JPS5918107B2 - Keiko Lamp Nosaident Souhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for electrostatically coating the inner surface of a bulb for a fluorescent lamp with a phosphor.

J ・■ Conventionally, butyl acetate was used to coat the inner surface of a fluorescent lamp bulb with a phosphor, a solution with nitrocellulose as a binder or city water was used, and an aqueous solution with an aqueous binder was used. A wet coating method is used in which a phosphor is dispersed and suspended and such a suspension is poured into a glass tube.

However, such a wet coating method requires a large amount of equipment and time to dry butyl acetate and water, and also requires 50% of the binder.
It must be removed by firing at a temperature of 00 to 600°C, which consumes a large amount of energy such as electricity and gas, and the firing process has a large effect on the luminance of the phosphor, the luminous flux of the lamp, and the maintenance rate. It had drawbacks such as being difficult to manage.
In order to improve these drawbacks, a method for dry coating the phosphor inside the glass tube is required, and research has been conducted on methods for electrostatic coating of the phosphor. However, fluorescent lamps have a narrow bulb diameter of 25 to 38 mm, and it is difficult to obtain a paint film with uniform coating thickness and strong adhesion over the pipe length range of 300 to 2,400 mm. However, a perfect coating method has not yet been established. 5. The present invention applies a phosphor coating with a uniform thickness over the length of the bulb and increases the adhesion strength.

As a result of various experiments, it was found that the uniformity and adhesion strength of the coating largely depended on the electrical charge of the powder, and it was found that most phosphor powders have a positive electrical charge of 6 to 8 KV I found out.

In order to electrostatically deposit the powder and increase the uniformity and adhesion strength of the coating, a high voltage with a polarity opposite to that of the powder's charge must be applied to the bulb side. Therefore, we used a coating device equipped with a roller for rotating the Nu-bulb, a linear burner for heating, and a phosphor injection nozzle that could move forward and backward, and applied a high voltage of approximately 20 to 25 KV so that the burner was negative and the nozzle positive. A coating experiment was conducted by placing the bulb on a rotating roller, rotating it, heating it, and spraying the phosphor from the nozzle. First, FIG. 1 shows the adhesion state and film thickness of the phosphor 3 when the nozzle 2 is inserted into the bulb 1, the nozzle 2 is fixed, and the phosphor 3 is ejected.

: A large amount of the phosphor 3 adheres over a range of about 20 to 30 mm (V7l) from a position approximately 3 to 5 cm in front of the tip of the nozzle 2, and the amount of phosphor 3 adhered is extremely small in front of it. Therefore, the thickness of the phosphor film 4 is thicker on the insertion end side and thinner on the other end side.

The reason why the phosphor hardly adheres to the area approximately 3 to 5 cm forward from the tip of the nozzle 2 is that in this range, the phosphor 3 tends to adhere to the inner surface of the bulb 1 due to electrostatic force. This seems to be because the air pressure for ejecting the phosphor from the nozzle 2 is stronger, so even if the phosphor 3 were to adhere to this part, it would be blown away by this air pressure. In this part, the air directly hits the inner surface of the valve 1. In the above case, the adhesion strength of the phosphor film 4 was strong in the thickly adhered parts, and weak in other parts. In this state, it cannot be put to practical use, so
Next, we experimented by moving the nozzle, and as shown in Figure 2, we inserted the nozzle 2 close to the other end of the bulb 1, and while retracting the nozzle 2 at a constant speed, It has been found that the thickness of the phosphor film 4 becomes more uniform than in the case described above.

Moreover, the film strength was strong overall and suitable for practical use. However, in this case, as shown in FIG. 3, if the ejection of the phosphor 3 was stopped just before the nozzle 2 exited from one end of the bulb 1, a phenomenon occurred in which the film thickness in front of the nozzle 2 became thinner. .

When used as a lamp, the thin part of the film would be in contact with the electrodes, making the electrodes transparent and the cathode spots appearing bluish-white, making them extremely unsightly. Therefore, in order to improve this drawback, as shown in Fig. 4, we tried spraying the phosphor 3 until the nozzle 2 came out from one end of the bulb 1, but the improvement effect was large, although the improvement was only slight. I stopped talking. In order to eliminate this drawback, the nozzle shape, dimensions,
Experiments were repeated with various changes in the injection air pressure, but no favorable results were obtained. However, by inserting the nozzle 2 from one end of the bulb 1 to near the other end and then retracting the nozzle 2 while ejecting the phosphor 3, the retraction speed of the nozzle 2 is gradually reduced.
It has been found that the uniformity of the phosphor coating 4 is significantly improved (see FIG. 5).

In other words, the valve is retracted at a constant speed until about 1/2 of the total length of the valve, and then the retraction speed to the nozzle insertion end is gradually reduced, so that the speed at which nozzle 2 exits valve 1 is the same as that of the first valve. By setting the length up to 1/2 at about 1/2 of the retracting speed, a phosphor coating 4 which was uniform over the entire length of the bulb and had strong adhesion strength was obtained. By the way, even with this method, the front part of nozzle 2
The phosphor 3 does not adhere to the range of 5CWL.

However, it is rather preferable that the phosphor does not adhere to this range, and as shown in Figure 6, when sealing the electrodes after painting, 4 to 5 cf.
The phosphor film at the n portion needs to be removed in order to improve the sealing properties of the glass, and even if there is an uncoated portion at the end on the nozzle insertion side, there is no practical problem. Also, when applying a phosphor to a bulb with a total length of 1,200mm or more, if you try to insert a nozzle from one end of the bulb to the other for painting, the total length of the nozzle will become longer, and the center of the bulb and nozzle will be longer. The deviation from the axial center became large, resulting in a problem of lack of uniformity of the coating.

Therefore, a uniform phosphor coating was obtained by inserting nozzles from both ends of the bulb and ejecting the phosphor while gradually reducing the speed by retracting the nozzles. In this case, the length of each nozzle is 1/2 of the entire valve.
It may be shorter than the following, and excellent results were obtained whether the phosphor was ejected from both nozzles at the same time or from one nozzle at a time. Example 1 Inner diameter 32mm, total length 640.1! m(7) While rotating the FL-20 type soda lime glass tube at 100 times per minute,
Heat to approximately 350℃ with a heating linear burner, and set the burner to negative.
A high voltage of 20K with positive polarity is applied to the nozzle.

Then, insert a nozzle with a length of 60011 mm into the rotating bulb from one end to the other end, and spray the calcium halophosphate phosphor along with the compressed air flow until it reaches about 1/2 of the entire length of the bulb. Reverse the nozzle at a speed of 600 mm per second, then gradually reduce the nozzle retract speed to 300 m2 per second! ! Paint deposition was carried out by passing the nozzle through the valve insertion end at a speed of . Excess powder was collected in a bag filter. Example 2 An FL-40W type soda lime glass tube was rotated at a speed of 100 times per minute and heated to approximately 350μ with a heating linear burner. Apply voltage.

Then, a nozzle with a length of 400 mm is inserted into the rotating bulb from both ends, and the calcium halophosphate phosphor is injected together with a stream of compressed air. When the nozzle has retreated to about 1/2 the length of the insertion part of the nozzle, gradually reduce the retreat speed and pass both nozzles through the insertion end of the valve at a speed of 300 pus per second to perform paint deposition. did. Excess powder was collected using a back filter. The phosphor coating obtained in each example was uniform over the entire length of the bulb, and when measuring the transmittance of each part, the transmittance was 30 (arbitrary unit) at the center of the bulb, and 30 at each end.
The thickness was very constant at 1.30 mm, the adhesion strength was strong, and after the coating was applied, baking was not required as in the conventional method, and the lamp luminous flux increased by about 4%.

Note that the same effect can be obtained with other phosphors other than calcium halophosphate phosphor, and a trace amount of dispersion in the phosphor,
A binder may be mixed.

[Brief explanation of drawings]

Figures 1 to 5 are cross-sectional views showing various states in which the phosphor sprayed from the nozzle adheres to the bulb, and Figure 6 shows the state with both ends of the phosphor film attached to the bulb removed. FIG. 1...Valve, 2...Nozzle, 3...
... phosphor, 4... phosphor membrane.

Claims (1)

[Claims] 1 Connect a high voltage generator so that the nozzle is positive and the bulb heating burner is negative, insert the nozzle from one or both ends of the heated bulb, and while retracting the nozzle, remove the phosphor from the nozzle. A method of spraying a fluorescent lamp, the method comprising: spraying the phosphor while gradually reducing the retraction speed of the nozzle, and coating the inner surface of the bulb with the phosphor. Electrostatic painting method.