JPS5922971A - Fluorescent paint composition - Google Patents

Abstract

PURPOSE:To prepare the titled composition composd of a fluorescent material, a water-soluble binder, a low-melting glass powder and ammonium nitrate, and giving a fluorescent film of a fluorescent lamp having stable luminescence and excellent lamp characteristics even after storing for a long period. CONSTITUTION:The objective paint can be prepared by mixing (A) a water-soluble binder (e.g. polyethylene oxide) with (B) a low-melting glass powder (e.g. La2O3.MgO.B2O3), (C) a fluorescent material and (D) 0.01-2.0wt%, preferably 0.1-1.0wt%, based on the fluorescent material, of ammonium nitrate. The paint is applied to the inner surface of the glass tube for a ring fluorescent lamp, and dried under the flow of hot air at about 60-70 deg.C to form a fluorescent layer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the improvement of a phosphor coating composition for applying and forming a phosphor film on the inner wall surface of a glass tube in the manufacturing process of a fluorescent lamp, and in particular, This invention relates to preventing a decrease in luminous flux of fluorescent lamps during use during lamp manufacturing after long-term storage.

Conventionally, when attaching a phosphor to the inner wall surface of a glass tube for a fluorescent lamp, for example, the phosphor and low-melting glass powder are suspended in a solution of nitrocellulose as a binder dissolved in butyl acetate. After applying this to the inner wall surface of a glass tube, a phosphor film was formed through a drying and firing process. If a fusing agent such as low-melting point glass is not added to the above-mentioned phosphor coating composition, the phosphor film will not firmly adhere to the inner wall surface of the glass tube, and the phosphor film will only peel off. I can't get it. In particular, in the case of annular fluorescent lamps,
The phosphor film tends to peel off during the process of forming the glass tube into an annular shape after the phosphor film has been applied.

Further, it is not preferable to use an organic solvent such as butyl acetate as in the above-mentioned phosphor coating composition from the viewpoint of flammability, toxicity to the human body, economic efficiency, and the like. However, if a water-soluble binder solution is used instead of a solution of nitrocellulose dissolved in butyl acetate, the above-mentioned low melting point glass will dissolve or decompose in the water solvent, resulting in poor lamp characteristics when manufacturing a fluorescent lamp. The problem arises that it has a negative impact on Various low melting point glasses have already been proposed, but for example, the commonly used Ca0-BaCIB203 glass decomposes in water and cannot be used.

On the other hand, there is also known glass that hardly decomposes or dissolves (hereinafter simply referred to as dissolution) in water and has a low melting point. The present inventors have also developed a glass with a new composition having such characteristics and have already filed a patent application (Japanese Patent Application No. 63935/1982).

However, these glasses also have extremely low dissolution in water, and are not completely insoluble.

Therefore, those who prepared phosphor coating compositions containing these glasses and immediately used them to manufacture lamps;
When the luminous flux of the lamp was compared with that of the lamp produced after it had been left for a long period of time, it was confirmed that the luminous flux of the latter lamp was clearly lower than that of the former lamp. In this case, the adhesion strength of the phosphor film to the inner wall surface of the glass tube remains almost unchanged for both cases. in general,
Industrially, when manufacturing fluorescent lamps, a certain amount of an aqueous suspension (slurry) of a phosphor coating composition is prepared, stored for a long period of time, and used once as necessary. However, the above-mentioned problems are important industrially.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a phosphor coating composition that does not cause a decrease in the luminous flux of a fluorescent lamp even if the composition is stored for a long period of time and then used to produce a fluorescent lamp.

In order to achieve the above object, the present invention is characterized in that ammonium nitrate is added to a phosphor coating composition comprising a phosphor, a water-soluble binder, and a low melting point glass powder.

Owing to the characteristic composition of the present invention, it has become possible to provide a phosphor coating composition that does not cause a decrease in the luminous flux of a fluorescent lamp even if it is used to manufacture a fluorescent lamp after being stored for a long period of time.

Further, a preferred embodiment of the phosphor coating composition of the present invention comprises a phosphor, a low melting point glass powder, a water bathable binder, and a phosphor coating composition of 0.01 to 2.0% for the phosphor. ．． It is characterized by consisting of ammonium nitrate added in a range of 0 weight percent.

The effect of adding ammonium nitrate to a phosphor coating composition is that by adding it from the beginning, the lamp luminous flux can be increased compared to one without it, and after long-term storage, A similar effect can be obtained by adding it to a phosphor coating composition.

Hereinafter, the present invention will be described in detail with reference to Examples.

First, the action and effect of ammonium nitrate, which is a feature of the present invention, will be described.

The action of ammonium nitrate is not completely understood, but it is thought to be as follows.

The glass powder used with the water-soluble binder is one that hardly dissolves in water, but as mentioned above, the water bath solubility is not zero, and most of the powder dissolves in water, albeit very slightly. The glass component dissolved in water in this way precipitates during the drying process, and since the precipitated glass component melts at a temperature lower than the firing temperature when burning the binder, it is absorbed into the molten glass component. It is thought that the binder causes incomplete combustion, and as a result, carbon remains in the phosphor film, causing a decrease in the luminous flux of the lamp. At this time, if ammonium nitrate is added, oxygen is released during the following decomposition process, and this released oxygen promotes complete combustion of the binder to help burn out the remaining carbon, resulting in the lamp It is thought that the luminous flux is improved.

NH4NO3 → NH4NO2+-02 After the firing process in which the binder is burned and removed, the phosphor from the lamp is peeled off and the powder brightness is measured, and it is clear that the powder with ammonium nitrate is brighter than the one without. It is presumed that decomposition is occurring.

Next, experiments and studies were conducted on the amount of ammonium nitrate added, and it was found that adding even a very small amount of ammonium nitrate can significantly improve the luminous flux.

Further investigation revealed that this luminous flux improving effect was more pronounced when the addition rate of ammonium nitrate to the phosphor was in the range of 0.01 to 2.0% by weight. Further detailed study revealed that the optimum range for the addition rate of ammonium nitrate was 0.1 to 1.0% by weight.

In this experiment, the low melting point glass used together with the aqueous binder has excellent water resistance (as described in the above-mentioned Japanese Patent Application No. 56-63935).

The composition of the glass is expressed by the general formula % (where Ln is at least one element selected from the group consisting of Y and lanthanum series elements, and M is Mg + C
a + S r ) B a and 7. At least one element selected from the group consisting of n, M' is At203°5
represents at least one kind of oxide selected from the group consisting of iQz and 5b20B, and X, y, W and 2 are respectively 1≦X≦30 mol%, 0≦y≦60 mol%, 0≦W≦2
0 mol%, 30≦2≦80 mol%, and
y+W is a value in the range of 0≦y + W≦60 mol%. ).

A more preferable glass composition has the general formula % (where Ln, M and M' represent the above-mentioned meanings, and M
"represents at least one element selected from the group consisting of Li, Na, and K; x, y.

W and 2 are the values mentioned above, and v is a value in the range of O<V≦15 mol%. ). It goes without saying that the glass powder is not limited to the above-mentioned glass powder, but may be any other glass powder as long as it is a poorly water-soluble glass powder.

The water-soluble binder used in the above experiment was polyethylene oxide, but other suitable water-soluble binders include hydroxyalkyl cellulose, ammonium methacrylate, carboxymethyl cellulose,
Examples include polyvinyl alcohol and isobutylene/maleic anhydride copolymer, and any of these may be used.

Next, the present invention will be explained using specific examples.

Example: La2O3, MgO, BzO, which is one of the glass compositions mentioned above, was added to 160 cc of 0.8% polyethylene oxide solution.
A (10:40:so mol %) glass powder was added in the amount listed in Table 1, finely pulverized in a ball mill, 100 g of white calcium halophosphate phosphor and ammonium nitrate listed in Table 1 were added, and further pulverized in a ball mill. Mix for 30 minutes to produce a phosphor paint. It should be noted that all of the amounts added above are percentages by weight relative to the phosphor.

This paint is applied to the inner wall surface of a 30 W glass tube for an annular fluorescent rung, and heated air at about 60 to 70 C is flowed into the tube to evaporate water and form a phosphor layer.

Thereafter, an annular fluorescent lamp was manufactured using a conventional manufacturing method. Thereafter, the luminous flux of the manufactured lamp was measured.

As a result, as is clear from Table 1, it can be seen that the luminous flux of the lamp of Comparative Example in which ammonium nitrate was not added was improved as well as the luminous flux of the lamp of Examples 1 and 20 in which ammonium nitrate was added. Furthermore, when the phosphor paint was left for the number of days listed in Table 1, the lamp luminous flux of the comparative example decreased even though it was left unused, but in the case of Examples 1 and 2, the lamp luminous flux did not decrease. First, the effect of adding ammonium nitrate is clearly visible.

In addition, in Example 3, ammonium nitrate was not added in advance, but ammonium nitrate was added after the phosphor paint was left to stand for 7 days, and the effect of its addition is clear.

Furthermore, the luminous flux maintenance rate of fluorescent lamps manufactured using ammonium nitrate-added phosphor paints after long-term operation is equal to or higher than that of fluorescent lamps manufactured using conventional phosphor paints. Ta.

Table 1 The phosphor is not only calcium halophosphate phosphor, but also other phosphors, for example, a so-called high color rendering fluorescent lamp that mixes three types of phosphors that emit blue, green, and red light. It was confirmed that similar effects can be obtained when used in

Claims (1)

[Claims] 1. A phosphor coating composition for applying and forming a phosphor film on the inner wall surface of a glass tube, wherein the phosphor coating composition comprises a phosphor and a water-soluble binder. , a phosphor coating composition comprising a low melting point glass powder and ammonium nitrate. 2. The ammonium nitrate has a concentration of 0.0% with respect to the phosphor.
2. The phosphor coating composition according to claim 1, wherein the phosphor coating composition is added in an amount of 0.01 to 2.0% by weight. 3. The ammonium nitrate has a concentration of 0.0% with respect to the phosphor.
2. The phosphor coating composition according to item 1, wherein the phosphor coating composition is added in an amount of 1 to 1.0% by weight. 4. The phosphor coating composition according to any one of items 1 to 3, wherein the water-soluble binder comprises polyethylene oxide.