JP2748706B2 - Production method of phosphor coating liquid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a phosphor coating solution for forming a phosphor film on the inner surface of a glass bulb of a discharge lamp.

[0002]

2. Description of the Related Art In general, a method of applying a phosphor to a discharge lamp, for example, a fluorescent lamp for illumination, includes an organic solvent system in which a binder in a dispersion of phosphor particles is dissolved in an organic solvent such as butyl acetate or xylene. However, the organic solvent system is difficult to control because of the safety management for workers, such as the effects on the human body. The method is heavily used.

[0003] By the way, in the aqueous phosphor coating method,
Lanthanum nitrate as a binder to increase the binding force between the glass bulb and the phosphor particles, or between the phosphor particles, for improving the initial luminance and the luminous flux maintenance when the discharge lamp is turned on,
It has been proposed that a water-soluble rare earth compound such as yttrium chloride is added to a phosphor coating solution mainly composed of an aqueous solution of polyethylene oxide to coat the surface of the phosphor particles with an oxide such as lanthanum or yttrium (Japanese Patent Application No. Hei. -2
66077).

[0004]

However, when a water-soluble rare earth compound such as lanthanum nitrate or yttrium chloride is added to a phosphor coating solution composed of an aqueous solution of polyethylene oxide, the pH of the phosphor coating solution becomes acidic and changes with time. At the same time, the viscosity of polyethylene oxide decreases, the viscosity becomes unstable, and if left unattended, it will cause mold and other foul odors.In addition, the phosphor coating solution under acidic conditions will reduce the durability of discharge lamp manufacturing equipment. And various other adverse effects.

Accordingly, an object of the present invention is to provide a method for producing a phosphor coating solution capable of improving the initial light emission luminance and luminous flux maintenance of a discharge lamp and enhancing the film strength without adversely affecting existing discharge lamp production equipment. Is to provide.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to suspend phosphor particles in an aqueous binder solution for forming a fluorescent film of a discharge lamp, and to suspend 100 g of the phosphor in the suspension with a rare earth oxide. The solution is achieved by adding 0.001 to 5 g of a water-soluble rare earth compound corresponding to the weight of the suspension and then adjusting the pH of the suspension from 7.3 to 10.5.

The water-soluble rare earth compound is preferably a compound which easily changes to a rare earth oxide by baking a coating film or the like, and the rare earth oxide is preferably a white substance which reflects light. For example, as rare earth, La,
Y, Gd, Dy, Sc, Sm, Eu, Ho, Tm, Lu
Is mentioned. Examples of the water-soluble rare earth compound include nitrate, chloride, halide of bromide, acetate, sulfate and the like. Preferably, the aqueous binder solution is mainly an aqueous solution of polyethylene oxide, the soluble rare earth oxide is an aqueous solution of lanthanum oxide and / or an aqueous solution of yttrium oxide, and the amount of the rare earth compound added is 100 g of the phosphor.
0.2 to 1.5 g as a rare earth oxide of lanthanum oxide and / or yttrium oxide.

Further, it is preferable that the soluble rare earth compound is an aqueous lanthanum nitrate solution, and the pH of the suspension is adjusted to about 8.5 to 9.8 with alkali hydroxide.

[0009]

By adding a soluble rare earth compound corresponding to 0.001 to 5 g as a rare earth oxide to 100 g of a phosphor to an aqueous binder solution, a binder such as fine particles of calcium pyrophosphate is added. As a result, the amount of the soluble rare earth compound added as a binder can be significantly reduced, and the initial emission luminance and maintenance of the luminous flux can be greatly improved. In particular, regarding the maintenance of the luminous flux, when a binder such as calcium pyrophosphate is added based on the discharge lamp coated with the fluorescent film without adding any binder, the luminous flux maintenance rate is lower than the standard. On the other hand, in the case where the soluble rare earth compound of the present invention is added, it is higher than the standard.

Further, a uniform and stronger film strength can be obtained by the binder of the soluble rare earth compound, and the pH of the coating solution containing the uniform soluble rare earth compound is increased from 7.3 to 10.5. Thereby, the adhesion of the rare earth compound to the surface of the phosphor particles is promoted, and conventionally, since the pH is low, the viscosity of the coating solution that has occurred is not reduced, and no mold or the like is generated by leaving the coating solution, and further, There is no deterioration in durability of existing equipment in the coating process.

[0011]

Embodiments of the present invention will be described below in detail.

Example 1 100 g of a calcium halophosphate phosphor was added to a 0.7% polyethylene oxide aqueous solution 14
Suspend to 0 g. 2. An aqueous lanthanum nitrate solution containing 0.5% by weight of lanthanum oxide with respect to the phosphor, based on the phosphor.
2 g (containing 13.3% as lanthanum) are added and the suspension is mixed well. Then, while stirring the suspension, aqueous ammonia was added until the pH of the suspension was 9.0, and then the suspension was stirred for about 2 to 5 minutes to obtain a phosphor coating solution. Was.

The pH of the phosphor coating solution similar to that described above except that the pH is not adjusted with ammonia water is about 4.0, whereas the pH of the phosphor coating solution of the present embodiment is 9.
Since it is 0, it can be used without damaging the existing equipment of the phosphor coating process in the discharge lamp, and the phosphor coating liquid hardly decreases in viscosity even if left for one month. Was.

Next, in order to evaluate the phosphor coating solution thus obtained, a 40 WSS straight tube fluorescent lamp was prepared as follows. That is, the above-mentioned phosphor coating solution is added to the straight pipe 4.
Apply to the inner surface of a 0WSS glass bulb, bake it in an electric furnace at 580 ° C for 15 minutes, cool, evacuate to both ends of the glass bulb, enclose ordinary rare gas and mercury (Hg), and attach a base Was.

For comparison, a phosphor coating solution was prepared by suspending 100 g of a phosphor in an aqueous solution of polyethylene oxide and adding a calcium pyrophosphate slurry to the suspension in an amount of 4% by weight based on 100 g of the phosphor. A 40 WSS fluorescent lamp was produced in the same manner as described above.

As a result, when calcium pyrophosphate was added, the initial luminous flux was 3200 lm, whereas in the present embodiment, a high initial luminous flux of 3240 lm was obtained.
In addition, in the luminous flux maintenance rate after lapse of 2000 hours, when calcium pyrophosphate was added, the luminous flux was 2,720 lm, which was about 15% lower than the initial luminous flux. It decreased only about 9% with respect to the luminous flux.

Further, in the film strength of the fluorescent film of the discharge lamp,
Compared with the size of the peeling of the film when air of a certain pressure is blown at a certain distance and time to the inner surface of the glass bulb with the base removed, the use of calcium pyrophosphate binder shows that
About 8 mm or less, which was peeled off by 0 mm or more, was 1/3 or less.

Example 2 A divalent europium-activated strontium-calcium-barium halophosphate phosphor as a blue light-emitting component, a cerium and terbium-activated lanthanum orthophosphate phosphor as a green light-emitting component and a trivalent as a red light-emitting component 100 g of the three-wavelength phosphor mixed with the europium-activated yttrium oxide phosphor is suspended in 150 g of a 0.7% polyethylene oxide aqueous solution. To this suspension, 3.2 g of an aqueous lanthanum nitrate solution containing 0.5% by weight of lanthanum oxide with respect to the phosphor (1% as lanthanum) was added.
(Containing 3.3%) and mix well. While stirring the suspension, the pH of the suspension was adjusted to 9.0 with aqueous ammonia.
To prepare a phosphor suspension.

As in Example 1, the pH of the phosphor coating solution was the same as that described above except that the pH was not adjusted with ammonia water, and was about 4.0. The existing equipment for the phosphor application process with the lamp could be used without any damage, and the viscosity was hardly reduced even after being left for 14 days.

A fluorescent lamp similar to that of Example 1 was manufactured using the above-mentioned phosphor coating solution. However, there was no change in the emission color and color rendering properties of this fluorescent lamp. In comparison with the case where the fine particle aluminum oxide slurry of 1.0% by weight was added,
In the same test method as in Example 1, the peel length was about 30 mm in the case of aluminum oxide, whereas in this example, it was about 5 mm, and excellent film strength was obtained.

In addition, the initial light flux of 3520 lm was obtained by adding the aluminum oxide slurry,
In the present embodiment, it was slightly improved to 3540 lm. Also, 5
When the aluminum oxide was added, the luminous flux maintenance factor after the lapse of 00 hours was reduced by about 5% with respect to the initial luminous flux, but in the present embodiment, it was reduced by only about 2% with respect to the initial luminous flux.

EXAMPLE 3 100 g of a tin-activated strontium pyrophosphate phosphor is suspended in 100 g of a 0.7% aqueous solution of polyethylene oxide. To this suspension, a 10% yttrium chloride aqueous solution which becomes 0.3% with respect to the phosphor as yttrium oxide is added. While stirring the suspension, the pH of the suspension is raised to 9.0 with aqueous ammonia.

In the same manner as in Example 1, except that the pH was not adjusted with ammonia water, the pH of the phosphor coating solution was the same as that described above, but was about 4.5. The existing equipment for the phosphor application process with the lamp could be used without any damage, and the viscosity was hardly reduced even after being left for 14 days.

Using the above-mentioned phosphor coating solution, a fluorescent lamp similar to that of Example 1 was manufactured. In this fluorescent lamp, a fine particle calcium pyrophosphate slurry having a weight of 4% by weight based on 100 g of the phosphor was added. In comparison with the above, in the same test method as in Example 1, the peel length was about 28 mm in the case of calcium pyrophosphate,
In this example, the thickness was about 20 mm, and a slightly excellent film strength was obtained.

In addition, the initial light flux of 1720 lm when calcium pyrophosphate was added was improved to 1750 lm in the present embodiment. Also, 500
With respect to the luminous flux maintenance rate after the lapse of time, when calcium pyrophosphate was added, the initial luminous flux was reduced by about 18%, whereas in the present embodiment, the luminous flux was reduced by only about 11% with respect to the initial luminous flux.

The invention has been described for the case of adding only polyethylene oxide solution as the aqueous binder according to the present invention, the aqueous binder solution may be other than aqueous solution of polyethylene oxide, for example, suitable water-soluble in an aqueous binder Cellulose (HPC, CM
C) and a water-soluble acrylate (PMA) ,
Needless to say, a surfactant and an antifoaming agent may be appropriately added thereto.

[0027]

As described above, according to the present invention,
It is possible to provide a method for producing a phosphor coating liquid capable of improving the initial emission luminance and luminous flux maintenance of a discharge lamp and enhancing the film strength without adversely affecting existing discharge lamp production equipment.

Continuing on the front page (72) Inventor Osamu Sakai 491, 100 Kaminakacho Oka, Anan City, Tokushima Prefecture Inside Nichia Chemical Industry Co., Ltd. In company

Claims (3)

(57) [Claims] A phosphor particle is suspended in an aqueous binder solution for forming a phosphor film of a discharge lamp.
0.001 as rare earth oxide per 100 g of phosphor
A method for producing a phosphor coating solution, comprising adding a water-soluble rare earth compound equivalent to 1 to 5 g, and then adjusting the pH of this suspension from 7.3 to 10.5. 2. The aqueous binder solution is mainly an aqueous solution of polyethylene oxide, the water-soluble rare earth oxide is an aqueous solution of lanthanum oxide and / or an aqueous solution of yttrium oxide, and the amount of the rare earth compound is 100%.
The method for producing a phosphor coating liquid according to claim 1, wherein the amount of the rare earth oxide of lanthanum oxide and / or yttrium oxide is 0.2 to 1.5 g based on g. 3. The water-soluble rare earth compound is an aqueous lanthanum nitrate solution, and the pH of the suspension is adjusted to 8.5 to 9.8 with alkali hydroxide.
13. The method for producing a phosphor coating liquid according to the above item.