JPH09286981A - Luminescent substance and luminescent lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a luminescent substance improved in luminous efficiency, capable of reducing color shift of a luminescent lamp and supplying a high- quality luminescent lamp having a long life and to provide a luminescent lamp using the luminescent substance. SOLUTION: This luminescent substance is a three wavelength type mixed luminescent substance comprising at least a blue, a green and a red fluorescent substances, and a coated film composed of fine particles of at least one metal oxide selected from MgO, Cab, SrO, BaO and Y2 O3 in the ratio of >=0.01 and <=3.0awt.% based on the blue luminescent substance is formed only on the surface of the blue luminescent substance. A luminescent film constituted of the luminescent substance 2 is formed in the inside of a glass bulb to give the objective luminescent lamp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phosphor and a fluorescent lamp, and more particularly to a phosphor having high luminous efficiency and little color shift or tube end color difference when used as a phosphor layer of a three-wavelength fluorescent lamp. And a fluorescent lamp using the same.

[0002]

2. Description of the Related Art As a fluorescent lamp for general illumination, a three-wavelength type fluorescent lamp which has a high efficiency and a high color rendering property at the same time is widely used. This three-wavelength type fluorescent lamp is formed by forming a phosphor layer (fluorescent film) in which three kinds of phosphors of blue, green, and red emission having a relatively narrow band emission spectrum distribution are mixed at an arbitrary ratio. It is a fluorescent lamp that emits light of a target color.

Recently, the above-mentioned three-wavelength fluorescent lamps have been rapidly used not only for general lighting but also as light sources for various OA devices and cold cathode tubes for backlights of liquid crystal displays. It is expanding.

[0004]

However, the above-mentioned conventional three-wavelength fluorescent lamp has not been able to sufficiently meet the technical requirements for new applications in the characteristics of the luminous flux maintenance factor and the color shift during lighting. That is, in the conventional three-wavelength fluorescent lamp, since mercury, a mercury compound, and the like enclosed in the fluorescent lamp have a property of easily adhering to and contaminating the surface of the fluorescent material, the fluorescent material brightness deteriorates with time, and the fluorescent lamp is deteriorated. However, there is a problem in that the luminous flux maintenance factor is likely to decrease.

As one means for solving the above problems, a metal oxide such as magnesium oxide is partially adhered to the surface of the phosphor to prevent the phosphor from being contaminated by mercury or a mercury compound in the fluorescent lamp. The method is also adopted. However, in the above method, the adhesion strength of the metal oxide to the surface of the phosphor is based on the electrostatic attraction between the particles, so that sufficient strength is not obtained. Therefore, since the metal oxide is peeled off with time, the effect of suppressing the decrease in the luminous flux maintenance factor in the fluorescent lamp is not always satisfactory.

On the other hand, the blue phosphor, the green phosphor and the red phosphor constituting the phosphor layer of the three-wavelength fluorescent lamp are greatly different in physical properties such as particle diameter and specific gravity. Even when is prepared, the fluidity of each component is significantly different. Therefore, when the phosphor composition is applied to the inner wall surface of the glass bulb, there is a problem that it is not evenly dispersed due to the difference in fluidity, and a so-called tube end color difference, which is different in the emission color depending on the portion of the glass bulb, occurs. In particular, among the above three types of phosphors, the blue phosphor has a smaller specific gravity and insufficient fluidity as compared with the other phosphors, so that it is difficult to disperse it uniformly over the entire glass bulb. . Therefore, there is a problem that the glass bulb cannot be used as a light source for an apparatus that requires uniform emission characteristics in the axial direction.

The present invention has been made to solve the above problems, and it is possible to improve the luminous efficiency, reduce the color shift and the tube end color difference of a fluorescent lamp, and have a long life and high quality. An object of the present invention is to provide a phosphor capable of obtaining a fluorescent lamp and a fluorescent lamp using the phosphor.

[0008]

In order to achieve the above object, the inventors of the present invention prepared a phosphor by forming various coatings on the surface of the phosphor, and using the phosphor to form a light emitting layer. Of the above-mentioned fluorescent lamps, and the effects of the kinds and contents of the constituents of the coating on the lamp characteristics such as the fluidity of the phosphor components, the luminous efficiency of the fluorescent lamps, the color shift, and the color difference at the tube end are compared by experiments. did.

As a result, among the three-wavelength type mixed phosphors consisting of blue, green and red phosphors, only the blue light emitting phosphor is coated with a predetermined amount of fine particles of metal oxide such as MgO on its surface. When uniformly formed, it is possible to effectively prevent the deterioration of brightness due to the deterioration of the phosphor contamination, and at the same time make the fluidity of each phosphor component uniform, which is the first fluorescent lamp with little color shift and tube end color difference. We obtained the finding that we can obtain it.

Further, when the above-mentioned coating is formed, the phosphor powder is suspended in a metal alkoxide solution, and a heat treatment is carried out with the metal alkoxide solution adhered to the surface of the phosphor powder, whereby the phosphor powder is obtained. A uniform and almost continuous metal oxide film is integrally formed on the surface with high bonding strength, and this high bonding strength film can prevent deterioration due to contamination of the phosphor for a long period of time, and change the lamp characteristics with a long life. It has been found that a fluorescent lamp with less emission can be obtained. The present invention has been completed based on the above findings.

That is, the phosphor according to the present invention is a three-wavelength type mixed phosphor composed of at least blue, green and red phosphors, and is 0.01% by weight or more and 3.0% by weight or less with respect to the blue phosphor. Of MgO, CaO, Sr
At least one selected from O, BaO and Y ₂ O ₃
It is characterized in that a coating film composed of fine particles of a kind of metal oxide is formed only on the surface of the blue phosphor.

In particular, in the case of forming a three-wavelength fluorescent lamp for general illumination, a blue phosphor is used as the general formula (M ₁ ,
Eu) ₁₀ (PO ₄ ) ₆ · X ₁ (however, M ₁ is Mg, C
At least one element selected from a, Ba and Sr, X ₁ represents at least one element selected from F, Cl and Br. It is preferable to use the phosphor represented by the formula (1). When a cold cathode tube for a backlight of a liquid crystal display or the like is formed, a blue phosphor is used as a general formula 3 (M ₂ , Eu) O.8Al ₂ O ₃ (however,
M ₂ represents at least one element selected from Ba, Mg and Mn. It is desirable to use the phosphor represented by

Further, it is desirable that the average particle diameter of the metal oxide fine particles constituting the coating is in the range of 0.1 to 1.0 μm. Further, the coating film made of a metal oxide may be formed by a fired product of a metal alkoxide compound attached to the surface of the blue phosphor. Furthermore, as the metal alkoxide compound, Mg (OC ₂ H ₅ ) ₂ or Y (OC ₂ H
₅ ) ₂ should be used.

The fluorescent lamp according to the present invention is a three-wavelength type mixed phosphor composed of at least blue, green and red phosphors, and is 0.01% by weight or more and 3.0% by weight or less with respect to the blue phosphor. Of MgO, CaO, Sr
At least one selected from O, BaO and Y ₂ O ₃
The present invention is characterized in that a fluorescent film made of a fluorescent material is formed on the inner surface of the glass bulb, in which a coating film made of fine particles of a kind of metal oxide is formed only on the surface of the blue fluorescent material.

In the present invention, the coating made of metal oxide fine particles formed on the surface of the phosphor particles contaminates the phosphor with mercury or a mercury compound enclosed in the arc tube (glass bulb) of the fluorescent lamp. It has a function as a protective film for preventing this and a function for improving the fluidity of the blue phosphor. As a result of the effect of preventing contamination by the coating film, the reduction of the emission brightness of the phosphor is suppressed, and as a result, a fluorescent lamp having a high luminous efficiency and a high luminous flux maintenance rate for a long period of time can be obtained. Further, since the fluidity of the blue phosphor is improved and the fluidity of the entire mixed phosphor including other phosphor components is made uniform, it is possible to uniformly disperse this mixed phosphor slurry on the inner surface of the glass bulb. it can. Therefore, it is possible to obtain a high-quality fluorescent lamp with less tube end color difference.

The coating composed of the above-mentioned fine particles of metal oxide contains 3 parts of metal alkoxide attached to the surface of the phosphor particles.
It is advisable to form the oxide by heating it at 00 to 400 ° C. for about 0.5 to 5 hours to convert it into an oxide. According to this forming method, as compared with the conventional method of partially adhering the metal oxide particles with weak bonding strength, a uniform and almost continuous metal oxide film is formed on the entire surface of the phosphor particles with high bonding strength. Can be formed with.

The coating weight of the above-mentioned metal oxide fine particles is set in the range of 0.01 to 3.0% by weight with respect to the blue phosphor particles. This adhesion weight is 0.01% by weight
When it is less than the above range, the effect of preventing contamination and improving the fluidity as a protective film cannot be sufficiently obtained. On the other hand, when the attached weight is over 3.0% by weight, the ratio of the metal oxide, which is a non-luminous substance, is relatively increased, so that the luminous efficiency of the entire phosphor layer is significantly reduced. .

When the average particle diameter of the metal oxide fine particles constituting the coating is less than 0.1 μm, the function as a protective film and the function for improving fluidity become insufficient. On the other hand, if the average particle size becomes coarser than 1.0 μm, the ratio of the metal oxide as a non-luminous substance in the entire phosphor increases, so that the luminous efficiency decreases.
Therefore, the average particle diameter of the metal oxide fine particles is 0.1 to
It is set in the range of 1.0 μm.

Further, as the metal alkoxide compound, in particular Mg (OC ₂ H ₅ ) ₂ or Y (OC ₂ H ₅ )
By using ₂ , it is possible to form a uniform and almost continuous metal oxide film on the surface of the phosphor particles with high bonding strength.

Then, the blue phosphor having the film formed as described above and the other green phosphor and red phosphor are mixed so as to have a predetermined color temperature to prepare the phosphor according to the present invention. Further, the above phosphor is uniformly dispersed in a binder in which polyethylene oxide or the like is dissolved to form a phosphor slurry, and this phosphor slurry is applied to the inner surface of the glass bulb, dried and baked to integrally form a light emitting layer (phosphor film). The fluorescent lamp according to the present invention is manufactured according to the normal lamp manufacturing process of forming the fluorescent lamp.

According to the phosphor and the fluorescent lamp having the above-mentioned structure, since the coating of fine particles of metal oxide such as MgO is formed on the surface of the blue phosphor, the phosphor can be effectively prevented from being contaminated. On the other hand, the fluidity of the blue phosphor is greatly improved. Therefore, by using this phosphor, it is possible to obtain a fluorescent lamp in which a decrease in the emission brightness of the phosphor is suppressed, there is no color shift, the luminous efficiency is high for a long period of time, and the luminous flux maintenance factor is high.

Further, since the fluidity of the blue phosphor is improved and the dispersibility similar to that of the other phosphor components is obtained, each component phosphor can be uniformly dispersed on the inner surface of the glass bulb,
A high-quality fluorescent lamp with little color difference at the tube end can be obtained.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described.
This will be described more specifically with reference to the following examples.

Example 1 As a blue phosphor, 3 (Ba, Mg) O.8Al
100 g of ₂ O ₃ : Eu-based blue phosphor was weighed, while 1.4 g of magnesium diethoxide (Mg (OC ₂ H ₅ ) ₂ ) as a metal alkoxide compound was weighed. The blue phosphor was dispersed in a solution prepared by dissolving this metal alkoxide compound in pure water, and sufficiently stirred to obtain a mixed solution. Then the mixture is filtered to dry the residue on the filter paper,
Furthermore, the blue phosphor for Example 1 was prepared by heating at 350 ° C. for 1 hour. When the prepared blue phosphor particles were analyzed, a film made of MgO was formed on the surface of the phosphor particles at a ratio of 0.2% by weight.

Next, the blue phosphor and the (La, Ce) (P, Si) O ₄ : Tb-based phosphor as a green phosphor,
Y ₂ O ₃ : Eu phosphor as a red phosphor is uniformly mixed at a mixing ratio such that the relative color temperature is 5000K,
A three-wavelength mixed phosphor according to Example 1 was prepared.

Next, the above-mentioned three-wavelength type mixed phosphor is uniformly dispersed in a binder to obtain a phosphor slurry, and this phosphor slurry is applied to the inner surface of the glass bulb 1 as shown in FIG. 1 and dried and fired. According to the first embodiment, the phosphor layer 2 is formed, and then the bases 3 provided with discharge electrodes and sockets are attached to both ends of the glass bulb 1 in accordance with a normal lamp manufacturing process. A 40 W straight tube fluorescent lamp was manufactured.

Example 2 As a blue phosphor, 3 (Ba, Mg) O.8Al
100 g of ₂ O ₃ : Eu-based blue phosphor was weighed and 2.0 g of yttrium diethoxide (Y (OC ₂ H ₅ ) ₂ ) as a metal alkoxide compound was weighed. The blue phosphor was dispersed in a solution prepared by dissolving this metal alkoxide compound in pure water, and sufficiently stirred to obtain a mixed solution. Next, the mixed solution was filtered, the residue on the filter paper was dried, and further heated at 350 ° C. for 1 hour to prepare a blue phosphor for Example 2. When the prepared blue phosphor particles were analyzed, Y was added to the surface of the phosphor particles at a ratio of 0.5% by weight.
_A film of ₂ O ₃ was formed.

Next, the blue phosphor and the (La, Ce) (P, Si) O ₄ : Tb type phosphor as the green phosphor,
Y ₂ O ₃ : Eu phosphor as a red phosphor is uniformly mixed at a mixing ratio such that the relative color temperature is 5000K,
A three-wavelength type mixed phosphor according to Example 2 was prepared.

Next, the above-mentioned three-wavelength type mixed phosphor is uniformly dispersed in a binder to form a phosphor slurry, and this phosphor slurry is applied to the inner surface of the glass bulb 1 as shown in FIG. 1 and dried and baked. According to the second embodiment, the phosphor layer 2 is formed, and then the bases 3 provided with discharge electrodes and sockets are attached to both ends of the glass bulb 1 in accordance with a normal lamp manufacturing process. A 40 W straight tube fluorescent lamp was manufactured.

Examples 3 to 7 As shown in Table 1, the kind of metal alkoxide compound attached to the blue phosphor and the weight ratio of the coating film formed by attachment were adjusted within the range of 0.01 to 3.0% by weight. Example 3 is repeated according to the same processing procedure as that of Example 1 except for the above.
The fluorescent lamps according to Examples 3 to 7 were manufactured by preparing the three-wavelength mixed phosphors according to Nos. 7 to 7 and applying each phosphor on the inner surface of the glass bulb, followed by drying and firing.

Comparative Example 1 On the other hand, in Example 1, a green phosphor and a red phosphor were added to a blue phosphor having no coating film and a relative color temperature of 500.
A conventional three-wavelength type mixed phosphor was prepared by blending at a predetermined mixing ratio so as to be 0K. Using this mixed phosphor, a 40 W straight tube fluorescent lamp according to Comparative Example 1 having the same size and structure as Example 1 was manufactured according to a normal lamp manufacturing process.

Comparative Example 2 100 g of the conventional three-wavelength type mixed phosphor prepared in Comparative Example 1 was weighed, magnesium diethoxide was adhered to it and dried as in Example 1, and heated at 350 ° C. for 1 hour. Thus, a coating film made of MgO particles was formed on all surfaces of each of the blue, green and red phosphor particles to prepare a phosphor according to Comparative Example 2. When the prepared phosphor particles were analyzed, a film made of MgO was formed on the surface of all the phosphor particles at an average ratio of 0.2% by weight. Further, using the three-wavelength type mixture having this coating formed thereon, Example 1
A 40 W straight tube fluorescent lamp according to Comparative Example 2 having the same size and structure as the above was manufactured.

Comparative Example 3 Example 1 was repeated except that Mg (OC ₂ H ₅ ) ₂ was adhered to the blue phosphor powder in an excessive amount in Example 1 to form an excessively large coating film with a weight ratio of 4.0% by weight. A 40 W straight tube fluorescent lamp according to Comparative Example 3 was manufactured by performing the same treatment procedure as described above.

For each of the fluorescent lamps according to Examples 1 to 7 and Comparative Examples 1 to 3 manufactured in this way, the initial total luminous flux and tube end color difference immediately after manufacturing are determined by JIS (Japanese Industrial Standard).
The total luminous flux and the color shift after 1000 hours of lighting were measured and the results shown in Table 1 below were obtained. Regarding the total luminous flux, the total luminous flux of the conventional fluorescent lamp according to Comparative Example 1 was relatively displayed with the reference value (100%).

[0035]

[Table 1]

As is clear from the results shown in Table 1,
According to the fluorescent lamps of the respective examples in which the coating film made of the metal oxide particles such as MgO, Y ₂ O ₃ , CaO, BaO, and SrO is formed on the surface of the blue fluorescent material, the conventional fluorescent lamp using no coating film is used. It was found that the initial luminous flux was increased by 0.5 to 2% and the luminous efficiency was increased, as compared with the fluorescent lamp according to Comparative Example 1.

Further, the tube end color difference of the fluorescent lamps of the respective embodiments is
It was confirmed that it was reduced to about 1/4 as compared with the conventional one shown in Comparative Example 1, and the uniform dispersibility of each phosphor component was improved.

Further, the total luminous flux of the fluorescent lamps of the respective examples after being lit for 1000 hours was significantly improved to 1.5 to 4% as compared with the conventional example of the comparative example 1. In addition, the color shift was reduced by about 0.003, demonstrating that the deterioration of each phosphor was small.

On the other hand, the effect of improving the total luminous flux can be confirmed in the fluorescent lamp according to Comparative Example 2 in which the coating is formed on the surface of all the blue (B), green (G) and red (R) phosphor particles. Since the fluidity of each phosphor component is not uniform, a uniform phosphor layer is not formed, and the effect of improving tube end color difference and color shift is small. Also, the coating is 4.0% by weight
In the fluorescent lamp according to Comparative Example 3 using the excessively formed blue phosphor, although the effect of improving the tube end color difference and the color shift is large, the total luminous flux becomes lower than that of the conventional example, so that it is practical. Turned out to be less.

Examples 8 to 14 3 (Ba, Mg) O.8Al used in Example 1
₂ O ₃ : In place of the Eu-based blue phosphor, 3 (Ba, Mg,
Eu, Mn) O.8Al ₂ O ₃ blue phosphor is used, and as shown in Table 2, the kind of the metal alkoxide compound attached to the blue phosphor and the weight ratio of the coating formed by the attachment are 0.01 to. The three-wavelength mixed phosphors according to Examples 8 to 14 were prepared according to the same procedure as in Example 1 except that the phosphor was adjusted in the range of 3.0% by weight, and each phosphor was applied to the inner surface of the glass bulb. After that, dry
By firing, the fluorescent lamps according to Examples 8 to 14 were manufactured.

Comparative Example 4 On the other hand, in Example 8, a green phosphor and a red phosphor were added to a blue phosphor having no coating film and a relative color temperature of 500.
A conventional three-wavelength type mixed phosphor was prepared by blending at a predetermined mixing ratio so as to be 0K. A 40 W straight tube fluorescent lamp according to Comparative Example 4 having the same dimensions and structure as those of Example 8 was manufactured by using this mixed phosphor according to a normal lamp manufacturing process.

Comparative Example 5 100 g of the conventional three-wavelength type mixed phosphor prepared in Comparative Example 4 was weighed, magnesium diethoxide was attached and dried as in Example 8, and heated at 350 ° C. for 1 hour. Thus, a coating film of MgO particles was formed on all surfaces of each of the blue, green, and red phosphor particles to prepare a phosphor according to Comparative Example 5. When the prepared phosphor particles were analyzed, a film made of MgO was formed on the surface of all the phosphor particles at an average ratio of 0.2% by weight. Also, using the three-wavelength type mixture having this coating, Example 8 was used.
A 40 W straight tube fluorescent lamp according to Comparative Example 5 having the same size and structure as the above was manufactured.

Comparative Example 6 Example 8 was repeated except that Mg (OC ₂ H ₅ ) ₂ was excessively adhered to the blue phosphor powder in Example 8 to form a film having an excessive weight ratio of 4.0% by weight. A 40 W straight tube fluorescent lamp according to Comparative Example 6 was manufactured by performing the same treatment procedure as described above.

For each of the fluorescent lamps of Examples 8 to 14 and Comparative Examples 4 to 6 thus manufactured, the initial total luminous flux immediately after manufacturing was measured by the method specified in JIS (Japanese Industrial Standard), and after lighting for 500 hours. And 100
Measure the total luminous flux and color shift after 0 hours of lighting,
The results shown in Table 2 below were obtained. Regarding the total luminous flux,
The total luminous flux of the conventional fluorescent lamp according to Comparative Example 4 is set to a reference value (1
00%).

[0045]

[Table 2]

As is clear from the results shown in Table 2 above,
According to the fluorescent lamps of the respective examples in which the coating film made of the metal oxide particles such as MgO, Y ₂ O ₃ , CaO, BaO, and SrO is formed on the surface of the blue fluorescent material, the conventional fluorescent lamp using no coating film is used. It was found that the initial luminous flux was increased by 0.5 to 1.8% and the luminous efficiency was increased as compared with the fluorescent lamp according to Comparative Example 4.

Further, the total luminous fluxes of the fluorescent lamps of the respective examples after 500 hours of lighting and 1000 hours of lighting were 1.0 to 2%, respectively, as compared with the conventional example of Comparative Example 4.
It was significantly improved to 5 to 2.5%. The color shifts are 0.0005 to 0.0015 and 0.0009 to
It was decreased by 0.0014, demonstrating that deterioration of each phosphor was small.

On the other hand, the effect of improving the total luminous flux can be confirmed in the fluorescent lamp according to Comparative Example 5 in which a coating is formed on the surface of all the blue (B), green (G) and red (R) phosphor particles. , Little effect of improving color shift. Further, in the fluorescent lamp according to Comparative Example 6 using the blue phosphor having the coating film formed in an excessive amount of 4.0% by weight, the effect of improving the color shift is great, but the total luminous flux is lower than that of the conventional example. Therefore, it turned out that it is not practical.

[0049]

As described above, according to the phosphor and the fluorescent lamp of the present invention, since the coating film composed of the fine particles of the metal oxide such as MgO is formed on the surface of the blue phosphor, the phosphor is contaminated. Can be effectively prevented and the fluidity of the blue phosphor is significantly improved. Therefore, by using this phosphor, the decrease in the emission brightness of the phosphor is suppressed, there is no color shift, and the luminous efficiency is high over a long period of time.
A fluorescent lamp having a high luminous flux maintenance factor can be obtained.

Further, since the fluidity of the blue phosphor is improved and the same dispersibility as that of the other phosphor components is obtained, each component phosphor can be uniformly dispersed on the inner surface of the glass bulb.
A high-quality fluorescent lamp with little color difference at the tube end can be obtained.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view showing a fluorescent lamp using a phosphor according to the present invention.

[Explanation of symbols]

 1 luminous tube (glass bulb) 2 phosphor layer 3 base

Claims (7)

[Claims] 1. A three-wavelength type mixed phosphor comprising at least blue, green and red phosphors, wherein the ratio is 0.01% by weight or more and 3.0% by weight or less with respect to the blue phosphor.
A phosphor characterized in that a coating film composed of fine particles of at least one metal oxide selected from MgO, CaO, SrO, BaO and Y ₂ O ₃ is formed only on the surface of the blue phosphor. 2. The blue phosphor has the general formula (M ₁ , Eu) ₁₀
(PO ₄ ) ₆ · X ₁ (wherein M ₁ is at least one element selected from Mg, Ca, Ba and Sr, and X ₁ is at least one element selected from F, Cl and Br) .) The phosphor according to claim 1, which is represented by the formula (1). 3. The blue phosphor has the general formula 3 (M ₂ , Eu).
O · 8Al ₂ O ₃ (However, M ₂ is Ba, Mg and Mn
At least one element selected from ) The phosphor according to claim 1, characterized in that 4. The phosphor according to claim 1, wherein the fine particles of the metal oxide forming the coating film have an average particle diameter in the range of 0.1 to 1.0 μm. 5. The phosphor according to claim 1, wherein the film made of a metal oxide is formed by a fired product of a metal alkoxide compound attached to the surface of the blue phosphor. 6. The metal alkoxide compound is Mg (OC).
The phosphor according to claim 5, which is ₂ H ₅ ) ₂ or Y (OC ₂ H ₅ ) ₂ . 7. A three-wavelength type mixed phosphor comprising at least blue, green and red phosphors, wherein the ratio is 0.01% by weight or more and 3.0% by weight or less with respect to the blue phosphor.
On the inner surface of the glass bulb, there is provided a fluorescent film made of a phosphor in which a coating film made of fine particles of at least one metal oxide selected from MgO, CaO, SrO, BaO and Y ₂ O ₃ is formed only on the surface of the blue phosphor. A fluorescent lamp characterized by being formed.