JPH0330427B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for manufacturing a fluorescent lamp, and more particularly to a method for electrostatically coating the inner surface of a glass tube for a fluorescent lamp with phosphor powder. Conventional structure and problems Conventionally, in order to electrostatically coat the inner surface of a glass tube for fluorescent lamps with phosphor powder, the glass tube is a non-conductor, so it was necessary to uniformly heat the glass tube with a burner. , to lower this electrical resistance, apply a high voltage between the electrostatic coating nozzle and the burner, insert the nozzle into this through one opening of the glass tube, rotate the glass tube, and retreat the nozzle. However, charged phosphor powder is sprayed from the injection hole of the nozzle and coated on the inner surface of the glass tube, but uncoated fluorescent powder is ejected from the other opening of the glass tube. Generally, body powder is collected using a dust collector. However, this recovered phosphor powder is contaminated with dust, dirt, etc. from the atmosphere, and the recovered phosphor is colored black, and a fluorescent lamp electrostatically coated using this recovered phosphor powder has a low luminous flux. It was difficult to reuse the recovered phosphor due to the significant decrease in the luminance. OBJECTS OF THE INVENTION The present invention provides a method for manufacturing a fluorescent lamp, which enables the reuse of recovered phosphors and suppresses deterioration in lamp characteristics, particularly luminous flux, even when recovered phosphors are used. Structure of the Invention The present invention is a method of electrostatically coating the inner surface of a glass tube for a fluorescent lamp with a phosphor powder made by mixing unused phosphor powder with recovered phosphor. By heating the tube to a temperature 20°C to 70°C higher than the maximum adhesion temperature of the body and further heating the electrostatically coated glass tube, the reduction in luminous flux due to the use of recovered phosphor is suppressed. Description of Examples The present invention will be described below. The amount of recovered phosphor described above depends on the phosphor powder injection air pressure, the voltage applied between the burner and the nozzle, and the heating temperature of the glass tube. The state of body membranes is greatly affected. This is due to the electrical resistance of the glass tube, and if this electrical resistance is too high or too low, the amount of phosphor recovered will increase and the condition of the phosphor film surface will also deteriorate. By the way, the heating temperature of the glass tube mentioned above varies greatly depending on its material, so it cannot be set uniformly.
When a glass tube is heated to around 10 ⁷ Ω·cm and electrostatically coated, a large amount of phosphor powder adheres to the tube, reducing the amount of phosphor powder recovered. Here, the temperature of the glass tube at this time is referred to as the phosphor maximum adhesion temperature. Next, an example in which soda glass is used as a glass tube for a fluorescent lamp will be described. SiO ₂ 72 as soda glass tube for fluorescent lamps
%, _{Al2O3 1.5} %, MgO2.5%, CaO5.4%,
Na ₂ O 16.9%, K ₂ O 1.1%, Sb ₂ O ₃ 0.4%, SO ₃ 0.1%
When using a composition consisting of the following, the maximum adhesion temperature of the phosphor in electrostatic coating is 250°C. When the glass tube is heated to this temperature and electrostatic coating is performed, the recovery rate of the phosphor powder is still about 23%, and a large amount of colored phosphor powder is recovered. When the luminance of the recovered phosphor was measured, assuming that the luminance of the new phosphor (hereinafter referred to as unused phosphor) was 100, it was found that the luminance had significantly decreased to 69. However, it can be said that discarding approximately 23% of this recovered phosphor is problematic from the standpoint of cost and resource conservation. Therefore, the inventor conducted various studies and experiments on methods for reusing recovered phosphor powder. That is, an attempt was made to mix recovered phosphor powder with unused phosphor powder and use it. First, when 40% by weight of recovered phosphor with a brightness of 69 is mixed with unused phosphor with a brightness of 100,
The luminance of this mixed phosphor was 81. next,
This mixed phosphor powder is electrostatically coated on the inner surface of the soda glass tube for the fluorescent lamp by heating the glass tube to a temperature of 250°C, which is the maximum temperature at which phosphors adhere, and then the phosphor is removed from the glass tube. When I stripped it off and measured the brightness, the brightness was 86. Furthermore, this painted glass tube was heated to 700℃ in a heating furnace to burn and scatter the impurities in the phosphor film, and then the phosphor was stripped from the glass tube and the brightness was measured, and the brightness was 90. . However, since a brightness of 90 was still insufficient, the inventors decided to increase the brightness from 81 to 90, as described above.
As a result of examining various factors that lead to 86 and making prototype lamps, we found that the brightness of the phosphor electrostatically coated on the inner surface of the glass tube changes significantly depending on the temperature at which the glass tube is heated during electrostatic coating. It was discovered that the decrease in initial luminous flux can be suppressed more than before. Such a phenomenon does not appear in electrostatic coating using only unused phosphor powder, but is a unique phenomenon that occurs when recovered phosphor powder is mixed with unused phosphor powder. In other words, a mixed phosphor with a luminance of 81, which is a mixture of recovered phosphor with a luminance of 69 and 40% by weight of unused phosphor, was used, and by varying the heating temperature of a soda glass tube for a fluorescent lamp, static electricity was generated on the inner surface of the glass tube. After painting, the phosphor was removed from the glass tube and the brightness of the phosphor was measured, with the results shown in the table below.
The table also shows the above results. In addition,
The number of samples is 8 each.

[Table] As is clear from the above table, by increasing the heating temperature of the glass tube by 20 degrees Celsius above the maximum adhesion temperature of the phosphor, the luminance of the phosphor becomes 88, and after further heating in a heating furnace, the luminance becomes 92. I understand that. On the other hand, if the heating temperature of the glass tube is less than 20° C. higher than the maximum phosphor deposition temperature, the brightness will be less than 92 even if heated in a heating furnace, and the initial luminous flux will not improve much. Also, from the maximum adhesion temperature of the phosphor
Even if the temperature exceeds 70° C., no improvement in the brightness of the phosphor can be expected, and the high temperature not only increases the cost but also makes the phosphor film surface rough, which is not preferable. Therefore, by increasing the heating temperature of the glass tube for fluorescent lamps by 20 to 70 degrees Celsius above the temperature at which most phosphors adhere, the brightness of the phosphor can be improved and a dense phosphor film surface can be obtained. It is. Of course, the above results can be obtained not only when soda glass is used as the glass tube for a fluorescent lamp, but also when glass made of lead glass or the like is used. Next, examples of the present invention will be shown. The recovered phosphor powder is mixed with 40% by weight of the unused phosphor powder to obtain a mixed phosphor powder. The luminance of the recovered phosphor was 69, but the luminance of this mixed phosphor was
It was 82. This mixed phosphor powder is then electrostatically coated on the inner surface of a glass tube for a fluorescent lamp, which has been heated to a temperature 60°C higher than the maximum adhesion temperature of the phosphor, and then the glass tube is heated to about 700°C in a heating furnace. The impurities in the phosphor film were fired and scattered, and a 30W round fluorescent lamp was manufactured using the usual method.The initial luminous flux was measured and a good result of 1800m was obtained. In addition, the phosphor is stripped from the glass tube,
When the brightness was measured, the brightness was 98, which was almost the same as when only unused phosphor was used. Furthermore, using the above mixed phosphor, the heating temperature of the glass tube was adjusted to 20°C, 30°C, and 40°C above the maximum adhesion temperature of the phosphor.
℃ and 50℃, a 30W round fluorescent lamp was manufactured in the same manner as above, and the initial luminous flux was measured, and the results shown in Figure 2 were obtained. In addition,
The figure shows the case where the heating temperature of the glass tube is the maximum phosphor adhesion temperature (represented as 0℃) and
The case where the temperature is 10℃ higher is also shown. Effects of the Invention As explained above, the present invention is a method for manufacturing a fluorescent lamp that can suppress a decrease in luminous flux as much as possible even when recovered phosphor is used, and is therefore excellent in terms of cost and resource saving. This is something that can be provided.

[Brief explanation of drawings]

The figure is a diagram showing the relationship between the heating temperature of the glass tube and the initial luminous flux compared to the maximum adhesion temperature of the phosphor during electrostatic coating.

Claims (1)

[Claims] 1. On the inner surface of a glass tube for a fluorescent lamp, apply a phosphor powder made by mixing unused phosphor powder with recovered phosphor powder.
A method for manufacturing a fluorescent lamp, which comprises performing electrostatic coating while heating to a temperature higher than 70°C, and further heating a glass tube coated with this mixed phosphor.