JP2010192254A - Cold-cathode fluorescent lamp, and aluminate-based phosphor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminate-based phosphor and a cold-cathode fluorescent lamp employing the same, enabling of: higher luminance with wide color reproduction maintained; stabilization of emission colors through restraint of changes of chromaticity in accordance with lighting time of a lamp; endowing an LCD used with stable characteristics; yet restraining thermal degradation of the aluminate-based phosphor in manufacturing processes; forming a uniform phosphor film on an inside wall of a narrow glass tube; and alleviating luminance unevenness and chromaticity shift in an axis direction of the glass tube. <P>SOLUTION: Of the cold-cathode fluorescent lamp equipped with an aluminate-based phosphor activated by bivalent Eu and bivalent Mn and with emission peaks at a blue-color region and a green-color region, a phosphor emitting blue colors and a phosphor emitting red colors, the aluminate-based phosphor has a content of the bivalent Mn adjusted so that changes of chromaticities of the light-emitting phosphors in accordance with the lighting time are to be restrained. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a cold cathode fluorescent lamp and an aluminate phosphor, and more specifically, suppresses a change in chromaticity associated with the lighting time of an aluminate phosphor having two main peaks of blue and green, The present invention relates to an aluminate phosphor capable of maintaining high luminance and a cold cathode fluorescent lamp using the same.

  In recent years, liquid crystal displays (hereinafter also referred to as LCDs) have attracted attention among flat panel displays because of their excellent characteristics of long life and high brightness. Unlike a plasma display or CRT, an LCD is a non-light emitting display that displays pixels by controlling the backlight light in combination with a liquid crystal shutter and color filter, instead of emitting pixels themselves for displaying images. A cold cathode fluorescent lamp used as a backlight of an LCD uses a red light emitting phosphor, a green light emitting phosphor, and a blue light emitting phosphor in combination. Specific examples of the combinations include those shown in Table 1.

As the green phosphor, LaPO ₄ : Ce, Tb (abbreviated as LAP), (Ba, Eu) (Mg, Mn) Al ₁₀ O ₁₇ (abbreviated as BAMEM) are used.

  BAMEM was developed by Philips in the early 1970s and was put to practical use as a high-efficiency, high-color-rendering three-wavelength fluorescent lamp (Patent Documents 1 and 2 and Non-Patent Document 1), and was excited by 180-300 nm wavelength light. , Green (510-525 nm) and blue (445-455 nm) have two main emission peaks. In order to obtain excellent color reproducibility in a liquid crystal display, it is important to use phosphors that emit red, blue, and green single colors with high color purity in the cold cathode fluorescent lamp of the backlight. In this respect, BAMEM is very advantageous as a green phosphor. However, in addition to low luminance, BAMEM is greatly damaged by lighting of the lamp, and the color change of the emitted color is more remarkable than other phosphors, so that the change in chromaticity is large in the cold cathode fluorescent lamp using this. In a cold cathode fluorescent lamp for LCD backlight, when LAP is used as a green phosphor, the luminance is excellent, but the color reproducibility is inferior, whereas when BAMEM is used, the color reproducibility is Although excellent, the luminance is insufficient, and the chromaticity changes with the cumulative lighting time. Although BAMEM has a large proportion of rare earths and the price is soaring, despite its superior price, the back of the LCD is used because of the lack of brightness and the color of the light that changes with the lamp lighting time. There are problems with light applications.

  In BAMEM, an aluminate phosphor (Patent Document 3) has been reported in which brightness is improved and deterioration due to heat is reduced. However, the brightness of this phosphor is insufficient compared to the LAP phosphor.

  In addition, a fluorescent lamp (Patent Document 4) that uses an aluminate phosphor as a blue phosphor to improve color rendering properties, a fluorescent lamp that maintains a luminous flux (Patent Document 5), and the like are known. It is not possible to suppress the thermal deterioration that is received in the process and to suppress the decrease in luminance associated with the lighting time.

  Further, the cold cathode fluorescent lamp sucks up the slurry containing the phosphor into the glass tube and applies the slurry to the inner wall surface to form the phosphor layer. The ring diameter of the glass tube is, for example, 2 It is difficult to form a phosphor layer that is as thin as -4 mm and contains the phosphor uniformly over the entire inner wall of the glass tube, especially when it contains phosphors with different specific gravities or when the particle shape is not substantially spherical It is difficult to form a uniform phosphor layer.

  As a method for uniformly forming the phosphor layer, the specific gravity and viscosity of the phosphor coating solution are strictly controlled as disclosed in Patent Document 4 (Patent Document 6), or the average particle diameter of the phosphor is in a specific range. (Patent Document 7) or using phosphor particles coated with an oxide (Patent Documents 5 and 8).

  A cold cathode fluorescent lamp having a phosphor layer that contains phosphors non-uniformly causes uneven luminance of light emission, chromaticity deviation, and the like, and therefore a phosphor layer that contains phosphors uniformly is required.

Japanese Examined Patent Publication No. 52-22836 Japanese Patent Laid-Open No. 56-152883 JP-A-2005-68403 JP 2002-3836 A JP 2006-274088 A JP 2003-45329 A JP2004-207073 JP-A-2005-11665 J.M.P.J.Verstegen, J. Electrochem.Soc., Vol. 121, 1623 (1974)

  It is an object of the present invention to achieve high brightness while maintaining wide color reproducibility, and further to suppress changes in chromaticity associated with lamp lighting time, to stabilize the emission color, and to the LCD used. Aluminic acid that can provide stable characteristics, can suppress thermal deterioration of the aluminate phosphor in the manufacturing process, and can reduce luminance unevenness and chromaticity deviation in the axial direction of the glass tube The object is to provide a salt-based phosphor and a cold cathode fluorescent lamp using the same.

  In order to obtain a high-luminance phosphor, it is common to include an activator at a concentration as high as possible within a range where concentration quenching does not occur. I did research and development. Concentration quenching refers to a phenomenon in which fluorescence becomes weaker as the concentration of a light emitting molecule increases, and is a phenomenon that occurs when a phosphor in an excited state and a phosphor in a ground state interfere with each other and are quenched.

First, the brightness of a cold cathode fluorescent lamp used for an LCD backlight is composed of a phosphor (also referred to as an RGB phosphor) that is a combination of a red light emitting phosphor, a green light emitting phosphor, and a blue light emitting phosphor. Rather than being determined only by an increase in the brightness of each phosphor, points due to the balance of the brightness, chromaticity, and composition of the RGB phosphors,
Secondly, since the brightness is reduced due to the deterioration of the phosphor due to the heat treatment in the manufacturing process, the thermal deterioration in the manufacturing process is suppressed,
Thirdly, the blue color emitted by the aluminate-based green light-emitting phosphor is the same as the emission wavelength of the blue light-emitting phosphor used in the cold cathode fluorescent lamp for the backlight of the LCD.

  When the aluminate phosphor is excited by excitation light having a wavelength of 254 nm, as shown in FIG. 1, when it does not contain divalent Mn (A in the figure), it has a peak at 445 to 455 nm. When the Mn content is 0.08 mol (C in the figure) and 0.22 mol (B in the figure), since it has a peak at 510 to 525 nm, divalent Eu emits light at 445 to 455 nm. It can be seen that divalent Mn contributes to light emission of 510 to 525 nm. And since C with a low content of divalent Mn has a higher luminance increase rate than B with a high content of divalent Mn, C in which the content of divalent Mn is low, It was thought that it contributed to light emission effectively.

  Furthermore, when B and C are compared, the emission intensity at 510 to 525 nm increases with an increase in the content of divalent Mn, while the content of divalent Eu is constant on the other hand. Regardless, since the emission intensity at 445 to 455 nm is reduced, energy is transferred from the divalent Eu doped in the crystal to the divalent Mn, thereby reducing the emission at 445 to 455 nm due to the divalent Eu. It was observed that the emission of 510 to 525 nm due to divalent Mn was increased. When bivalent Mn exists in the vicinity of divalent Eu, energy exchange occurs between them, and when there is no divalent Mn in a range where energy can be exchanged, bivalent Eu is considered to emit light at 445 to 455 nm. It is done. It is considered that the divalent Mn present in the crystal becomes surplus Mn that does not contribute to light emission due to a change in valence due to heating or the like, causing deterioration of the phosphor. Therefore, it is considered that as the excessive amount of Mn that does not contribute to light emission increases, the deterioration of the phosphor is promoted, the light emission chromaticity changes with the lighting time of the cold cathode fluorescent lamp, and the light emission intensity decreases.

  In the aluminate-based phosphor, phosphors with various contents of divalent Eu and divalent Mn were prepared, the emission intensity was measured, and the range and manufacturing conditions of the doped light emission center most efficiently emitted Study was carried out. Curve A in FIG. 2 shows that the brightness of the fluorescent light emitted from the aluminate-based phosphor increases as the Mn concentration increases, reaches the maximum luminance when the Mn is around 0.35, and thereafter concentration quenching occurs. Is shown. Curve B showing the PG / PB value of the fluorescence emitted from the aluminate phosphor indicates that the proportion of green light emission increases as the Mn concentration increases. As a result, by adjusting the ratio of the blue light emission intensity to the green light emission intensity to a specific value, it is possible to suppress the change in light emission chromaticity associated with the use, and in addition, the phosphor that is subjected to heat treatment in the manufacturing process That it is possible to suppress deterioration of the LED, and to improve the brightness as a cold cathode fluorescent lamp by adjusting the brightness, chromaticity, and blending ratio of the RGB phosphor and balancing the RGB phosphor Got.

  Furthermore, although the reason is not clear, when controlling the content of Mn, a very small amount of P (phosphorus) was mixed to obtain higher suppression of luminance and chromaticity change. Based on these findings, the present invention has been completed.

  That is, the present invention relates to an aluminate-based phosphor activated by divalent Eu and divalent Mn and having emission peaks in the blue region and the green region, a phosphor emitting blue light, and a phosphor emitting red light. The aluminate phosphor has a divalent Mn content adjusted so that the amount of change in chromaticity associated with the lighting time of the emitted fluorescence is suppressed. The present invention relates to a cold cathode fluorescent lamp.

The present invention also relates to an aluminate-based phosphor activated by divalent Eu and divalent Mn and having emission peaks in the blue region and the green region.
_{(Ba 1- αEuα) (Mg 1-} βMnβ) (Al 1- γPγ) 10 O 17 (1)
(In the formula, α, β, and γ satisfy 0.05 ≦ α ≦ 0.25, 0 <β <0.20, 0.50 <α / β <2.2, and 0 <γ ≦ 0.01. The divalent Mn content was adjusted so that the emission peak intensity ratio PG / PB of the green region to the emission peak intensity of the blue region was 1 or more and 7 or less. The present invention relates to an aluminate-based phosphor.

  The aluminate phosphor of the present invention and the cold cathode fluorescent lamp using the phosphor achieve high brightness while maintaining a wide color reproducibility, and further suppress the change in chromaticity with the lamp lighting time. In addition, the emission color can be stabilized, stable characteristics can be given to the LCD used, and thermal deterioration of the aluminate phosphor in the manufacturing process can be suppressed. Further, even in a cold cathode fluorescent lamp having a thin glass tube diameter, a uniform fluorescent film can be formed on the inner wall of the glass tube, and luminance unevenness and chromaticity deviation in the axial direction of the glass tube can be reduced. Furthermore, since it is excellent in the energy conversion efficiency which converts excitation light into visible light, the energy saving of a liquid crystal display can be achieved.

It is a figure which shows the emission spectrum of the aluminate type light-emitting body of this invention. It is a figure which shows the brightness | luminance and emission peak intensity ratio PG / PB of the aluminate-type fluorescent substance of this invention. It is a schematic block diagram which shows an example of the cold cathode fluorescent lamp of this invention. It is a figure which shows the relationship between the light-emitting luminance of the cold cathode fluorescent lamp of this invention, and bivalent Mn content in the aluminate-type fluorescent substance to be used. It is a figure which shows the relationship between the maintenance factor of the luminescent brightness of the cold cathode fluorescent lamp of this invention, and divalent Mn content in the aluminate type fluorescent substance to be used. It is a figure which shows the chromaticity change of x in the CIE chromaticity coordinate with the lighting time of the cold cathode fluorescent lamp of this invention. It is a figure which shows the chromaticity change of y in the CIE chromaticity coordinate with the lighting time of the cold cathode fluorescent lamp of this invention.

  The cold cathode fluorescent lamp of the present invention is activated by divalent Eu and divalent Mn, and has an aluminate-based phosphor having emission peaks in the blue region and the green region, a phosphor emitting blue light, and red light. This is a cold cathode fluorescent lamp having a phosphor, and the aluminate phosphor adjusts the content of divalent Mn so that the amount of change in chromaticity with the lighting time of the emitted fluorescence is suppressed. It is characterized by that.

  The aluminate-based phosphor used in the cold cathode fluorescent lamp of the present invention is activated by divalent Eu and divalent Mn, and when irradiated with ultraviolet light of 180 to 300 nm as excitation light, it has a wavelength of 445 to 455 nm by divalent Eu. It emits fluorescence having an emission peak in the blue region and an emission peak in the green region of 510 to 525 nm due to divalent Mn. In the aluminate phosphor, divalent Mn exists in the vicinity of divalent Eu in a region where energy can be imparted from divalent Eu, and receives energy from divalent Eu in addition to energy from excitation light. Emits fluorescence of 510 to 525 nm. The emission of 445 to 455 nm by divalent Eu reduces the considerable amount of energy imparted to divalent Mn.

  The content of divalent Mn in the aluminate-based phosphor is adjusted so that the amount of change in the chromaticity of fluorescence accompanying the lamp lighting time is suppressed. If the bivalent Mn exists in the vicinity of the bivalent Eu within a range in which energy can be transferred between the divalent Eus, and if it exists in excess, the valence of the divalent Mn is increased due to heat treatment in the manufacturing process and lighting of the lamp. Since it changes and deteriorates the crystal of the aluminate-based phosphor, the content of divalent Mn is set to an amount excluding excess Mn that does not contribute to light emission.

  The content of divalent Mn in the aluminate phosphor is such that the ratio PG / PB of the emission peak intensity PG in the green region to the emission peak intensity PB in the blue region of the aluminate phosphor is 1 or more, 7 It is preferably adjusted to have: If PG / PB is within this range, energy transfer from divalent Eu to divalent Mn is performed well, and light emission at 510 to 525 nm due to divalent Mn increases, thereby enabling high-luminance light emission. A fluorescent lamp is obtained. Further, excess Mn that does not contribute to light emission can be reduced, deterioration of the aluminate phosphor is suppressed, and the color of the fluorescence emitted from the aluminate phosphor with the lighting time of the cold cathode fluorescent lamp The degree of change is suppressed and fluorescence with stable chromaticity is obtained. PG / PB is preferably 1.5 ≦ PG / PB ≦ 5.0.

  Specifically, PG / PB can employ a value obtained by a method of calculating a ratio of two peak intensities observed in a blue region and a green region obtained from an emission spectrum. The peak intensity is a value obtained by measuring the emission from the sample using a spectroscope and a photomultiplier tube or a photo detector such as a CCD, using only an ultraviolet light source with a mercury lamp wavelength of 254 nm as an excitation source. Can be adopted.

  The aluminate-based phosphor has a chromaticity of fluorescence emitted when irradiated with excitation light, and x in the CIE chromaticity coordinates is 0.10 to 0.20, and y is 0.25 to 0.55. Preferably there is. By having such emission chromaticity, a high-intensity cold cathode fluorescent lamp can be obtained.

  The amount of change in the chromaticity of the fluorescence with the lighting time of the lamp that emits light from the aluminate-based phosphor is such that x in the CIE chromaticity coordinates after 2000 hours from lighting is 0.007 or less, and y is 0.009. The following is preferable. If the change in chromaticity associated with the lighting time is in the above range of x and y, stable chromaticity fluorescence can be obtained.

  Here, the CIE chromaticity coordinate means an XYZ color system that is a standard color system defined by the International Commission on Illumination.

As the aluminate phosphor, the composition formula (1)
_{(Ba 1- αEuα) (Mg 1-} βMnβ) (Al 1- γPγ) 10 O 17 (1)
What is represented by these is preferable. In the formula, α, β, and γ are numerical values satisfying 0.05 ≦ α ≦ 0.25, 0 <β <0.20, 0.50 <α / β <2.2, and 0 <γ ≦ 0.01. Indicates. Furthermore, β is more preferably in the range of 0.06 ≦ β ≦ 0.19, and more preferably in the range of 0.07 ≦ β ≦ 0.15. In the formula, in the range where β is smaller than 0.20, it is possible to suppress the presence of excess divalent Mn that does not contribute to light emission in the aluminate-based phosphor, which is accompanied by the operating time of the cold cathode fluorescent lamp. A change in chromaticity of fluorescence emitted from the aluminate phosphor can be suppressed. Further, if α / β is in a range larger than 0.50 and smaller than 2.2, chromaticity change due to light emission caused by Mn and light emission caused by Eu can be suppressed.

  The aluminate-based phosphor preferably contains P (phosphorus). When P contains a small amount of Mn, P is considered to have an effect of promoting the introduction of Mn into the crystal lattice and a flux effect on Mn. The content of P in the aluminate phosphor is preferably 0.01 mol or less. In the formula (1), γ preferably shows a numerical value of 0.01 or less. If γ is 0.01 or less, the brightness of Mn can be increased.

  Furthermore, the ratio PG / PB of the emission peak intensity in the green region to the emission peak intensity in the blue region can be set to 1 or more and 7 or less.

  As the aluminate phosphor, in the formula (1), a part of Ba is substituted with Sr or Ca, a part of Mg is substituted with Ga or Zn, a part of Al is another atom In addition to the above-mentioned ones, those in which the composition ratio of Al or O is changed, or those containing a small amount of other elements other than these may be used.

The aluminate-based phosphor preferably has a tap density of 1.3 g / cm ³ or more and 1.8 g / cm ³ or less. The particle shape of the aluminate phosphor is a hexagonal plate and has a specific gravity smaller than those of other phosphors shown in Table 1. For this reason, when a slurry for a coating solution for forming a phosphor layer is prepared using the aluminate phosphor, the dispersibility of the aluminate phosphor particles is poor, agglomeration occurs, It is difficult to form a phosphor layer having a high packing density, and irregularities are likely to occur on the surface of the formed phosphor layer, and brightness tends to vary. Dispersibility can be improved because the aluminate phosphor has the above tap density.

  The aluminate phosphors are manufactured using Ba, Eu, Mg, Mn, Al oxides, carbonates, hydroxides, carbonates, etc., with Ba, Eu, Mg, Mn, Al in the above composition. And mixed with a fluxing agent as necessary, and baked in a reducing atmosphere of nitrogen containing hydrogen, an atmosphere containing carbon monoxide, a reducing atmosphere containing carbon, etc. in a heat-resistant container, for example, 1350 Bake at ~ 1700 ° C. The firing may be performed once or a plurality of times, and the obtained fired product may be crushed with a ball mill or a sieve.

As the phosphor emitting blue light used for the cold cathode fluorescent lamp, those having a light emission peak in the blue region of 445 to 455 nm are preferable. Specifically, as a phosphor emitting blue light, BaMgAl ₁₀ O ₁₇ : Eu (also referred to as BAM), (Sr, Ba, Ca, Mg) ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu (also referred to as SCA). ), CaMgSi ₂ O ₆ : Eu, (Sr, Ca, Ba) ₅ (PO ₄ ) ₃ Cl: Eu, Sr ₅ (PO ₄ ) ₃ Cl: Eu, and the like.

As the phosphor emitting red light used in the cold cathode fluorescent lamp, those having a light emission peak in a red region of 590 to 630 nm are preferable. Specific examples of phosphors that emit red light include Y ₂ O ₃ : Eu (also referred to as YOX), Y (P, V) O ₄ : Eu (also referred to as YVO), 3.5 MgO · 0.5MgF. ₂ · GeO ₂ : Mn.

In addition to the cold cathode fluorescent lamp, if necessary, a phosphor emitting green light other than the aluminate-based phosphor, such as LAP, Ce _1-x Tb _x MgAl ₁₁ O ₁₉ (also referred to as CAT), or the like. Can be used.

  These phosphors are used in proportion to the brightness of the aluminate phosphor, the phosphor emitting blue light, and the phosphor emitting red light. It can be selected as appropriate. Specific examples of the usage ratio of the phosphor include a ratio in which x is 0.250 and y is 0.230 in the CIE chromaticity coordinates.

  The cold cathode fluorescent lamp may be any one as long as it uses the phosphor, and examples thereof include an ultraviolet ray emitted from mercury as excitation light.

  As an example of the cold cathode fluorescent lamp of the present invention, a cold cathode fluorescent lamp for backlight of a liquid crystal panel can be exemplified. As shown in the schematic cross-sectional view of FIG. 3, the cold cathode fluorescent lamp 21 is configured such that both ends of a transparent tube 22 made of glass or the like are hermetically sealed with a sealing member 23 such as bead glass. The outer diameter of the transparent tube 22 is in the range of 1.5 to 6.0 mm, preferably in the range of 1.5 to 5.0 mm. The inner wall surface of the transparent tube is excited by ultraviolet rays such as 253.7 nm and 365.0 nm emitted from mercury over almost the entire length, and the aluminate phosphor, the phosphor emitting blue light, and the red A phosphor layer 24 containing a phosphor that emits light is provided. A predetermined amount of mercury and a rare gas such as argon or xenon is introduced into the internal space 25 of the transparent tube, and the internal pressure is reduced to about several tenths of the atmospheric pressure. At both ends in the longitudinal direction of the transparent tube, cup-shaped electrodes 27 are arranged so that the openings 20 face each other. One end of each lead wire 29 is welded to the bottom surface of the electrode 27, and the other end penetrates the sealing member 23 and is drawn out of the transparent tube.

  In such a cold cathode fluorescent lamp, when a voltage is applied between the electrodes, the rare gas is ionized by slightly existing electrons in the transparent tube, and the ionized rare gas collides with the electrode to emit secondary electrons. A discharge is caused to excite mercury, and ultraviolet rays such as 253.7 nm and 365.0 nm are emitted, and green, blue and red fluorescences are emitted from the phosphor provided on the inner wall of the transparent tube. These are rendered to emit white light.

  The cold cathode fluorescent lamp may be manufactured using the aluminate phosphor, the phosphor emitting red light, or the phosphor emitting blue light. For example, the light emission in the cold cathode fluorescent lamp is CIE and the chromaticity coordinate x is x. Mix at a predetermined blending ratio so that 0.250 and y are 0.230. The mixed phosphor is mixed with a mixture of nitrified cotton and the like in a mixed solvent of butyl acetate and isopropyl alcohol to prepare a phosphor slurry. Using this phosphor slurry, a phosphor layer is formed on the inner surface of the glass tube by processes such as coating, drying, and firing. Thereafter, both ends of the glass tube are sealed with a sealing material, the interior is evacuated, and then a cold cathode fluorescent lamp is manufactured by introducing mercury, a rare gas or the like into the interior.

  The cold cathode fluorescent lamp of the present invention is suitable for various displays and illuminations that require white light emission in addition to the backlight of the LCD.

The aluminate phosphor of the present invention is activated by divalent Eu and divalent Mn, and has an emission peak in a blue region and a green region.
_{(Ba 1- αEuα) (Mg 1-} βMnβ) (Al 1- γPγ) 10 O 17 (1)
(Where α, β, and γ are numerical values satisfying 0.05 ≦ α ≦ 0.25, β <0.20, 0.50 <α / β <2.2, and 0 <γ ≦ 0.01. The content of divalent Mn is adjusted so that the emission peak intensity ratio PG / PB of the green region to the emission peak intensity of the blue region is 1 or more and 7 or less. And

  The aluminate phosphor of the present invention can be the same as the aluminate phosphor used in the cold cathode fluorescent lamp, and can be applied to display and illumination using various phosphors.

Hereinafter, the phosphor of the present invention will be described in more detail with reference to examples.
[Example 1]
Alumina, barium carbonate, magnesium hydroxide, diammonium hydrogen phosphate, europium oxide and manganese carbonate are in proportions of α = 0.10, β = 0.06, and γ = 0.01 in the composition formula (1). In this way, a small amount of alumina fluoride was added as a reaction aid to obtain a raw material mixture. The raw material mixture was put in an alumina crucible and fired at 1500 ° C. for 5 hours in a nitrogen gas atmosphere containing 4% by volume of hydrogen gas in an electric furnace. The fired product is dispersed, washed, dried and sieved, and the aluminate phosphor (Ba _0.9 Eu _0.1 ) (Mg _0.94 Mn _0.06 ) (Al _0.99 P _0.01 ) with a particle size (median diameter D50) of 5.5 μm ₁₀ O ₁₇ was obtained.

  The obtained aluminate-based phosphor, red phosphor YOX, and blue phosphor BAM were mixed so that the chromaticity coordinates of the cold cathode fluorescent lamp were x = 0.250 and y = 0.230. The mixed phosphor was mixed at a mass ratio of 1: 1 with a vehicle in which nitrified cotton was mixed with a mixed solvent of 50% by mass of butyl acetate and 50% by mass of isopropyl alcohol to prepare a phosphor slurry. The phosphor slurry was sucked and applied in a vertically arranged glass tube having a diameter of 3.4 mm and a length of 900 mm, dried, and heated at 600 ° C. to prepare a phosphor layer. Thereafter, both ends of the glass tube were sealed, and after evacuation, mercury and a rare gas were sealed to obtain a cold cathode fluorescent lamp.

[Brightness of cold cathode fluorescent lamp]
The luminance of the cold cathode fluorescent lamp was measured with a luminance meter (SR-3 manufactured by Topcon), and the relative luminance was determined on the basis of the luminance of Comparative Example 1 in which β in Formula (1) was 0.20. The results are shown in FIG.

[Phosphor brightness maintenance ratio]
The phosphor slurry is fired under the same conditions as those for the phosphor layer of the cold cathode fluorescent lamp, the fired phosphor is collected, irradiated with 180-300 nm wavelength light, and the luminance is measured with a luminance meter (SR-TOP manufactured by Topcon). 3). The luminance ratio with respect to the luminance of the phosphor slurry before firing measured under the same conditions was determined and used as the luminance maintenance rate of the phosphor. The results are shown in FIG.

[Examples 2 to 9, Comparative Examples 1 to 5]
In the composition formula (1), an aluminate-based phosphor was prepared in the same manner as in Example 1 except that the ratio of the raw materials to be mixed was changed so that the values of α, β, and γ were as shown in Table 2. Then, a cold cathode fluorescent lamp was manufactured, the luminance was determined, and the luminance maintenance ratio of the phosphor was determined. The results are shown in FIGS. The median diameter of the aluminate-based phosphor was 5.4 to 5.7 μm. For the cold cathode fluorescent lamps obtained in Examples 5 and 9 and Comparative Example 1, the change in chromaticity with the lighting time was measured by the following method. The results are shown in FIGS.

[Chromaticity change with lighting time]
A cold cathode fluorescent lamp was lit by applying a voltage of 1200 V and a current of 10 mA, and the change in chromaticity was measured at each elapsed time to determine the amount of change in x and y in the CIE chromaticity coordinates.

  From Examples 1 to 9 and Comparative Examples 1 to 5, in Examples 1 to 9 where β in the formula (1) is smaller than 0.2, the luminance of the cold cathode fluorescent lamp is improved, whereas β is 0. In Comparative Examples 1 to 5 in the range of 2 or more, the luminance of the cold cathode fluorescent lamp was lowered although the emission luminance in the green region of the aluminate phosphor was increased. It can be seen that the luminance maintenance ratio decreased as the content of divalent Mn increased, and the content of excess divalent Mn in the crystal increased, causing thermal deterioration and concentration quenching.

[Examples 10 to 14]
In the composition formula (1), γ = 0.01 and aluminate except that the ratio of raw materials to be mixed was changed so that the values of α and β were as shown in Table 3. A phosphor was prepared, and a cold cathode fluorescent lamp having CIE chromaticity coordinates x = 0.250 and Y = 0.230 was produced. The luminance of the obtained cold cathode fluorescent lamp was measured using a luminance meter (SR-3 manufactured by Topcon). Table 3 shows the luminance obtained with reference to the luminance of the cold cathode fluorescent lamp of Comparative Example 1.

21 cold cathode fluorescent lamp 22 glass tube 24 phosphor layer 25 internal space 27 cup-shaped electrode 29 lead wire

Claims (6)

  A cold cathode fluorescent lamp having an aluminate-based phosphor activated by divalent Eu and divalent Mn and having emission peaks in the blue region and the green region, a phosphor emitting blue light, and a phosphor emitting red light The aluminate-based phosphor is characterized in that the content of divalent Mn is adjusted so that the amount of change in chromaticity associated with the lighting time of the emitted fluorescence is suppressed. Cold cathode fluorescent lamp.   The aluminate phosphor was adjusted so that the content of divalent Mn was such that the ratio PG / PB of the emission peak intensity in the green region to the emission peak intensity in the blue region was 1 or more and 7 or less The cold cathode fluorescent lamp according to claim 1.   2. The amount of change in chromaticity associated with the lighting time of the fluorescence emitted from the aluminate phosphor is such that x of CIE chromaticity coordinates after 2000 hours from lighting is 0.007 or less. Or the cold cathode fluorescent lamp of 2.   2. The amount of change in chromaticity associated with the lighting time of fluorescence emitted from the aluminate phosphor is such that y of the CIE chromaticity coordinates after 2000 hours from lighting is 0.009 or less. 4. The cold cathode fluorescent lamp according to any one of items 1 to 3. The aluminate phosphor has the composition formula (1)
_{(Ba 1- αEuα) (Mg 1-} βMnβ) (Al 1- γPγ) 10 O 17 (1)
(Where α, β, and γ are numerical values satisfying 0.05 ≦ α ≦ 0.25, β <0.20, 0.50 <α / β <2.2, and 0 <γ ≦ 0.01. The cold cathode fluorescent lamp according to claim 1, wherein the cold cathode fluorescent lamp is expressed by: In an aluminate phosphor activated by divalent Eu and divalent Mn and having emission peaks in blue and green regions, the composition formula (1)
_{(Ba 1- αEuα) (Mg 1-} βMnβ) (Al 1- γPγ) 10 O 17 (1)
(Where α, β, and γ are numerical values satisfying 0.05 ≦ α ≦ 0.25, β <0.20, 0.50 <α / β <2.2, and 0 <γ ≦ 0.01. The content of divalent Mn is adjusted so that the emission peak intensity ratio PG / PB of the green region to the emission peak intensity of the blue region is 1 or more and 7 or less. An aluminate phosphor.

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