JP2012111665A - Heat conductive glass, and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a thermally conductive glass that can be applied to a glass lining, has excellent thermal conductivity, and has little expansion due to foaming of the glass, and a method for producing such a thermally conductive glass. To provide.
When adding SiC as a heat conductive filler to a glass frit, firing is performed at a temperature range of 600 ° C. or higher and lower than 720 ° C. The surface of SiC may be oxidized to form a SiO ₂ film. The glass frit mixed with the heat conductive filler may be fired in an inert gas atmosphere, or may be fired under reduced pressure or under pressure.
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Description

  The present invention relates to a thermally conductive glass having excellent thermal conductivity and less foaming of the glass, and a method for producing such a thermally conductive glass.

The conventional glass has a thermal conductivity of about 1 W / mK, which is lower than that of a metal material or the like, so that it takes time to raise and cool in the firing step. For the purpose of improving the thermal conductivity of glass, metal oxides such as Al ₂ O ₃ and ZrO ₂ ; metals such as Au and Pt; carbides such as SiC and the like are mixed with glass frit as thermal conductive fillers. It has been.

For example, in Patent Document 1, in order to improve the heat resistance of glass ceramics, one or more fillers selected from the group consisting of Al ₂ O ₃ , ZrO ₂ and MgO are mixed into a glass frit to increase the heat resistance. It is disclosed to obtain a composite glass ceramic having strength and excellent heat resistance.

  In Patent Document 2, in order to improve the thermal conductivity of the glass paste composition and suppress bubbles remaining in the glass frit, the low melting point glass frit mainly composed of vanadium has a higher thermal conductivity than the low melting point glass frit. It is disclosed that a filler higher than 3.7 W / mk is blended.

Patent Document 3 is characterized by containing an inorganic refractory powder selected from the group consisting of silica, Al ₂ O ₃ and AlN, in an external ratio of 1 to 20% by weight with respect to 100% by weight of the glass frit. A glass lining composition for overcoating is disclosed. This glass lining composition is said to improve thermal conductivity by enabling thin film processing of the glass layer.

Japanese Patent No. 42200113 JP 2008-247658 A JP 2010-195640 A

  When the thermal conductivity of the glass is improved by the addition of the thermal conductive filler, the effect of adding the thermal conductive filler cannot be obtained because the thermal conductivity of the air is low if bubbles are included in the glass. . When heat conductive fillers other than oxides are mixed in the glass frit, there is a problem that the heat conductive glass foams due to gas generation accompanying oxidation of the heat conductive filler in the firing step. Further, even when a thermally conductive filler that is an oxide is mixed with a glass frit, it is desired to suppress the generation of bubbles in the firing step as much as possible and form the glass surface smoothly.

  However, the glass ceramic disclosed in Patent Document 1 has a high firing temperature of 1120 to 1250 ° C., and there is a high possibility that bubbles are generated. Further, the glass ceramic disclosed in Patent Document 1 cannot be fired when applied to glass lining because the base metal is distorted at a high temperature of 1000 ° C. or higher. Moreover, what is disclosed in Patent Document 2 is a glass paste for sealing substrates together, and the pre-baking temperature in the examples is 440 ° C. At such a low temperature, the glass frit for glass lining cannot be fired. Furthermore, in Patent Document 3, as a result of improving the strength of the glass layer, the thermal conductivity is improved by forming the glass layer thin, and the inorganic refractory powder is applied to the glass frit for the purpose of improving the thermal conductivity. Not mixed.

  The present invention is a thermally conductive glass that can also be applied to glass lining, has excellent thermal conductivity, and has little expansion due to foaming of the glass, and production of such thermally conductive glass The purpose is to provide a method.

If the present inventors form an oxide film on the surface of the thermally conductive filler (except those used as oxides), and mix the thermally conductive filler with the oxide film into the glass frit, It was found that unlike the heat conductive filler, foaming hardly occurs in the firing process. Specifically to form the SiO ₂ film on the SiC surface, by mixing the glass frit SiC forming the SiO ₂ film as a heat conductive filler, unlike the conventional SiC, found that hardly cause foaming in the baking step It was.

  In addition, when SiC is mixed (added) to the glass frit as a thermally conductive filler, it is mixed with the glass frit at a ratio of 20 wt% to 60 wt% and fired at a temperature range of 600 ° C. to less than 720 ° C. It has been found that a thermally conductive glass that can also be used for glass lining can be produced.

  The present inventors have also found that foaming can be suppressed by mixing a thermally conductive filler with glass frit and then performing a firing step in a low oxygen state or a reducing atmosphere.

Specifically, the first invention of the present application is
Step A of heat-treating the thermally conductive filler in the temperature range of 450 ° C. or higher and 1500 ° C. or lower in the presence of oxygen;
Step B, in which the thermally conductive filler after Step A is mixed in a glass frit at a ratio of 20 wt% to 60 wt% and fired,
It is related with the manufacturing method of the heat conductive glass which has this.

For example, for SiC, which is a thermally conductive filler, heat treatment is performed at a temperature range of 800 ° C. or higher and 1500 ° C. or lower, more preferably 900 ° C. or higher and 1500 ° C. or lower, whereby the SiC surface is oxidized and a SiO ₂ film is formed. The SiC coated with a SiO ₂ film whose surface is an oxide, when mixed at a ratio of 20 wt% to 60 wt% with a glass frit as a thermally conductive filler, Bubbles derived from the conductive filler are less likely to occur in the glass.

Here, the thermally conductive filler is not limited to SiC, and TiC, ZnC, TaC, W ₂ C, BN, AlN, TaN, TiN, ZrN, Si ₃ N _4, or the like can also be used.

  In addition, the “glass frit” of the present invention means a glass frit that can be used as a glass frit for an overcoating glass lining.

  In the said manufacturing method, it is preferable that baking time shall be 10 minutes or more and 4 hours or less. From the viewpoint of forming an oxide film on the surface of the thermally conductive filler, the surface is sufficiently oxidized if baked for 4 hours, so that it is not necessary to heat more than necessary.

The second invention of the present application is
Heat conductive filler (for example, SiC) is mixed with glass frit at a ratio of 20 wt% or more and 60 wt% or less, and is fired at a temperature range of 600 ° C. or higher and lower than 720 ° C. Regarding the method.

  If SiC is mixed as a heat conductive filler in such a ratio with respect to the glass frit and fired in a temperature range of 600 ° C. or higher and lower than 720 ° C., bubbles are formed in the glass while improving the heat conductivity of the glass. Generation | occurrence | production can be suppressed. In addition, it is preferable that a baking temperature is 680 degreeC or more from a viewpoint of constructing as glass lining.

The third invention of the present application is
The present invention relates to a method for producing a heat conductive glass, characterized in that a heat conductive filler is mixed with a glass frit and then fired in an inert gas atmosphere.

  After mixing a thermally conductive filler, particularly a thermally conductive filler other than an oxide, into a glass frit, if a normal firing step is performed, bubbles are likely to be generated in the glass, but by firing in an inert gas atmosphere, Bubbles derived from the thermally conductive filler are less likely to occur in the glass.

The fourth invention of the present application is
The present invention relates to a method for producing a thermally conductive glass, characterized in that a thermally conductive filler is mixed with glass frit and then fired under reduced pressure or under pressure.

  After mixing a thermally conductive filler, especially a thermally conductive filler other than an oxide, into a glass frit, if a normal firing process is performed, bubbles are likely to be included in the glass due to foaming of the filler, but firing under reduced pressure. Thus, the generated bubbles can be defoamed and suppressed from being encapsulated in the glass. Even when the thermally conductive filler is an oxide, the air mixed in the glass frit can be defoamed and entrapped in the glass by firing under reduced pressure. Moreover, when degassing under reduced pressure is difficult, the bubble diameter contained by making it baked under pressure can be made small, and the deterioration of the thermal conductivity by the bubble included can be suppressed.

The third invention of the present application and the fourth invention of the present application are nonconductive oxides such as SiC, TiC, ZrC, TaC, W ₂ C, AlN, BN, TaN, TiN, ZrN, or Si ₃ N ₄ . In addition to the filler, when using a thermally conductive filler that is an oxide such as Al ₂ O ₃ , ZrO ₂ , MgO, ZnO, or TiO ₂ , inclusion of bubbles can be suppressed.

  According to the present invention, it is possible to produce glass having a smooth surface with less expansion due to the generation of bubbles while improving thermal conductivity.

It is an external appearance photograph in the process which heats up SiC / glass composite material pellet to 840 degreeC, (a) is Example 1, (b) is Example 2, (c) is Comparative Example 1. FIG. It is the external appearance photograph after baking a SiC / glass composite material pellet for 1 hour, (a) is Example 3, (b) is the comparative example 2. FIG. It is a graph showing the relationship between the SiC mixing amount with respect to a glass frit, and the thermal conductivity of glass. It is a cross-sectional SEM photograph of the glass of Examples 3-5.

  Embodiments of the present invention will be described based on examples. The present invention is not limited to the following description.

(Low temperature firing)
[Example 1]
20% by weight of SiC (Kishida Chemical Co., Ltd., Carborundum # 400) as a heat conductive filler was mixed with the glass frit for the top-coated glass lining. The SiC / glass composite slurry was poured into an acrylic cylindrical mold having a diameter of 12 mm and a height of 20 mm, and dried at 60 ° C. for 6 hours to form pellets. The pellets were put in an electric furnace, and the temperature in the electric furnace was increased to 600 ° C. at a rate of 10 ° C. per minute. Carborundum # 400 has a maximum particle size (dv-0 value) of 75 μm; a particle size of 3% cumulative height (dv-3 value) of 58 μm or less; a particle size of 50% cumulative height (dv-50) Value) is 30.0 ± 2.0 μm; the particle size (dv-94 value) at a cumulative height of 94% is 20 μm or more.

[Example 2]
The same operation as in Example 1 was performed except that the firing temperature was 700 ° C.

[Comparative Example 1]
The same operation as in Example 1 was performed except that the temperature was 840 ° C. in the electric furnace.

  1 (a) to 1 (c) show photographs of the appearances of pellets of Example 1, Example 2 and Comparative Example 1, respectively, at a set temperature. The pellet diameter was initially 12 mm, and in Example 1 and Example 2, the pellet diameter was hardly changed before and after firing.

  On the other hand, in Comparative Example 1, when the temperature in the furnace reached 730 ° C. or higher, the pellets started to expand due to foaming due to oxidation of SiC, and after being heated to 840 ° C., the pellets fired for 1 hour had a diameter of 28 mm. It was.

[Example 3]
When the firing temperature was 680 ° C., the temperature was raised to 680 ° C. at a temperature increase rate of 10 ° C. per minute in the same manner as in Example 1, and when it was held for 1 hour, it was confirmed that the pellet hardly expanded.

[Example 4]
When the same operation as in Example 3 was performed except that the firing temperature was set to 700 ° C., it was confirmed that the pellet hardly expanded.

  As described above, when the firing temperature was changed in the range of 600 to 840 ° C, it was confirmed that the pellet hardly expands in the range of 600 ° C or higher and lower than 720 ° C. Further, when the firing temperature was 600 ° C. or higher and lower than 720 ° C., it was confirmed that the pellets could hardly be expanded and used as a fired glass when the firing time was 1 hour. In addition, when baking as glass lining, it is preferable to baking at 680 degreeC or more and 700 degrees C or less from a viewpoint of baking as low temperature as possible, suppressing foaming.

(SiC pretreatment)
[Example 5]
SiC was heated at 1500 ° C. for 1 hour using an electric furnace to form a SiO ₂ film on the SiC surface. This pretreated SiC was mixed with a glass frit for overcoating glass lining as a heat conductive filler by 20% by weight. This SiC / glass composite was formed into the same pellets as in Example 1 and baked in an electric furnace at 720 ° C. for 1 hour.

[Comparative Example 2]
All the same operations as in Example 5 were performed except that SiC was not pretreated.

  2 (a) and 2 (b) show photographs of the appearance of pellets of Example 5 and Comparative Example 2 one hour after the start of firing, respectively. Although expansion of the glass was also observed in the pellets of Example 5 after firing, the degree of expansion was small.

  On the other hand, in the pellet of Comparative Example 2 after firing, the glass expanded greatly. Moreover, the pellet of Comparative Example 2 after firing had a very large amount of bubbles in the glass, and it was impossible to measure the thermal conductivity by the laser flash method.

[Example 6]
All the same operations as in Example 5 were performed except that the pretreatment SiC mixed amount in the glass frit for overcoating glass lining was 40% by weight.

[Example 7]
All the same operations as in Example 5 were performed except that the pretreatment SiC mixed amount in the glass frit for overcoating glass lining was 60% by weight.

[Comparative Example 3]
The same operation as in Example 3 was performed except that the pretreated SiC was not mixed with the glass frit for top-coated glass lining.

  FIG. 3 is a graph showing the results of measuring the thermal conductivity of the fired pellets of Examples 5 to 7 and Comparative Example 3 by the laser flash method. The SiC mixing amounts of 0, 20, 40, and 60% by weight indicate Comparative Example 3, Example 5, Example 6, and Example 7, respectively. As the pretreated SiC content increased, the thermal conductivity of the glass tended to increase.

  4 (a) and 4 (b) are cross-sectional SEM photographs of the glasses of Examples 5 and 6, respectively. Even if air bubbles of about the glass of Example 6 shown in FIG. 4B were included, it was judged that there was practicality as a glass lining use.

  In addition, after performing the pre-processing which heats SiC at 900 degreeC, 1200 degreeC, and 1400 degreeC for 1 hour or 4 hours, when adding to the glass frit for overcoating glass lining similarly to Examples 5-7, Example The tendency for the thermal conductivity of glass to rise was recognized, suppressing foaming similarly to 5-7.

(Baking in an inert gas atmosphere)
A thermally conductive filler that is not an oxide reacts with oxygen in the air during firing and changes to an oxide. At that time, gas is generated, and the generated gas causes foaming of the glass. For this reason, if the heat conductive filler is mixed with the glass frit and then fired in an inert gas atmosphere, the heat conductive filler can be prevented from reacting with oxygen and changing to an oxide.

  Nitrogen gas, helium gas, neon gas, argon gas, etc. can be used as the inert gas.

(Baking under reduced pressure or under pressure)
After mixing the heat conductive filler into the glass frit, firing is performed under reduced pressure, thereby degassing the generated bubbles and suppressing inclusion in the glass. Even when the thermally conductive filler is an oxide, the air mixed between the glass frit and the filler can be degassed and suppressed from being encapsulated in the glass by firing under reduced pressure. Moreover, when defoaming is difficult under reduced pressure, the bubble diameter contained can be made small by baking under pressure, and the deterioration of the heat conductivity by the bubble included can be suppressed.

  When performing a baking process under reduced pressure, it is preferable to reduce pressure so that it may become a pressure range of 0.1-1000 Pa. On the other hand, when performing a baking process under pressure, it is preferable to pressurize so that it may become a pressure range of 0.2-1 Mpa.

  The thermally conductive glass of the present invention and the method for producing the same are useful in the fields of glass lining products and the like that require corrosion resistance of the glass and require temperature rise and cooling efficiency.

Claims (8)

Step A of heat-treating the thermally conductive filler in the temperature range of 450 ° C. to 1500 ° C. in the presence of oxygen;
Step B, in which the thermally conductive filler after Step A is mixed in a glass frit at a ratio of 20 wt% to 60 wt% and fired,
The manufacturing method of the heat conductive glass which has this. The heat-conductive filler is any one of SiC, TiC, ZnC, TaC, W ₂ C, BN, AlN, TaN, TiN, ZrN, or Si ₃ N _{4 according} to claim 1. A method for producing thermally conductive glass.   The manufacturing method of the heat conductive glass of Claim 1 or 2 whose said process A is 10 minutes or more and 4 hours or less.   A method for producing a heat conductive glass, comprising mixing a heat conductive filler in a glass frit at a ratio of 20 wt% or more and 60 wt% or less and firing at a temperature range of 600 ° C. or more and less than 720 ° C. The thermal conductive filler is any one of SiC, TiC, ZnC, TaC, W ₂ C, BN, AlN, TaN, TiN, ZrN, or Si ₃ N ₄ , according to claim 4. A method for producing thermally conductive glass.   A method for producing a thermally conductive glass, comprising mixing a thermally conductive filler into a glass frit and then firing in an inert gas atmosphere.   A method for producing a thermally conductive glass, comprising: mixing a thermally conductive filler into a glass frit and then firing under reduced pressure or under pressure. A thermally conductive glass characterized in that SiC having a SiO ₂ coating formed on the surface thereof is contained in a glass frit at a ratio of 20 wt% to 60 wt%.