JPH05320636A - Phosphor for fluorescent lamp - Google Patents

Abstract

PURPOSE:To obtain a phosphor which can give a fluorescent lamp having excel lent luminous flux retention and excellent start-up characteristics and not caus ing the blackening of tube ends by adhering magnesium hydroxide and lantha num hydroxide to the surfaces of the phosphor particles. CONSTITUTION:Fired phosphor particles (e.g. europium (II)-activated strontium pyrophosphate particles) for a fluorescent lamp are thoroughly suspended in ion-exchanged water. An aqueous solution containing manganese ions and an aqueous solution containing lanthanum ions are added to this suspension under agitation, and an aqueous alkali hydroxide solution is added dropwise to the resulting suspension to adjust its pH to about 10-12, whereby magnesium hydroxide and lanthanum hydroixde are deposited on the surfaces of the phosphor particles in the suspension. After stopping the agitation, the suspension is left at rest to precipitate the phosphor particles, the supernatant liquid is discarded, deionized water is added again, and the resulting mixture is agitated. This operation is repeated several times. The phosphor particles are then separated and dried to produce the objective phosphor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phosphor for a fluorescent lamp, and more particularly to a phosphor capable of improving the luminous flux maintenance factor of the fluorescent lamp and the blackening of the tube end.

[0002]

2. Description of the Related Art It is known that when a fluorescent lamp is turned on for a long time, the luminous flux of the lamp decreases. The cause of the decrease in luminous flux has not been fully clarified yet, but the cause is the discoloration of the glass bulb due to the reaction of Na and mercury in the glass bulb. Decrease in luminous efficiency due to adsorption of mercury on phosphor. Generation of color center of phosphor by 185 nm mercury beam. It is believed that most of them are caused by the reaction between mercury and a fluorescent substance or between mercury and a glass bulb.

As a method of preventing the adsorption of mercury and improving the luminous flux maintenance factor, for example, a method of providing a protective film of alumina, magnesium oxide or the like on the inner surface of the glass bulb, a method of containing a metal oxide in the glass bulb, or a fluorescent light is used. A method of mixing a white substance such as alumina or magnesium oxide into the body has been carried out, and Japanese Patent Application Laid-Open No. 61-23678 discloses a method of forming a continuous alumina coating on the surface of the phosphor.

Meanwhile, SnO _2, In ₂ O rapid-start type fluorescent lamps, called NESA film as a starting aid
_{3. A} transparent conductive film made of conductive metal oxide such as ITO is provided. By providing this nesa film, the light emission starting voltage of the fluorescent lamp is lowered, and the lamp can be turned on without using the lighting tube. It is known to be possible. Also in this rapid start type fluorescent lamp, in addition to the improvement of the luminous flux maintenance rate as in the case of a normal fluorescent lamp, it is desired to make the light emission starting voltage of the lamp as low as possible, that is, to improve the starting characteristics of the fluorescent lamp.

It prevents the adsorption of mercury on the phosphor, and
As a technique for improving the starting characteristics of a rapid start type fluorescent lamp, in Japanese Patent Application No. 3-204869, we have proposed a technique in which a fluorescent substance for a lamp is surface-treated with magnesium hydroxide to positively charge the fluorescent substance surface. Proposed.

[0006]

Although the above-mentioned technique surely improves the lamp starting characteristics and the luminous flux maintenance factor, only the filament periphery is limited depending on the type of the lamp, the fluorescent film forming method, etc., as in the conventional fluorescent lamp. However, there is still an inadequate point with respect to the problem called tube-end blackening, in which mercury is adsorbed on the fluorescent material and the fluorescent film is blackened in a ring shape.

Therefore, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fluorescent lamp having an excellent luminous flux maintenance rate and an excellent starting characteristic, and a tube end black. The present invention provides a fluorescent substance for a lamp, which is for realizing a fluorescent lamp that does not cause deterioration.

[0008]

Means for Solving the Problems As a result of improving the phosphor surface by applying various treatments to the phosphor, which has been previously developed by the present inventors, the phosphor surface-treated with magnesium hydroxide was used. The inventors have newly found that the above problem can be solved by adding a specific substance to magnesium hydroxide and adhering it to the present invention, and the present invention has been accomplished. That is, the lamp phosphor of the present invention is characterized in that lanthanum hydroxide is attached to the surface of the phosphor in addition to magnesium hydroxide.

The adhered amount of magnesium hydroxide is usually about 5% by weight or less, more preferably 0.01% to 2.0, based on the amount of Mg contained in the phosphor.
It is preferable to adjust the content within the range of wt%. As magnesium hydroxide adheres, the phosphor becomes positively charged, preventing the adsorption of mercury and improving the luminous flux maintenance rate of the fluorescent lamp.
If the amount exceeds 5% by weight, the phosphors tend to aggregate in the coating slurry, making it difficult to obtain a uniform phosphor screen. Further, there is a tendency that improvement of luminous flux maintenance of the fluorescent lamp and improvement of starting voltage of the rapid start type fluorescent lamp cannot be expected.

The amount of lanthanum hydroxide attached can be adjusted to about 1% by weight or less, more preferably 0.05% to 0.5% by weight, in terms of the amount of La contained therein. preferable. As lanthanum hydroxide is attached,
It works effectively with the magnesium hydroxide for maintaining the luminous flux, but if it is adhered in an amount of more than 1% by weight, the initial luminous flux of the lamp is lowered, which is not so preferable. On the other hand, magnesium hydroxide does not reduce the initial luminous flux.

The phosphor of the present invention can be obtained, for example, by the method described below. First, the phosphor for a fluorescent lamp that has been baked is put into ion-exchanged water and sufficiently suspended. While stirring this suspension, an aqueous solution containing magnesium ions and an aqueous solution containing lanthanum ions were added, and then an aqueous alkali hydroxide solution was added dropwise to adjust the pH to 10
Adjust to ~ 12. By adjusting the pH to the alkaline side, magnesium hydroxide and lanthanum hydroxide deposited in the suspension adhere to the phosphor. After they adhere to the phosphor, stop stirring and let stand. After waiting for the phosphor to settle, the supernatant is discharged, pure water is added again, and the phosphor is washed with water by stirring. This operation is repeated 2-3 times. Then, the phosphor of the present invention can be obtained by separating and drying the phosphor according to a conventional method.

The phosphor used in the present invention can be any phosphor as long as it is a phosphor for a lamp. For example, a halophosphate phosphor represented by antimony activated calcium halophosphate phosphor, a phosphate phosphor represented by divalent europium activated strontium pyrophosphate, and a silicic acid represented by manganese activated zinc silicate phosphor. Salt phosphors, tungstate phosphors typified by calcium tungstate, aluminate phosphors typified by divalent europium activated barium magnesium aluminate phosphors, typified by trivalent europium activated yttrium oxide phosphors Examples thereof include rare earth phosphors.

As the aqueous solution containing magnesium ions to be added, for example, an aqueous solution of magnesium halide such as MgCl ₂ or MgF ₂ or a water-soluble magnesium salt such as Mg (NO ₃ ) ₂ or MgSO ₄ can be used. Further the aqueous solution containing lanthanum ions LaCl _3, LaI ₃ and halogenated lanthanum, an aqueous solution of _{La (NO) 3, La (} CH 3 COO) 3 aqueous lanthanum salts and the like can be used.

Further, when manufacturing a fluorescent lamp using the phosphor of the present invention, a phosphor slurry in which an organic / inorganic binder and a phosphor are mixed is applied to a glass bulb and dried, and then the organic substance is removed. In order to form the fluorescent screen, there is a step of baking the glass bulb at a temperature of 500 ° C. or higher for several minutes. In this step, magnesium hydroxide and lanthanum hydroxide attached to the phosphor of the present invention partially change to oxides, but this does not particularly affect the characteristics of the fluorescent lamp.

[0015]

The function of the phosphor of the present invention is as follows:
By attaching lanthanum hydroxide in addition to magnesium hydroxide, which is easily charged, blackening of the tube end is less likely to occur and deterioration of the luminous flux is less. Further, as will be described later, lanthanum hydroxide also acts as a binder for the fluorescent substance to the glass bulb, and has an action of improving the binding force. Further, in the rapid start type fluorescent lamp, there is an effect that the light emission starting voltage can be lowered by the positive charging property of magnesium hydroxide.

[0016]

EXAMPLES The phosphor of the present invention will be described in detail in the following examples.

[Example 1] Cool Whi was placed in a beaker containing 100 ml of ion-exchanged water (hereinafter referred to as water).
Te antimony and manganese-activated calcium halophosphate phosphor 100 g were added and well stirred to suspend the phosphor. 1% Mg (NO ₃ ) ₂ content converted to Mg in the suspension
20 ml of the aqueous solution and 20 ml of the La-converted content 1% La (NO ₃ ) ₃ aqueous solution were added. After the addition, 2% aqueous ammonia was added dropwise to the suspension with stirring to adjust the pH to 10.6 to precipitate magnesium hydroxide and lanthanum hydroxide. While the pH was maintained at 10.6, stirring was continued for 30 minutes to uniformly deposit the precipitated magnesium hydroxide and lanthanum hydroxide on the phosphor. After that, stirring was stopped, and the supernatant was discarded after waiting for the phosphor to settle, water was added again, and the phosphor was washed with water. After washing the phosphor 2-3 times with water, the suspension was transferred to a nutche lined with filter paper and suction-filtered to separate the phosphor. The separated phosphor is dried at 150 ° C. for 5 hours,
The phosphor for a lamp of the present invention was obtained by passing through a 250 mesh screen.

30 g of the phosphor thus obtained and 1%
30 g of a nitrocellulose-butyl acetate solution was mixed with 0.5 g of CBBP (a mixture of calcium barium borate and calcium phosphate) as a binder to form a phosphor coating slurry.

According to a conventional method, this coating slurry was applied to an FL40SS bulb whose inner surface was preliminarily coated with SnO ₂ as a conductive oxide film and then dried to obtain 6
After firing at 00 ° C. for 5 minutes to form a fluorescent film, a base was attached to manufacture a rapid start type fluorescent lamp.

[Examples 2 to 6] The same as Example 1 except that the addition amounts of the magnesium aqueous solution and the lanthanum aqueous solution were appropriately changed to change the attached amounts of magnesium hydroxide and lanthanum hydroxide as shown in Table 1. After obtaining the phosphor of the present invention, a rapid start type fluorescent lamp was produced in the same manner.

[Comparative Examples 1 to 3] For the same phosphor as in Example 1, as shown in Table 1, a phosphor to which only magnesium hydroxide was attached, a phosphor to which only lanthanum hydroxide was attached, Also, a fluorescent lamp was produced in the same manner for the fluorescent material to which nothing was attached, and the fluorescent lamp was evaluated in the following manner together with the fluorescent lamp made of the fluorescent material of the present invention. The results are shown together in Table 1.

In this table, the amounts of Mg (OH) ₂ and La (OH) ₃ attached to the phosphor are all Mg and L.
The luminous flux maintenance factor is shown as the a conversion amount, and the luminous flux is measured as the initial luminous flux after 30 minutes from the time when the lamp is lit and the lamp is stabilized,
The luminous flux after continuous lighting for 1000 hours is shown by the luminous flux maintenance ratio with respect to the initial luminous flux. Further, the starting voltage (Vs) indicates the voltage required for lighting the lamp at a constant current value, and the tube end blackening occurs when the blackening occurs at the tube end within 200 hours after continuous lighting of the lamp in x, and 200 to 1000 hours. The results are determined by visual observation, with Δ being the one and ◯ being the one that did not occur even after 1000 hours or more. Margin below

[0023]

[Table 1]

As shown in Table 1, the rapid start type fluorescent lamp using the phosphor of the present invention is excellent in the luminous flux maintenance factor and can lower the light emission starting voltage. Further, in the case of magnesium hydroxide alone or lanthanum hydroxide alone, the tube end blackening occurred, whereas when both coexisted, the tube end blackening did not occur at all, and very good characteristics were shown.

Further, although not particularly shown in the table, the glass bulb was flipped with a piano wire from a certain distance with a certain force, so that the fluorescent lamp obtained in Example 1 and the fluorescent lamp of Comparative Example 3 were When the peeling of the fluorescent film was tested, the fluorescent film of the lamp of Comparative Example 3 was peeled off by 10 cm ² or more, whereas the fluorescent film of the lamp of the present invention was peeled off by 5 cm ² or less. From this, it was found that the lanthanum hydroxide attached to the phosphor of the present invention also has a function as a binder for increasing the binding force between the phosphor and the glass bulb.

[0026]

As described above, the phosphor of the present invention is
Since magnesium hydroxide and lanthanum hydroxide are attached to the surface of the particles, it is possible to improve the luminous flux maintenance factor of the fluorescent lamp and the blackening of the tube end. Can be lowered. Also, the binding force of the fluorescent film can be increased.

Claims (1)

[Claims] 1. Magnesium hydroxide on the surface of phosphor particles,
And phosphor to which lanthanum hydroxide is attached.