JPH08293285A - Fluorescent lamp - Google Patents

Abstract

PURPOSE: To improve flux of light in the visible range and a maintenance factor of a light flux by setting the average grain size of an LiAlO2 : Fe phosphor at a specific percentage of the average grain size of a coexisting phosphor or more. CONSTITUTION: A lithium oxide or a compound which produces a lithium oxide on heating, and alumina or a compound which produces an aluminum oxide on heating are baked together with an activator to obtain an LiAlO2 : Fe phosphor. A grain size of the phosphor is controllable depending on the baking temperature, and for an average grain size of about 4μ, for example, a temperature of 1200 deg.C is appropriate. A phosphor for use in a normal fluorescent lamp is employed as the one which coexists with the LiAlO2 : Fe phosphor, and on amount of light emission in the visible range can be varied by varying the mixing ratio of the phosphors. Also, by setting the average grain size of the near-infrared light emitting LiAlO2 : Fe phosphor at 1/2 the average grain size of the coexisting phosphor or more, flux of light in the visible range and a maintenance factor of the light flux can be greatly improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorescent lamp having a near-infrared emitting LiAlO ₂ : Fe phosphor and a phosphor coexisting therewith in a phosphor layer of the fluorescent lamp, which is excellent in luminous flux and luminous flux maintenance rate. .

[0002]

2. Description of the Related Art The luminous flux of a fluorescent lamp decreases when it is lit for a long time. One of the causes is that a black-brown mercury amalgam is formed by the reaction between sodium contained in the glass tube and mercury enclosed in the fluorescent lamp, which adheres to the inner surface of the glass tube. In particular, near-infrared emission LiA
The chemical properties of the lO ₂ : Fe phosphor are unstable, such as being easily dissolved in water and having a high hygroscopicity. Therefore, when this phosphor is applied to a fluorescent lamp, there is a problem that mercury is particularly likely to adhere and blackening is likely to occur.

Although such a fluorescent substance is prone to deterioration, it still has a strong emission output in the near-infrared region. Therefore, it is a fluorescent lamp for a light source of an optical character reader (OCR) (Japanese Patent Publication No. 62-35439). ) Used alone. Further, by coating the glass tube with other phosphors at the same time, it has been attempted to give the light emission in the near infrared region to the light emission of a normal fluorescent lamp.
Again, this phosphor is preferred because it has a strong emission output in the near infrared region. As a typical fluorescent lamp that mixes the near-infrared light emitting LiAlO ₂ : Fe phosphor and the light emitted from another phosphor, for example, there is a plant growing fluorescent lamp.

In recent years, plants such as vegetables have been artificially controlled.
A so-called plant factory that grows and produces under the environment
Research has become active, and some have been put to practical use.
There is. Above all, it is the place of the plant factory by the completely artificial light method.
The ratio of light energy cost to production cost.
The major issue is how to reduce it. On the other hand, specific
Of blue, green, and red emission phosphors in the wavelength range of
And a phosphor having an emission peak at 700 to 800 nm is used
The plant growing fluorescent lamp was opened in Japanese Patent Laid-Open No. 2-60525.
It is shown. Near infrared emitting phosphor that can be used for this
Then LiAlO ₂: Fe phosphor is selected. Toko
Of other phosphors that are used at the same time as this phosphor
Even if the luminous flux or the luminous flux maintenance factor is excellent,
This kind of fluorescent lamp is used by being mixed.
Does not significantly reduce luminous performance such as luminous flux and luminous flux maintenance factor.
There was a problem of waiting.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and includes a near-infrared emitting LiAlO ₂ : Fe phosphor and another phosphor, which is represented by a plant growing fluorescent lamp. It is an object of the present invention to improve luminous performance such as luminous flux and luminous flux maintenance factor of a fluorescent lamp obtained by mixing

[0006]

DISCLOSURE OF THE INVENTION As a result of intensive studies made by the present inventors in order to solve the above-mentioned problems, as a result, the emission performance of fluorescent lamps and near-infrared emission LiA which is a constituent of the fluorescent film are
The inventors have newly found that there is a quantitative relationship between the lO ₂ : Fe phosphor and the particle size of the phosphor coexisting with it, and have completed the present invention.

That is, in the fluorescent lamp of the present invention, a transparent glass tube filled with a filling gas containing mercury and a rare gas, and a fluorescent layer containing fluorescent particles provided on the inner wall surface of the transparent glass tube. And a means for maintaining a positive discharge in the enclosed gas, the phosphor layer comprising at least a near-infrared emitting LiAlO ₂ : Fe phosphor and a phosphor coexisting therewith. The average particle size of the near-infrared emitting LiAlO ₂ : Fe phosphor is ½ or more of the average particle size of the coexisting phosphor.

Further, near-infrared light emitting Li occupying the phosphor layer
The average particle size of the AlO ₂ : Fe phosphor is more preferably equal to or larger than the average particle size of the above-mentioned phosphor coexisting with it.

The near-infrared light emitting LiAlO ₂ : Fe phosphor that can be used in the fluorescent lamp of the present invention is a part of Li containing Na and K.
Al, a part of Al may be replaced with a trivalent element of B, Ga, In, and Tl, and a part of Fe may be replaced with Cr. It emits light in the infrared region and has basically the same effect.

The LiAlO ₂ : Fe phosphor can be generally obtained as follows. First, as a lithium raw material, lithium oxide, or a compound that easily produces lithium oxide by heating, such as lithium carbonate or lithium hydroxide, and alumina, or a compound that easily produces aluminum oxide by heating, such as aluminum nitrate,
Aluminum hydroxide is dry- or wet-mixed so as to have almost the same amount, and further, as an iron raw material for the activator, a trivalent iron salt such as ferric ammonium sulfate is added in an amount of 0.001 to 0.001 with respect to 1 mol of Li. Mix to 0.1 mole. Then, the mixture can be obtained by putting the mixture in an alumina crucible or the like and firing in an air atmosphere at a temperature of 1000 ° C. or higher for 2 to 4 hours.

LiAl which is of particular importance in the present invention
The particle size of the O ₂ : Fe phosphor can be controlled by controlling the temperature when firing the phosphor. That is, the particle size is increased by baking at a higher temperature, and the particle size is decreased by baking at a lower temperature. For example, in order to obtain an average particle size of about 4 μ, it is fired at a temperature of 1200 ° C. for several hours.

Near-infrared emission occupying the phosphor layer of a fluorescent lamp
LiAlO₂: The phosphor that coexists with the Fe phosphor is
If it is one that is usually used as a
Wear. As a fluorescent substance for a fluorescent lamp, for example, (SrCa
BaMg)_Five(PO_Four)₃Cl: Eu, BaMg₂A1₆O
₂₇: Eu, Sr_Five(PO_Four)₃Cl: Eu, LaPO_Four: C
e, Tb, MgAl₁₁O₁₉: Ce, Tb, Y₂O₃: E
u, Y (PV) O_Four: Eu, 3.5MgO ・ 0.5MgF₂・ Ge
O₂: Mn, Ca_Ten(PO_Four)₆FCl: Sb, Mn, S
r_Ten(PO_Four)₆FCl: Sb, Mn, (SrMg)₂P₂
O₇: Eu, Sr₂P₂O₇: Eu, CaWO_Four, CaW
O_Four: Pb, MgWO_Four, (BaCa)_Five(PO _Four)₃C
l: Eu, Sr_FourAl₁₄O_{twenty five}: Eu, Zn₂SiO_Four: M
n, BaSi₂O_Five: Pb, SrB_FourO₇: Eu, (CaZ
n)₃(PO_Four)₂: Tl, LaPO_Four: Ce, etc. can be used
It

Near-infrared emitting LiAlO ₂ : Fe phosphor is 7
It has an emission peak near 35 nm and it has a peak of 450 nm.
A blue-emitting phosphor having an emission peak in the vicinity, a green-emitting phosphor having an emission peak in the vicinity of 545 nm, and 610 nm
By mixing a three-wavelength mixed phosphor composed of a red light emitting phosphor having an emission peak in the vicinity, it is particularly useful as a fluorescent lamp for growing plants, and as a blue light emitting phosphor (SrC
aBaMg) ₅ (PO ₄ ) ₃ Cl: Eu, and BaMg ₂ A
1 ₆ O ₂₇ : Eu serves as a green light emitting phosphor, and LaPO ₄ : Eu:
Ce, Tb, and MgAl ₁₁ O ₁₉ : Ce, Tb phosphors, and Y ₂ O ₃ : Eu can be preferably used as the red-emitting phosphor.

Near infrared emitting LiAl occupying the phosphor layer
The mixing ratio of the O ₂ : Fe phosphor and the phosphor coexisting with the O ₂ : Fe phosphor can be freely changed depending on the purpose of use. For example, if more emission in the visible region is required, the proportion of visible region emitting phosphors can be increased and vice versa.

Further, in the production of the fluorescent lamp of the present invention, the usual method for producing a fluorescent lamp can be applied as it is. For example, near-infrared emitting LiAlO ₂ : Fe phosphor,
A phosphor coexisting therewith and a binder such as alumina or calcium pyrophosphate, calcium barium borate, etc. are added to a nitrocellulose / butyl acetate solution, and these are mixed and suspended to prepare a phosphor-coated suspension. The obtained phosphor-coated suspension is poured onto the inner surface of the glass tube, and then dried by passing hot air through it, followed by baking, evacuation, attachment of a filament, attachment of a base, etc. according to the usual procedure of the present invention. You can finish the lamp.

It is also possible to form a protective film of alumina or the like at the time of application to the glass tube and then form a phosphor layer, and the luminous performance such as luminous flux and luminous flux maintenance rate can be further improved.

[0017]

[Function] FIG. 1 shows near-infrared light-emitting LiAlO ₂ having various particle sizes:
Fe phosphor and three-wavelength mixed phosphor having an average particle diameter of 4.2 μm (as (SrCaBaMg) ₅ (P
O ₄ ) ₃ Cl: Eu, as a green-emitting phosphor, LaP
O ₄ : Ce, Tb, and Y as a red light emitting phosphor
_Of the LiAlO ₂ : Fe phosphor and the relative output after 30 minutes of lighting of the FL40SS fluorescent lamp produced by mixing ₂ O ₃ : Eu) in a ratio of 1: 4 and 2: 3. Was plotted. Here, the relative output is LiAl
O ₂ : Fe phosphor wavelength range 650 nm to 800 nm
The integrated value of the emission energy at is the percentage of that of the reference lamp. Curves (a) and (b) are for the phosphor mixing ratios of 1: 4 and 2: 3, respectively. The relative output in the near infrared region is LiAlO ₂ :
It is almost constant irrespective of the particle size of the Fe phosphor, and naturally increases as the blending ratio of this phosphor increases.

In the visible light range of the fluorescent lamp shown in FIG. 1 in FIG. 2, the near-infrared emission LiAlO ₂ :
It was plotted against the particle size of the Fe phosphor. Curves (a), (b)
And the mixing ratio of the phosphors is 1: 4, respectively,
2: 3 relationship. The luminous flux in the visible region is higher as the particle size of the LiAlO ₂ : Fe phosphor is larger at any mixing ratio, and tends to increase up to about twice the particle size of the three-wavelength mixed phosphor, and if it is larger than twice, it is almost the same. It is saturated. Further, it can be seen that the relative luminous flux is remarkably reduced when the particle diameter is smaller than 1/2 of the particle diameter of the three-wavelength mixed phosphor, that is, when it is about 2 μ or less in this case. In addition, LiAlO
_As the mixing ratio of the ₂ : Fe phosphor increases, the relative luminous flux naturally decreases.

FIG. 3 shows near-infrared light emitting LiAlO ₂ : Fe phosphors having average particle sizes of 6.2 μm and 4.2 μm, respectively.
FL3SS fluorescent lamps were manufactured by mixing 3.0 μm of each three-wavelength mixed phosphor at a ratio of 1: 4. LiAlO
₂ : The relationship between the particle size of the Fe phosphor and the relative luminous flux was plotted on curves (a), (b), and (c), respectively. From these, it is possible to obtain LiAlO over the entire particle size range of the three-wavelength mixed phosphor.
_When the average particle size of the ₂ : Fe phosphor is smaller than 1/2 of the average particle size of the three-wavelength mixed phosphor, the relative luminous flux is significantly reduced.
Therefore, it is found that the average particle size of the LiAlO ₂ : Fe phosphor is preferably equal to or larger than the average particle size of the three-wavelength mixed phosphor.

The average particle diameters are 6.5 μm and 4.2 μm, respectively.
m, 2.2 μm, and 1.6 μm LiAlO ₂ : Fe
The FL40SS fluorescent lamp was manufactured by mixing the phosphor and the three-wavelength mixed phosphor having an average particle size of 4.2 μm at a ratio of 1: 4. The change with time of the light emission output in the near infrared region with respect to the lighting time is plotted in FIG. 4, and the change with time of the relative luminous flux with respect to the lighting time is plotted in FIG. Where the curves (a), (b), (c),
And (d), the average particle size of the LiAlO ₂ : Fe phosphor is 6.5 μm, 4.2 μm, 2.2 μm, and 1.6 μm, respectively.
m fluorescent lamp. Although the luminous flux of the fluorescent lamp gradually decreases with the lighting time, from FIG.
If the average particle size of the iAlO ₂ : Fe phosphor is smaller than 1/2 of the average particle size of the three-wavelength mixed phosphor, the luminous flux maintenance factor is remarkably reduced. The particle size of the LiAlO ₂ : Fe phosphor is 1.
Comparing the case of 6 μm and the case of 4.2 μm, the luminous flux exceeds 30% or more after 500 hours of lighting. Therefore,
It is understood that the average particle size of the LiAlO ₂ : Fe phosphor is preferably equal to or larger than the average particle size of the three-wavelength mixed phosphor. On the other hand, the rate of decrease in output in the near infrared region is L
The iAlO ₂ : Fe phosphor can be kept substantially constant regardless of the particle size.

The coating amount of the phosphor of the above-mentioned fluorescent lamp is about 3.5 g, and the relative luminous flux and the relative output are based on LiAlO ₂ : Fe phosphor having an average particle diameter of 4.2 μm and the above three wavelengths. Mixing phosphors in a ratio of 1: 4 is 10
It was set to 0%.

The deterioration of the light emission of the fluorescent lamp having the LiAlO ₂ : Fe fluorescent substance in the fluorescent substance layer is caused by the following mechanism. Li contained in the phosphor base is partially ionized and released by baking during the phosphor manufacturing process, and this reacts with mercury enclosed in the fluorescent lamp by adhering to the particle surface of the coexisting phosphor. However, the formation of a black-brown mercury amalgam reduces the light emission performance.

When the particle size of the LiAlO ₂ : Fe phosphor in the phosphor layer becomes smaller, the LiA becomes closer to other coexisting phosphors.
The probability of the presence of the lO ₂ : Fe phosphor increases, and the above-described Li deposition on the surface of the phosphor increases due to heating during the manufacturing process. On the contrary, the specific surface area can be reduced by increasing the particle size of the LiAlO ₂ : Fe phosphor, and as a result, the free Li
The amount of ions decreases, and the decrease in light emission performance can be minimized.

On the other hand, when the particle size of the phosphor coexisting with LiAlO ₂ : Fe in the phosphor layer is large, the specific surface area becomes small and the existence probability of the nearby LiAlO ₂ : Fe phosphor increases, so that light emission occurs. It leads to performance degradation. When the coexisting phosphor is small, the specific surface area increases, and the nearby LiAl
The existence probability of O ₂ : Fe phosphor decreases, and the decrease in light emission performance can be suppressed to a small extent.

As described above, in order to improve the luminous performance of the fluorescent lamp, it is necessary that the particle size of the LiAlO ₂ : Fe phosphor is large, but it is relative, and the phosphor layer is always used. It is important to balance the particle size with the phosphor that coexists in the. In the present invention, the particle size of the LiAlO ₂ : Fe phosphor is set to ½ or more of the average particle size of the phosphor coexisting in the phosphor layer of the fluorescent lamp on the basis of such a physical basis.

[0026]

EXAMPLE A fluorescent lamp for growing plants, which is one of the objects of the present invention, will be described below as an example. In the process of plant growth, white light close to sunlight is required, and the most efficient fluorescent lamp that can achieve that is basically a blue-emitting phosphor having an emission peak near 450 nm.
A three-wavelength fluorescent lamp having a three-wavelength mixed phosphor composed of a green-emitting phosphor having an emission peak near 545 nm and a red-emitting phosphor having an emission peak near 610 nm in a phosphor layer. An example of mixing near-infrared light with this fluorescent lamp will be described below.

[Example 1] As phosphor raw materials, 121.9 g of lithium carbonate, 169.0 g of alumina, and 8.1 g of ferrous nitrate nonahydrate were weighed out, and these were put in an alumina ball to obtain a magnetic material having a capacity of 500 ml. The mixture was put in a pot and rolled on a roller for 5 hours to pulverize and mix to obtain a raw material mixture. Next, this was filled in an alumina crucible, covered with a lid, and then fired at 1200 ° C. for 2 hours in an air atmosphere. The fired product was crushed and passed through a 300-mesh sieve to obtain an average particle size of 4.2 μm having an emission peak at 735 nm.
A near-infrared emitting LiAlO ₂ : Fe phosphor was obtained.

The obtained LiAlO ₂ : Fe phosphor and 4
Has emission peak at 53 nm (SrCaBaMg)
₅ (PO ₄ ) ₃ Cl: Eu blue light emitting phosphor 30%, 54
_{3. An} average particle size obtained by mixing 30% of LaPO ₄ : Ce, Tb green emitting phosphor having an emission peak at 4 nm and 40% of Y ₂ O ₃ : Eu red emitting phosphor having an emission peak at 611 nm. The 2 μm three-wavelength mixed phosphor is mixed thoroughly in a ratio of 1: 4.

8 g of the mixed phosphor was mixed with 15 g of butyl acetate.
g and sufficiently mixed in a magnetic pot to prepare a phosphor coating slurry. This was poured into a glass tube, coated on its inner surface, dried with warm air, and the coating valve was baked at 450 ° C. for 15 minutes to form a fluorescent film. The amount of fluorescent substance applied per fluorescent lamp was 3.5 g. After that, according to a usual method, exhaustion, filament attachment, and attachment of a base were performed to produce a FL40SS fluorescent lamp for growing plants.

When this fluorescent lamp was turned on and the lamp output in the near infrared region and the luminous flux in the visible region were measured after 30 minutes,
Compared with a conventional fluorescent lamp manufactured by the same method except that a LiAlO ₂ : Fe phosphor having an average particle diameter of 1.9 μm was mixed, the output in the near infrared region was almost the same, but the visible region was about 12%. The improvement was seen.

[Example 2] L having an average particle size of 6.5 µm was prepared in the same manner as in Example 1 except that firing was performed at 1300 ° C for 2 hours.
An iAlO ₂ : Fe phosphor was obtained, and a fluorescent lamp was manufactured by the same method as in Example 1. LiA with an average particle size of 1.9 μm
Compared with the conventional fluorescent lamp manufactured by the same method except that the lO ₂ : Fe phosphor was mixed, the output in the near infrared region was almost the same, but the visible region was improved by about 19%.

[Embodiment 3] The same LiAlO ₂ : Fe phosphor as shown in Embodiment 2, a three-wavelength mixed phosphor and a calcium halophosphate phosphor Ca ₁₀ capable of achieving a color temperature of 5000 K with an average particle size of 4.2 μ. (PO ₄ ) ₆ FCl: Sb, M
A fluorescent lamp was manufactured in the same manner as in Example 1, except that n was mixed at a ratio of 1: 2: 2. LiA with an average particle size of 1.9 μm
Comparing conventional fluorescent lamps manufactured by the same method except mixing the lO ₂ : Fe phosphor, the outputs in the near infrared region were almost the same, but an improvement in the visible region of about 15% was observed.

[Embodiment 4] Same as the embodiment 2
LiAlO₂: Fe phosphor and emission peak at 450 nm
With BaMg₂A1₆O₂₇: Select Eu blue light emitting phosphor
Other than that, a fluorescent lamp is made using the same three-wavelength mixed phosphor.
Made. LiAlO with an average particle size of 1.9 μm ₂: Fe fluorescence
A conventional fluorescent lamp made in exactly the same way except that the bodies are mixed
Comparing the pumps, the output in the near infrared region was almost the same.
However, the visible range was improved by about 14%.

[0034]

As described above, according to the present invention, a fluorescent lamp having a near-infrared emitting LiAlO ₂ : Fe phosphor in the fluorescent layer and a phosphor layer made of a phosphor coexisting with the near-infrared light is used, and LiAlO ₂ : Fe By setting the average particle size of the phosphor to be at least ½ of the average particle size of the coexisting phosphor, the luminous flux in the visible region and the luminous flux maintenance factor can be significantly increased without lowering the emission performance in the near infrared region. Can be improved.

In particular, when the phosphor coexisting with the LiAlO ₂ : Fe phosphor is a white-light emitting phosphor, especially a three-wavelength mixed phosphor, it has a high commercial value with significantly improved luminous flux and luminous flux maintenance rate. A fluorescent lamp can be provided, and the production cost of a plant production factory can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a near-infrared emission LiAl of the fluorescent lamp of the present invention.
O _2: graph showing the relationship between the relative output in the particle diameter and the near-infrared region of the Fe phosphor.

FIG. 2 Near-infrared emission LiAl of the fluorescent lamp of the present invention
O _2: graph showing the relationship between the relative luminous flux in particle size and the visible range of the Fe phosphor.

FIG. 3 is a near-infrared emission LiAl of the fluorescent lamp of the present invention.
O _2: graph showing the relationship between the relative luminous flux in particle size and the visible range of the Fe phosphor.

FIG. 4 is a characteristic diagram showing the relationship between the lighting time of the fluorescent lamp of the present invention and the relative output in the near infrared region.

FIG. 5 is a characteristic diagram showing the relationship between the lighting time and the relative output in the visible range of the fluorescent lamp of the present invention.

Claims (3)

[Claims] 1. A transparent 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 transparent glass tube, and the filling gas. In the fluorescent lamp including means for maintaining discharge in positive light, the phosphor layer includes at least a near-infrared light emitting LiAlO ₂ : Fe phosphor and a phosphor coexisting with the near-infrared light emitting LiAlO 2. ₂ : A fluorescent lamp characterized in that the average particle size of the Fe phosphor is ½ or more of the average particle size of the coexisting phosphor. 2. The fluorescent lamp according to claim 1, wherein the fluorescent layer includes a white light emitting phosphor as a phosphor coexisting with the near-infrared light emitting LiAlO ₂ : Fe phosphor. 3. The white light emitting phosphor comprises a blue light emitting phosphor having an emission peak near 450 nm, a green light emitting phosphor having an emission peak near 545 nm, and a red light emitting phosphor having an emission peak near 610 nm. The fluorescent lamp according to claim 2, which is a three-wavelength mixed phosphor.