JPH021330B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a curved fluorescent lamp,
In particular, the present invention relates to an improvement in a method for manufacturing a curved fluorescent lamp using a light-transmitting airtight container made of soda lime glass. In the production of curved fluorescent lamps, for example ring-shaped fluorescent lamps, a binder such as a borate of an alkaline earth metal such as barium or calcium is added to the inner wall of a straight glass light-transmitting airtight container using fluorescent weight. 1
A phosphor containing 3% to 3% by weight of phosphor is applied, and a stem holding an electrode coated with an electron-emitting substance is sealed on both ends of the phosphor. This is heated in a furnace or the like to a high temperature to soften it, and then attached to a drum. It is rolled up and formed into a ring shape, the interior of the translucent airtight container is evacuated to introduce an easily dischargeable electrical element and a small amount of mercury, and then the exhaust pipe is sealed. The glass that forms this translucent airtight container contains 22 to 29% by weight of lead oxide because it can be easily formed into a ring.
A glass with a low softening temperature, usually called lead glass, was used. This lead glass contains a large amount of lead oxide, an expensive raw material, which increases the price of the glass, which not only increases the manufacturing cost of curved fluorescent lamps such as annular fluorescent lamps, but also reduces pollution. Since it contains lead, which is a contributing factor, it has the disadvantage of causing problems in the disposal of discarded lamps. In order to solve these drawbacks, soda lime glass, which is used in the light-transmitting airtight containers of straight tube fluorescent lamps, has recently been replaced with light-transmitting airtight containers of curved fluorescent lamps such as annular fluorescent lamps. Although it has been planned and tested for use in lead glass containers, the light output, such as the initial luminous flux and its working range, is significantly reduced compared to a transparent airtight container made of lead glass. A fatal drawback occurred in that the strength of the translucent airtight container was reduced. The oxide composition and physical properties of examples of lead glass and soda lime glass are shown in Table 1 below.

[Table] A white annular fluorescent lamp using a light-transmitting airtight container made of soda lime glass shown in Table 1 above, for example, 100V30WFCL-30W, has an initial luminous flux compared to a similar lamp using a light-transmitting airtight container made of lead glass. 4
%, the luminous flux after 1000 hours of lighting decreases by 5.6%, and the strength of the translucent airtight container decreases by 45%. The above-mentioned decrease in light output is caused by the exposure of the light-transmitting airtight container to high temperatures when it is formed into a ring. More than three times as much alkali, mainly sodium, as in the lead glass precipitates and diffuses into phosphors such as antimony and manganese activated calcium halophosphate phosphors, reducing the luminous efficiency of the phosphors, In addition, the ultraviolet rays generated when fluorescent lamps are turned on cause a photochemical reaction with iron in the glass, which colors the glass yellowish-brown and reduces the light transmittance.It also reacts with the mercury present in the fluorescent lamps, forming a sodium amalgam. It is thought that this reduces the working range of optical output.
In addition, during high-temperature processing when forming a translucent airtight glass container into an annular shape, phosphor particles may sink into the surface of the softened glass.Especially with soda lime glass, whose softening temperature is nearly 80 degrees Celsius higher than that of lead glass, annular formation occurs. Because the heating temperature for the glass must be higher than the difference in softening temperature, the penetration of the phosphor into the glass surface becomes large in some parts, which causes many scratches on the glass surface and impairs the transparency and airtightness of the glass. It is thought that the strength of the container decreased significantly. As a method of preventing such problems, there is a method of providing a metal phosphate coating such as calcium phosphate between the light-transmitting airtight glass container and the phosphor coating coated on the inner surface of the container. In order to apply the above-mentioned metal phosphate, for example, a calcium phosphate coating, to the inner surface of a translucent airtight glass container, powder of calcium phosphate is applied using nitrified cotton, similar to the method used to apply a phosphor coating. A conventional method has been to form a film by coating the inner surface of a light-transmitting airtight container with a suspension prepared by dispersing it in a 1% solution of butyl acetate and drying it. However, this method uses an organic solvent such as butyl acetate, and also uses nitrified cotton to adjust the viscosity, so the suspension is applied to protect against explosive and flammable organic solvents. Drying requires a strong and explosion-proof facility, requiring a large investment in equipment, and the process for producing the suspension also has the disadvantage of requiring extremely careful attention. The present invention was made in view of the above-mentioned drawbacks, and the formation of a film made of calcium phosphate or the like poses no risk of explosion, and therefore can be carried out using a simple device that does not require explosion-proof measures, thus reducing equipment costs. An object of the present invention is to provide an improved method for manufacturing a curved tube fluorescent lamp, which is inexpensive and has an easy-to-work process of applying and drying a calcium phosphate film. The progress of the experiments conducted until the production method of the present invention was completed will be described in detail below. The present inventors have constructed a light-transmissive airtight container made of soda lime glass, which is bent into an annular shape and has a phosphor coating on its inner surface, and an electrode structure coated with an electron emitting material is sealed to both ends of the light-transparent airtight container. A step of depositing a calcium phosphate film before the step of forming a phosphor film on the inner surface of the translucent airtight container when manufacturing an annular fluorescent lamp in which an easily dischargeable electric material is sealed inside the container. In this paper, we investigated conventional methods that do not use organic solvents, and after various trials and errors, we tested the use of water-soluble binders.
An aqueous solution of calcium pyrophosphate (Ca ₂ P ₂ O ₇ ) was prepared using polyammonium methacrylate as a water-soluble binder having a thickening effect. First, the concentration of polyammonium methacrylate is
A water-soluble binder solution was prepared by varying the amount from 0.005% by weight to 0.3% by weight, and the weight per 1 c.c. of water suspension was
Varying the amount of calcium pyrophosphate powder in the range of 0.01×10 ^-2 g to 5×10 ^-2 g to make an aqueous suspension of calcium phosphate, add both and stir thoroughly to dissolve phosphoric acid. A calcium aqueous solution was prepared. In the first step, this is coated and dried on the inner surface of a transparent glass airtight container, and then in the second step, a layer of 1% by weight (based on a fluorescent weight of 100) is applied onto the calcium phosphate coating. A phosphor suspension containing a B ₂ O ₃ -CaO-BaO binder is applied and dried, followed by a firing process in which the water-soluble binder and others are removed by firing to produce a 100V30W circular curved tube fluorescent lamp. did. The incidence of peeling of the phosphor film and the light output of the above ring-shaped fluorescent lamp of 100 V and 30 W were tested. The results of the above test are shown in Table 2 below and the attached figures. Table 2 shows the weight (g) of calcium pyrophosphate per c.c. of water suspension and the incidence (%) of peeling of the phosphor coating. In this case, the concentration of the water-soluble binder solution was kept constant at 0.05% by weight.

[Table] As is clear from the results in Table 2, when the weight of calcium pyrophosphate exceeded 3.5×10 ^-2 g/cc, the incidence of peeling of the phosphor coating increased rapidly. This means that if the thickness of the calcium phosphate film becomes too thick, the film thickness including the phosphor film deposited on top of it will increase, reducing the adhesion of the phosphor film and reducing the thickness of the calcium phosphate film. It is believed that this caused the phosphor coating separated from the glass inner surface of the light-transmitting airtight container to peel off. If the weight of calcium phosphate is less than 0.3×10 ^-2 g/cc, the above-mentioned phosphor coating will not peel off, but for the same reason as stated in the explanation of Table 2, the desired thickness of the calcium phosphate coating cannot be obtained. This is not possible because the effect of the calcium phosphate coating will be lost. The attached diagram shows an aqueous suspension of calcium pyrophosphate 1c.c.
The variation of the light output of an annular fluorescent lamp when the unit weight (g) is varied is shown. The light output is expressed as a percentage when the maximum value is 100. As is clear from the figure, the light output decreases if the weight of calcium phosphate is too small or too large. Then, the weight of calcium phosphate is 0.3×10 ^-2 g/cc
It has been found that if it is smaller, a sharp drop in optical output occurs. As mentioned in the explanation of Table 2 above, this is due to the fact that the desired thickness of the calcium phosphate coating cannot be obtained, so it does not function as a protective film, and during heating processing during the manufacture of annular fluorescent lamps, etc. It is thought that the light output decreased due to sodium precipitated from the glass. Therefore, the weight of calcium phosphate is 0.3×10 ^-2 g to 3.5× per c.c. of water suspension, as is clear from Table 3 and the attached figures.
It was found that 10 ^-2 g is good. In the above-mentioned test, calcium pyrophosphate (Ca ₂ P ₂ O ₇ ) was used as the calcium phosphate, and polyammonium methacrylate was used as the water-soluble binder, but the present invention is not limited to this. - Ca ₃ (Po ₄ ) ₂ , Ca ₄ P ₂ O ₉ , etc. have exactly the same effect, and the present invention also shows that water-soluble binders having a thickening effect are not limited to the above polyammonium methacrylate. They confirmed this through experiments. Furthermore, if the concentration of the water-soluble binder solution is greater than 1% by weight, it is not acceptable because the calcium pyrophosphate coating will cause poor coloring of the light-transmitting airtight container during baking after deposition of the phosphor coating. This seems to indicate that if the concentration of the water-soluble binder solution exceeds 1% by weight, it will not burn and coloring defects will occur. When the concentration of the water-soluble binder solution is less than 0.02% by weight, the viscosity becomes too small and the desired thickness of the calcium phosphate film cannot be obtained. This is not possible because precipitation cannot be prevented, resulting in a decrease in light output and a decrease in the strength of the translucent airtight container. Next, the present inventors conducted an experiment on a binder to be added to a phosphor suspension applied to a calcium phosphate coating applied to the inner surface of a translucent airtight container. A commonly used antimony- and manganese-activated calcium halophosphate phosphor is dispersed in a 1% butyl acetate solution of nitrified cotton, and B ₂ O ₃ -CaO-
A 100 V 30 W annular fluorescent lamp was manufactured using a phosphor suspension prepared by adding a BaO-based low melting point compound in an amount of 0.2% to 5% by weight based on the weight of the above phosphor and stirring thoroughly. The incidence of peeling of the phosphor coating was tested. As a result, it was found that if the B ₂ O ₃ -CaO-BaO type low melting point compound binder added to the phosphor was less than 0.5% by weight, the phosphor film peeled off by 0.5%.
It was found that more than % of Furthermore, if the above-mentioned binder is added in an amount exceeding 3% by weight of the fluorescent weight, the light output of the annular fluorescent lamp may decrease, so the above-mentioned B ₂ O ₃ -CaO-BaO-based low melting point compound binder is 0.5% to 3% by weight of the fluorescent weight is preferred. Further, the solvent for the phosphor suspension is preferably an organic solvent so as not to change the thickness of the calcium phosphate coating when the calcium phosphate is deposited in an aqueous solution. As described in detail above, the present invention provides a light-transmitting airtight container made of bent soda lime glass having a phosphor coating on the inner surface, and an electron-radioactive substance sealed at both ends of the light-transmitting airtight container. an attached electrode structure;
In the production of a product containing mercury and an easily dischargeable electric body sealed inside a translucent airtight container, aqueous suspension 1
An aqueous suspension of calcium phosphate having a weight per cc of 0.3×10 ^-2 g to 3.5×10 ^-2 g, and a solution of a water-soluble binder having a thickening effect having a concentration of 0.02% to 1% by weight. a first step of applying and drying an aqueous calcium phosphate solution containing a phosphor to the inner surface of the glass bulb; and a phosphor suspension containing a phosphor and a binder placed on the coating formed in the first step. A method for manufacturing a curved fluorescent lamp, the method comprising: a second step of coating a curved fluorescent lamp with a light-transmitting airtight container made of soda lime glass; It is now possible to manufacture curved tube fluorescent lamps without deteriorating the optical characteristics and the strength of the light-transmitting airtight container using conventional manufacturing equipment without explosion-proof measures. Therefore, the equipment investment is small, and the calcium phosphate coating can be applied in the process of cleaning and drying the conventional glass translucent airtight container before the phosphor coating process. This has the effect of providing a shaped fluorescent lamp. Although the above experimental example was explained using annular fluorescent lamps, the manufacturing method of the present invention is not limited to annular fluorescent lamps, but can also be applied to bent tubes such as U-shape, saddle-shape, three-dimensional W-shape, etc. It is effective when applied to all fluorescent lamps.

[Brief explanation of drawings]

The figure is a curve diagram showing the relationship between the weight of an aqueous suspension of calcium pyrophosphate and the light output of an annular fluorescent lamp.

Claims (1)

[Scope of Claims] 1. A translucent airtight container made of bent soda lime glass and having a phosphor coating on the inner surface, and an electron radioactive substance sealed and coated on both ends of the translucent airtight container. In the method for manufacturing a curved tube fluorescent lamp having an electrode structure, mercury sealed inside a translucent airtight container, and an easily discharging electric body, the weight per 1 c.c. of water suspension is 0.3 × 10 g to 3.5 g. A calcium phosphate aqueous solution containing x10g of an aqueous suspension of calcium phosphate and a solution of a water-soluble binder having a thickening effect with a concentration of 0.02% to 1% by weight is applied to the inner surface of the glass bulb and dried. A curved tube comprising the steps of step 1 and a second step of applying a phosphor suspension containing a phosphor and a binder onto the coating formed in the first step. Method of manufacturing shaped fluorescent lamps. 2. The method for manufacturing a curved tube fluorescent lamp according to claim 1, wherein the water-soluble binder contained in the calcium phosphate aqueous solution is polyammonium methacrylate. 3 The phosphor suspension contains the phosphor and 0.5% to 3% by weight of BO-CaO when its weight is taken as 100.
2. A method for manufacturing a curved fluorescent lamp according to claim 1, wherein the organic suspension contains: - a BaO-based binder.