JP4463121B2 - Glass material for sintering, method for producing the same, and method for producing a glass sintered product - Google Patents

Description

  The present invention relates to a glass material for sintering for manufacturing a quartz glass product at low cost with high accuracy, a method for manufacturing the glass material, and a method for manufacturing a sintered glass product using the glass material for sintering.

Quartz glass is expected to be used in backlight light source units of liquid crystal projectors because of its excellent optical characteristics.
However, since it is difficult to process complex shapes and skill of skilled workers is required, it is difficult to form according to the design dimensions, and the same shape and quality cannot be mass-produced. There was also a problem that it was extremely expensive.
In addition, since the processing temperature is as high as about 2000 ° C., there is a concern that the energy consumption is large, leading to a large amount of CO ₂ being a global warming gas.

Therefore, the present applicant creates a sintered compact by adding a binder to spherical silica, putting the glass material for sintering granulated into a mold and dry press molding, and forming this molding. A method for producing quartz glass products by heating and sintering the body in an oxidizing or reducing atmosphere in the atmosphere was proposed.
JP 2004-131351 A

According to this, when manufacturing quartz glass products of any shape, skill is not required and the dimensional system is ensured even in mass production, so the manufacturing cost can be significantly reduced, and the sintering temperature is also compared. Therefore, there is an advantage that energy consumption can be reduced and generation of CO ₂ can be suppressed correspondingly.

However, a reflector for a light source device for a projector is produced by such a method, and when compared with a reflector created manually by a skilled worker, there are some that are not inferior to a reflector made by hand. It has been found that reflectors with extremely poor brightness may be manufactured.
Comparing these reflectors, the non-defective product has a dense glass structure on the surface of the reflector and no irregularities, while the reflector surface with inferior brightness is compared with the glass structure of a part or the entire surface. It was found that there were some rough and satin-like fine irregularities formed.

In this way, if a part of the rough surface is formed on the mirror surface, even if the linear light emitted from the lamp is incident on the reflecting mirror, it is scattered by the rough surface and is not reflected at the desired design angle. When used as a reflector of a light source device, the brightness is notably inferior, but not only is scattered light incident on the liquid crystal panel surface at a right angle but is not radiated, but the liquid crystal panel surface is heated excessively. Cause the problem.
For this reason, the inventors conducted tests and research to find out the cause of the formation of the rough surface, and it was mixed with the spherical silica used in the glass material for sintering granulated. It was found that the binder aspect was affected.

FIG. 4 is a schematic diagram when the glass material for sintering granulated is enlarged. As shown in FIG. 4A, the binder particles 41 are smaller and more uniform than the spherical silica 42. When distributed, it is difficult to form a rough surface on the surface. As shown in FIG. 4B, some of the binder particles 41 are larger than the spherical silica 42, and when unevenly distributed, the surface is rough. Turned out to be easy to form.
In other words, the larger the binder particles, the lower the density of the spherical silica, so that the nests are likely to enter during sintering, and it takes time to volatilize and burn the binder. It was found that a rough surface was formed by being confined.

  Accordingly, as shown in FIG. 4 (a), if the binder particles 41 are made smaller and uniform than the spherical silica 42, a high-quality quartz glass product is produced. It is difficult, costly and time consuming, so it is not practical anyway if it is a laboratory level study.

  Therefore, the present invention has been made on the basis of such inventor's knowledge. A sintered compact obtained by putting a sintering glass material into a mold and dry press molding is heated and sintered to obtain quartz. When manufacturing glass products, it is possible to produce high-quality quartz glass products at low cost even when mass-produced, without the formation of fine irregularities with a rough texture on the product surface. It is a technical issue.

  In order to solve this problem, the glass material for sintering according to the present invention has a binder containing one or both of a paraffin binder and a stearic acid binder coated on the surface of a core containing silica as a main component without gaps. The glass raw material powder is formed into a granular shape by assembling.

  Further, the method for producing a sintering glass material according to the present invention produces a suspension in which a core mainly composed of silica and a binder solution containing one or both of a paraffinic binder and a stearic acid binder are produced. By spraying the suspension into hot air flowing in the chamber, the glass raw material powder in which the binder is coated on the surface of the core is aggregated and formed into a granular shape, and then into the hot air chamber. Both the inflow temperature and the outflow temperature are set higher than the melting point of the binder.

  Furthermore, in the method for producing a sintering glass according to the present invention, when the sintered compact obtained by filling the sintering glass material into a molding die and dry press molding is heated and sintered, The glass material for sintering is made by assembling a glass raw material powder in which a binder containing one or both of a paraffin binder and a stearic acid binder is coated on the surface of a core mainly composed of silica without gaps. It is characterized by being formed.

According to the present invention, a suspension is prepared by mixing a core mainly composed of silica and a binder solution containing one or both of a paraffinic binder and a stearic acid binder, both of which have an inflow temperature and an outflow temperature. By spraying the suspension into a chamber in which hot air set higher than the melting point of the binder flows, a granular sintering glass material in which glass raw material powders coated with a binder on the surface of the core without gaps is collected. Generated.
Therefore, since the binder is coated on the surface of the glass raw material powder of the glass material for sintering without gaps, it is not necessary to produce binder particles with a small diameter around the glass particles or evenly distribute them. A particle distribution equivalent to the above can be formed.

Moreover, since the glass raw material powder of the glass material for sintering produced in this way has a binder layer formed on its surface by coating the core with a binder, it is assembled into granules. When formed into a shape, the density of the glass raw material powder becomes high.
Therefore, when this is put into a mold and dry-pressed, the binder attached to the surface serves as a lubricant to flow the individual glass raw material powders, and the glass raw material powders are densely consolidated.
Further, the nest is difficult to enter when heated and sintered, and at the same time, the binder layer formed on the surface thereof is relatively thin and uniform, so that the binder is easily volatilized and burned.
Accordingly, there is no effect of forming a textured fine irregularity with a rough glass structure on the product surface, and it is possible to mass-produce a high-quality quartz glass product having a dense glass structure at a low cost.

  In this example, a sintered glass material for dry press molding is used for the purpose of mass-producing high-quality quartz glass products at low cost without the formation of fine irregularities with a rough texture on the product surface. Achieved by improvement.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
FIG. 1 is an enlarged schematic view showing a glass material for sintering according to the present invention, FIG. 2 is an explanatory view showing a manufacturing method thereof, and FIG. 3 is an explanatory view showing a manufacturing method of a glass sintered product.

  The sintering glass material 1 according to the present example is manufactured by filling a molding die and performing dry press molding to form a sintered compact, and then heating and sintering the compact to produce a quartz glass product. A glass raw material powder 4 is formed by assembling a binder 2 containing one or both of a paraffinic binder and a stearic acid binder on the surface of a core 3 mainly composed of silica without gaps. It is formed into granules.

  The binder 2 is 1.0% by weight (melting point = 55 ° C.) of a paraffinic binder as a forming aid for fine ceramics, 1.0% by weight (melting point = 100 ° C.) of a stearic acid binder, and other PVA and resin In addition, the total amount is about 3.4% by weight of the core 3.

The core 3 is made of spherical silica having an outer diameter of 0.3 to 1.5 μm.
The spherical silica is ideally 100% silica, but alumina is mixed as an impurity during the production process, and the amount of the silica affects the sintering temperature and the properties of the sintered quartz glass product.
In other words, spherical silica is produced by crushing a residue (cut pieces) or a defective silicon wafer cut from a silicon wafer, which is a substrate often used in the semiconductor industry, and then pulverizing it with an alumina ball mill. When forming, alumina (Al ₂ O ₃ ) is mixed, and the amount thereof varies depending on the grinding time.
The pulverization time is not constant because it depends on the size of the silicon wafer debris that is put into the ball mill, and the aluminum component (Al) is the designation of the insulating material in the semiconductor package that uses the most spherical silica. Since the impurities are not regulated, there is a large variation in the amount of mixture.

And when coating the binder 2 on the core 3 produced | generated with the silica which contains such an aluminum component in an impurity, since the binder 2 does not contain the aluminum component, the aluminum component contained in the core 3 is the glass raw material as it is. It becomes an impurity of the powder 4.
When the aluminum component exceeds 70 ppm relative to silica, the sintering temperature exceeds 1350 ° C., and when it is 70 ppm or less, the sintered body has a dense glass structure and no distortion at a sintering temperature of 1300 ° C. to 1350 ° C. Was found to be obtained.
It has been found that when the aluminum component is 100 ppm or more with respect to silica, the sintering temperature exceeds 1370 ° C., and when it exceeds 220 ppm, even if heated to 1400 ° C. or more, it does not sinter and becomes cristoperlite.
Therefore, if the aluminum component is 70 ppm or less with respect to silica, a good sintered body can be obtained at a low temperature of 1300 to 1350 ° C. even in a quartz glass product having a working temperature (softening point) near 2000 ° C. during processing. it can.

Moreover, if the weight ratio of aluminum is 50 ppm or less with respect to silica, the lower limit of the sintering temperature can be lowered to 1280 ° C., and up to 1350 ° C., as described above, the glass structure is dense and sintered without distortion. It turns out that a body is obtained.
However, when the temperature exceeds 1350 ° C., distortion occurs, and at a high temperature such as 1400 ° C., cristobalite is formed with a few impurities as nuclei.
Therefore, when the aluminum component is 50 ppm or less with respect to silica, a good sintered body can be obtained at a low temperature of 1280 ° C. or higher and 1350 ° C. or lower.

A granular sintering glass material 1 in which glass raw material powders 4 formed by coating such a binder 2 on the surface of the core 3 without gaps is assembled in the following procedure.
First, about 3.4% by weight of the binder 2 is mixed with the spherical silica used as the core 3, pure water is added so that the viscosity value becomes 10 to 20 mPa · s, and the moisture content is adjusted to 60%. A foreign material is removed by a filter whose openings are designed to be 38 μm in length and breadth to obtain a slurry (suspension).
The core 3 is controlled so that an aluminum component as an impurity is 70 ppm or less with respect to silica.

A spray dryer is then used to make granules from this slurry.
Figure 2 shows the mists dryer 11, the ceiling portion center of the granules recovery port 12 is about the formed diameter 1.5m hopper shaped chamber 13 to the lower end, with a rotary atomizing disk 14a for spraying the slurry An atomizer 14 is arranged.
An air supply duct 15 that allows hot air to flow in from a horizontal tangential direction is connected to the peripheral wall surface on the upper end side of the chamber 13, and an exhaust duct 16 that opens facing the granule recovery port 12 is disposed in the chamber 13. ing.

A hot air generator 17 is connected to the air supply duct 15, and a temperature sensor 18 disposed at an inlet 15 a where the air supply duct 15 opens into the chamber 13 and an exhaust duct 16 open into the chamber 13. The temperature of the hot air is controlled by the temperature sensor 19 disposed at the outlet 16a.
In this example, since the melting points of the paraffin binder and the stearic acid binder are both 100 ° C. or less, the inflow hot air temperature at the opening of the air supply duct 15 is 220 ° C., and the exhaust hot air temperature at the opening of the exhaust duct 16 The temperature of the hot air is controlled to be 130 ° C. so as to be higher than the melting point of the binder 2.
Note that if the exhaust hot air temperature is higher than the melting point of the binder 2, the inflow hot air temperature is always higher than that temperature, so that the temperature sensor 19 is disposed only at the outlet 16a to control the temperature.

Then, hot air having an inflow hot air temperature of 220 ° C. is supplied from the hot air generator 17 through the air supply duct 15, and the chamber 13 is heated until the exhaust hot air temperature reaches 130 ° C. Then, the atomizing disk 14 a of the atomizer 14. The number of rotations is 12000 rpm, and the slurry is supplied at 100 ml / min for atomization.
The hot air flowing into the chamber 13 from the air supply duct 15 flows down spirally while rotating along the peripheral wall of the chamber 13.

At this time, both the inflow hot air temperature and the exhaust hot air temperature are higher than the melting point of the binder 2, and thus the temperature in the chamber 13 is maintained higher than the melting point of the binder 2, so that the slurry including the binder and the core 3 is atomized. When this occurs, the binder 2 melts and adheres to the surface of the core 3.
Further, since the surface temperature of the core 3 is higher than the melting point of the binder 2, the binder 2 flows on the surface of the core 3 to form a glass raw material powder 4 in which a uniform thin film-like coating layer is formed without a gap. The
In the course of drying a large number of glass raw material powders 4 on the hot air in the chamber 13, the glass material powder 1 is sintered in the form of granules having a diameter of about 50 μm. Is generated.

The chamber 13 has an internal pressure in the vicinity of the granule recovery port 12 at the lower end of the hopper as hot air flows down the hopper-like portion where the cross-sectional area gradually decreases, so that the hot air opens opposite to the granule recovery port 12. The exhaust duct 16 is discharged.
At that time, the granular sintering glass material 1 carried by the hot air flowing down spirally is separated from the hot air when the hot air flow is reversed upward and falls to the granule recovery port 12. And recovered.
FIG. 1 is a schematic diagram of granules of the sintered glass material 1 produced in this way, and it can be seen that the glass raw material powder 4 on which the binder 2 is coated without gaps is densely assembled.

FIG. 3 is an explanatory diagram showing a method of manufacturing a reflecting mirror-shaped quartz glass product (glass sintered product) using the sintering glass material 1 manufactured as described above.
First, after putting the granular glass material 1 for sintering into the barrel 22 of the molding die 21 (FIG. 3A), the plunger 23 is lowered, and the central rod of the barrel 22 is inserted into the insertion hole 24. When a pressing pressure is applied while 25 is inserted, a sintered compact F is formed (FIG. 3B).
Thereafter, the plunger 23 is pulled up, the bottom frame 26 of the body mold 22 is removed from the outer frame 27 and separated (FIG. 3C), and the sintered compact F is extracted from the bottom frame 26 (FIG. 3D). ) ).

The sintered compact F thus prepared is placed in a firing furnace 28 and sintered by an oxidizing atmosphere heating sintering method and a reducing atmosphere heating sintering method to produce a reflector-shaped quartz glass product M. (FIG. 3 (e)).
In this case, in any method, in order to completely volatilize and burn the binder, first, preheating is performed in an oxidizing atmosphere of 300 to 1000 ° C.
Since the temperature at which the binder is volatilized and burned varies depending on the type of binder used, it is necessary to confirm in advance a temperature suitable for combustion removal by differential thermal analysis or the like.

In the oxidizing atmosphere heating and sintering method, after the preliminary heating was completed, the binder was burned and removed in the oxidizing atmosphere, and then the sintering was performed at 1280 to 1350 ° C. in the oxidizing atmosphere as it was. In this example, it was held at 1300 ° C. for 1 hour.
In the reducing atmosphere heating and sintering method, after preliminary heating, the sintering is performed at 1280 to 1350 ° C. in a reducing atmosphere using carbon monoxide. In this example, it was held at 1300 ° C. for 30 minutes.

When heat-sintered at such a relatively low temperature, a reflecting mirror-shaped quartz glass product (glass sintered product) M was obtained.
Although the surface of this quartz glass product M was observed with a microscope of several thousand times, no rough portion was found no matter where it was observed, and it was possible to produce an extremely dense and good quartz glass product M without irregularities. did it.
Then, a cold mirror of a multilayer film was formed on the inner surface to form a reflecting mirror, and a light source unit combined with a 200 W rated high-pressure mercury vapor discharge lamp was created. The same brightness was obtained compared to the combined light source unit.
Further, when the life test of the light source unit was conducted, good results were obtained up to 2000 hours at the end of the life without any inferiority in optical characteristics with the prototype reflector of the expert.

As described above, according to the present invention, when the suspension in which the core and the binder are mixed is spray-dried, both the inflow hot air temperature and the exhaust hot air temperature of the chamber are set higher than the melting point of the binder. Therefore, a glass raw material powder coated on the surface of the core without any gaps is generated in a state where the binder is melted, and the binder is welded to gather the glass raw material powder to form a granular glass material for sintering.
Therefore, since the binder is coated in a thin film on the surface of the glass raw material powder of this sintering glass material without gaps, it is not necessary to uniformly distribute the binder particles having a small diameter, so that granules having substantially the same structure as this can be obtained. Obtainable.

And since the binder is coated in a thin film shape, the glass material for sintering formed into a granular form is densely assembled with the glass raw material powder and adheres to the surface when this is put into a mold and dry-pressed As the binder is used as a lubricant to flow the individual glass raw material powders, the glass raw material powders are densely consolidated.
Therefore, when this is heat-sintered, the nest is difficult to enter, and at the same time, the binder formed on the surface is thin and uniform, so that it is easy to volatilize and burn.
As a result, there is no effect on the surface of the product that a fine texture with a rough glass structure is not formed, and a high-quality quartz glass product with a dense glass structure can be mass-produced at low cost.

  INDUSTRIAL APPLICABILITY The present invention can be used for applications in which a mirror, an optical element and other quartz glass products having extremely good optical properties are mass-produced with high accuracy and low cost.

The expansion schematic diagram which shows the glass material for sintering which concerns on this invention. Explanatory drawing which shows the manufacturing method. Explanatory drawing which shows the manufacturing method of a glass sintered product. The expansion schematic diagram which shows the conventional glass material for sintering.

Explanation of symbols

1 Glass material for sintering 2 Binder 3 Core 4 Glass raw material powder

Claims (6)

A sintering glass material for forming a sintered compact by filling a molding die and dry press molding,
A binder containing one or both of a paraffin binder and a stearic acid binder is formed into a granule by assembling glass raw material powder that is coated on the surface of a core mainly composed of silica without gaps. Glass material for sintering.   The glass material for sintering according to claim 1, wherein a weight ratio of an aluminum component present as an impurity in the glass raw material powder is selected to be 70 ppm or less with respect to silica. A method for producing a sintered glass material, which is formed by filling a molding die and dry press molding to form a sintered compact. A core mainly composed of silica, a paraffin binder, and a stearic acid binder Producing a suspension mixed with a binder solution containing one or both of
By spraying the suspension into hot air flowing in the chamber, when the glass raw material powder formed by coating the binder on the surface of the core is aggregated and formed into granules, the hot air flows into the chamber. A method for producing a glass material for sintering, wherein both the inflow temperature and the outflow temperature are set higher than the melting point of the binder. A method for producing a sintered glass product in which a sintered compact obtained by filling a molding die with a glass material for sintering and dry press molding is heated and sintered,
The glass material for sintering is made by assembling a glass raw material powder in which a binder containing one or both of a paraffin binder and a stearic acid binder is coated on the surface of a core mainly composed of silica without gaps. A method for producing a sintered glass product, which is formed. The weight ratio of the aluminum component which exists as an impurity in the said glass raw material powder is selected as 70 ppm or less with respect to a silica, The sintering temperature of the said molded object for sintering is 1300 degreeC or more and 1350 degrees C or less. A method for producing a sintered glass product. The weight ratio of the aluminum component which exists as an impurity in the said glass raw material powder is selected to 50 ppm or less with respect to a silica, and the sintering temperature of the said molded object for sintering is 1280 degreeC or more and 1350 degrees C or less. A method for producing a sintered glass product.

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