JPS63168933A - Formation of phosphor film - Google Patents

Abstract

PURPOSE:To allow high-speed production by inserting a nozzle in turn into a bulb through both opening ends of the bulb while slantly holding the bulb, injecting air to dry a phosphor suspension, further holding the bulb vertically to dry the phosphor suspension. CONSTITUTION:A glass bulb 1 is slantly held so that the angle between the vertical axis and a plane containing both leg sections of the glass bulb 1 is made about 3 deg.. An air injecting nozzle 2 is inserted into the glass bulb 1 through one of its opening ends along its center lined, and air is injected through the air injecting nozzle 2 for a fixed time. This work is repeated, and first the phosphor suspension coated on the bent portion of the U-shaped glass bulb 1 is dried. Then, the holding state of a vertical state, and the phosphor suspension coated on both leg sections of the glass bulb 1 is dried by natural drying.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for forming a phosphor coating on the inner surface of a U-shaped bulb.

Conventional technology Highly efficient, long-life fluorescent lamps have been made more compact in size, such as single-base fluorescent lamps in which the cap is combined into one end, and bulb-base fluorescent lamps in which the ballast and lighting tube are integrated with the arc tube. In today's era of energy saving, it has become an important power source for lighting. Fluorescent lamps with a compact design using a folded discharge path method are usually manufactured using a U-shaped bulb in order to ensure mechanical strength. However, in a bulb having such a shape, both open ends are located in one direction, so the process of forming a phosphor coating on the inner surface of the bulb is significantly different from that for a straight tube bulb. That is,
In the case of a straight tube bulb, hold the bulb vertically, pour the phosphor suspension from the upper open end to coat the inner surface, then let the excess liquid drip from the lower open end, and pour the phosphor suspension from the upper open end. A uniform phosphor coating can be obtained over the entire length of the bulb by blowing air into the bulb. But U
In the case of a type valve, air can only be blown from the lower open end. In the case of a compact design, the inner diameter of the valve is usually as small as 18 mm or less. As a result, if the air blowing flow rate is increased (the film surface becomes rough), and conversely, if the same flow rate is restricted, the phosphor film near the opening end of the bulb becomes very thick (but the film thickness at the upper part of the bulb, i.e., the bent part) becomes very thick. Fluorescent lamps with such non-uniform phosphor coatings have a thin film thickness per unit area at the bent portion of the bulb, leading to early blackening and difficulty maintaining luminous flux. resulting in a decrease in rate.

Problems to be Solved by the Invention In order to form a uniform and sufficiently thick phosphor coating over the entire length of the U-shaped bulb, it is necessary to increase the coating thickness at the bent portion of the bulb. An effective way to do this is to blow air into the valve to speed up the drying of this area. Therefore, the air blowing nozzle is usually installed below the opening end of the valve and in the vicinity of the opening end. Even in this case, if the air flow rate is such that the phosphor film does not become noticeably uneven, it is necessary to
Drying is promoted only within the range of III+.

For example, U with an inner diameter of 13.5 mm and a length of 100 aun or more
In the case of a shaped bulb, the amount of phosphor deposited per unit area of the bent portion is not increased. In such cases, the purpose can be achieved by extending the air blowing nozzle and inserting it into the valve. However, in either case, the phosphor suspension dripping from the open end of the bulb adheres to the nozzle, requiring frequent cleaning of the nozzle, which becomes a serious hindrance during high-speed production.

As a countermeasure to this problem, it has been proposed to hold the U-shaped valve at an angle so that excess liquid drips only from the lowest end of the valve opening, and to install the air blowing nozzle to avoid that dripping position. (Unexamined Japanese Patent Publication No. 1983-13)
Publication No. 8826).

However, according to this method, since the U-shaped bulb is held obliquely throughout, there is a problem in that the thickness of the phosphor coating inevitably varies in the circumferential direction of the bulb's cross section.

The present invention has been made to solve these problems, and is designed to prevent excess phosphor suspension dripping from the open end of the U-shaped bulb from adhering to the air blowing nozzle, and to The present invention provides a method for forming a phosphor film that eliminates irregularities in the thickness of the phosphor film in the cross-sectional circumferential direction of a shaped bulb.

Means for Solving the Problems The method for forming a phosphor film of the present invention includes a U-shaped bulb whose inner surface is coated with a phosphor suspension, with the open end facing downward, and including a vertical axis and both legs of the bulb. While holding the bulb at an angle so that the angle with the surface is 3 degrees or more, nozzles are alternately inserted into the bulb from both open ends and air is blown into the phosphor suspension. The bulb is further dried by changing the tilted holding of the bulb to the vertical holding to dry the phosphor suspension, thereby forming a phosphor coating on the inner surface of the bulb.

With this configuration, all excess phosphor suspension droplets dripping from the open end of the bulb fall from the lowest end of the open end. Therefore, no problems such as droplet adhesion occur on the nozzle. Also, by blowing air into the U-shaped bulb, the phosphor suspension applied to the bent portion of the U-shaped bulb is first dried. Next, the phosphor suspension applied to the legs of the bulb is dried. Therefore, unevenness in the thickness of the phosphor coating in the circumferential direction of the cross section of the U-shaped bulb can be eliminated.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a side view for explaining the present invention in detail.

In FIG. 1, 1 is a U-shaped glass bulb, and 2 is an air blowing nozzle that can move forward and backward in diagonal directions.

First, the upper bent part of the U-shaped glass bulb 1 is hooked onto the hook 5 (see Figure 2), and the lower legs are held with spring holders (not shown) to hold the glass bulb 1 vertically. After applying the phosphor suspension to the inner surface of the glass bulb 1 from the lower opening end while holding the glass bulb 1, excess phosphor suspension is discharged from the glass bulb 1. This glass bulb 1 has an inner diameter of 13.5+mn and a total length of 180mm.

Next, remove the lower part of the glass bulb 1 from the spring holder, and as shown in FIG. The glass bulb 1 is held tilted so that θ is about 3°. While the glass bulb 1 is stationary in this held position, the air blowing nozzle 2 is inserted into the glass bulb 1 from one open end along its center line as shown in FIG. Blow nozzle 2
Air is blown in for a certain period of time. Then, the air blowing nozzle 2 is moved backward and taken out from the glass bulb 1, the glass bulb 1 is moved by one position, and the air blowing nozzle 2 is inserted from the other open end of the glass nozzle bulb 1 into its center. After inserting it along the line and blowing air from the air blowing nozzle 2 for a certain period of time, the air blowing nozzle 2 is moved back. By repeating this operation over several positions, the phosphor suspension applied to the bent portion of the U-shaped glass knob 1 is first dried.

The excess phosphor suspension remaining in the glass bulb 1 drips from the lowest end 4 of the open end 3 of the glass bulb 1 as shown by arrow A in FIG. Will not stick. Thereafter, the holding state of the glass bulb 1 is changed from the inclined state to the vertical state, and the phosphor suspension applied to both legs of the glass bulb 1 is dried by natural drying. By adopting such a drying method, the phosphor coating formed on the inner surface of the glass bulb 1 in the cross-sectional circumferential direction does not have any density or density, and also has a uniform thickness over the entire length including the bent portion. It is possible to obtain a phosphor coating of approximately 100 mL.

If the inclination angle θ of the glass bulb 1 is less than 3°, the excess phosphor suspension will be removed from the lowermost end 4 of the glass bulb 1.
Since the liquid drips from other places as well, the object of the present invention cannot be achieved.

The air blowing nozzle 2 has an inner diameter of 21 m1, and the insertion length of the air blowing nozzle 2 into the glass bulb 1 is 100 mm. At a temperature of 30° C. and a flow rate of 5 e/min, the air blowing nozzle 2 was inserted into both legs of the glass bulb 1 alternately for 4 seconds six times to blow air into the inside thereof. Thereafter, the tilted holding state of the glass bulb 1 was changed to the vertical holding state, and air drying was performed without blowing air, etc., to form a phosphor coating on the inner surface of the glass bulb 1. When the amount of phosphor adhered per unit area of the formed phosphor film was examined, the results were as shown in the table below.

(Unit: mg/cn?) As is clear from the above table, the method of the present invention resulted in a more uniform amount of phosphor deposited over the entire length of the glass bulb than the conventional method. At the same time, no density or density of the phosphor coating in the circumferential direction was observed due to the tilted holding of the glass bulb.

A U-shaped single-cap fluorescent lamp was manufactured using the phosphor-coated glass bulb obtained by the method of the embodiment of the present invention, and its operating characteristics were investigated. In addition, no discoloration of the phosphor occurred at the bent portion, and an extremely good luminous flux maintenance rate was exhibited.

As described in detail, according to the method of the present invention, the phosphor suspension dropped from the open end of the bulb does not adhere to the nozzle, so high-speed production is possible.
Moreover, it is possible to form a uniform phosphor film in both the circumferential direction and the length direction of the bulb, and it is possible to reduce the thickness of the film in localized areas. The produced single-cap fluorescent lamp has no deterioration in operating characteristics due to partial discoloration of the phosphor, and can maintain a good appearance and high lamp efficiency until the end of its life, which is extremely effective.

[Brief explanation of the drawing]

FIG. 1 is a side view for explaining the present invention in detail, and FIG. 2 is a front view. 1...Glass bulb, 2...Air blowing nozzle, 3...Opening end of glass bulb,
4... Bottom end of the glass bulb. Name of agent: Patent attorney Toshio Nakao and one other person T-U type glass bulbs Figure 2 J

Claims (1)

[Claims] The opening end of a U-shaped bulb whose inner surface is coated with a phosphor suspension is directed downward, and the bulb is tilted so that the angle formed between the vertical axis and a plane including both legs of the bulb is 3° or more. The phosphor suspension is dried by alternately inserting nozzles into the bulb from both open ends and blowing air while holding the bulb vertically. A method for forming a phosphor film, comprising forming a phosphor film on the inner surface of the bulb by drying a phosphor suspension.