JP4729705B2 - Method for producing translucent alumina sintered body and method for producing optical filter - Google Patents

Description

  The present invention relates to a translucent alumina sintered body having translucency and an optical filter using the same.

  Alumina sintered bodies are materials having excellent mechanical strength, electrical insulation, and heat and corrosion resistance, and have been widely used. In addition to these excellent characteristics, an alumina sintered body having translucency is used for high-intensity discharge lamps (HID) such as arc tubes for high-pressure sodium lamps and metal halide lamps.

Conventionally, as the light-transmitting alumina sintered body, one having MgO added (Patent Document 1) is generally used. In addition to MgO, La2O3 and Y2O3 are added to form a grain boundary phase, and crystal It has also been reported to improve translucency by making particles uniform (Patent Document 2).
US Patent 3026,210 Japanese Patent Publication No.57-37554

However, since the conventional translucent alumina sintered body needs to be fired at a relatively high temperature of 1600 ° C. or higher and needs to be fired in hydrogen or vacuum, it can be manufactured at low cost. There was a problem that it was difficult.
Moreover, the conventional translucent alumina sintered body has been used only for limited applications such as arc tubes for high-pressure sodium lamps.

Accordingly, a first object of the present invention is to provide a method for producing a translucent alumina sintered body that can be fired at a relatively low temperature and can be produced at low cost.
Moreover, this invention makes it the 2nd objective to provide the manufacturing method of an optical filter .

In order to achieve the first object described above, a method for producing a translucent alumina sintered body according to the present invention includes manganese oxide (MnO) in an alumina powder in a range of 0.01 wt% to 0.4 wt%. It is characterized by including baking the molded object formed by mixing at the temperature of 1400 degrees C or less .
According to the method of manufacturing the translucent alumina sintered body according to the present invention, it is possible to produce by firing at a lower temperature than in the and conventional translucent alumina sintered body air atmosphere.

In order to achieve the second object, an optical filter manufacturing method according to the present invention is formed by mixing alumina powder with manganese oxide (MnO) in a range of 0.01 wt% to 0.4 wt%. The formed body is fired at a temperature of 1400 ° C. or less to produce a translucent alumina sintered body, the sintered body is blocked from transmitting light in a specific stop band, and has a wavelength longer than the stop band. And an optical filter that transmits light having a wavelength shorter than the stop band .

Since the method for producing a translucent alumina sintered body according to the present invention configured as described above can be fired in an air atmosphere at a relatively low temperature, it can be produced at a low cost.
Further, the present invention in the production method translucent alumina sintered body produced by, since the light transmittance has a wavelength dependency, can be used in applications other than light emission tube.

Embodiments according to the present invention will be described below with reference to the drawings.
The translucent alumina sintered body of the present embodiment is made of alumina containing manganese and has high translucency.
That is, as a result of intensive studies by the present inventors, the present invention provides a translucent alumina sintered body having translucency by adding, for example, manganese oxide (MnO) containing Mn to alumina and firing. I found out and completed it.

  Specifically, manganese oxide (MnO) is added to alumina powder in a range of 0.01 wt% to 0.4 wt%, for example, and then mixed and then molded and fired. Thus, by adding manganese oxide (MnO), a translucent alumina sintered body having good translucency can be obtained even in the atmosphere and sintered at a relatively low temperature of 1600 ° C. or less. It has the following effects. The

First, since it can be fired at a relatively low temperature of 1600 ° C. or less without using a special atmosphere, an expensive furnace is not required, and it can be manufactured at low cost.
In addition, according to the present invention, since it can be fired at a lower temperature of 1400 ° C. or lower, it is needless to say that abnormal crystal grain growth can be suppressed. Can increase the mechanical strength.
Furthermore, the translucent alumina sintered body to which Mn is added has a wavelength dependency in which the translucency changes depending on the wavelength. For example, light having a specific wavelength can be removed or light having a specific wavelength can be removed. It can be applied to new uses such as a filter that allows the filter to pass through.

As Example 1, six types of alumina sintered bodies having different amounts of addition of manganese oxide (MnO) were produced and the transmittance was evaluated.
The amount of manganese oxide (MnO) added to each sample, the firing temperature, and the firing time were as shown in Table 1 below.

Table 1

Further, in Example 1, samples each having a thickness of 0.5 mm were manufactured by the following steps.
1. Weighing First, the alumina powder and manganese oxide are weighed so as to have the ratio shown in Table 1.
In Example 1, alumina powder having an average particle diameter of 0.2 μm and a purity of 99.99% and manganese oxide having a purity of 99.9% were used as raw materials.

2. Mixing and grinding The weighed alumina powder and manganese oxide were mixed and ground in ethanol using a ball mill for 24 hours.
3. Dehydration and drying The mixed and ground material is dehydrated and dried.

4). Molding The powder after drying was pressure-molded at 20 MPa and then cold isostatically pressed (CIP) at 200 MPa for 2 minutes.
5. Firing Firing was performed under the conditions shown in Table 1. The temperature raising speed and the cooling speed were 400 ° C./1 hour.
6). Cutting and polishing After cutting the fired body, surface polishing was performed until the thickness became 0.5 mm.

  The light transmittance of samples 1 to 6 produced as described above is shown in the graph of FIG. As shown in FIG. 1, Samples 1 to 6 each showed permeability according to the amount of MnO added, and selective permeability was confirmed in any sample.

For example, it can be seen that Sample 6 to which 0.4 wt% of MnO is added transmits light having a wavelength of 600 nm or more, but hardly transmits light having a wavelength of 550 nm or less.
In addition, for example, sample 4 to which 0.1 wt% of MnO is added has a certain range centered on 500 nm (for example, ± 50 nm for those to which 0.2 wt% of MnO is added, for example, 0.05 wt% of MnO is added) Then, light having a wavelength of ± 20 nm is blocked, and light on both sides of the blocking band is transmitted.

  By the above Example 1, it was confirmed that translucency can be obtained by adding MnO to alumina and firing, and that the translucency has wavelength dependency.

In Example 2, five types of samples 7 to 11 having different firing conditions were produced and evaluated.
Table 2 shows the firing conditions for each sample. Sample 7 is the same sample as sample 3 of Example 1. The production conditions other than those shown in Table 2 are the same as those of the sample of Example 1.

Table 2

  According to the above Example 2, it was confirmed that substantially the same transmittance was obtained even when the firing temperature was changed, and the light transmittance characteristics were not greatly changed depending on the firing conditions.

In Example 3, the change of the particle size with respect to the added amount of MnO and the change of the particle size due to the firing temperature were confirmed.
Specifically, Samples 12 to 21 were produced under the conditions shown in Table 3, and the average particle size was evaluated.

Table 3

The evaluation results are shown in FIG. As shown in FIG. 3, when the amount of MnO added is 0.2 wt% or less, the particle size tends to increase as the amount of MnO added increases. It is almost constant regardless of the amount.
In addition, in any case of adding MnO, the particle size increases when the firing temperature is high.
Thus, for example, by setting MnO to 0.01 to 0.1 wt% and firing at a relatively low temperature of about 1250 ° C., for example, crystals after sintering while ensuring a relatively high transmittance Since the particle size can be reduced, a translucent alumina sintered body having translucency and high mechanical strength can be obtained.

  In addition, as shown in Examples 1 and 2, the translucent alumina sintered body according to the present invention has selective permeability according to the amount of Mn added, so that it can be used for new applications such as filters. Deployment is possible.

  As described above, the translucent alumina sintered body according to the present invention can be used not only for an arc tube for a high pressure sodium lamp but also for other uses such as an optical filter.

It is a graph which shows the light transmittance of each sample in Example 1 which concerns on this invention. It is a graph which shows the light transmittance of each sample in Example 2 which concerns on this invention. It is a graph which shows the average particle diameter of each sample (sintered body) in Example 3 which concerns on this invention.

Claims (2)

  Translucent alumina sintering including firing a molded body obtained by mixing and molding alumina oxide (MnO) in a range of 0.01 wt% to 0.4 wt% at a temperature of 1400 ° C. or lower. Body manufacturing method. A compact formed by mixing alumina powder with manganese oxide (MnO) in the range of 0.01 wt% to 0.4 wt% is fired at a temperature of 1400 ° C. or lower to obtain a translucent alumina sintered body. A light characterized in that the sintered body is used for an optical filter that blocks transmission of light in a specific stop band and transmits light having a wavelength longer than the stop band and light having a wavelength shorter than the stop band. A method for manufacturing a filter.

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