JP3607183B2 - Film removal method for tube with multilayer interference film - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a film removal method for a tube with a multilayer interference film having a multilayer interference film consisting of a plurality of alternating layers of silicon dioxide and tantalum pentoxide on the outer surface.
[0002]
[Prior art]
As one means for improving the efficiency of a filament bulb, a filament bulb using a film that reflects infrared rays and transmits visible light has been developed and put into practical use. This film is formed by alternately forming layers having different refractive indexes on the outer surface of the bulb glass bulb, and is generally formed by a CVD method, a sputtering method, a dip method or the like. By the way, in any method, the film thickness of the formed film may be non-uniform. In such a case, it has been desired to remove the defective multilayer film and reuse the tube from the viewpoint of cost reduction, environmental protection, resource saving, and the like. Thus, conventionally, attempts have been made to use hydrofluoric acid in order to remove the defective multilayer film.
[0003]
[Problems to be solved by the invention]
However, a material of the moth Rasubarubu quartz (silicon dioxide), when the multilayer film is of silicon and tantalum pentoxide dioxide, because the dissolution rate of silicon dioxide is greater than the dissolution rate of tantalum pentoxide for hydrofluoric acid, pentoxide There was a problem that the film made of silicon dioxide on the inner side started to dissolve before the film made of tantalum was completely dissolved. This process is repeated, and the surface of the glass bulb from which the multilayer film has been completely removed becomes uneven. Therefore, the tube cannot be returned to the process of attaching the multilayer film again.
[0004]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a film removal method for a tube with a multilayer interference film that can remove the multilayer film without making irregularities on the surface of the quartz bulb. To do.
[0005]
[Means for Solving the Problems]
As a result of intensive studies in view of the above circumstances, the present inventors have found that the above object can be achieved by immersing a tube with a multilayer interference film in a specific alkaline solution, to complete the present invention. It came.
[0006]
That is, the method of removing a film of a tube with a multilayer interference film according to the present invention is a method of removing a film of a tube with a multilayer interference film having a multilayer film consisting of a plurality of alternating layers of silicon dioxide and tantalum pentoxide on the outer surface of a quartz bulb . The tube is immersed in an aqueous alkali solution having a concentration of 50% by mass or more or an alkali melt at 200 to 370 ° C. to dissolve and remove the multilayer film composed of the plurality of alternating layers. According to this method, the dissolution rate of each monolayer of silicon dioxide and tantalum pentoxide is close, and the multilayer film can be removed without making irregularities on the outer surface of the quartz bulb of the tube.
[0007]
In the film removal method, the alkali is preferably potassium hydroxide. By using potassium hydroxide, no salt of tantalum remains on the surface of the quartz bulb at the time of dissolution, so it can be easily confirmed visually that the film has been removed. When the multilayer film is dissolved and removed by immersion in a strong alkaline aqueous solution, the liquid temperature of the strong alkaline aqueous solution is preferably 60 ° C. or higher .
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The multilayer interference film of the present invention is composed of a plurality of alternating layers (for example, 39 layers) of silicon dioxide and tantalum pentoxide, each single layer made of silicon dioxide has a thickness of 125 μm to 250 μm, and each single layer made of tantalum pentoxide. The layer has a thickness of 250 μm to 500 μm and is formed by a normal method such as a CVD method, a sputtering method, or a dip method.
[0009]
In the present invention, in order to remove a multilayer film composed of a plurality of alternating layers, the tube with the multilayer interference film is immersed in a strong alkaline aqueous solution having a concentration of 50% by mass or more. By setting the concentration of the strong alkaline aqueous solution to 50 mass or more, the dissolution rate of each monolayer of silicon dioxide and tantalum pentoxide becomes close, and the coating film can be removed without leaving irregularities on the surface of the glass bulb. The strong alkaline aqueous solution is composed of a strong alkali having a mass ratio of 50% or more and water.
[0010]
Examples of the alkali include sodium hydroxide and potassium hydroxide. Potassium hydroxide is particularly preferred because no tantalum salt remains on the surface of the glass bulb during dissolution, and it can be easily confirmed visually that the film has been removed.
[0011]
When the glass bulb is immersed in the strong alkaline aqueous solution, the liquid temperature of the strong alkaline aqueous solution is preferably 60 ° C. or higher, more preferably 110 to 140 ° C. Since it is desirable that the strong alkaline aqueous solution is heated to such an extent that it does not boil, for example, when the alkali concentration is 70% by mass, 120 to 130 ° C., and when it is 80% by mass, 110 to 120 ° C. is particularly preferable. Further, the immersion time is appropriately set according to the liquid temperature.
[0012]
Further, in the present invention, in order to remove the multilayer interference film composed of a plurality of alternating layers, the tube with multilayer interference film is immersed in an alkali melt. Here, the alkali melt is a liquid obtained by heating a solid alkali (at room temperature) in air. Therefore, the alkali melt contains very little moisture in the air when the alkali is heated.
[0013]
Examples of the alkali include sodium hydroxide and potassium hydroxide. Potassium hydroxide is particularly preferred because no tantalum salt remains on the surface of the glass bulb during dissolution, and it can be easily confirmed visually that the film has been removed.
[0014]
When the glass bulb is immersed in the alkali melt, the melt temperature is preferably 200 to 370 ° C, more preferably 200 to 300 ° C. Further, the immersion time is appropriately set according to the liquid temperature. In addition, it is considered that the liquid temperature of the melt is lower than the melting temperature of the alkali because it absorbs moisture in the air.
[0015]
When the tube bulb is immersed in an alkaline aqueous solution or an alkali melt, the tube bulb cap (or lead wire) is grasped, and only the glass bulb is immersed in the solution so that this portion does not touch the solution. Thereafter, it is preferable to move the tube.
[0016]
After immersing the tube in alkali, the tube is washed with 1000 to 10,000 times (volume) of pure water per tube to remove alkali and salt from the surface of the glass bulb. The tube from which the multilayer interference film has been removed can be used, for example, in a process of forming a multilayer film on the outer surface of the tube again.
Next, the present invention will be specifically described with reference to the drawings.
[0017]
【Example】
FIG. 1 is an enlarged cross-sectional view of a glass bulb portion of a tube formed with a coating composed of alternating plural layers of silicon dioxide and tantalum pentoxide to be removed by the present invention. In FIG. 1, alternating multiple layers of silicon dioxide 1 and tantalum pentoxide 2 are formed on the outer surface of a glass bulb 3.
[0018]
Example 1
The tube with multilayer interference film shown in FIG. 1 is immersed in an aqueous solution of potassium hydroxide (concentration 50 mass%) at a liquid temperature of 60 ° C. for 50 hours. Subsequently, by pulling up the tube from the potassium hydroxide aqueous solution and washing with pure water, it was possible to remove only the multilayer film without forming irregularities on the outer surface of the glass bulb. The regenerated tube could be reused without any problems.
[0019]
Example 2
The tube with multilayer interference film shown in FIG. 1 is immersed in a potassium hydroxide aqueous solution (concentration 60 mass%) for 12 minutes at a liquid temperature of 130 ° C. Subsequently, by pulling up the tube from the potassium hydroxide aqueous solution and washing with pure water, it was possible to remove only the multilayer film without forming irregularities on the outer surface of the glass bulb. The regenerated tube could be reused without any problems.
[0020]
Example 3
In the same manner as in Example 1, the tube with a multilayer interference film shown in FIG. 1 is immersed in a potassium hydroxide melt having a melt temperature of 250 ° C. for 30 seconds. Next, the tube is pulled out of the potassium hydroxide melt, and after the molten alkali adhering to the surface of the glass bulb has solidified, it is washed with pure water, so that only the multilayer film is formed without creating irregularities on the outer surface of the glass bulb. Could be removed. The regenerated tube could be reused without any problems.
[0021]
【The invention's effect】
According to the film removing method of the present invention, a quartz bulb having a multilayer interference film composed of a plurality of alternating layers of silicon dioxide and tantalum pentoxide formed on the outer surface is used as a strong alkaline aqueous solution having a concentration of 50% by mass or more or 200 to 370 ° C. by immersion in an alkaline melt, so as not dissolution rate of each single layer of silicon and tantalum pentoxide dioxide becomes close, leave uneven completely quartz bulb surface the film after the removal, that is, quartz bulb Only the multilayer interference film can be removed without damaging the film.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a multilayer interference film on the outer surface of a tube of the present invention.
[Explanation of symbols]
1 Silicon dioxide 2 Tantalum pentoxide 3 Glass bulb

Claims (5)

A film removal method for a tube with a multilayer interference film in which a multilayer interference film composed of a plurality of alternating layers of silicon dioxide and tantalum pentoxide is formed on the outer surface of a quartz bulb ,
A film removal method for a tube with a multilayer interference film, wherein the quartz bulb is immersed in a strong alkaline aqueous solution having a concentration of 50% by mass or more, and the multilayer interference film is dissolved and removed. The method of removing a film of a tube with a multilayer interference film according to claim 1, wherein the alkali is potassium hydroxide. The method of removing a membrane of a tube with a multilayer interference film according to claim 1 or 2, wherein the liquid temperature of the strong alkaline aqueous solution is 60 ° C or higher. A film removal method for a tube with a multilayer interference film in which a multilayer interference film composed of a plurality of alternating layers of silicon dioxide and tantalum pentoxide is formed on the outer surface of a quartz bulb ,
A film removal method for a tube with a multilayer interference film, wherein the quartz bulb is immersed in an alkali melt at 200 to 370 ° C. to dissolve and remove the multilayer interference film. The method of removing a film of a tube with a multilayer interference film according to claim 4, wherein the alkali is potassium hydroxide.

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