JP3336598B2 - Capillary fluorescent lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin tube fluorescent lamp used for a backlight of a liquid crystal display and the like, and more particularly to a thin tube fluorescent lamp having improved light emission luminance.

[0002]

2. Description of the Related Art A liquid crystal display is widely used for a display of a notebook personal computer or a word processor, and an extremely thin fluorescent lamp called a thin tube fluorescent lamp is used for a liquid crystal backlight. A great deal of research has been conducted on fluorescent lamps for lighting from the development stage to the present, with the result that the performance of fluorescent lamps has been greatly improved. However, the tube-type fluorescent lamp has only a short history, and the best performance has not yet been achieved.

For example, a fluorescent lamp for general illumination has a tube diameter of about 12 mm to 36 mm, whereas a thin tube fluorescent lamp is as thin as 4 mm to 6 mm, and recently a very thin fluorescent lamp having a diameter of 3.6 mmφ or less is used. Is being produced. However, optimization based on the research on the physical properties is hardly performed, and the technology used for the fluorescent lamp for illumination is simply applied to the thin-tube fluorescent lamp as it is. In the current design of the tube-type fluorescent lamp, the discharge phenomenon of the fluorescent lamp and the excitation efficiency of the phosphor should be further reexamined.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to form a phosphor layer suitable for a discharge structure of a thin tube fluorescent lamp in order to further improve the emission luminance of the thin tube fluorescent lamp.

[0005]

Means for Solving the Problems The present inventor has made intensive studies on a phosphor layer most suitable for improving the emission luminance of a tubular fluorescent lamp for the purpose of solving the above-mentioned problems.
In addition, the inventors have found that the problem can be solved by coating the phosphor layer in a rough state, and have completed the present invention.

That is, the tubular fluorescent lamp of the present invention is
A translucent glass tube filled with a sealing gas containing mercury and a rare gas, a phosphor layer containing phosphor particles provided on the inner wall surface of the translucent glass tube, and maintaining a positive discharge in the sealing gas. A fluorescent lamp comprising:
The tube diameter of the fluorescent lamp is 3.6 mm or less, and the phosphor coating amount per unit area of the phosphor layer is 3 to 8 mg / cm.
2, and the porosity represented by the following formula is 40 to 80%.
It is characterized by being. Porosity e = (Vl−Vp) / Vl × 100 (%) Vl; phosphor layer volume Vp; phosphor volume

The tube diameter of the fluorescent lamp to which the present invention is preferably applied is limited, and the effect cannot be expected unless the diameter is 3.6 mmφ or less. If the tube diameter is larger than this, the difference in the discharge phenomenon between the fluorescent lamp for general illumination and the narrow tube-type fluorescent lamp becomes smaller, and a remarkable effect cannot be obtained.

The amount of the phosphor applied is 3 to 8 mg.
/ Cm2, and more preferably in the range of 4 to 7 mg / cm2. This is 2-4mg which is usually used for general lighting
It can be understood that the application amount is considerably larger than that in the range of / cm <2>.

Further, the central technology of the present invention is that the luminosity of a thin-tube fluorescent lamp can be greatly improved by defining the porosity and setting a specific porosity for the phosphor layer occupied by the phosphor. . The porosity is calculated by the above formula, and is preferably in the range of 40 to 80%, particularly 50 to 80%.
Is more preferable.

When the porosity is large, the phosphor layer becomes coarse, the phosphor density of the phosphor layer decreases, and the phosphor layer thickness (film thickness) increases. In the case of a fluorescent lamp for general illumination, the higher the density, that is, the lower the porosity, the higher the emission luminance. In general, fluorescent lamps for general lighting have a porosity of 20
It is used in the range of ４０40%. It is common sense to form a phosphor layer in this range, and in this regard, the thin tube fluorescent lamp behaves exactly the opposite.

As a specific method of setting the porosity of the phosphor layer to a target range, a method of controlling the concentration of an organic binder used for preparing a phosphor suspension, a method of controlling the particle size of the phosphor, and the like are possible. is there. For example, by increasing the binder concentration, the viscosity of the phosphor suspension is increased, and the resulting phosphor layer is thicker than the one using a low-viscosity suspension with the same coating amount. Alternatively, the phosphor layer thickness can be increased by broadening the particle size distribution of the phosphor.

[0012]

FIG. 1 shows a fluorescent lamp for general illumination having a tube diameter of 26.
The relationship between the relative luminous brightness and the porosity e in the case of a glass tube having a diameter of 2.5 mm and in the case of a thin tube fluorescent lamp having a diameter of 2.6 mm is shown. Here, 5 mg /
A three-wavelength mixed phosphor of cm 2 is applied. The porosity was changed by changing the organic binder concentration of the application suspension. As is clear from FIG. 1, when the porosity exceeds 45%, the relative light emission luminance decreases in the case of a fluorescent lamp having a tube diameter of 26 mm, but is improved in the case of a thin tube fluorescent lamp having a tube diameter of 2.6 mm. .

This phenomenon is closely related to the distribution of Hg (I) line intensity in the positive column formed by the low-pressure mercury discharge in the glass bubble. The Hg (I) ray emits 253.7 nm ultraviolet light, has the highest intensity in low-pressure mercury vapor discharge, and is used for 90% or more of the excitation of the phosphor applied to the fluorescent lamp. The intensity distribution in the radial direction from the center of the Hg (I) 253.7 nm line is high at the center as shown in FIG. 2 and decreases with distance. The electron distribution also tends to gradually decrease as the distance from the tube center increases, as calculated by the Bessel function.

In the case of a relatively thick fluorescent lamp having a tube diameter of 15 mm or more, the radiation intensity of the Hg (I) 253.7 nm line gradually decreases as the distance from the tube to the tube increases due to elastic collision of Hg and electrons. In contrast, Hg (I) 253.
In order to efficiently absorb the 7 nm line, it is necessary to efficiently output visible light from the phosphor excited and emitted on the discharge portion side of the phosphor layer to the outside of the fluorescent lamp. In order to use ultraviolet rays most efficiently, it is advantageous that the phosphor forms a dense phosphor layer.

On the other hand, the situation is slightly different in the case of a thin tube fluorescent lamp having a tube diameter of 3.6 mm or less. Hg
(I) Since the intensity of the 253.7 nm line has a distribution structure as shown in FIG.
The entire glass tube shows almost the same value as the ultraviolet intensity distribution at the center of the tube, and the ultraviolet intensity does not decrease even on the tube wall coated with the phosphor.

Therefore, the influence of the 253.7 nm line of Hg (I) generated in the gap between the phosphor layers (between the phosphor particles) cannot be ignored. In such a case, it is possible to efficiently excite the phosphor by using more ultraviolet light generated in the gap between the phosphors as shown in FIG. 3A than by using a phosphor layer having a small gap as shown in FIG. 3B. As a result, the lamp brightness can be increased. As described above, in the case of the thin tube fluorescent lamp, it is preferable that the porosity is large in order to effectively use the Hg (I) 253.7 nm line near the phosphor layer.

Further, since the porosity is large, light emitted from the phosphor is not absorbed by other phosphors, and can be efficiently output.
As a result, the brightness increases.

[0018]

EXAMPLE In this example, one method of controlling the porosity e was carried out by changing the concentration of an organic binder used in a phosphor-coated suspension.
Other than this, a method such as controlling the particle size of the phosphor can be applied, and the method is not limited by the present embodiment.

[Example 1] Mixing ratio: BaMg2Al16O27: Eu 40% as blue light emitting phosphor LaPO4: Ce, Tb 30% as green light emitting phosphor Y2O3: Eu30% as red light emitting phosphor The bodies are mixed to give a total density of 4.6 g / cm3 triple wavelength mixed phosphor. Nitrocellulose / butyl acetate 1.6 seconds for 2000 seconds with respect to 100 g of the obtained mixed phosphor.
% Solution is added, a binder is added if necessary, and the mixture is stirred to prepare a slurry in which the phosphor is dispersed.

The obtained phosphor suspension was placed in a glass tube (tube diameter: 2.6 mm, tube length: 200 m) of a thin tube type fluorescent lamp.
m), and the coated surface was dried with warm air. By measuring the weight of the coating bulb obtained after drying, the total weight of the phosphor layer is obtained, and the amount of coating per unit area is calculated by dividing by the coating surface area. In this example, 5.2 mg / cm 2 was obtained.

Thus, the volume Vp of the phosphor particles is as follows: Vp = (5.2 × 10 −3 g) / (4.6 g / cm 3) =
1.13.times.10@-3 cm @ 3.

When the thickness of the coated glass bulb was measured, it was 27 μm. In this case, the phosphor layer volume Vl per unit area is as follows: Vl = (2.7.times.10@-3 cm) .times.1 cm @ 2 = 2.7 cm @ 3

From these, the porosity e is calculated by the following equation. Porosity e = (Vl−Vp) / Vl × 100 (%) = (2.7−1.13) /2.7×100=58%

[Examples 2 to 11] When the porosity is higher than in Example 1, the concentration of the nitrocellulose / butyl acetate solution is increased, and when the porosity is low, the concentration of the nitrocellulose / butyl acetate solution is increased. I went by lowering it. When the phosphor coating amount is increased, 100 g of the mixed phosphor is used.
In the case where the amount of the nitrocellulose / butyl acetate solution is reduced and the amount of the phosphor applied is reduced, the amount can be controlled by increasing the amount of the nitrocellulose / butyl acetate solution. However, these are relative and may vary even if the type of phosphor, the particle size of the phosphor, and the drying conditions are changed, so that an optimization trial must be performed each time.

Comparative Example 1 Same Mixed Phosphor 1 as in Example 1
To 100 g, 100 g of a nitrocellulose / butyl acetate 1.0% solution for 2000 seconds is added and stirred to prepare a slurry in which the phosphor is dispersed. A coated glass bulb of a thin tube fluorescent lamp was obtained in the same manner as in Example 1.

[Comparative Examples 2 to 6] As in the example, when the porosity is increased, the concentration of the nitrocellulose / butyl acetate solution is increased, and when the porosity is decreased, the concentration of the nitrocellulose / butyl acetate solution is increased. Was made lower. When the phosphor coating amount is increased, 100 g of the mixed phosphor is used.
In the case where the amount of the nitrocellulose / butyl acetate solution is reduced and the amount of the phosphor applied is reduced, the amount can be controlled by increasing the amount of the nitrocellulose / butyl acetate solution.

The glass bulbs obtained in Examples 1 to 11 and Comparative Examples 1 to 6 were baked and mounted with electrodes by a usual method to obtain a cold cathode fluorescent lamp. The relative luminance of the obtained cold cathode fluorescent lamp with respect to the comparative example was determined and summarized in Table 1. The luminance was measured at the center of the fluorescent lamp.

[0028]

[Table 1]

It can be seen from Table 1 that the emission luminance of the thin tube fluorescent lamp is greatly improved by increasing the porosity. In addition, since the amount of application per unit area is large due to the large number of voids, luminance saturation does not occur up to a position where the amount of application is larger than that of a general fluorescent lamp. As a result, the application amount of the phosphor can be increased, and the luminance of the thin-tube fluorescent lamp can be greatly improved.

[0030]

As described above, according to the present invention, a large gap is provided between the phosphor particles in the coating film, and the coating amount is increased to a specific range, so that the tube diameter becomes 3.6 mm.
The brightness of the following tubular fluorescent lamps can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing a relationship between relative light emission luminance and porosity e of a tube-type fluorescent lamp of the present invention, a comparative product, and a general fluorescent lamp.

FIG. 2 shows the distance from the pipe center to the pipe radial direction and Hg (I) 25.
3.7nm line intensity distribution

FIG. 3 is a view showing a gap of a phosphor occupying a phosphor layer;

[Explanation of symbols]

 1 ... phosphor particles 2 ... translucent glass

Claims (1)

(57) [Claims] 1. A light-transmitting glass tube filled with a filling gas containing mercury and a rare gas, a phosphor layer containing phosphor particles provided on an inner wall surface of the light-transmitting glass tube, and in the fluorescent lamp and means for maintaining in sunlight discharge, before Symbol pipe diameter of the fluorescent lamp is not more than 3.6 mm, the phosphor coating amount per unit area of the phosphor layer 3
細 8 mg / cm 2, and the porosity represented by the following formula is 40-80%. Porosity e = (Vl−Vp) / Vl × 100 (%) Vl; phosphor layer volume Vp; phosphor volume