JPH04248891A - Production of coating liquid of fluorescent material - Google Patents

Abstract

PURPOSE:To provide a process for producing a fluorescent coating liquid capable of improving the initial intensity and the stability of the light flux of a luminescent lamp and increasing the film strength without giving undesirable influence on the existing production line of luminescent lamp. CONSTITUTION:The objective coating liquid of fluorescent material can be produced by suspending particles of a fluorescent material in an aqueous binder solution for the production of a fluorescent film of a luminescent lamp, adding 0.001-5g (in terms of rare-earth metal oxide based on 100g of the fluorescent material) of a soluble rare-earth metal compound to the suspension and adjusting the pH of the suspension to 7.3-10.5.

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 liquid for forming a phosphor film on the inner surface of a glass bulb of a discharge lamp.

0002

[Prior Art] In general, a method for applying phosphor to a discharge lamp, for example, a fluorescent lamp for lighting, uses 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. This is divided into aqueous systems in which the binder is dissolved in pure water, but organic solvent systems have difficulties in process control from the viewpoint of safety management for workers such as the impact on the human body, so aqueous phosphor coating is recommended. Many methods are used.

By the way, in the aqueous phosphor coating method,
In order to improve the initial brightness and maintenance of luminous flux when the discharge lamp is lit, lanthanum nitrate,
It has been proposed to coat the surfaces of phosphor particles with oxides such as lanthanum and yttrium by adding a water-soluble rare earth compound such as yttrium chloride to a phosphor coating solution mainly consisting of an aqueous solution of polyethylene oxide (Patent Application No. -2
66077).

0004

[Problems to be Solved by the Invention] However, when a water-soluble rare earth compound such as lanthanum nitrate or yttrium chloride is added to a phosphor coating solution made of an aqueous polyethylene oxide solution, the pH of the phosphor coating solution becomes acidic and changes over time. At the same time, the viscosity of polyethylene oxide decreases, making it unstable, and if left untreated, it can cause the generation of mold and other bad odors.In addition, the phosphor coating liquid under acidic conditions decreases the durability of discharge lamp manufacturing equipment. It causes various adverse effects such as

Therefore, an object of the present invention is to provide a method for producing a phosphor coating liquid that can improve the initial luminance and maintenance of luminous flux of a discharge lamp and strengthen the film strength without adversely affecting existing discharge lamp production equipment. Our goal is to provide the following.

[0006]

[Means for Solving the Problems] An object of the present invention is to suspend phosphor particles in an aqueous binder solution for creating a phosphor film for a discharge lamp, and to add rare earth oxide to 100 g of the phosphor to this suspension. A water-soluble rare earth compound corresponding to 0.001 to 5 g is added as a liquid, and then the pH of this suspension is adjusted to 7.
．． This can be solved by adjusting from 3 to 10.5.

[0007] The water-soluble rare earth compound is preferably one that can be easily converted into a rare earth oxide by baking the coating film, etc., and it is also desirable that the rare earth oxide is a white substance that reflects light. For example, as rare earths, La,
Y, Gd, Dy, Sc, Sm, Eu, Ho, Tm, Lu
can be mentioned. Examples of water-soluble rare earth compounds include nitrates, chlorides, halides of bromides, acetates, and sulfates. Preferably, the aqueous binder solution is mainly an aqueous polyethylene oxide solution, the soluble rare earth oxide is an aqueous lanthanum oxide solution and/or an aqueous yttrium oxide solution, and the amount of the rare earth compound added is 100 g of the phosphor.
0.2 to 1.5 g of rare earth oxide of lanthanum oxide and/or yttrium oxide.

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

[0009]

[Effect] By adding a soluble rare earth compound equivalent to 0.001 to 5 g of rare earth oxide per 100 g of phosphor to the aqueous binder solution, compared to adding a binder such as particulate calcium pyrophosphate. Therefore, the amount of the soluble rare earth compound added as a binder can be significantly reduced, and the initial luminance and luminous flux maintenance can also be significantly improved. In particular, regarding luminous flux maintenance, the luminous flux maintenance rate is lower than the standard for discharge lamps coated with a fluorescent film without any binder added, but for discharge lamps with binders such as calcium pyrophosphate added. On the other hand, when the soluble rare earth compound of the present invention is added, the performance is improved over the standard.

[0010] Furthermore, by using the soluble rare earth compound binder, uniform and stronger film strength can be obtained, and furthermore, the pH of the coating solution to which the soluble rare earth compound is added can be increased from 7.3 to 10.5. This promotes the adhesion of the rare earth compound to the surface of the phosphor particles, and since the pH is low, there is no reduction in the viscosity of the coating liquid, which has conventionally occurred, and there is no occurrence of mold or the like when the coating liquid is left standing. There is no deterioration in the durability of existing equipment during the coating process.

[0011]

[Examples] Examples of the present invention will be described in detail below.

(Example 1) 100 g of calcium halophosphate phosphor was added to a 0.7% polyethylene oxide aqueous solution 14
Suspend at 0g. Add to this suspension a lanthanum nitrate aqueous solution containing 0.5% by weight of the phosphor as lanthanum oxide.
2 g (containing 13.3% as lanthanum) are added and the suspension is thoroughly mixed. Next, while stirring this suspension, ammonia water 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 liquid. Ta.

The pH of the phosphor coating solution similar to the above except that the pH is not adjusted with ammonia water is around 4.0, whereas the pH of the phosphor coating solution of this example is about 9.0.
0, it can be used without causing any damage to existing equipment in the phosphor coating process using discharge lamps, and this phosphor coating liquid shows almost no decrease in viscosity even after being left for one month. Ta.

Next, in order to evaluate the phosphor coating liquid thus obtained, a 40 WSS straight fluorescent lamp was manufactured as follows. That is, the above phosphor coating liquid is passed through the straight pipe 4.
It is applied to the inner surface of the 0WSS glass bulb, then baked in an electric furnace at 580°C for 15 minutes, and after cooling, both ends of the glass bulb are evacuated and filled with ordinary rare gas and mercury (Hg), and a cap is attached. Ta.

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

As a result, when calcium pyrophosphate was added, the initial luminous flux was 3,200 lm, whereas in this example, a high initial luminous flux of 3,240 lm was obtained. In addition, in the luminous flux maintenance rate after 2000 hours, when calcium pyrophosphate was added, the luminous flux was 2720 lm, which was about 15% lower than the initial luminous flux, whereas in this example, the luminous flux was 2940 lm, which was about 15% lower than the initial luminous flux. The luminous flux decreased by only about 9%.

Furthermore, the film strength of the fluorescent film of the discharge lamp is as follows:
When comparing the amount of film peeling when air at a certain pressure is blown at a certain distance and for a certain time on the inner surface of a glass bulb with the cap removed, when using calcium pyrophosphate binder, 3.
Less than one-third of the cases had peeling of about 8 mm or more, whereas the peeling of 0 mm or more was about 8 mm.

(Example 2) A divalent europium-activated strontium-calcium-barium halophosphate phosphor was used as the blue light-emitting component, a cerium and terbium-activated lanthanum orthophosphate phosphor was used as the green light-emitting component, and a trivalent europium-activated lanthanum orthophosphate phosphor was used as the red light-emitting component. 100 g of a three-wavelength phosphor mixed with 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 a lanthanum nitrate aqueous solution (13.5 g as lanthanum) was added to give 0.5% by weight of lanthanum oxide based on the phosphor.
(containing 3%) and mix thoroughly. A phosphor suspension was prepared by raising the pH of the suspension to 9.0 with aqueous ammonia while stirring the suspension.

Similar to Example 1, the pH of the phosphor coating solution similar to that described above is around 4.0, except that the pH is not adjusted with ammonia water. Existing equipment for the phosphor coating process in lamps could be used without any damage, and there was almost no decrease in viscosity even after being left for 14 days.

A fluorescent lamp similar to that of Example 1 was manufactured using the above phosphor coating liquid, but there was no change in the emission color or color rendering properties of this fluorescent lamp, and the film strength was also lower than that of 100 g of phosphor. Compared to the one to which fine particle aluminum oxide slurry was added at 1.0% by weight,
In the same test method as in Example 1, the length of peeling was approximately 30 mm in the case of aluminum oxide, whereas in this example it was approximately 5 mm, and excellent film strength was obtained.

[0021] In addition, while the initial luminous flux of the one to which aluminum oxide slurry was added was 3520 lm,
In this example, it was slightly improved to 3540 lm. Also, 5
The luminous flux maintenance rate after 00 hours was reduced by about 5% compared to the initial luminous flux when aluminum oxide was added, whereas in this example, it was reduced by only about 2% compared 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% polyethylene oxide aqueous solution. To this suspension, a 10% aqueous yttrium chloride solution is added, representing 0.3% of yttrium oxide based on the phosphor. While stirring the suspension, raise the pH of the suspension to 9.0 with ammonia water.

Similar to Example 1, the pH of the phosphor coating solution similar to that described above is around 4.5, except that the pH is not adjusted with ammonia water. Existing equipment for the phosphor coating process in lamps could be used without any damage, and there was almost no decrease in viscosity even after being left for 14 days.

[0024] A fluorescent lamp similar to that in Example 1 was manufactured using the above phosphor coating liquid, but in order to increase the film strength in this fluorescent lamp, a fine particle calcium pyrophosphate slurry was added at a concentration of 4% by weight per 100 g of the phosphor. In comparison with that, in the case of calcium pyrophosphate, the peeling length was about 28 mm in the same test method as in Example 1;
In this example, the thickness was around 20 mm, and slightly superior film strength was obtained.

Furthermore, while the initial luminous flux of the one to which calcium pyrophosphate was added was 1,720 lm, this was slightly improved to 1,750 lm in this example. Also, 500
The luminous flux maintenance rate after the passage of time decreased by about 18% compared to the initial luminous flux when calcium pyrophosphate was added, whereas in this example, it decreased by only about 11% compared to the initial luminous flux.

[0026] The case where only the polyethylene oxide aqueous solution is added as the aqueous binder solution has been described above, but according to the present invention, the aqueous binder solution may be other than the polyethylene oxide aqueous solution, and the aqueous binder of polyethylene oxide may be added. Suitable water-soluble cellulose (HPC.CMC) and water-soluble acrylate (PM
It goes without saying that A) and the surfactants and antifoaming agents mentioned above may be added as appropriate.

[0027]

[Effects of the Invention] As explained above, according to the present invention,
It is possible to provide a method for producing a phosphor coating liquid that can improve the initial luminance and luminous flux maintenance of a discharge lamp and strengthen the film strength without adversely affecting existing discharge lamp production equipment.

Claims (3)

[Claims] 1. Fluorescent particles are suspended in an aqueous binder solution for creating a fluorescent film for a discharge lamp, and 0.00 g of rare earth oxide is added to this suspension per 100 g of the phosphor.
A method for producing a phosphor coating solution, which comprises adding 1 to 5 g of a water-soluble rare earth compound, and then adjusting the pH of this suspension to 7.3 to 10.5. 2. The aqueous binder solution is mainly a polyethylene oxide aqueous solution, the water-soluble rare earth oxide is a lanthanum oxide aqueous solution and/or a yttrium oxide aqueous solution, and the amount of the rare earth compound added is 10% of the phosphor.
2. 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 per 0 g. 3. Claim 2, wherein the water-soluble rare earth compound is an aqueous solution of lanthanum nitrate, and the pH of the suspension is adjusted to 8.5 to 9.8 with alkali hydroxide.
A method for producing a phosphor coating liquid as described in 2.