JPH04248894A - Production of coating liquid of fluorescent material and luminescent lamp - Google Patents

Abstract

PURPOSE:To provide a process for producing a fluorescent coating liquid, capable of forming an excellent fluorescent film without necessitating the time- consuming crushing process of a binder for the preparation of a fluorescent coating liquid for luminescent lamp and to provide a luminescent lamp having excellent initial light intensity and lumen maintenance factor. CONSTITUTION:The fluorescent coating liquid can be produced by suspending a fluorescent material in an aqueous binder solution and adding 0.001-5g (in terms of rare-earth metal oxide based on 100g of the fluorescent material) of an aqueous solution of a water-soluble rare-earth metal compound and at least one kind of aqueous solution of a boric acid salt, phosphoric acid group, boric acid and phosphoric acid to the suspension. The luminescent lamp of the present invention is produced by using the above fluorescent coating liquid.

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 coating on the inner surface of a glass bulb of a discharge lamp, and a discharge lamp manufactured by this method.

0002

[Prior Art] Generally, in the process of forming a fluorescent film for a discharge lamp, phosphor particles are suspended in a binder solution, and a binder is added to this suspension along with a suitable surfactant and antifoaming agent, and the mixture is mixed. By doing so, a phosphor coating liquid is formed.

[0003] The binder is used in the fluorescent film of the discharge lamp.
This is an inorganic substance that is mixed into the phosphor coating solution to prevent the phosphor particles from peeling off the glass bulb.As a binder for water-based coatings, silica, alumina, phosphates such as calcium pyrophosphate, etc. In addition, frit glass of calcium pyrophosphate and calcium tetraborate (Ca2P2
O7・CaB4O7) and water-resistant low melting point glass [Ln
2O3-MO-B2O3 system (Ln: Y and at least one rare earth element of the lanthanum series, M: Mg, Ca, S
r, Ba, and Zn)] are known.

0004

[Problem to be Solved by the Invention] However, since all of these binders are made into fine particles, there is a problem in that they must be ground into a slurry before being mixed into the phosphor coating solution. . In other words, in the case of a water-based binder, a water-resistant binder is selected, and non-water-resistant or water-soluble binders are considered to not perform their function and are therefore avoided. Therefore, it took tens of hours of grinding time to select a water-resistant binder and turn it into fine particles. In addition, in discharge lamps using fine particle binders, in order to increase the film strength, it is necessary to add a large amount of binder, and a large amount of binder reduces the initial luminous flux and luminous flux maintenance rate. There was a problem.

Therefore, an object of the present invention is to provide a phosphor coating solution that can form an excellent phosphor film without requiring a lot of time to crush the binder used in preparing the phosphor coating solution for discharge lamps. The object of the present invention is to provide a manufacturing method and a discharge lamp having excellent initial luminous flux and luminous flux maintenance rate.

[0006]

[Means for Solving the Problems] As shown in the previously filed Japanese Patent Application No. 2-266077, the present inventors have
It has been discovered that rare earth compounds such as lanthanum and yttrium, which contain yttrium, are extremely excellent as binders for discharge lamps in terms of initial brightness and maintenance of luminous flux.As a result of intensive research into solutions containing these rare earth compounds, the present invention has been developed. I was able to complete it.

That is, in the method for producing a phosphor coating liquid of the present invention, a phosphor is suspended in an aqueous binder solution, and 0.00 g of rare earth oxide is added to this suspension solution as a rare earth oxide per 100 g of the phosphor.
It is characterized in that an aqueous solution of a water-soluble rare earth compound corresponding to 1 to 5 g and an aqueous solution of at least one of borates, phosphates, boric acid, and phosphoric acid are added.

Even if the ratio of the cations in the aqueous solution of the water-soluble rare earth compound to the anions in the aqueous solution of at least one of the borate, phosphate, boric acid, and phosphoric acid is approximately 1:1, the cations may be in excess. Alternatively, the anion may be in excess, and preferably, after the addition step, an alkaline hydroxide solution is added to bring the pH of the suspension to 8.5 to 9.8.

[0009] 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 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. The water-soluble rare earth compound may be lanthanum borate or lanthanum phosphate.

Further, the discharge lamp of the present invention is characterized in that it is manufactured by the above method for manufacturing a phosphor coating liquid.

[0011]

[Operation] A phosphor is suspended in an aqueous binder solution.
．． By adding an aqueous solution of a water-soluble rare earth compound equivalent to 0.001 to 5 g and an aqueous solution of at least one of borates, phosphates, boric acid, and phosphoric acid, compared to the case of adding a particulate binder, , the amount of binder added 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, whereas for discharge lamps using fine particle binders, the luminous flux maintenance rate is lower than the standard. Those using the binder of the present invention are better than the standard.

[0012] Furthermore, the water-soluble binder of the present invention allows
Since uniform and stronger film strength can be obtained, it is particularly effective for annular lamps that require high film strength. Furthermore, by raising the pH of the suspension from 8.5 to 9.8, the viscosity of the coating liquid, which conventionally occurs due to low pH, can be reduced.
There is no generation of mold or the like when the coating liquid is left unused, and the existing equipment used in the coating process is highly durable and does not deteriorate.

[0013]

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

(Example 1) 217.2 g of a calcium halophosphate phosphor is suspended in 200 g of a 0.5% polyethylene oxide aqueous solution. To this suspension, 5.26 g of a lanthanum nitrate aqueous solution (containing 17.6% as lanthanum) which is 0.5% by weight as lanthanum oxide based on the phosphor, and BO
3 as 19.4% ammonium borate aqueous solution 2.0
Add 3g and mix the suspension thoroughly. 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.

Since the pH of the phosphor coating liquid of this example is 9.0, it can be used without causing any damage to existing equipment for the phosphor coating process in discharge lamps. There was almost no decrease in viscosity even after leaving it for one month.

Next, a 40 WSS straight tube fluorescent lamp was manufactured as follows using the phosphor coating liquid thus obtained. That is, the above phosphor coating liquid was applied to a straight tube 40WSS.
Coated on the inner surface of the glass bulb, and then heated in an electric furnace for 58 hours.
After baking at 0° C. for 15 minutes and cooling, both ends of the glass bulb were evacuated and filled with ordinary rare gas and mercury (Hg), and a cap was attached.

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 3,250 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 3120 lm, which was about 15% lower than the initial luminous flux. Approximately 4 for luminous flux
It decreased by only %.

In addition, 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.
The amount of peeling was about 6 mm, which was excellent compared to 0 mm or more.

(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. 105 g of a three-wavelength phosphor mixed with europium-activated yttrium oxide phosphor was suspended in 150 g of a 0.5% polyethylene oxide aqueous solution. To this suspension, 2.54 g of a lanthanum nitrate aqueous solution (17
．． (containing 6%) and 1.54 g of a 19.9% phosphoric acid aqueous solution as PO4 were added and mixed thoroughly. While stirring this suspension, adjust the pH of the suspension to 9.0 with aqueous ammonia.
A phosphor suspension was prepared by raising the temperature to .

Since the pH is around 9.0, the phosphor coating solution of this example can also be used without damaging existing equipment for the phosphor coating process in discharge lamps.
Even after being left for 14 days, there was almost no decrease in viscosity.

A fluorescent lamp similar to that of Example 1 was manufactured using the above phosphor coating liquid, but the luminescent color and color rendering properties of this fluorescent lamp did not change, and the film strength did not change with 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 about 15 mm in the case of aluminum oxide, whereas in this example it was around 5 mm, and excellent film strength was obtained.

[0023] 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 3550 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.

[0024] 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 a water-based binder solution suitable for the aqueous binder may be used. It goes without saying that water-soluble cellulose (HPC.CMC) and water-soluble acrylate (PMA), as well as surfactants and antifoaming agents associated with these may be added as appropriate.

[0025]

[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, and this method In a discharge lamp manufactured using a phosphor coating liquid according to the present invention, a phosphor film with strong film strength and an excellent coated surface can be obtained, and both initial luminous flux and luminous flux maintenance rate are excellent.

Claims (7)

[Claims] Claim 1: A phosphor is suspended in an aqueous binder solution,
To this suspension solution, an aqueous solution of a water-soluble rare earth compound corresponding to 0.001 to 5 g of rare earth oxide per 100 g of the phosphor, and an aqueous solution of at least one of borates, phosphates, boric acid, and phosphoric acid. 1. A method for producing a phosphor coating liquid, which comprises adding. 2. A claim characterized in that the cations of the water-soluble rare earth compound aqueous solution are added in an excess proportion than the anions of the aqueous solution of at least one of the borate, phosphate, boric acid, and phosphoric acid. A method for producing a phosphor coating liquid according to item 1. 3. Claim 1, wherein the anion of the aqueous solution of at least one of the borate, phosphate, boric acid, and phosphoric acid is added in excess of the cation of the aqueous solution of the water-soluble rare earth compound. A method for producing a phosphor coating liquid as described in . 4. A ratio of cations in the water-soluble rare earth compound aqueous solution to anions in the aqueous solution of at least one of the borate, phosphate, boric acid, and phosphoric acid is approximately 1:1. A method for producing a phosphor coating liquid according to claim 1. 5. The water-soluble rare earth compound and the aqueous solution of at least one of borates, phosphates, boric acid and phosphoric acid are the same and are lanthanum borate and/or lanthanum phosphate. The method for producing a phosphor coating liquid according to claim 1. 6. After the addition step, an alkali hydroxide solution is added to adjust the pH of the suspension to 8.5 to 9.8. A method for producing a phosphor coating liquid as described in 2. 7. A discharge lamp manufactured by the method for manufacturing a phosphor coating liquid according to claim 1.