JPH0992215A - Fluorescent lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration in the performance of a fluorescent lamp such as a color rendering characteristic, luminance or the like caused by a protection film, prevent the deterioration in the function as the protection film under the manufacturing conditions of various kinds of fluorescent lamps, and improve the luminance itself. SOLUTION: On the inner surface 3a of a glass tube 3 in which ionization medium including mercury is sealed and on which a pair of electrodes 2 are arranged at its both ends, a coated film 4 having fluorescent ultra fine particles of the average particle dia. 150nm or less is formed as an ultraviolet ray reflection and absorbing film (protection film). A light emitting layer 5 made of coated film having one or two kinds of fluorescent particles is formed thereon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorescent lamp in which an undercoat layer as an ultraviolet reflection / absorption film improves the luminous efficiency of a light emitting layer.

[0002]

2. Description of the Related Art Fluorescent lamps are used for general lighting, and recently, for light sources for OA equipment, pixel light sources for huge screens,
Widely used in various fields such as backlights for liquid crystal displays. In such a fluorescent lamp,
The effectiveness of various non-emissive granular material films formed as an undercoat layer of a light emitting layer composed of a coating film of phosphor particles has been recognized. In a fluorescent lamp, ultraviolet rays generated by mercury discharge stimulate phosphors in a light emitting layer to emit light, and this luminous efficiency is improved by back reflection of incident incident light emitted from the light emitting layer.

For example, in fluorescent lamps, a non-luminous granular material film as a protective film (undercoat layer) is used as an ultraviolet reflecting film or an ultraviolet absorbing film. As the non-luminous granular material, silicon dioxide or dioxide is used. Titanium, aluminum oxide, cerium oxide and the like are used (see JP-A-63-58756 and JP-A-63-58756).
Cerium oxide is used as the ultraviolet reflecting film.
In order to function as a protective film, it is first important not to absorb any visible light emitted by the phosphor.

[0004] In addition, in a lamp not using a protective film, the glass forming the lamp may be directly irradiated with ultraviolet rays that have passed through the light emitting layer, or the glass and mercury may react with each other, resulting in the solarization of soda glass. Due to this, there is a problem that deterioration of luminous flux and apparent color shift occur. The UV reflection and absorption layer effectively functions to prevent such problems.

On the other hand, however, the fluorescent lamp using the protective film has the following problems as compared with the fluorescent lamp not using the protective film. First, when titanium oxide or the like is used, since titanium oxide or the like absorbs ultraviolet rays and blue light, the light color of the fluorescent lamp is different from that of a normal lamp, and there is a problem that the color rendering property is deteriorated. Further, when used in a ring-type fluorescent lamp, the heat treatment temperature for bending the glass is high, so that the glass is vitrified and the effect as a protective film cannot be obtained. When alumina is used,
There is a drawback that the protective film itself is easily peeled off.

[0006]

As described above, the protective film formed as the undercoat layer of the light emitting layer enhances the luminous efficiency of the phosphor forming the light emitting layer and contributes to the improvement of the emission brightness. In addition, although various effects such as prevention of solarization of glass tubes have been recognized, the protective film used in conventional fluorescent lamps absorbs ultraviolet rays and blue light to lower the color rendering properties, etc. Moreover, particularly in the case of the ring-type fluorescent lamp, there is a problem that the function of the protective film is impaired in the manufacturing process, and the protective film is peeled off. In addition to these, further improvement in brightness is required in order to improve the performance of fluorescent lamps.

As described above, in the conventional fluorescent lamp, the deterioration of the lamp performance such as color rendering and brightness due to the protective film is suppressed, and the function as the protective film is impaired under the manufacturing conditions of various fluorescent lamps. It has been a problem to prevent the above and to improve the emission brightness itself of the fluorescent lamp.

The present invention has been made in order to solve such a problem, and after effectively preventing the deterioration of the lamp performance by the protective film and the deterioration or loss of the function of the protective film itself, the lamp by the protective film is provided. It is an object of the present invention to provide a fluorescent lamp capable of sufficiently obtaining the effect of improving the performance and further improving the emission brightness itself.

[0009]

The fluorescent lamp of the present invention comprises:
As described in claim 1, a glass tube in which an ionizable medium containing mercury is enclosed and a pair of electrodes is arranged at both ends, and an average particle diameter formed on the inner surface of the glass tube 1
It is characterized by comprising a coating film of phosphor ultrafine particles of 50 nm or less and a light emitting layer formed on the coating film of the phosphor ultrafine particles, which is formed of a coating film of one or more kinds of phosphor particles. There is.

As described in claim 2, the fluorescent lamp of the present invention is characterized in that, in the above-mentioned fluorescent lamp, the light emitting layer comprises a coating film of spherical phosphor particles having an average particle diameter of 1 μm or more. .

The coating film of the phosphor ultrafine particles having an average particle diameter of 150 nm or less has both ultraviolet reflectiveness and visible light transmissive properties because it is ultrafine particles. Therefore, the function as a protective film can be sufficiently obtained without inhibiting the light emission from the light emitting layer. Further, the coating film of the phosphor ultrafine particles reflects ultraviolet rays and absorbs a part of the ultraviolet rays, so that the phosphor ultrafine particles themselves emit light. This makes it possible to improve the emission brightness itself of the fluorescent lamp. Further, by using spherical phosphor particles having an average particle diameter of 1 μm or more in the light emitting layer, the visible light transmittance of the light emitting layer itself is improved, so that the emission brightness of the fluorescent lamp can be further improved.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Modes for carrying out the present invention will be described below.

FIG. 1 is a partial cross-sectional view showing the structure of an embodiment in which the fluorescent lamp of the present invention is applied to a straight tube type fluorescent lamp. The fluorescent lamp 1 shown in the figure has a glass tube 3 on which electrodes 2 and 2 are attached inside both ends.
On the inner surface 3a of the glass tube 3, a coating film 4 of phosphor ultrafine particles having an average particle diameter of 150 nm or less is formed as an undercoat layer. A light emitting layer 5 made of a coating film of phosphor particles is provided on the coating film 4 of the phosphor ultrafine particles. The glass tube 3 is filled with an ionizing medium containing mercury to form the fluorescent lamp 1.

A coating film of the above-mentioned phosphor ultrafine particles (hereinafter,
The phosphor ultrafine particle film 4 has both ultraviolet light reflectivity and visible light transmissive property because the phosphor that constitutes it is ultrafine particles. Therefore, the phosphor ultrafine particle film 4 effectively functions as an ultraviolet reflecting film without inhibiting light emission from the phosphor forming the light emitting layer 5. The ultraviolet light reflected by the ultraviolet reflective film is indirectly absorbed by the light emitting layer 5 formed on the ultraviolet light reflecting film, and as a result, the phosphor particles forming the light emitting layer 5 are not limited to the surface facing the discharge space. Therefore, it is also excited from the surface on the opposite side to efficiently emit light.

Further, the phosphor ultrafine particle film 4 scatters (reflects) ultraviolet rays, and also absorbs part of the ultraviolet rays so that the phosphor ultrafine particles themselves emit light. Thereby, for example, the light emitting layer 5
If the weight of the phosphor particles constituting the same is the same, it is possible to improve the brightness compared to the conventional fluorescent lamp in which the ultraviolet reflecting film is formed of alumina particles or titanium dioxide particles, and to obtain the same brightness. Can reduce the weight of the phosphor constituting the light emitting layer 5 to reduce the manufacturing cost.

As described above, the phosphor ultrafine particle film 4 has a mean particle size of 150 nm or less in order to make the phosphor ultrafine particle film 4 function as an ultraviolet reflecting film and efficiently transmit visible light. Use ultrafine particles. That is, in the reflection of light by fine particles, the particle size of the strongest reflection is generally determined by the following relational expression.

[0017]

[Equation 1] Therefore, it efficiently reflects (scatters) ultraviolet light with a wavelength of 254 nm.
In addition, phosphor ultrafine particles having an average particle diameter of 150 nm or less are used so that visible light having a wavelength of 400 to 750 nm is sufficiently transmitted. When the average particle size of the phosphor ultrafine particles exceeds 150 nm, the visible light transmittance is reduced together with the ultraviolet ray reflection efficiency. The average particle size of the phosphor ultrafine particles is more preferably in the range of 10 to 100 nm, and even more preferably in the range of 10 to 50 nm. Further, even if the average particle size is in the range of 150 nm or less,
If the abundance of coarse particles is high, the transmittance of visible light and the reflectance of ultraviolet rays may be reduced. Therefore, the proportion of particles having a particle diameter of 300 nm or more is preferably 5 number% or less.

Such ultrafine-particle phosphor powder is vaporized in high-frequency thermal plasma having a boiling point or sublimation point of a normal phosphor (raw phosphor) or higher, and then cooled and solidified. Can be easily obtained. The phosphor ultrafine particles thus produced include many particles having a particle size of 100 nm or less, and are suitable for producing the phosphor ultrafine particle film 4. In addition, it is effective for ultraviolet ray reflectivity and visible light transmissivity to remove particles of 150 nm or more by classification to sharpen the particle size distribution.

As described above, when the raw material phosphor is subjected to thermal plasma treatment, the evaporated raw material phosphor becomes ultrafine particles,
The melted raw material phosphor becomes spherical. Not only can the phosphor ultrafine particles be used for producing the phosphor ultrafine particle film 4, but the spherical phosphor particles can be used for producing the light emitting layer 5 described in detail later. Thus, by treating the phosphor with the thermal plasma, it is possible to simultaneously obtain the manufacturing materials for both the phosphor ultrafine particle film 4 and the light emitting layer 5.
In addition, the phosphor ultrafine particles produced by thermal plasma treatment are
Unlike ultra-fine particles produced by a wet method, etc., it has high crystallinity because it is produced at high temperatures, and even if it is exposed to high temperatures in the manufacturing process of fluorescent lamps, it does not cause vitrification or decomposition. Absent. Therefore, the function as the protective film is not impaired even after the high temperature heat treatment. This is particularly effective for a ring fluorescent lamp that is heat-treated at a high temperature.

In the above-mentioned phosphor ultrafine particle film 4, the amount of the phosphor ultrafine particles deposited on the inner surface 3a of the glass tube 3 is preferably in the range of 5 to 500 μg / cm ² . If the coating amount of the ultrafine phosphor particles is less than 5 μg / cm ² , the above-mentioned ultraviolet ray reflection effect may not be obtained sufficiently efficiently, while if it exceeds 500 μg / cm ² , visible light from the light-emitting layer 5 may be exceeded. There is a possibility that the permeability of the may decrease. The coating amount of the ultrafine phosphor particles is more preferably in the range of 5 to 50 μg / cm ² .

The phosphor used for forming the phosphor ultrafine particle film 4 is preferably the same as the phosphor generally used in a fluorescent lamp. For example, phosphate complex phosphors, halophosphate phosphors, silicate phosphors, tungstate phosphors, aluminate phosphors, germanate phosphors, arsenate phosphors, and other complex acid salt phosphors. And rare earth oxide phosphors. The fluorescent substance for these lamps is 254
Since it is a material that efficiently absorbs the wavelength of nm, and does not absorb in the blue region around 400 nm, color shift due to the conventional protective film using titanium dioxide particles does not occur. Further, the phosphor ultrafine particle film 4 is preferably formed of a phosphor having the same composition as that of the phosphor forming the light emitting layer 5, whereby color shift or the like can be prevented. The light emitting layer 5
In the case of forming a mixed phosphor by mixing a plurality of phosphors, it is preferable to use a phosphor having the same composition as at least one kind of the mixed phosphor.

The coating film 4 of the phosphor ultra-fine particles can be formed only with a solvent such as water or alcohol without using a binder, but the phosphor ultra-fine particles may be coated with a binder. In that case, as a binder, a nitrocellulose dissolved in butyl acetate, a water-soluble binder such as ammonium polymetaacrylate, or the like that is used for coating the fluorescent film of the lamp is used, and the same coating process is applied. Can be formed.

The light emitting layer 5 formed on the phosphor ultrafine particle film 4 as described above can be formed of various phosphor particles similar to a general fluorescent lamp, for example, monochromatic phosphor particles, A mixture of phosphor particles that emit blue, green, and red colors, to which blue-green phosphor particles that enhance color rendering, deep red phosphor particles, and the like are further added. Depending on the emission color 2
There is no particular limitation to the type of phosphor, such as a mixture of more than one type of phosphor particles.

The shape of the phosphor particles forming the light emitting layer 5 is not particularly limited, but spherical phosphor particles, particularly spherical phosphor particles having an average particle diameter in the range of 1 to 20 μm, are preferably used. By forming the light emitting layer 5 with spherical phosphor particles, the visible light transmittance of the light emitting layer 5 itself is improved, and the brightness of the fluorescent lamp 1 can be improved. The average particle size of the spherical phosphor particles is more preferably in the range of 1 to 10 μm. Further, in the case of spherical phosphor particles, there is an advantage that the phosphor ultrafine particles and the thermal plasma treatment can be simultaneously obtained as described above.

The above-described embodiment is an application of the present invention to a straight tube type fluorescent lamp, but the fluorescent lamp of the present invention has various shapes such as a ring type fluorescent lamp, a U type fluorescent lamp and a paddle type fluorescent lamp. Can be applied to the above fluorescent lamps, and the same effects as those of the above-described embodiments can be obtained.

[0026]

EXAMPLES Specific examples of the present invention will be described below.

Example 1 and Comparative Example 1 First, a raw material phosphor (calcium halophosphate phosphor) having an average particle size of about 7 μm was melted by a high frequency thermal plasma method, partially vaporized, and then cooled, A fine particle phosphor and a spherical phosphor were prepared at the same time. These were classified to obtain calcium halophosphate phosphor ultrafine particles having an average particle diameter of 30 nm and calcium halophosphate spherical phosphor particles having an average particle diameter of 5 μm. The ratio of particles having a particle size of 300 μm or more in the phosphor ultrafine particles was 1 number% or less.

First, the above-mentioned calcium halophosphate phosphor ultrafine particles were used and applied on the inner surface of the tubular glass tube at an adhesion amount of 0.5 mg / cm ² . Next, calcium halophosphate spherical phosphor particles were applied at an adhesion amount of 4.5 mg / cm ² . Then, while enclosing a small amount of mercury and Ar rare gas in the glass tube, and attaching a base (including an electrode),
A 40 watt straight tube fluorescent lamp with a tube diameter of 32 mm was manufactured by a usual method. The fluorescent lamp thus produced did not cause peeling of the phosphor ultrafine particle film.

On the other hand, as Comparative Example 1 of the present invention, the above calcium halophosphate phosphor having an average particle diameter of 7 μm was directly used and 4.5 mg / cm ² on the inner surface of the tubular glass tube.
It was applied directly with the attached amount of. Then, a small amount of mercury and Ar noble gas are enclosed and a mouthpiece is attached, and the pipe diameter of 40 mm
A watt straight tube fluorescent lamp was produced.

A lighting test of each fluorescent lamp according to Example 1 and Comparative Example 1 was conducted. Table 1 shows the results. The lumen ratio in Table 1 is a value when the lumen of the fluorescent lamp according to Example 1 after one hour of lighting is 100.

[0031]

[Table 1] As is clear from Table 1, the fluorescent lamp of Example 1 has significantly improved brightness as compared with the lamp of Comparative Example 1 in which the protective film is not formed.

Example 2 Raw materials for each phosphor shown below were melted by a high frequency thermal plasma method, partially vaporized, and then cooled to prepare phosphor ultrafine particles. And the average particle size 30
nm 2 (Sr _0.98 Eu _0.02 O) ・ 0.84P ₂ O ₅・ 0.16B ₂
O ₃ phosphor ultrafine particles 46 parts by weight, average particle size 20 nm (S
r, Mg) ₃ (PO ₄ ) ₂ : Sn phosphor ultrafine particles 48 parts by weight, Zn ₂ SiO ₄ : Mn phosphor ultrafine particles 1 part by weight having an average particle diameter of 20 nm, and Ca ₁₀ (P
O ₄ ) ₆ (F, Cl) ₂ : Sb, Mn phosphor ultrafine particles 5
Parts by weight were mixed and suspended in butyl acetate. This suspension was applied on the inner surface of the tubular glass tube at a deposition amount of 0.5 mg / cm ² .

Next, each of the above-mentioned phosphors (average particle diameter of about 3 μm) before being treated with high-frequency thermal plasma was mixed and coated on the coating film of the above-mentioned phosphor ultrafine particles at a deposition amount of 4.5 mg / cm ² . .
Then, a small amount of mercury and a rare gas of Ar were enclosed and a base was attached to produce a 40 watt straight tube fluorescent lamp having a tube diameter of 32 mm, which was subjected to the characteristic evaluation described later. This lamp is a high color rendering fluorescent lamp with an average color rendering index Ra of 98 and a color temperature of 5000K. The fluorescent lamp thus produced did not cause peeling of the phosphor ultrafine particle film.

Example 3 Ultrafine phosphor particles were produced by melting the following raw materials for each phosphor by a high frequency thermal plasma method, partially vaporizing them, and then cooling them. And the average particle size 30
nm 2 (Sr _0.98 Eu _0.02 O) ・ 0.84P ₂ O ₅・ 0.16B ₂
O ₃ phosphor ultrafine particles 46 parts by weight, average particle size 20 nm (S
r, Mg) ₃ (PO ₄ ) ₂ : Sn phosphor ultrafine particles 48 parts by weight, Zn ₂ SiO ₄ : Mn phosphor ultrafine particles 1 part by weight having an average particle diameter of 20 nm, and Ca ₁₀ (P
O ₄ ) ₆ (F, Cl) ₂ : Sb, Mn phosphor ultrafine particles 5
Parts by weight were mixed and suspended in butyl acetate. This suspension was applied onto the inner surface of a tubular glass tube at an adhesion amount of 0.5 mg / cm ² and baked.

Next, each of the above phosphors (average particle diameter of about 3 μm) before being treated with the high frequency thermal plasma was mixed and coated on the coating film of the above phosphor ultrafine particles in an amount of 3.0 mg / cm ² . .
Then, a small amount of mercury and a rare gas of Ar were enclosed and a base was attached to produce a 40 watt straight tube fluorescent lamp having a tube diameter of 32 mm, which was subjected to the characteristic evaluation described later. This lamp is a high color rendering fluorescent lamp with an average color rendering index Ra of 98 and a color temperature of 5000K. The fluorescent lamp thus produced did not cause peeling of the phosphor ultrafine particle film.

Comparative Example 2 The above phosphors having an average particle diameter of 3 μm used in Example 2 were mixed and directly coated on the inner surface of a tubular glass tube at an adhesion amount of 4.5 mg / cm ² . Then, a small amount of mercury and a rare gas of Ar were enclosed and a base was attached to manufacture a 40 watt straight tube fluorescent lamp having a tube diameter of 32 mm.

Lighting tests of the fluorescent lamps of Examples 2 and 3 and Comparative Example 2 were conducted. The results are shown in Table 2. The lumen ratio in Table 2 is the value after each lighting time when the lumen of the fluorescent lamp according to Example 2 after one hour lighting is 100.

[0038]

[Table 2] As is clear from Table 2, the fluorescent lamp of Example 2 is brighter than the fluorescent lamp of Comparative Example 2 in which the protective film is not formed, and the luminous flux maintenance factor after long-time lighting is also improved. I understand. Further, it can be seen that the fluorescent lamp of Example 3 manufactured by reducing the weight of the phosphor has the same brightness as the fluorescent lamp of Comparative Example 2 in which the protective film is not formed. That is, when a fluorescent lamp having the same brightness as the fluorescent lamp of Comparative Example 2 is manufactured with the configuration of the present invention, the amount of phosphor can be reduced by nearly 30%. That is, the cost of the phosphor could be reduced by nearly 30%.

Example 4, Comparative Example 3 Y ₂ O ₃ : Eu phosphor was melted by a high frequency thermal plasma method, partially vaporized and then cooled to prepare ultrafine phosphor particles and spherical phosphor particles. did. The average particle size of the ultrafine phosphor particles was about 40 nm, and the average particle size of the spherical phosphor particles was about 5 μm. Ultrafine phosphor particles were suspended in a mixed solvent of butyl acetate and nitrocellulose. This suspension was applied on the inner surface of the tubular glass tube at a deposition amount of 0.5 mg / cm ² .

Next, spherical phosphor particles were coated on the coating film of the above-mentioned phosphor ultrafine particles at an adhesion amount of 4.0 mg / cm ² . Then, while enclosing a small amount of mercury and Ar noble gas in the glass tube, and attaching the base (including the electrode),
A watt straight tube fluorescent lamp was produced.

On the other hand, as a comparative example 3 with the present invention, the Y ₂ O ₃ : Eu phosphor (average particle size 4.5
μm) was applied on the inner surface of the tubular glass tube at a deposition amount of 4.0 mg / cm ² . Then, a small amount of mercury and a rare gas of Ar were enclosed, and a base was attached to manufacture a 40 watt straight tube fluorescent lamp with a tube diameter of 32 mm.

A lighting test of each fluorescent lamp according to the above-mentioned Example 4 and Comparative Example 3 was conducted. Table 3 shows the results.

[0043]

[Table 3] As is clear from Table 3, the fluorescent lamp of Example 4 is brighter than the lamp of Comparative Example 3 which does not use the ultrafine particles and the spherical phosphor.

Example 5, Comparative Example 4 Y ₂ O ₃ : Eu phosphors were melted by a high frequency thermal plasma method, partially vaporized and then cooled to prepare ultrafine phosphor particles. The average particle size of the phosphor ultrafine particles was about 30 nm. The phosphor ultrafine particles were suspended in a 1 wt% nitrocellulose + butyl acetate solution. This suspension
The amount of 0.5 mg / cm ² was applied to the inner surface of the tubular glass tube.

Next, Y ₂ O ₃ : Eu phosphor, LaPO 4
: Ce, Tb phosphor, (Sr, Ca) ₅ (PO ₄ ) ₃
Cl: Eu phosphor, (Ba, Ca, Mg) ₅ (PO ₄ ).
Cl: Eu phosphor, and Mg-fluorogermanate: Mn
Mixing phosphors, 4.0m on the coating film of the phosphor ultrafine particles
The amount applied was g / cm ² . Then, a small amount of mercury and a rare gas of Ar were sealed in the glass tube, and a base (including an electrode) was attached to manufacture a 40 watt straight tube fluorescent lamp having a tube diameter of 32 mm.

On the other hand, as Comparative Example 4 with the present invention, the mixed phosphor (average particle size 5 μm) used in Example 5 was applied at an amount of 4.0 mg / cm ² on the inner surface of the tubular glass tube. Applied. Then, a small amount of mercury and a rare gas of Ar were enclosed, and a base was attached to manufacture a 40 watt straight tube fluorescent lamp with a tube diameter of 32 mm.

A lighting test of each fluorescent lamp according to the above-mentioned Example 5 and Comparative Example 4 was conducted. The results are shown in Table 4.

[0048]

[Table 4] Example 6, Comparative Example 5 Y ₂ O ₃ : Eu phosphor was melted by a high-frequency thermal plasma method, partially vaporized, and then cooled to prepare phosphor ultrafine particles. The average particle size of the phosphor ultrafine particles was about 30 nm. The phosphor ultrafine particles were suspended in a 1 wt% nitrocellulose + butyl acetate solution. This suspension
The amount of 0.5 mg / cm ² was applied to the inner surface of the tubular glass tube.

Next, Y ₂ O ₃ : Eu phosphor, GdMgB
₅ O ₁₀ : Ce, Tb phosphor, BaMg ₂ Al ₁₆ O ₂₇ : E
u phosphor, (Ba, Ca, Mg) ₅ (PO ₄ ) Cl: E
The u phosphor and the Mg-fluorogermanate: Mn phosphor were mixed and coated on the coating film of the phosphor ultrafine particles in an amount of 4.0 mg / cm ² . Then, while enclosing a small amount of mercury and Ar noble gas in the glass tube and attaching a base (including the electrode), the tube diameter is 16 mm, the tube length is 210 mm, and the wall load is 2050 W / m ^2.
The fluorescent lamp of was produced.

On the other hand, as Comparative Example 5 with the present invention, the mixed phosphor (average particle size 5 μm) used in Example 6 was applied at an amount of 4.0 mg / cm ² on the inner surface of the tubular glass tube. Applied. Then, a small amount of mercury and Ar noble gas are enclosed and a mouthpiece is attached to make the pipe diameter 16 mm, pipe length 210 mm, and pipe wall load.
A 2050 W / m ² fluorescent lamp was produced.

A lighting test of each fluorescent lamp according to the above-mentioned Example 6 and Comparative Example 5 was conducted. The results are shown in Table 5.

[0052]

[Table 5]

[0053]

As described above, according to the fluorescent lamp of the present invention, the light emitting layer emits light efficiently due to the reflection of ultraviolet rays by the coating film of the ultrafine phosphor particles formed on the inner surface of the glass. Since the coating film of the ultrafine phosphor particles itself also emits light, it is possible to significantly improve the luminance of the lamp as compared with the conventional fluorescent lamp. Further, by using spherical phosphor particles in the light emitting layer, the brightness can be further improved.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing the structure of a fluorescent lamp according to an embodiment of the present invention.

[Explanation of symbols]

 1 ... Fluorescent lamp 2 ... Electrode 3 ... Glass tube 4 ... Coating film of phosphor ultrafine particles 5 ... Emitting layer

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masaaki Tamaya 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Incorporated Toshiba Research and Development Center

Claims (4)

[Claims] 1. A glass tube in which an ionizable medium containing mercury is enclosed, and a pair of electrodes is arranged at both ends, and phosphor ultrafine particles having an average particle diameter of 150 nm or less formed on the inner surface of the glass tube. And a light-emitting layer formed on the coating film of the ultrafine phosphor particles, the light emitting layer comprising a coating film of one or more kinds of phosphor particles. 2. The fluorescent lamp according to claim 1, wherein the light emitting layer is made of a coating film of spherical phosphor particles produced by thermal plasma treatment having an average particle diameter of 1 μm or more. 3. The fluorescent lamp according to claim 1, wherein the phosphor ultrafine particles have the same composition as at least one kind of phosphor forming the light emitting layer. 4. The fluorescent lamp according to claim 1, wherein the fluorescent ultrafine particles are fluorescent particles produced by thermal plasma treatment.