the molten glass 54, and an inhomogeneous portion is generated in the molten glass 54 by the erosion reaction. There is a possibility that cord striae may occur in the glass formed mainly of inhomogeneous portions. On the other hand, in the case where the inner wall surface of the tank is constituted by the platinum surface 62a, the refractory 52 is prevented from being eroded by the molten glass 54, so that the durability of the tank material is increased and the striae generated in the glass are small. However, in the case where the inner wall surface of the tank is the platinum surface 62a, there arises a problem that platinum foreign matter increases in the glass.

  Thus, the platinum foreign matter which is a foreign matter defect was investigated and analyzed, and it was found that most of the platinum foreign matter contained in the glass was generated in the raw material melting tank for melting the glass raw material.

  In other words, the glass is volatilized by contacting platinum with the atmosphere at the upper part of the raw material melting tank in order to melt the glass, and then the glass raw material is newly added to the glass so that the temperature is lower than the temperature of the upper atmosphere of the tank. Platinum volatilized in the raw material solidifies. The solidified platinum is taken into the molten glass as a foreign substance. The platinum foreign matter once taken into the molten glass has a high melting point and cannot be easily ionized, and remains as a defect in the formed glass as it is. And since a new glass raw material is thrown into the raw material melting tank as the molten glass flows out, the volatilized platinum is continuously present in the atmosphere at the top of the tank, and the platinum foreign matter is continuously taken into the glass. Become.

  For this reason, in order not to volatilize platinum, it is necessary to prevent platinum from coming into contact with the atmosphere at the upper part of the raw material dissolution tank, and in this way, platinum does not volatilize, Platinum foreign matter is not taken into the glass. Moreover, if the inner wall surface of the raw material dissolution tank is made of refractory instead of platinum, platinum volatilized from the inner wall surface into the high-temperature atmosphere does not exist in the first place, so that platinum foreign matter is not taken into the glass. In other words, if the inner wall surface of the upper part of the raw material dissolution tank is made of refractory instead of platinum, and platinum is prevented from coming into contact with the atmosphere at the upper part of the tank, the incorporation of platinum foreign matter into the glass can be suppressed. become. The inventors completed the present invention based on the knowledge obtained through such investigation and analysis.

  In order to prevent particulate platinum from being taken into the glass, oxygen is burned in a glass melting furnace, and the oxygen concentration in the combustion space in which the glass is melted is maintained at 5% to 50%. Some of them are ionized and dissolved in glass to reduce platinum foreign matter (for example, see Patent Document 1). However, when platinum is ionized and melted in this way, it may be impossible to ionize sufficiently depending on the glass composition and melting temperature, and further, the transmittance of light in the visible region is reduced by platinum ions. For example, glass or the like used for a cover glass of a solid-state image sensor is not preferable because high transmittance is required for light in the visible range and mixing of coloring components should be avoided as much as possible.

  In addition, when a raw material batch is made into molten glass in a platinum container and further refined in a platinum container, a large amount of platinum is generated, so at least the raw material batch is made into molten glass with a refractory container (crucible). In some cases, the generation of platinum bumps is suppressed (see, for example, Patent Document 2). According to Patent Document 2, the use of a refractory container reduces the amount of radioactive isotopes U (uranium) and Th (thorium) mixed into the glass and solid-state imaging the formed glass. Soft errors can be reduced when used for the cover glass of the element. On the other hand, since refractory containers are easily corroded by molten glass, conventionally, it has been difficult to produce optical glass with high homogeneity. It is said that it was not used.

JP 2001-10822 A JP-A-7-237933

  The present invention has been made in view of the above situation. The object of the present invention is to melt the molten glass in the melting tank while feeding the glass raw material, and when the molten glass is continuously discharged, the molten glass is not suitable. Glass melting furnace and glass melting that can form high-quality glass with low yield, with little chance of homogeneous parts, less chance of platinum foreign matter being incorporated, and few optical defects such as cord striae and foreign matter defects It is to provide a method.

The glass melting furnace and glass melting method of the present invention are:
A glass melting furnace comprising a raw material melting tank configured to melt while adding a glass raw material and to continuously flow the molten glass obtained by melting to the next stage, wherein the raw material melting tank is a ceiling portion The upper inner wall surface of the ceiling part and the raw material dissolution tank body is a refractory surface from which the refractory forming the tank is exposed, and the lower inner wall surface of the raw material dissolution tank body is platinum. Alternatively , a platinum member made of a platinum alloy is formed by a platinum surface lined on the refractory, and the platinum surface is formed such that the upper end thereof is not exposed to the atmosphere above the molten glass. It is characterized by that,
Furthermore, the platinum surface is characterized in that the area is 70% or more of the area where the molten glass is in contact with the inner wall surface of the raw material melting tank,
Furthermore, after the next stage of the raw material dissolution tank, along the flow direction of the molten glass, at least one clarification tank, a stirring tank is sequentially disposed,
Furthermore, the raw material dissolution tank is characterized in that fossil fuel is heated by burning with a burner.

Further, in the glass melting method, the upper inner wall surface of the raw material melting tank body closed by providing a ceiling is a refractory surface from which the refractory forming the tank is exposed, and the lower inner wall surface of the raw material melting tank body The molten glass obtained by melting the molten glass obtained by melting and melting the glass material through the raw material melting tank formed by the platinum surface lined with platinum or platinum alloy made of platinum or platinum alloy in the next process. A glass melting method in which the glass raw material is charged into the raw material melting tank and the molten glass is poured out from the raw material melting tank, and an upper end of the platinum surface is above the molten glass. The area of the platinum surface is located below the interface between the upper atmosphere of the tank and the molten glass, and the area of the platinum surface is 70% or more of the area of the molten glass contacting the inner wall surface of the raw material melting tank. That It is a method for the butterflies.

  As is clear from the above description, according to the present invention, when the raw glass is continuously melted and discharged, there is less risk of inhomogeneous parts being generated in the molten glass and platinum foreign matter being taken in, and High-quality glass with few optical defects such as cord striae and foreign matter defects can be obtained with good yield.

It is sectional drawing which shows the glass melting furnace of one Embodiment of this invention. It is a longitudinal cross-sectional view which shows the raw material dissolution tank in one Embodiment of this invention. It is a fragmentary sectional view of the raw material dissolution tank in one embodiment of the present invention. It is a figure which shows the glass melting example in each Example which concerns on one Embodiment of this invention, FIG. 4 (a) is a figure which shows a glass melting result, FIG.4 (b) is a figure which shows a glass raw material composition. It is sectional drawing of schematic structure which shows the 1st prior art of a raw material dissolution tank. It is sectional drawing of schematic structure which shows the 2nd prior art of a raw material dissolution tank.

  An embodiment of the present invention will be described below with reference to FIGS. 1 is a sectional view showing a glass melting furnace, FIG. 2 is a longitudinal sectional view showing a raw material melting tank, FIG. 3 is a partial sectional view of the raw material melting tank, and FIG. 4 is a glass melting example in each embodiment. FIG. 4A is a diagram showing a glass melting result, and FIG. 4B is a diagram showing a glass raw material composition.

  1 to 3, a glass melting furnace 1 includes a raw material melting tank 2, a clarification tank 3, and a homogenization tank 4, which are placed sideways along the flow direction of the molten glass 7 by glass flow path tubes 5 and 6, respectively. It is comprised so that it may continue in the direction. The glass melting furnace 1 is a furnace configured to melt a glass raw material by a heating method by a burner combustion method using fossil fuels such as LPG (liquefied petroleum gas), heavy oil, and LNG (liquefied natural gas). ing. And the molten glass 7 obtained by melting | dissolving the glass raw material in the raw material melting tank 2 through the inlet which is not shown in figure is clarified and homogenized by the clarification tank 3 and the homogenization tank 4. FIG. Thereafter, the glass is continuously fed from a glass outflow nozzle 8 provided in the homogenization tank 4 to a molding apparatus (not shown) or the like and molded into a required glass product.

  Moreover, about the raw material melt | dissolution tank 2, the ceiling part 9 is provided, it obstruct | occludes by covering the upper part of the tank main body 10, has the structure made into the substantially rectangular parallelepiped shape, and is formed using the refractory. Further, in the raw material dissolution tank 2, the ceiling portion 9 and the upper inner wall surface of the tank body 10 are a refractory surface 11a from which the refractory material 11 forming the tank is exposed, and the lower inner wall surface of the tank body 10 is made of platinum. Further, a platinum surface 12a is formed by lining a refractory 11 with a platinum member 12 such as a platinum film or a platinum plate formed of platinum alloy. Furthermore, the raw material dissolution tank 2 is attached to the tank lower side wall so that one end of the glass flow channel pipe 5 communicates with the lower part in the tank and is inclined upward in the downstream direction. In the raw material melting tank 2 configured in this way, melting and removal of large bubbles in the molten glass 7 are performed while adding the glass raw material, and then the molten glass 7 passes through the glass flow path tube 5. And then poured out into the clarification tank 3.

Further, the clarification tank 3 has a structure in which the inside of the tank is sealed, for example, is lined with platinum or a platinum alloy so that the inner surface becomes a platinum surface (not shown), and the inner shape of the tank is melted. The glass 7 is horizontally installed in a flat and substantially rectangular parallelepiped shape having a longitudinal direction in the flow direction. Furthermore, the other end of the glass flow path tube 5 is attached to the central portion of the side wall at one end which is the upstream side in the longitudinal direction of the clarification tank 3. Moreover, it attaches so that the one end may communicate with the center part of the side wall of the other end used as the downstream of a longitudinal direction so that the glass flow path tube 6 may become horizontal. Further, a degassing pipe 13 is erected at the ceiling portion of the clarification tank 3 so as to communicate with the upper part in the tank. Then, the molten glass 7 that has flowed from the raw material melting tank 2 flows through the tank while the molten state is maintained in the downstream direction, as a fining agent during, e.g., _{As 2 O 3, Sb 2 O} 3, NaCl, Na 2 Clarification is performed using SO ₄ , SnO _2, etc., and the dissolved gas is discharged to the outside of the tank through the gas vent pipe 15, and then flows out to the homogenization tank 4 through the glass flow path pipe 6. It is.

  Further, the homogenization tank 4 is configured such that it is lined with, for example, platinum or a platinum alloy and the inner surface is a platinum surface (not shown), and is not shown in an upright cylindrical container 14 having an opening in the upper part. A stirrer 15 that stirs by a drive source is provided. The stirring device 15 includes a stirring member 17 at a lower end portion of a rotating shaft 16 provided vertically in the container 14. Moreover, the glass outflow nozzle 8 is attached to the container 14 so that the other end of the glass flow path tube 6 communicates with the inside of the container 14 at the upper part of the side wall surface and further communicates with the bottom part. And the molten glass 7 from which the fine bubble which flowed into the homogenization tank 4 via the glass flow path pipe 6 from the clarification tank 3 was removed is stirred by the stirring apparatus 15 within the container 14, and is homogenized. Thereafter, the homogenized molten glass 7 is continuously sent out from the glass outflow nozzle 8 to a molding apparatus or the like.

In the glass melting furnace 1 configured as described above, the glass raw material of the raw material composition A shown in FIG. 4B is melted while being introduced into the raw material melting tank 2 to obtain a molten glass 7, and further the molten glass 7 was continuously poured out into the clarification tank 3 and the homogenization tank 4, and further sent out from the homogenization tank 4 to a molding apparatus to form a glass. Incidentally, the glass raw material of the raw material composition A has a composition of each weight%, SiO ₂ : 68.2%, Al ₂ O ₃ : 3.2%, B ₂ O ₃ : 18.8%, Li ₂ O: 1.2%, Na ₂ O: 0.8%, K ₂ O: 7.5%, Cl: 0.2%, SO ₃ : 0.1%.

  Further, the relationship between the amount of glass raw material charged and the amount of molten glass 7 poured out when melting and pouring out the glass raw material in the raw material melting tank 2 is as follows: from the molten glass surface 7a to the platinum surface 12a of the molten glass 7 in the tank. For example, the molten glass 7 has a surface tension so that the upper end 12b is not exposed in the tank upper atmosphere 2a, that is, below the interface between the tank upper atmosphere 2a above the molten glass 7 and the molten glass 7. The portion 18 that comes into contact with the inner wall surface of the tank and gets wet is adjusted so as to be positioned below the interface.

The adjustment position of the level of the molten glass surface 7a in the raw material melting tank 2 at this time is relative to the total contact area of the molten glass 7 in contact with the inner wall surface of the raw material melting tank 2 including the refractory surface 11a and the platinum surface 12a. The area of the platinum surface 12a was 70% (platinum contact area ratio). Moreover, the clarification process in the clarification tank 3 after melt | dissolving the glass raw material in the raw material dissolution tank 2 performed clarification at 1450 degreeC, and also homogenized in the homogenization tank 4. FIG. Then, a glass block having a predetermined shape was formed on the glass thus obtained, polished, and observed with a 50-fold stereomicroscope to check for foreign platinum particles and bubbles (the following examples and comparative examples) The same applies to the above). As a result of the check, platinum foreign matter was as small as 10 pieces / kg, and foam was 0.4 pieces / kg, and no striae was observed. Further, when the amount of α-ray emission was measured, it was a low level of 0.002 c / cm ² · h.

Next, in the same glass melting furnace 1 as in Example 1, the glass raw material having the raw material composition B shown in FIG. The glass 7 was continuously poured out into the clarification tank 3 and the homogenization tank 4, and further sent out from the homogenization tank 4 to a molding apparatus to form the glass. By the way, the glass raw material of the raw material composition B has a composition of each weight%, SiO ₂ : 73.0%, Al ₂ O ₃ : 4.3%, B ₂ O ₃ : 12.5%, Li ₂ O: It is 1.8%, Na ₂ O: 7.6%, ZnO: 0.6%, Sb ₂ O ₃ : 0.2%.

  About the adjustment position of the level of the molten glass surface 7a in the raw material melting tank 2 at this time, with respect to the total contact area of the molten glass 7 in contact with the refractory surface 11a and the platinum surface 12a of the inner wall surface of the raw material melting tank 2 The area of the platinum surface 12a is 80% (platinum contact area ratio), and the relationship between the amount of the glass raw material charged into the raw material melting tank 2 and the amount of the molten glass 7 poured out is determined by melting the molten glass 7 in the tank. It adjusted so that the upper end 12b of the platinum surface 12a might not be exposed in the tank upper atmosphere 2a from the glass surface 7a. Moreover, the clarification process in the clarification tank 3 after melt | dissolving the glass raw material in the raw material dissolution tank 2 performed clarification at 1420 degreeC, and also homogenized in the homogenization tank 4. FIG.

And the platinum foreign material in the glass obtained in this way was 0.3 pieces / kg and still less than Example 1, a bubble was 0.1 piece / kg, and it was not seen about striae. . Further, when the amount of α-ray emission was measured, it was a very low level of 0.0001 c / cm ² · h.

Comparative Example 1

  Compared to Example 1 above, the raw material composition of the glass raw material is the same raw material composition B as in Example 2, and the area of the platinum surface 12a with respect to the total contact area of the molten glass 7 to the inner wall surface of the raw material melting tank 2 is Except for changing to 50% (platinum contact area ratio), glass was molded using the same apparatus.

In Comparative Example 1 in which glass was melted in this manner, platinum foreign matter in the obtained glass was not exposed from the molten glass surface 7a of the molten glass 7 to the upper end 12b of the platinum surface 12a in the tank upper atmosphere 2a. However, since the area where the molten glass 7 contacts the refractory surface 11a is large, the refractory 11 is eroded by the molten glass 7 and the striae is very small. 25% produced. The α ray emission amount was a low level of 0.004 c / cm ² · h.

Next, in the same glass melting furnace 1 as in Example 1, the glass raw material of the raw material composition C shown in FIG. The glass 7 was continuously poured out into the clarification tank 3 and the homogenization tank 4, and further sent out from the homogenization tank 4 to a molding apparatus to form the glass. By the way, the glass raw material of the raw material composition C is SiO ₂ : 60.5%, Al ₂ O ₃ : 13.2%, B ₂ O ₃ : 7.5%, Li ₂ O: 4.2%, Na ₂ O: 2.7%, MgO: 0.3%, CaO: 1.0%, ZnO: 10.0%, SO ₃ : 0.1%, SnO ₂ : 0.5% It is.

  About the adjustment position of the level of the molten glass surface 7a in the raw material melting tank 2 at this time, with respect to the total contact area of the molten glass 7 in contact with the refractory surface 11a and the platinum surface 12a of the inner wall surface of the raw material melting tank 2 The area of the platinum surface 12a is 90% (platinum contact area ratio), and the relationship between the amount of the glass raw material charged into the raw material melting tank 2 and the amount of the molten glass 7 poured out is determined by the melting of the molten glass 7 in the tank. It adjusted so that the upper end 12b of the platinum surface 12a might not be exposed in the tank upper atmosphere 2a from the glass surface 7a. Moreover, the clarification process in the clarification tank 3 after melt | dissolving the glass raw material in the raw material dissolution tank 2 performed clarification at 1550 degreeC, and also homogenized in the homogenization tank 4. FIG.

And the platinum foreign material in the glass obtained in this way was as very few as 5 piece / kg, and a bubble was 0.8 piece / kg, and it was not seen about striae. Further, when the amount of α-ray emission was measured, it was a very low level of 0.0008 c / cm ² · h.

Next, in the same glass melting furnace 1 as in Example 1, the glass raw material having the raw material composition D shown in FIG. The glass 7 was continuously poured out into the clarification tank 3 and the homogenization tank 4, and further sent out from the homogenization tank 4 to a molding apparatus to form the glass. By the way, the glass raw material of the raw material composition D has a composition of each weight%, SiO ₂ : 65.0%, Al ₂ O ₃ : 18.0%, B ₂ O ₃ : 4.0%, Li ₂ O: 2.5%, MgO: 0.9%, CaO: 2.0%, ZnO: 7.5%, Cl: 0.05%, SO 3: 0.05%.

  About the adjustment position of the level of the molten glass surface 7a in the raw material melting tank 2 at this time, with respect to the total contact area of the molten glass 7 in contact with the refractory surface 11a and the platinum surface 12a of the inner wall surface of the raw material melting tank 2 The area of the platinum surface 12a is set to 95% (platinum contact area ratio), and the relationship between the amount of the glass raw material charged into the raw material melting tank 2 and the amount of the molten glass 7 poured out is determined by the melting of the molten glass 7 in the tank. It adjusted so that the upper end 12b of the platinum surface 12a might not be exposed in the tank upper atmosphere 2a from the glass surface 7a. Moreover, the clarification process in the clarification tank 3 after melt | dissolving the glass raw material in the raw material dissolution tank 2 performed clarification at 1520 degreeC, and also homogenized in the homogenization tank 4. FIG.

And the platinum foreign material in the glass obtained in this way was very few at 2 pieces / kg, and bubbles were 1.3 pieces / kg, and no striae was seen. Further, when the amount of α-ray emission was measured, it was a very low level of 0.0002 c / cm ² · h.

Comparative Example 2

Compared to Example 4 above, the raw material composition of the glass raw material is the same raw material composition D as Example 4, and the relationship between the platinum surface 12a on the inner wall surface of the raw material melting tank 2 and the molten glass 7 is determined by melting the molten glass 7. The glass surface 7a is adjusted so that the upper end 12b and part of the upper end side portion of the platinum surface 12a are exposed to the upper tank upper atmosphere 2a (platinum contact area ratio: 100%). The clarification process in the clarification tank 3 after dissolving the raw material was clarified at 1520 ° C., and further homogenized in the homogenization tank 4. The glass raw material was melted and poured out. The platinum foreign matter of the glass in Comparative Example 2 thus obtained exceeded 3000 pieces / kg because the platinum surface 12a was exposed and volatilized in the high-temperature tank upper atmosphere 2a, resulting in a very large amount. Note that no striae was observed, and the α ray emission amount was 0.0002 c / cm ² · h, which was a very low level as in Example 4. In addition, when a platinum contact area ratio is 100%, it means that the platinum surface 2a is exposed to the tank upper atmosphere 2a.

  As described above, according to the present embodiment, since the platinum is not exposed to the high-temperature tank upper atmosphere 2a in the raw material dissolution tank 2, there is little volatilization of platinum into the tank upper atmosphere 2a and the temperature is relatively low. Even if the glass raw material is continuously charged, platinum hardly solidifies in the glass raw material, so that there is little possibility that foreign matter of platinum is mixed in the molten glass 7.

  Moreover, the platinum surface 12a lined under the inner wall surface of the tank body of the raw material melting tank 2 has an area of 70% or more of the area where the molten glass 7 is in contact with the inner wall surface of the raw material melting tank 2. In addition, since the contact area between the molten glass 7 and the refractory surface 11a of the tank material is very small, there is little possibility that an inhomogeneous portion is generated due to the erosion reaction, and there are few optical defects such as cord striae and foreign matter defects. Quality glass can be obtained with high yield. In addition, since the platinum surface 12a lining the lower part of the inner wall surface of the raw material dissolution tank 2 is not exposed to the upper atmosphere of the tank above the molten glass 7, the lower surface of the inner wall surface of the raw material dissolution tank 2 is The upper limit of the area where the molten glass 7 is in contact with the inner wall surface of the raw material melting tank 2 should be less than 100% of the lined platinum surface 12a.

  In addition, when the raw material dissolution tank 2 is drained out once for replacement of the glass type, etc., the platinum surface 12a of the raw material dissolution tank 2 is exposed to the atmosphere 2a and volatilized into the newly introduced replacement glass material. There is a possibility that the platinum that has been agglomerated may be incorporated into the glass. However, since the melting of the glass raw material in the raw material melting tank 2 is performed by a heating method by a burner combustion method using fossil fuel such as LPG, heavy oil, LNG, etc., it is volatilized when exhaust gas exhausted by combustion is exhausted. Platinum is discharged with the combustion exhaust gas less, and it is possible to reduce contamination of the platinum foreign matter into the glass as compared with a heating method such as an electric heater method without exhaust.

Furthermore, zirconia electrocast bricks, Al ₂ O ₃ —ZrO ₂ —SiO ₂ (AZS) electrocast bricks, alumina electrocast bricks, and the like can be used as the material for the raw material dissolution bath 2. In particular, in order to reduce the amount of radioisotope mixed in the molten glass 7 from the tank upper atmosphere 2a, the tank upper inner wall surface exposed to the tank upper atmosphere 2a of the raw material melting tank 2 has a radioactive material such as U or Th as a raw material. It is preferable to use an alumina electrocast brick with a low isotope content or to line a silica block on the inner wall surface. Thereby, the alpha ray discharge | release amount of glass can be decreased.

DESCRIPTION OF SYMBOLS 1 ... Glass melting furnace 2 ... Raw material melting tank 2a ... Atmosphere 7 ... Molten glass 9 ... Ceiling part 10 ... Tank main body 11 ... Refractory 11a ... Refractory surface 12 ... Platinum member 12a ... Platinum surface 12b ... Upper end

Claims (5)

A glass melting furnace provided with a raw material melting tank configured to melt while melting a glass raw material and to continuously flow the molten glass obtained by melting to the next stage,
The raw material dissolution tank is closed by a ceiling part, and the upper inner wall surface of the ceiling part and the raw material dissolution tank body is a refractory surface from which the refractory forming the tank is exposed, and the raw material dissolution tank body The lower inner wall surface is formed by a platinum surface in which a platinum member made of platinum or a platinum alloy is lined on the refractory , and the upper end of the platinum surface is not exposed in the atmosphere above the molten glass. A glass melting furnace formed so as to be in a position.   The glass melting furnace according to claim 1, wherein the platinum surface has an area of 70% or more of an area where the molten glass is in contact with an inner wall surface of the raw material melting tank.   2. The glass melting furnace according to claim 1, wherein at least one clarification tank and a stirring tank are sequentially arranged along the flow direction of the molten glass after the next stage of the raw material melting tank.   The glass melting furnace according to claim 1, wherein the raw material melting tank heats by burning a fossil fuel with a burner. The upper inner wall surface of the raw material melting tank body closed by providing a ceiling is a refractory surface from which the refractory forming the tank is exposed, and the lower inner wall surface of the raw material melting tank body is made of platinum or a platinum alloy . A glass melt that melts molten glass obtained by melting the molten glass obtained by melting the glass material with a raw material melting tank formed on the platinum surface with the platinum member lined on the refractory. A method,
The introduction of the glass raw material into the raw material melting tank, and the flow of the molten glass out of the raw material melting tank, the upper end of the platinum surface from the interface between the upper atmosphere of the tank above the molten glass and the molten glass The glass melting method is performed in such a manner that the area of the platinum surface is 70% or more of the area where the molten glass contacts the inner wall surface of the raw material melting tank.

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