JP4044946B2 - Fluorescent lamp, backlight device, and method of manufacturing fluorescent lamp - Google Patents

Description

  The present invention relates to a fluorescent lamp, and more particularly to a technique for improving a luminous flux maintenance factor.

In recent years, cold cathode fluorescent lamps (see Patent Document 1) and external electrode fluorescent lamps using dielectric barrier discharge (see Patent Document 2) are used as light sources for backlight devices such as liquid crystal displays.
A cold cathode fluorescent lamp can be said to be a light source suitable for a backlight device for a thin display device because it can be easily made into a thin tube.

In addition, the external electrode fluorescent lamp is easier to control the brightness of a plurality of lamps than an internal electrode discharge lamp having an electrode in a glass tube. Therefore, a large screen in which a large number of fluorescent lamps are used. It can be said that this is a light source suitable for a backlight device for use.
JP-A-9-147802 JP 2004-95378 A

However, in both cold cathode type and external electrode type fluorescent lamps, the luminous flux maintenance factor during the life period cannot be said to be sufficient, and therefore, improvement thereof is desired.
The present invention has been made in view of the above points, and an object of the present invention is to provide a fluorescent lamp, a backlight device, and a method for manufacturing the fluorescent lamp with improved luminous flux maintenance factor.

As a result of intensive studies by the present inventors, it has been derived that mercury tends to adhere to the alumina-containing phosphor particles containing alumina, and this is the main factor in reducing the luminous flux maintenance factor.
Therefore, in order to achieve the above object, the fluorescent lamp according to the present invention includes mercury enclosed in a glass bulb, and alumina-containing phosphor particles and non-alumina-containing phosphor particles inside the glass bulb. A fluorescent lamp in which a phosphor layer is formed, wherein the phosphor layer includes at least green phosphor particles, and the green phosphor particles are the alumina-containing phosphor particles, and the alumina-containing phosphor It is characterized in that the metal oxide is adhered to the surface of the body particles more widely than the surface of the alumina-free phosphor particles. In this specification, “alumina-containing phosphor particles” refers to those containing Al _X O _{Y in the} chemical formula representing the phosphor particles, and “alumina-free phosphor particles” refers to phosphors This means that the chemical formula representing the particles does not contain Al _X O _Y.

In the above configuration, the metal oxide is adhered in a wider area on the surface of the alumina-containing phosphor particles, and the mercury adhesion to the phosphor particles can be effectively suppressed, so the luminous flux maintenance factor is improved. Can be measured.
Furthermore, since the metal oxide raw material that adheres to the surface of the phosphor particles is expensive, the amount of metal oxide that adheres to the surface of the alumina-containing phosphor particles, to which mercury easily adheres, is increased so that mercury adheres. Manufacturing cost can be suppressed by setting it as the structure which reduces the quantity of the metal oxide made to adhere to the surface of the alumina non-containing fluorescent substance particle which is difficult.

  Here, it is desirable that the metal oxide does not adhere to the surface of the alumina-free phosphor particles, and the metal oxide adheres only to the surface of the alumina-containing phosphor particles. In the above configuration, since the metal oxide is adhered to the alumina-containing phosphor particles, the adhesion of mercury to the phosphor particles can be effectively suppressed, and the luminous flux maintenance factor can be improved.

In addition, when metal oxide is present on the surface of the phosphor particles, ultraviolet rays are reflected by the metal oxide, and the phosphor particles are less likely to be excited. Since no metal oxide adheres to the surface, no reduction in luminance is observed as described above, and a high-intensity fluorescent lamp can be obtained.
Further, since the metal oxide raw material to be attached to the surface of the phosphor particles is expensive, the metal oxide is attached only to the alumina-containing phosphor particles, and the metal oxide is not attached to the alumina-free phosphor particles. With the configuration, the cost can be suppressed.

  In addition, although it is described that “the metal oxide is attached only to the surface of the alumina-containing phosphor particles”, the phosphor layer is made of alumina-free phosphor particles and alumina to which the metal oxide is attached. Since the phosphor particles are in a mixed state, there may be a slight amount of metal oxide on the surface of the phosphor particles not containing alumina. It is included in the concept of “the metal oxide is attached only to”.

In the above structure, the metal oxide includes Y ₂ O ₃ , MgO, La ₂ O ₃ , SiO ₂ , ZrO ₂ , HfO ₂ , Y ₂ O ₅ , Nb ₂ O ₅ , CaO, MgO, SrO, BaO. Or at least one of Gd ₂ O ₃ is desirable.
By using these as the metal oxide, mercury adhesion to the phosphor particles can be suppressed. In addition, since these metal oxides easily transmit ultraviolet light having a wavelength of 254 nm emitted from mercury, the phosphor particles are easily excited by the ultraviolet light.

Here, it is desirable that the metal oxide is adhered at a ratio of 0.005 wt% to 5.0 wt% with respect to the alumina-containing phosphor particles.
This is because it has been confirmed that when the metal oxide deposition ratio is less than 0.005 wt%, the luminous flux maintenance factor decreases, and when it is greater than 5.0 wt%, it is confirmed that the initial luminance decreases. Because.

Here, it is desirable that a protective film is formed between the glass bulb and the phosphor layer. By setting it as the said structure, it can suppress that the mercury enclosed with the glass bulb and the glass bulb reacts.
Further, the glass bulb may have a tubular shape, and external electrodes may be provided on the outer circumferences of both ends. The external electrode type fluorescent lamp is easier to control the brightness of a plurality of lamps than an internal electrode type discharge lamp having an electrode in a glass tube, and is particularly suitable for a large screen for which a large number of fluorescent lamps are used. It can be said that the light source is suitable for a backlight device.

Here, it is desirable that the phosphor layer is formed in a region corresponding to the space between the external electrodes in the glass bulb.
Conventionally, even if the phosphor layer formed at a position corresponding to the external electrode in the glass bulb is removed, mercury adheres to the slightly remaining alumina-containing phosphor particles, so that mercury is consumed and luminance decreases. In addition, the electric field concentrates on the mercury adhering to the alumina-containing phosphor particles, and there is a problem that pinholes are generated in the glass bulb. In the present invention, since the metal oxide for suppressing the adhesion of mercury is attached to the surface of the alumina-containing phosphor particles, even if the alumina-containing phosphor particles remain in the region corresponding to the external electrode in the glass bulb. In addition, mercury does not easily adhere to the alumina-containing phosphor particles, so that mercury consumption is suppressed, and as described above, the electric field concentrates on the mercury adhering to the alumina-containing phosphor particles, and pinholes are formed in the glass bulb. The phenomenon that occurs is also unlikely to occur.

In order to achieve the above object, a backlight device according to the present invention includes any one of the fluorescent lamps described above as a light source.
Since the fluorescent lamp described above is provided as a light source, a backlight device with improved luminous flux maintenance factor can be provided.
In order to achieve the above object, a method for manufacturing a fluorescent lamp according to the present invention includes mercury enclosed in a glass bulb, and alumina-containing phosphor particles and alumina-free phosphor particles inside the glass bulb. A method of manufacturing a fluorescent lamp in which a phosphor layer containing phosphine is formed, comprising an adhesion step of depositing a metal oxide on the surface of alumina-containing phosphor particles containing alumina, and metal oxidation on the surface by the deposition step A suspension creating step of mixing a phosphor-containing phosphor particle to which an object is adhered and an alumina-free phosphor particle not containing alumina to create a phosphor suspension; and And a phosphor layer forming step of forming the phosphor layer by coating the inside of the glass bulb.

According to this method, it is possible to easily manufacture a fluorescent lamp in which a metal oxide is attached only to the surface of alumina-containing phosphor particles.
In addition, the fluorescent lamp manufactured by the above manufacturing method has a metal oxide adhered to the surface of the alumina-containing phosphor particles, so that mercury adhesion to the phosphor particles can be effectively suppressed, and the luminous flux is maintained. The rate can be improved.

  Furthermore, since the raw material of the metal oxide attached to the phosphor particles is expensive, the metal oxide is attached only to the surface of the alumina-containing phosphor particles, and the metal oxide is not attached to the alumina-free phosphor particles. With the configuration, the cost can be suppressed.

Hereinafter, a fluorescent lamp and a backlight device according to embodiments of the present invention will be described with reference to the drawings.
<Configuration of backlight device>
First, the configuration of the backlight device according to the present embodiment will be described with reference to FIG. FIG. 1 is a schematic perspective view showing a configuration of a liquid crystal display backlight device 1 having an aspect ratio of 16: 9 according to the present embodiment. In the figure, a part of the front panel 16 is cut away to show the internal structure.

As shown in FIG. 1, the backlight device 1 includes a plurality of lamps 20, a housing 10 that has openings and accommodates the lamps 20, and a front panel 16 that covers the openings of the housing 10. Prepare.
The housing 10 is made of, for example, polyethylene terephthalate (PET) resin, and a reflective surface is formed by depositing a metal such as silver on the inner surface 11 thereof.

The lamp 20 has a straight tube shape, and in the present embodiment, 14 lamps 20 are arranged in the casing 10 in a direct-down manner and are electrically connected in parallel. The configuration of the lamp 20 will be described later.
The opening of the housing 10 is covered with a translucent front panel 16 formed by laminating a diffusion plate 13, a diffusion sheet 14, and a lens sheet 15, so that foreign matters such as dust and dust do not enter inside. It is sealed.

The diffusion plate 13 and the diffusion sheet 14 in the front panel 16 scatter and diffuse the light emitted from the lamp 20, and the lens sheet 15 arranges the light in the normal direction of the sheet 15, Thus, the light emitted from the lamp 20 is configured to irradiate the front uniformly over the entire surface (light emitting surface) of the front panel 16.
<First Embodiment>
1-1. (Configuration of cold cathode fluorescent lamp)
Next, the configuration of a cold cathode fluorescent lamp 20A (hereinafter referred to as “lamp 20A”) that is the lamp 20 according to the first embodiment will be described with reference to FIG. FIG. 2 is a partially cutaway view showing a schematic configuration of the cold cathode fluorescent lamp 20A.

The lamp 20A includes a glass bulb 30 having a substantially circular cross section and a straight tube shape. The glass bulb 30 is made of, for example, borosilicate glass. The glass bulb 30 has a length of 720 mm and an inner diameter of 8 mm or less, for example, 3.0 mm.
The lead wire 21 is a connection between an internal lead wire made of tungsten and an external lead wire made of nickel, and the glass bulb 30 is hermetically sealed at both ends corresponding to the internal lead wire.

  The electrode 22 is joined to the end portion of the internal lead wire inside the glass bulb 30 by laser welding or the like. The electrode 22 is a so-called hollow electrode having a bottomed cylindrical shape, and is obtained by processing a niobium rod or a nickel rod. The reason why the hollow electrode is used as the electrode 22 is that it is effective for suppressing sputtering in the electrode caused by the discharge when the lamp is turned on.

The glass bulb 30 is filled with, for example, a predetermined amount of mercury and a rare gas (Ar: 5%, Ne: 95%) having a gas pressure of 60 Torr. A protective film 32 is formed on the inner surface of the glass bulb 30, and a phosphor layer 34 is attached to the protective film 32.
The protective film 32 is made of a metal oxide such as yttrium oxide (Y ₂ O ₃ ), for example, and has a function of suppressing the reaction between mercury enclosed in the glass bulb 30 and the glass bulb 30. . Further, by forming the protective film 32 with, for example, titanium oxide (TiO ₂ ) or cerium oxide (CeO), it has a function of blocking the ultraviolet rays emitted from mercury so that the ultraviolet rays emitted from the mercury do not leak from the glass bulb. It can also be made.

The phosphor layer 34 emits red, green and blue light when excited, and emits red phosphor particles (Y ₂ O ₃ : Eu ³⁺ ) (alumina-free phosphor particles), green phosphor particles. Including a rare earth phosphor in which (LaPO ₄ : Tb ³⁺ , Ce ³⁺ ) (alumina-free phosphor particles) and blue phosphor particles (BaMg ₂ Al ₁₆ O ₂₇ : Eu ²⁺ ) (alumina-containing phosphor particles) are mixed. Yes.

In the present embodiment, in the phosphor layer 34, as shown in the enlarged view in the figure, the surface of the blue phosphor particle 34B (BaMg ₂ Al ₁₆ O ₂₇ : Eu ²⁺ ) is coated with yttrium oxide (as the metal oxide 36). Y ₂ O ₃ ) is coated. The red phosphor particles 34R and the green phosphor particles 34G may also adhere to the metal oxide on the contact surface with the blue phosphor particles 34B.

1-2. (Method for forming phosphor layer 34)
Hereinafter, a method for forming the phosphor layer 34 will be described. First, the process of coating the blue phosphor particles (alumina-containing phosphor particles) with a metal oxide will be described.
As materials, blue phosphor particles (BaMg ₂ Al ₁₆ O ₂₇ : Eu ²⁺ ) powder, yttrium octylate [Y (C ₇ H ₁₅ COO) ₃ ], and butyl acetate are prepared.

Blue phosphor particle powder and yttrium octylate are charged into a container containing butyl acetate and stirred. After sufficiently stirring, the container is allowed to stand at room temperature for a sufficient time to spontaneously evaporate butyl acetate in the solution.
Next, the powder remaining in the beaker is fired at 600 ° C. for 5 minutes. Since the powder obtained by baking is agglomerated and the particle size is not uniform, it is pulverized by a ball mill to adjust the particle size. Through the above steps, blue phosphor particles having a yttrium oxide film formed on the surface can be obtained.

In addition, it is conceivable to cover the blue phosphor particles with a metal oxide using YH (C ₇ H ₁₅ COO) ₂ instead of Y (C ₇ H ₁₅ COO) ₃ described above. This is not preferable from the viewpoint of the covering state of the phosphor particles.
FIG. 3 is an enlarged photograph showing a state when a metal oxide film is formed on the surface of the blue phosphor particles. FIG. 3A is a film using Y (C ₇ H ₁₅ COO) _3. FIG. 3B shows a state when a film is formed using YH (C ₇ H ₁₅ COO) ₂ .

When Y (C ₇ H ₁₅ COO) ₃ is used, a dense coating is formed on the surface of the phosphor particles as shown in FIG. This is because the coating is composed of molecules having a three-dimensional cyclic structure.
On the other hand, when YH (C ₇ H ₁₅ COO) ₂ is used, as shown in FIG. 3B, the film formed on the surface of the phosphor particles becomes scaly, and Y (C ₇ H _{15 COO) 3} not a dense film as in the case of using. This is because the coating consists of a collection of molecules having a chain structure.

If the metal oxide film is not dense, mercury tends to adhere to the phosphor particles. Therefore, the film is formed using Y (C ₇ H ₁₅ COO) ₃ instead of YH (C ₇ H ₁₅ COO) _2. It is preferable to do.
In place of yttrium octylate [Y (C ₇ H ₁₅ COO) ₃ ], yttrium acetate [Y (CH ₃ COO) ₃ ], yttrium nitrate [Y (NO ₃ ) ₃ ], yttrium propionate [Y (C _{2 H 5 COO) 3 · H} 2 O] may be used. Even when these are used, the coating film is composed of molecules having a cyclic structure, so that the phosphor particles are covered with a dense coating film.

In addition, the metal oxide is preferably attached at a ratio of 0.005 wt% to 5.0 wt% with respect to the phosphor particles. This is because it has been confirmed that when the adhesion ratio of the metal oxide to the phosphor particles is less than 0.005 wt%, the luminous flux maintenance factor is lowered, and when it is greater than 5.0 wt%, the initial luminance is lowered. This is because it has been confirmed.
Next, a process for preparing the phosphor suspension will be described.

As materials, red phosphor particles (Y ₂ O ₃ : Eu ³⁺ ) (alumina-free phosphor particles) and green phosphor particles (LaPO ₄ : Tb ³⁺ , Ce ³⁺ ) (with no metal oxide attached to the surface) ( Non-alumina-containing phosphor particles), blue phosphor particles having a yttrium oxide coating formed by the above-mentioned steps, binders, thickeners, dispersions mainly composed of calcium-barium-boron-phosphorus oxides. An agent and butyl acetate are prepared.

First, a predetermined amount of butyl acetate, a binder, a thickener, and a dispersant are put in a beaker and mixed. Then, red phosphor particles, green phosphor particles, and blue phosphor particles having a film formed of yttrium oxide are put into this solution and sufficiently stirred. Thereby, a phosphor suspension is obtained.
Then, using a known technique, this phosphor suspension is applied to the inside of the glass bulb to form a phosphor layer, so that only blue phosphor particles (alumina-containing phosphor particles) are covered with yttrium oxide. Thus, the phosphor layer 34 can be obtained.

1-3. (Background)
Hereinafter, the background of coating the metal oxide only on alumina-containing blue phosphor particles (BaMg ₂ Al ₁₆ O ₂₇ : Eu ²⁺ ) will be described.
First, the present inventors, in a white-light cold cathode fluorescent lamp formed with a phosphor layer by mixing phosphor particles emitting red, green, and blue light when excited, each color phosphor The luminous flux maintenance factor of the main wavelength emitted by the particles was measured.

FIG. 4 is a graph showing the measurement results of the luminous flux maintenance factors of the main wavelengths emitted by the phosphor particles of each color in the three-wavelength type white cold cathode fluorescent lamp. The vertical axis of the graph is the luminous flux maintenance factor (%), and the horizontal axis is the life time (h). The main wavelengths emitted by the respective color phosphor particles are 613 nm for red phosphor particles (Y ₂ O ₃ : Eu ³⁺ ), 545 nm for green phosphor particles (LaPO ₄ : Tb ³⁺ , Ce ³⁺ ), and blue phosphor particles ( BaMg ₂ Al ₁₆ O ₂₇ : Eu ²⁺ ) is 450 nm.

From the graph of FIG. 4, it can be seen that the luminous flux maintenance factor of the main wavelength of each color decreases as the life time elapses. In particular, it can be seen that the luminous flux maintenance factor of the main wavelength emitted by the blue phosphor particles is the lowest.
Subsequently, the present inventors have used red phosphor particles (Y ₂ O ₃ : Eu ³⁺ ), green phosphor particles (LaPO ₄ : Tb ³⁺ , Ce ³⁺ ), blue phosphor particles (BaMg ₂ Al ₁₆ O ₂₇ : Eu). ²⁺ ) each of which has a phosphor layer formed, and three kinds of cold cathode fluorescent lamps emitting single colors of red, green, and blue are prototyped. It was measured.

FIG. 5 is a graph showing the measurement results of the luminous flux maintenance factor of each single-color cold cathode fluorescent lamp. The vertical axis of the graph is the luminous flux maintenance factor (%), and the horizontal axis is the life time (h).
The graph shows that the red and green cold cathode fluorescent lamps have a relatively high luminous flux maintenance factor, and the blue cold cathode fluorescent lamp has a significantly lower luminous flux maintenance factor than these.
From this result, it can be inferred that the blue phosphor particles are less likely to emit light than the red phosphor particles and the green phosphor particles in the elapse of time from the start of lighting.

Here, when FIG. 4 is compared with FIG. 5, the light emitted from the red phosphor particles and the green phosphor particles has a high luminous flux maintenance factor in the result shown in FIG. 5, but in the result shown in FIG. 4, The luminous flux maintenance factor is significantly low.
This is because, in a white cold cathode fluorescent lamp in which phosphor layers are formed by mixing phosphor particles of red, green, and blue, blue phosphor particles that tend to be less likely to emit light in the phosphor layer, In order to influence the light emitted from the red and green phosphor particles or the red and green phosphor particles, the light emitted from the red and green phosphor particles as shown in FIG. It is thought that the maintenance rate of the was reduced.

That is, it is estimated that the fact that the blue phosphor particles are less likely to emit light is the main cause of the decrease in the luminous flux maintenance factor of the white fluorescent lamp.
Furthermore, the present inventors repeated various tests to investigate the cause of the decrease in luminous flux maintenance factor. Among them, it was possible to estimate the factor of the decrease in luminous flux maintenance rate by the test of heating the lamp at the end of life. Hereinafter, this test will be described.

Specifically, the present inventors conducted a test in which a cold-cathode fluorescent lamp at the end of its life was installed in an electric furnace, and the temperature of the electric furnace was increased to gradually heat the lighting lamp. .
FIG. 6 is a graph showing changes in luminance and chromaticity when a three-wavelength white cold cathode fluorescent lamp at the end of life is heated. The vertical axis of the graph is the luminance (cd / m ² ) and chromaticity, and the horizontal axis is the heating temperature (° C.).

From the graph shown in FIG. 6, it can be seen that the luminance gradually recovers as the heating temperature increases. It can also be seen that the chromaticity changes as the heating temperature increases.
First, consider changes in chromaticity. When the heating temperature is 0 ° C., the light emitted from the cold cathode fluorescent lamp has chromaticity x≈0.310 and chromaticity y≈0.309 on the chromaticity diagram, that is, white.

It can be seen that the chromaticity x and the chromaticity y decrease as the heating temperature increases. In other words, in the chromaticity diagram, the color changes from the white region toward the lower left, and as the heating temperature rises, the blue component increases, resulting in a bluer white than before heating. You can see that it is changing.
It can be considered that the reason why the luminance recovered as the heating temperature increased was mainly due to the increase in the light component emitted from the blue phosphor particles.

Next, the change in luminance is examined. As the heating temperature rises, the brightness is recovered, but this rise in brightness starts when the heating temperature is around 200 ° C.
This is because the temperature of the phosphor layer exceeds 356.58 ° C., which is the boiling point of mercury, and the mercury adhering to the phosphor particles evaporates due to the heat generated by the discharge accompanying lighting and the forced heating by the electric furnace. It is estimated that

  That is, the brightness of blue light recovered by heating shown in FIG. 6 is presumed to be due to the mercury adhering to the blue phosphor particles evaporating and the blue phosphor particles recovering to a state where they easily emit light. Is done. In other words, it is considered that the main factor that decreases the luminance in the cold cathode fluorescent lamp is that the blue phosphor particles are hardly excited by ultraviolet rays due to the adhesion of mercury to the blue phosphor particles.

In addition, the present inventors investigated the relationship between the type of binder contained in the phosphor layer and the luminous flux maintenance factor by an experiment different from the above. Specifically, fluorescence is obtained using a binder mainly composed of aluminum oxide (Al ₂ O ₃ ) and a binder mainly composed of each oxide of calcium-barium-boron-phosphorus (CBBP). Two types of cold cathode fluorescent lamps having a body layer were prepared, and the luminous flux maintenance factor of each lamp was measured. The binder content in the phosphor layer was adjusted so that the weight ratio of each lamp was 1.5% with respect to the phosphor.

As a result, the luminous flux maintenance factor at 500 hours of lighting was 92.6% in the lamp using CBBP as the binder. On the other hand, in the lamp using Al ₂ O ₃ as the binder, it was 88.3%, and the luminous flux maintenance factor was lower than that in the case of using CBBP. This is considered to be due to the fact that mercury tends to adhere to the binder Al ₂ O ₃ .
Based on this result, the present inventors examined the cause of the tendency for mercury to adhere to the blue phosphor particles. The inventors of the present invention are that mercury is likely to adhere to the blue phosphor particles (BaMg ₂ Al ₁₆ O ₂₇ : Eu ²⁺ ) because the chemical formula representing the blue phosphor particles includes Al _X O _Y. I came to get the inference that it might be caused by.

Therefore, the present inventors have used fluorescence of BaAl ₈ O ₁₃ : Eu ²⁺ , Ba ₃ MgSi ₂ O ₈ : Eu ²⁺ , SrMgP ₂ O ₇ : Eu ²⁺ , and CaWO ₄ as the blue phosphor particles. The luminous flux maintenance factor of the lamp was measured. As a result, it was found that only the lamp using BaAl ₈ O ₁₃ : Eu ²⁺ had a significantly lower luminous flux maintenance factor than other lamps.

That is, when Al _X O _{Y is} embedded in the blue phosphor particles, the inference that mercury easily adheres to the blue phosphor particles, which causes a decrease in the luminous flux maintenance factor, is correct. it is conceivable that. Based on the above circumstances, the present inventors have come to coat only the alumina-containing phosphor particles with the metal oxide.
Although it is conceivable that the surface of the phosphor particles not containing alumina (Al _X O _Y ) does not contain alumina, a metal oxide may be coated. It is considered that the luminance is lowered because the phosphor particles are hardly excited by being reflected by the oxide. Therefore, it can be said that the metal oxide is preferably coated only on the alumina-containing phosphor particles that are likely to be attached with mercury.

1-4. (Example)
Hereinafter, effects of the lamp 20A according to the present embodiment will be described based on examples.
As an example, the fluorescent lamp emitting white light according to the present embodiment in which only the above-described blue phosphor particles are coated with a metal oxide is used, and as a comparative example, the phosphor particles are not coated with any metal oxide. A conventional fluorescent lamp emitting white light was used.

The inventors measured the change in luminous flux maintenance factor and luminance over time for the examples and comparative examples. FIG. 7 is a graph showing the results of measuring the luminous flux maintenance factor for Examples and Comparative Examples.
FIG. 7 shows that the luminous flux maintenance factor is improved in the example compared to the comparative example. In this example, since the blue phosphor particles (alumina-containing phosphor particles) that easily adhere to mercury are coated with a metal oxide for suppressing the adhesion of mercury, the decrease in the luminous flux maintenance factor is moderate. It is thought that it became.

  In the comparative example, the blue phosphor particles that tend to be less likely to emit light affect the light emitted by the red and green phosphor particles or the red and green phosphor particles. It was also confirmed that the luminous flux maintenance factor of the main wavelength emitted by the red, green phosphor particles was also lowered. On the other hand, in the example, since the blue phosphor particles are coated with the metal oxide, the luminous flux maintenance factor of the main wavelength emitted by the blue phosphor particles is improved, and the presence of the blue phosphor particles is red and green. Since it does not affect the light emission of each phosphor particle, the improvement of the luminous flux maintenance factor was confirmed for the main wavelengths emitted by the red and green phosphor particles.

  FIG. 8 is a graph showing measurement results of luminance change over time for Examples and Comparative Examples. Referring to FIG. 8, the initial luminance is higher in the comparative example than in the example. This is because the blue phosphor particles are coated with the metal oxide in the examples, and the ultraviolet rays are reflected by the metal oxide, so that the phosphor particles are hardly excited.

However, when the life time is about 80 hours, the luminance of the example and the comparative example becomes comparable, and after that, the luminance of the example is higher.
In this embodiment, since the blue phosphor particles (alumina-containing phosphor particles) are coated with a metal oxide, mercury is prevented from adhering to the phosphor particles, so that the luminance is gradually reduced. On the other hand, in the comparative example, since the surface of the blue phosphor particles is not coated with a metal oxide, mercury adheres to the blue phosphor particles, and the blue phosphor particles are less likely to be excited by ultraviolet rays. This is because it is large and decreases.

Incidentally, since the lifetime of the cold cathode fluorescent lamp is about 60,000 hours or more, the brightness of the example is higher over a longer life period.
By providing the configuration of the lamp 20A according to the present embodiment based on the above comparative test, it is possible to improve the luminous flux maintenance factor as compared with the conventional configuration of the lamp, and to provide a lamp with high brightness over the long life period. It can be concluded that

<Second Embodiment>
Hereinafter, a fluorescent lamp according to a second embodiment of the present invention will be described.
2-1. (Configuration of external electrode fluorescent lamp)
With reference to FIG. 9, an external electrode fluorescent lamp 20B (hereinafter referred to as “lamp 20B”), which is the lamp 20 according to the second embodiment, will be described.

9A and 9B are diagrams showing the configuration of the lamp 20B according to the second embodiment, in which FIG. 9A is a plan view of the lamp 20B, and FIG. 9B shows the end of the lamp 20B. It is an expanded sectional view when cut | disconnecting by the plane containing a pipe axis.
As shown in FIG. 9A, the lamp 20B includes a glass bulb 40 in which both ends of a straight cylindrical glass tube are sealed, and external electrodes 51 formed on the outer circumferences of both ends of the glass bulb 40, 52.

The glass bulb 40 is made of, for example, borosilicate glass, and has a substantially circular cross section when cut along a plane perpendicular to the tube axis. The glass bulb 40 has a length of 720 mm and an inner diameter of 8 mm or less, for example, 3.0 mm.
The external electrodes 51 and 52 are made of, for example, aluminum metal foil, and are attached so as to cover the outer periphery of the glass bulb 40 with a conductive adhesive in which metal powder is mixed with silicon resin. As the conductive adhesive, fluorine resin, polyimide resin, epoxy resin, or the like may be used instead of silicon resin.

Further, instead of attaching the metal foil to the glass bulb 40 with the conductive adhesive, the external electrodes 51 and 52 may be formed by applying silver paste to the entire circumference of the electrode forming portion of the glass bulb 40. Further, the external electrodes 51 and 52 may have a cylindrical shape or a cap shape that covers the end of the glass bulb 40.
As shown in FIG. 9B, a protective film 42 made of, for example, yttrium oxide (Y ₂ O ₃ ) is formed on the inner surface of the glass bulb 40. The protective film 42 has a function of suppressing the reaction between the mercury enclosed in the glass bulb 40 and the glass bulb 40.

A phosphor layer 44 is deposited on the protective film 42. The phosphor layer 44 emits red, green, and blue light when excited, red phosphor particles (Y ₂ O ₃ : Eu ³⁺ ) (alumina-free phosphor particles), green phosphor Includes rare earth phosphors in which particles (LaPO ₄ : Tb ³⁺ , Ce ³⁺ ) (alumina-free phosphor particles) and blue phosphor particles (BaMg ₂ Al ₁₆ O ₂₇ : Eu ²⁺ ) (alumina-containing phosphor particles) are mixed. It is.

As shown in FIG. 9A, when the position of the end portion on the lamp center side of the external electrodes 51 and 52 is B, the phosphor layer 44 is formed in a region corresponding to between B and B in the glass bulb 40. Has been.
A phosphor layer is not formed in the region R (between A and B) corresponding to the external electrodes 51 and 52 in the glass bulb 40. This is because if the phosphor layer is present in the region R, it reacts with mercury during lamp operation and is consumed.

In the present embodiment, in the phosphor layer 44, as shown in the enlarged view in the figure, a metal is formed on the surface of the blue phosphor particles 44B (BaMg ₂ Al ₁₆ O ₂₇ : Eu ²⁺ ) (alumina-containing phosphor particles). Yttrium oxide (Y ₂ O ₃ ) is coated as the oxide 46. The red phosphor particles 44R and the green phosphor particles 34G may also adhere to the metal oxide on the contact surface with the blue phosphor particles 44B.

2-2. (Method for forming phosphor layer 44)
Next, a method for forming the phosphor layer 44 will be briefly described.
First, a phosphor suspension is prepared by the same process as described in the first embodiment.
This phosphor suspension is applied to the inner surface of the glass bulb on which the protective film 42 has been formed using a known method to form a phosphor layer. Here, the phosphor layer in the region R where the external electrodes 51 and 52 are disposed on the outer periphery is removed.

Thereby, in the glass bulb 40, the phosphor layer 44 is formed in a region corresponding to between the external electrode 51 and the external electrode 52 and between BB.
2-3. (effect)
When a test for comparing the lamp characteristics of the lamp 20B according to the second embodiment and the external electrode type fluorescent lamp having the conventional configuration was performed, the lamp 20B according to the second embodiment was found to have blue phosphor particles ( Since the alumina-containing phosphor particles are coated with a metal oxide, the luminous flux maintenance factor is improved as compared with the external electrode fluorescent lamp having the conventional configuration, as in the lamp 20A according to the first embodiment. It was confirmed that a lamp with high brightness can be obtained over a long lifetime.

Further, in the lamp 20B according to the second embodiment, the following specific effects in the external electrode type fluorescent lamp can be obtained.
Even if the phosphor layer existing in the region R is removed in the manufacturing process of the external electrode type fluorescent lamp, a small amount of phosphor particles remain in the region R. Conventionally, there has been a problem that mercury consumption is induced by the presence of the remaining phosphor particles.

According to the diligent research of the present inventors, the main cause of mercury consumption is that mercury tends to adhere particularly to alumina-containing phosphor particles (in this example, blue phosphor particles) of the phosphor particles. It has been found that when the contained phosphor particles remain in the region R, the mercury easily reacts with mercury during lamp operation and is easily consumed.
In the present embodiment, the blue phosphor particles (alumina-containing phosphor particles) remaining in the region R are also coated with a metal oxide, and mercury is not easily attached to the blue phosphor particles. Since the phenomenon that the electric field concentrates on the blue phosphor particles to which is attached is difficult to occur, the above-described effect of suppressing mercury consumption can be obtained.

<Modification>
As described above, the present invention has been described based on the embodiments. However, the content of the present invention is not limited to the specific examples shown in the above embodiments. For example, the following modifications are possible. Can think.
(1) In the above description, the metal oxide is coated on the surface of only the alumina-containing phosphor particles. However, the metal oxide may also adhere to the surface of the alumina-free phosphor particles. However, from the viewpoint of increasing the luminance of the lamp, the amount of the metal oxide attached to the alumina-free phosphor particles is preferably very small compared to the amount of the metal oxide attached to the alumina-containing phosphor particles. .

  That is, it is preferable that the metal oxide is attached to the surface of the alumina-containing phosphor particles in a wider area than the surface of the alumina-free phosphor particles. As a result, the mercury adhesion to the alumina-containing phosphor particles can be suppressed and the decrease in the luminous flux maintenance factor can be suppressed, and the non-alumina-containing phosphor particles are easily excited by ultraviolet rays. Can be obtained.

  (2) In the second embodiment, as shown in FIG. 9, a configuration in which the phosphor layer 44 is formed only between the external electrode 51 and the external electrode 52 and only in a region corresponding to BB is described. However, a phosphor layer may be formed in a region corresponding to the external electrodes 51 and 52 (for example, between A and B in FIG. 9B). Also in this case, mercury consumption is suppressed because the surface of the blue phosphor particles (alumina-containing phosphor particles) is coated with the metal oxide.

(3) In the above description, the case where the aluminate phosphor BaMg ₂ Al ₁₆ O ₂₇ : Eu ²⁺ is used as the blue phosphor particle has been described, but instead of BaMg ₂ Al ₁₆ O ₂₇ : Eu ²⁺ Blue phosphor particles of aluminate phosphor, for example, BaAl ₈ O ₁₃ : Eu ²⁺ , BaMg ₂ Al ₁₆ O ₂₇ : Eu ²⁺ , Mn ²⁺ , Sr ₄ Al ₁₄ O ₂₇ : Eu ²⁺ , or SrMgAl ₁₀ O ₁₇ : Similar results and effects were obtained even when Eu ²⁺ was used.

(4) In the above description, the configuration using yttrium oxide (Y ₂ O ₃ ) as the metal oxide covering the blue phosphor particles has been described. However, magnesium oxide (MgO), lanthanum oxide is used instead of yttrium oxide. (La ₂ O ₃ ), silicon oxide (SiO ₂ ), zirconium oxide (ZrO ₂ ), hafnium oxide (HfO ₂ ), yttrium oxide (Y ₂ O ₅ ), niobium oxide (Nb ₂ O ₅ ), calcium oxide (CaO) ), Magnesium oxide (MgO), strontium oxide (SrO), barium oxide (BaO), or gadolinium oxide (Gd ₂ O ₃ ). The metal oxide includes yttrium oxide (Y ₂ O ₃ ), magnesium oxide (MgO), lanthanum oxide (La ₂ O ₃ ), silicon oxide (SiO ₂ ), zirconium oxide (ZrO ₂ ), and hafnium oxide (HfO ₂ ). ), Yttrium oxide (Y ₂ O ₅ ), niobium oxide (Nb ₂ O ₅ ), calcium oxide (CaO), magnesium oxide (MgO), strontium oxide (SrO), barium oxide (BaO), or gadolinium oxide (Gd _2). Any two or more of O ₃ ) may be mixed.

(5) In the above description, the example in which yttrium oxide (Y ₂ O ₃ ) is used as the material of the protective films 32 and 42 has been described. However, instead of yttrium oxide, titanium oxide (TiO ₂ ), cerium oxide (CeO) is used. ₂ ), magnesium oxide (MgO), lanthanum oxide (La ₂ O ₃ ), or two or more of these may be used.
(6) In the above description, the configuration in which the protective films 32 and 42 are formed has been described. However, the phosphor layer may be formed directly on the inner surface of the glass bulb without forming the protective film. Good.

  In this case, in the external electrode type fluorescent lamp, even if the phosphor layer formed at the position corresponding to the external electrode in the glass bulb is removed, the remaining blue phosphor particles (alumina-containing phosphor particles) remain slightly. Adhering to mercury has an adverse effect that an electric field concentrates on the mercury and pinholes are generated in the glass bulb. However, in the second embodiment, since the metal oxide for suppressing the adhesion of mercury is attached to the surface of the blue phosphor particles, the region corresponding to the external electrode in the glass bulb (FIG. 9B) Even if the blue phosphor particles remain in the region R), mercury does not easily adhere to the blue phosphor particles, and as described above, an electric field concentrates on the mercury and a pinhole is generated in the glass bulb. The effect that it hardly occurs is obtained.

(7) In the above, among the phosphor particles of each color, the blue phosphor particles (BaMg ₂ Al ₁₆ O ₂₇ : Eu ²⁺ ) contain Al _X O _Y in the chemical formula. However, instead of LaPO ₄ : Tb ³⁺ and Ce ³⁺ described above, for example, BaMg ₂ Al ₁₆ O ₂₇ : Eu containing Al _X O _Y in the chemical formula is used as a green phosphor particle. ^{When 2+} , Mn ²⁺ or the like is used, mercury easily adheres to the green phosphor particles, so that it is preferable to coat the metal oxide.

  (8) In the above description, the glass bulb has been described as having a straight tube shape. However, for example, the glass bulb may have a bent shape. The gas pressure in the glass bulb may be 30 Torr to 100 Torr. Furthermore, it has been confirmed that the inner diameter of the glass bulb may be 1.2 mm to 6 mm, and the length of the glass bulb may be 1.5 m or less.

  The present invention can be widely applied to cold cathode type and external electrode type fluorescent lamps. Moreover, since the present invention can provide a fluorescent lamp and a backlight device having a high luminous flux maintenance factor, its industrial utility value is extremely high.

It is a schematic perspective view which shows the structure of the backlight apparatus 1 for liquid crystal displays of the aspect ratio 16: 9 which concerns on this Embodiment. It is a partially cutaway view showing a schematic configuration of a cold cathode fluorescent lamp 20A. FIG. 3A is an enlarged photograph showing a state when a metal oxide film is formed on the surface of the blue phosphor particles, and FIG. 3A is a diagram when the film is formed using Y (C ₇ H ₁₅ COO) _3. FIG. 3B shows a state when a film is formed using YH (C ₇ H ₁₅ COO) ₂ . It is the graph which showed the measurement result of the luminous flux maintenance factor of the main wavelength which each color fluorescent substance particle | grain emits in the white fluorescent lamp which formed the fluorescent substance layer by mixing each color fluorescent substance particle of red, green, and blue. It is the graph which showed the measurement result of the luminous flux maintenance factor of each monochromatic cold cathode fluorescent lamp. It is a graph which shows the change of a brightness | luminance and chromaticity when the cold cathode fluorescent lamp of the end of life is heated. It is a graph which shows the result of having measured the luminous flux maintenance factor about an example and a comparative example. It is a graph which shows the measurement result of the time change of a brightness about an example and a comparative example. It is a figure which shows the structure of the lamp | ramp 20B which concerns on 2nd Embodiment, Comprising: Fig.9 (a) is a top view of the lamp | ramp 20B, FIG.9 (b) shows the edge part of the lamp | ramp 20B, and a tube axis. It is an expanded sectional view when it cut | disconnects in the plane containing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Backlight apparatus 20A Cold cathode fluorescent lamp 20B External electrode type fluorescent lamp 30, 40 Glass bulb 32, 42 Protective film 34, 44 Phosphor layer 34B, 44B, 64B Blue phosphor particle 34R, 44R, 64R Red phosphor particle 34G , 44G, 64G Green phosphor particles 36, 46 Yttrium oxide coating 66 Metal oxide particles 51, 52 External electrode

Claims (9)

A fluorescent lamp in which mercury is enclosed in a glass bulb, and a phosphor layer containing alumina-containing phosphor particles and non-alumina-containing phosphor particles is formed inside the glass bulb,
The phosphor layer includes at least green phosphor particles,
The green phosphor particles are the alumina-containing phosphor particles,
A fluorescent lamp characterized in that a metal oxide adheres more widely on the surface of the alumina-containing phosphor particles than on the surface of the non-alumina-containing phosphor particles. The metal oxide does not adhere to the surface of the alumina-free phosphor particles,
The fluorescent lamp according to claim 1, wherein the metal oxide is attached to a surface of the alumina-containing phosphor particles. Examples of the metal oxide include Y ₂ O ₃ , MgO, La ₂ O ₃ , SiO ₂ , ZrO ₂ , HfO ₂ , Y ₂ O ₅ , Nb ₂ O ₅ , CaO, MgO, SrO, BaO, or Gd ₂ O. The fluorescent lamp according to claim 1, wherein at least one of ₃ is included. The metal oxide is attached to the alumina-containing phosphor particles at a ratio of 0.005 wt% or more and 5.0 wt% or less. The described fluorescent lamp. The fluorescent lamp according to any one of claims 1 to 4, wherein a protective film is formed between the glass bulb and the phosphor layer. The fluorescent lamp according to any one of claims 1 to 5, wherein the glass bulb has a tubular shape, and external electrodes are provided on outer circumferences of both ends thereof. The fluorescent lamp according to claim 6, wherein the phosphor layer is formed in a region corresponding to the space between the external electrodes in the glass bulb. A backlight device comprising the fluorescent lamp according to any one of claims 1 to 7 as a light source. A method of manufacturing a fluorescent lamp, wherein mercury is enclosed in a glass bulb, and a phosphor layer containing alumina-containing phosphor particles and non-alumina-containing phosphor particles is formed inside the glass bulb. ,
The phosphor layer includes at least green phosphor particles,
The green phosphor particles are the alumina-containing phosphor particles,
An attachment step of attaching a metal oxide to the surface of the alumina-containing phosphor particles;
A suspension creating step of creating a phosphor suspension by mixing the alumina-containing phosphor particles having a metal oxide adhered to the surface thereof by the attaching step, and the alumina-free phosphor particles.
And a phosphor layer forming step of forming the phosphor layer by applying the phosphor suspension to the inside of the glass bulb.

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