JP2009068001A - Phosphor and fluorescent lamp using the same - Google Patents

Abstract

An object of the present invention is to improve a luminous flux maintenance factor, a chromaticity change with time, and a color difference at the end of a tube in a fluorescent lamp for backlight, and further, a color using an SCA phosphor or the like. It is to improve these characteristics in a fluorescent lamp for backlight with an expanded reproduction range.
A fluorescent lamp using a phosphor, characterized in that the surface of the phosphor particle is coated with a surface treatment material containing a rare earth metaphosphate and a rare earth hydroxide. Therefore, since the lamp luminous flux maintenance factor is high and the change in lamp chromaticity with time is small, it can be suitably used for a light source such as a backlight of a color liquid crystal display device.
[Selection] Figure 3

Description

  The present invention relates to a phosphor and a fluorescent lamp using the same, and more particularly to a cold cathode fluorescent lamp used for a backlight of a liquid crystal display device.

  A fluorescent lamp causes a discharge in a light-transmitting hermetic container such as a glass bulb, and ultraviolet rays emitted from the discharge medium at that time excite the phosphor in the phosphor layer formed on the inner wall of the hermetic container. It is a light-emitting device that utilizes emitted light. The emission spectrum of the lamp can be controlled by changing the type, mixing ratio, etc. of the phosphor in the phosphor layer, and has been used for various lighting applications.

  In recent years, cold cathode fluorescent lamps are mainly used as backlights for color liquid crystal display devices. As a configuration of the color liquid crystal display device, for example, light emitted from the backlight is introduced as a surface light source on the back of the liquid crystal panel by a light guide plate or the like, and each display pixel of the liquid crystal panel specifies light in a specific wavelength range by a liquid crystal layer and a color filter. Arbitrary colors are reproduced by passing only the strength.

  Unlike the fluorescent lamp for illumination, the backlight fluorescent lamp has the following problems. That is, since the backlight is used as a light source of the display device, not only the luminous flux maintenance factor of the entire fluorescent lamp but also the maintenance factor of the relative intensity of each color component, that is, the chromaticity maintenance factor of the whole fluorescent lamp is important. Further, since the entire display surface of the display device needs to be illuminated uniformly both in terms of luminance and chromaticity, the luminance and chromaticity distribution of the fluorescent lamp are required to be uniform. In particular, the chromaticity distribution strongly affects the image quality of the display device. For this reason, the fluorescent lamp for backlight has a strong demand for a chromaticity difference (referred to as a tube end color difference) at both ends.

  In addition, the fluorescent lamp for backlight has a smaller tube diameter than the fluorescent lamp for general illumination. However, since the load on the tube wall becomes stronger in such a lamp, the luminous flux maintenance rate is good in the general fluorescent lamp. Even the phosphors that have been used tend to have a low retention rate, and countermeasures are required.

  Patent Document 1 and the like disclose a treatment with a composite oxide composed of a specific metal oxide and phosphorus oxide in order to improve the life characteristics of a fluorescent lamp for general illumination. Was not enough.

  As described above, in the fluorescent lamps for backlights, there is currently no established method for improving the luminance maintenance ratio, the chromaticity change with time, and the tube end color difference to a level that satisfies the market demand.

Furthermore, in recent years, there has been a demand for an extended color reproduction range for backlight fluorescent lamps. As a blue phosphor, a conventional divalent europium-activated barium magnesium aluminate phosphor (hereinafter referred to as a BAM phosphor) is used. In contrast, a divalent europium-activated strontium chloroapatite phosphor or an alkaline earth chloroapatite phosphor in which a part or all of the strontium of this phosphor is replaced with another alkaline earth metal (both are collectively referred to as an SCA phosphor below). In particular, in backlight fluorescent lamps that expand the color reproduction range using SCA phosphors, etc., it is required to improve the emission luminance maintenance rate, the chromaticity change over time, and the tube end color difference. It has been.
Japanese Patent Publication No. 7-779

  The present invention has been made to solve the above problems. An object of the present invention is to improve the luminous flux maintenance factor at the time of lighting, the chromaticity change with time, and the tube end color difference in the backlight fluorescent lamp, and further, the color reproduction range can be increased by using an SCA phosphor or the like. It is to improve these characteristics in an expanded backlight fluorescent lamp.

  In order to achieve the above object, the present inventors have conducted intensive studies and have completed the present invention. The present inventors have coated a phosphor with a surface treatment substance containing a specific rare earth phosphate and a rare earth hydroxide, and in a fluorescent lamp for backlight, a luminous flux maintenance factor at the time of lighting, a change with time of chromaticity, and a tube It has been found that the edge color difference is improved. The configuration of the present invention and its features are as follows.

(1) The phosphor of the present invention is characterized in that the surface of a phosphor particle is coated with a surface treatment substance containing a rare earth metaphosphate and a rare earth hydroxide.

(2) The phosphor of the present invention is the phosphor according to (1), wherein the rare earth elements constituting the rare earth metaphosphate and the rare earth hydroxide are Y, La, Ce, Gd, Eu, It is at least one element selected from the group consisting of Tb, Dy, Lu, and Sc.

(3) The phosphor of the present invention is the phosphor according to (1) or (2), wherein the coating amount of the surface treatment substance is 0.1 in terms of the amount of rare earth elements with respect to the phosphor. It is characterized by being in a range of ˜20 mol%.

(4) A fluorescent lamp of the present invention includes a light-transmitting airtight container, a phosphor layer formed in the light-transmitting airtight container, a discharge medium sealed in the light-transmitting airtight container, and an electrode. In the fluorescent lamp, the phosphor layer includes the phosphor according to any one of claims 1 to 3.

(5) The fluorescent lamp of the present invention is the fluorescent lamp described in (4), wherein the fluorescent lamp is a cold cathode fluorescent lamp.

  Since the present invention has the above features, a fluorescent lamp can be obtained in which the color difference at the tube end when the lamp is turned on is suppressed, the lamp luminous flux maintenance factor is high, and the change in lamp chromaticity with time is small.

  Hereinafter, a phosphor and a fluorescent lamp according to the present invention will be described with reference to embodiments and examples. However, the present invention is not limited to these embodiments and examples.

  Here, the phosphor surface treatment method according to the embodiment of the present invention will be described in detail. First, a phosphor is produced according to a normal method. Next, this phosphor is dispersed in a dispersion medium such as pure water or an aqueous ethanol solution, and a water-soluble rare earth compound and metaphosphoric acid or metaphosphate are added and stirred. A pH is adjusted by adding a base to the phosphor suspension, and a surface treatment substance containing a rare earth metaphosphate and a rare earth hydroxide is deposited on the phosphor surface. Thereafter, the treated phosphor and the dispersion medium are separated and dried to obtain the phosphor of the present invention.

As the phosphor to be surface-treated, a phosphor that emits light by ultraviolet excitation can be used. For example, the general formula M ₁₀ (PO ₄ ) ₆ X ₂ : Eu (where M is at least one element selected from the group consisting of Sr, Ca, Ba, and Mg, X is F, Cl, Br, and I) A divalent europium-activated alkaline earth halophosphate represented by the general formula M ₂ P ₂ O ₇ : Eu (where M is Sr, Ca, Ba, And at least one element selected from the group consisting of Mg), a divalent europium-activated alkaline earth pyrophosphate represented by the general formula (Ba, M) ₂ Al ₁₀ O ₁₇ : Eu (where M is A divalent europium-activated alkaline earth aluminate represented by the general formula (Ba, M) ₂ Al ₁₀ O ₁₇ : Eu, represented by at least one element selected from the group consisting of Sr, Ca, and Mg) , Mn ( M is at least one element selected from the group consisting of Sr, Ca, and Mg) and a divalent europium and divalent manganese co-activated alkaline earth aluminate represented by the general formula Ce (Mg , Zn) _a Al ₁₁ O _19-a : trivalent cerium and divalent manganese co-activated zinc magnesium aluminate represented by Mn (where 0.4 ≦ a ≦ 1.0), the general formula Zn ₂ Divalent manganese-activated zinc silicate represented by SiO ₄ : Mn, general formula Zn ₂ (Si, Ge) O ₄ : Divalent manganese-activated zinc silicate / germanate represented by Mn, general Formula LaPO ₄ : Trivalent cerium and trivalent terbium co-activated lanthanum phosphate represented by Ce, Tb, General formula CeMgAl ₁₁ O ₁₉ : Trivalent cerium and trivalent terbium represented by Tb Activated Magnesium Aluminates, formula _YVO 4: 3-valent europium-activated yttrium vanadate represented by Eu, general formula _{Y (P, V) O 4} : 3 -valent europium activated yttrium Lynn represented by Eu Vanadate, general formula aMgO · bMgF ₂ · GeO ₂ : tetravalent manganese-activated magnesium fluorinated germanate represented by Mn (where a + b = 4), general formula R ₂ O ₂ S: Eu (where R Is a trivalent europium-activated rare earth oxysulfide represented by one or more rare earth elements excluding europium, and a general formula R ₂ O ₃ : Eu (where R is one or two excluding europium) And trivalent europium activated rare earth oxides represented by the above rare earth elements).

As the water-soluble rare earth compound, a halide, sulfate, nitrate, or the like of at least one rare earth element selected from the group consisting of Y, La, Ce, Gd, Eu, Tb, Dy, Lu, and Sc is used. it can. For example, yttrium chloride, yttrium sulfate, yttrium nitrate and the like can be preferably used. As metaphosphoric acid or metaphosphate, metaphosphoric acid such as trimetaphosphoric acid (H ₃ P ₃ O ₉ ), tetrametaphosphoric acid (H ₄ P ₄ O ₁₂ ), hexametaphosphoric acid (H ₆ P ₆ O ₁₈ ), or a salt thereof is used. it can. Here, the metaphosphoric acid is generally represented by (HPO ₃ ) _x (where x ≧ 3) and is a trimer or higher (polymerization degree of 3 or higher) phosphoric acid containing 3 mol or more of phosphorus element in 1 mol. . Metaphosphate is generally represented by (MPO ₃ ) _x (where x ≧ 3), and is a trimer or higher (polymerization degree of 3 or more) phosphate containing 3 mol or more of phosphorus element in 1 mol. is there. In view of availability and cost, it is advantageous to use hexametaphosphoric acid and a salt thereof. As the base, an aqueous solution of ammonia, alkali metal hydroxide or the like can be used.

  The coating amount of the surface treatment substance (in terms of rare earth element) is preferably in the range of 0.1 mol% to 20 mol%, more preferably in the range of 1 mol% to 12 mol% with respect to the phosphor to be coated. In this range, a cold cathode fluorescent lamp having a high lamp luminous flux and a luminous flux maintenance factor and little chromaticity change can be obtained.

  The rare earth element constituting the rare earth metaphosphate and rare earth hydroxide contained in the surface treatment material is at least one selected from the group consisting of Y, La, Ce, Gd, Eu, Tb, Dy, Lu, and Sc. The above elements are preferable, and the effect of the present invention is great. More preferable is at least one element selected from the group consisting of Y, La, Gd, Eu, Tb, Dy, and Lu, and at least one element selected from the group consisting of Y, La, Eu, and Dy. These elements are more preferable.

  The pH adjustment is preferably 1.0 to 3.5 higher than the value at which the insoluble salt of rare earth ions precipitates. For example, when adding a water-soluble yttrium compound and adjusting the pH with aqueous ammonia, it is preferable to adjust the pH to a range of 7.3 to 9.8 higher than pH 6.3 at which yttrium hydroxide begins to precipitate, If the pH value is lower than this range, the precipitation of hydroxide is reduced, so the coating effect is reduced.

  In this way, by coating the surface of the phosphor particles with a surface treatment substance containing a rare earth metaphosphate and a rare earth hydroxide, the luminous flux maintenance factor at the time of lighting in the backlight fluorescent lamp, chronological change in chromaticity, In addition, the phosphor of the present invention with improved tube end color difference can be obtained.

  Next, a cold cathode fluorescent lamp is produced using the phosphor of the present invention. First, a phosphor and a binder such as calcium pyrophosphate and calcium barium borate 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 into the inner surface of the glass tube, and then dried by passing hot air through it, followed by baking, evacuation, and electrode attachment to obtain a cold cathode fluorescent lamp.

  FIG. 1 shows an example of the cold cathode fluorescent lamp of the present invention. A phosphor layer 12 made of one or more phosphors and a binder is formed on the inner wall of the light-transmitting hermetic container 11 made of glass or the like. Inside the translucent airtight container 11, a discharge medium 13 made of a rare gas such as neon and mercury vapor is sealed, and both ends of the translucent airtight container 11 are sealed by a pair of electrodes 14a and 14b. A voltage is applied between both electrodes to cause discharge in the discharge medium 13, and ultraviolet rays are emitted from the excited mercury, and the phosphors in the phosphor layer 12 are excited by the ultraviolet rays to emit light.

  Whether the fluorescent lamp of the present invention is a white lamp or a monochromatic lamp used in a field sequential type liquid crystal display device, the luminous flux maintenance factor at the time of lighting, chronological change in chromaticity, and tube end color difference are improved.

  In the case of a white lamp, a blue phosphor (B: emission peak around 420 nm to 480 nm), a green phosphor (G: emission peak around 500 nm to 560 nm), a red phosphor (R: emission peak around 620 nm to 680 nm) The mixing ratio is B: 25% to 55%, G: 15% to 35%, R: 25% to 55% (B + G + R = 100%).

  At least selected from the group consisting of a divalent europium activated alkaline earth halophosphate, a divalent europium activated alkaline earth pyrophosphate, and a divalent europium activated alkaline earth aluminate as a blue phosphor One or more phosphors are selected from the group consisting of divalent europium and divalent manganese-activated alkaline earth aluminate, trivalent cerium and divalent manganese-activated zinc magnesium aluminate as the green phosphor. At least one or more of the phosphors used as red phosphors are trivalent europium activated yttrium vanadate, trivalent europium activated yttrium phosphorus vanadate, and tetravalent manganese activated magnesium fluorogermanic acid. Use at least one phosphor selected from the group consisting of salts, trivalent europium activated rare earth oxides It is.

  In particular, divalent europium-activated alkaline earth halophosphates as blue phosphors, especially SCA phosphors (divalent europium-activated strontium chloroapatite phosphors and some or all of the strontium of this phosphor In a fluorescent lamp for backlights that uses an alkaline earth chloroapatite phosphor substituted with an alkaline earth metal), the luminous intensity maintenance rate, chromaticity change with time, and tube end color difference are improved. There is.

  Next, characteristics of the phosphor and the fluorescent lamp of the present invention will be described with reference to the drawings. A cold cathode fluorescent lamp was prepared for the phosphor obtained by changing the amount of yttrium nitrate added in Example 1, and the Y amount (mol%) of the surface treatment substance coated on the phosphor and the characteristics of the cold cathode fluorescent lamp. The relationship is shown in FIGS. That is, FIG. 2 shows the relationship with the initial luminous flux (%) of the cold cathode fluorescent lamp, FIG. 3 shows the relationship with the luminous flux maintenance factor (%), and FIG. 4 shows the relationship with the change amount Δx of chromaticity x. The relationship between the degree y and the amount of change Δy is shown in FIG. From these figures, the range of Y amount with high luminous flux and luminous flux maintenance factor of the cold cathode fluorescent lamp and little change in chromaticity is preferably in the range of 0.1 mol% to 20 mol% with respect to the phosphor, and 1 mol% to 12 mol%. It can be seen that the range of is more preferable.

  A cold cathode fluorescent lamp was produced for the phosphor obtained by changing the pH value when adjusting the pH in Example 1, and changes in the luminous flux (%), luminous flux maintenance rate (%), and chromaticity x of the cold cathode fluorescent lamp. The amount Δx and the change amount Δy of the chromaticity y are measured. The relationship between the pH value and each characteristic of the cold cathode fluorescent lamp is shown in FIGS. That is, FIG. 6 shows the relationship with the initial luminous flux (%) of the cold cathode fluorescent lamp, FIG. 7 shows the relationship with the luminous flux maintenance factor (%), and FIG. 8 shows the relationship with the change amount Δx of chromaticity x. The relationship between the degree y and the amount of change Δy is shown in FIG. The horizontal axis of each figure plots the difference between the pH value after pH adjustment (pHF) and the pH value (pHS) at which hydroxide begins to precipitate, that is, pH (FS). From these figures, it can be seen that the pH (FS) value of the cold cathode fluorescent lamp having a high luminous flux and luminous flux maintenance factor and little chromaticity change is preferably in the range of +1.0 to +3.5.

  Examples of the present invention will be described below, but it goes without saying that the present invention is not limited to specific examples.

[Example 1]
100 g of divalent europium-activated strontium chloroapatite phosphor (SCA phosphor) represented by the general formula (Sr _0.99 Eu _0.01 ) ₁₀ (PO ₄ ) ₆ Cl ₂ is suspended in 200 ml of pure water. To do. Add 11.2 ml of a solution adjusted to 0.3 mol / l using yttrium nitrate.n hydrate (manufactured by Soekawa Riken, purity 99.99%). Further, 13.5 ml of a solution prepared by using sodium hexametaphosphate having a polymerization degree of 6 (manufactured by Kanto Chemical Co., Ltd., deer special grade) to 2.25 wt% is added dropwise. Thereafter, the pH is adjusted to 9.5 using a solution adjusted to 1.7 wt% using potassium hydroxide (manufactured by Kanto Chemical Co., Ltd., special grade). After completion of dropping, washing, draining, drying and sieving are performed sufficiently to obtain an SCA phosphor coated with yttrium metaphosphate and hydroxide.

[Example 2]
A lanthanum was prepared in the same manner as in Example 1 except that 12.0 ml of a solution adjusted to 0.3 mol / l using lanthanum nitrate hexahydrate instead of yttrium nitrate n hydrate was added. An SCA phosphor coated with a metaphosphate and a hydroxide is obtained.

[Example 3]
A cerium was prepared in the same manner as in Example 1 except that 11.9 ml of a solution adjusted to 0.3 mol / l using cerium nitrate hexahydrate instead of yttrium nitrate.n hydrate was added. An SCA phosphor coated with a metaphosphate and a hydroxide is obtained.

[Example 4]
A gadolinium was prepared in the same manner as in Example 1 except that 10.6 ml of a solution adjusted to 0.3 mol / l using gadolinium nitrate pentahydrate instead of yttrium nitrate.n hydrate was added. An SCA phosphor coated with a metaphosphate and a hydroxide is obtained.

[Example 5]
A europium was prepared in the same manner as in Example 1 except that 11.0 ml of a solution adjusted to 0.3 mol / l using europium nitrate · n hydrate instead of yttrium nitrate · n hydrate was added. An SCA phosphor coated with a metaphosphate and a hydroxide is obtained.

[Example 6]
A terbium was prepared in the same manner as in Example 1 except that 10.5 ml of a solution adjusted to 0.3 mol / l using terbium nitrate.n hydrate instead of yttrium nitrate.n hydrate was added. An SCA phosphor coated with a metaphosphate and a hydroxide is obtained.

[Example 7]
Prepared in the same manner as in Example 1 except that 10.3 ml of a solution adjusted to 0.3 mol / l using dysprosium nitrate pentahydrate instead of yttrium nitrate.n hydrate was added. An SCA phosphor coated with dysprosium metaphosphate and hydroxide is obtained.

[Example 8]
A lutetium was prepared in the same manner as in Example 1 except that 9.5 ml of a solution adjusted to 0.3 mol / l using lutetium nitrate.n hydrate instead of yttrium nitrate.n hydrate was added. An SCA phosphor coated with a metaphosphate and a hydroxide is obtained.

[Example 9]
A scandium was prepared in the same manner as in Example 1 except that 37.1 ml of a solution adjusted to 0.3 mol / l using scandium nitrate · n hydrate instead of yttrium nitrate · n hydrate was added. An SCA phosphor coated with a metaphosphate and a hydroxide is obtained.

[Example 10]
A lanthanum nitrate was prepared in the same manner as in Example 1 except that 18.7 ml of a solution adjusted to 0.3 mol / l using lanthanum nitrate hexahydrate instead of yttrium nitrate.n hydrate was added. An SCA phosphor coated with a metaphosphate and a hydroxide is obtained.

[Example 11]
It was prepared in the same manner as in Example 1 except that 18.7 ml of a solution adjusted to 0.3 mol / l using cerium nitrate hexahydrate instead of yttrium nitrate.n hydrate was added. An SCA phosphor coated with a metaphosphate and a hydroxide is obtained.

[Example 12]
A gadolinium was prepared in the same manner as in Example 1 except that 18.7 ml of a solution adjusted to 0.3 mol / l using gadolinium nitrate pentahydrate instead of yttrium nitrate.n hydrate was added. An SCA phosphor coated with a metaphosphate and a hydroxide is obtained.

[Example 13]
Preparation of europium in the same manner as in Example 1 except that 18.7 ml of a solution adjusted to 0.3 mol / l using europium nitrate.n hydrate instead of yttrium nitrate.n hydrate was added. An SCA phosphor coated with a metaphosphate and a hydroxide is obtained.

[Example 14]
A terbium was prepared in the same manner as in Example 1 except that 18.7 ml of a solution adjusted to 0.3 mol / l using terbium nitrate.n hydrate instead of yttrium nitrate.n hydrate was added. An SCA phosphor coated with a metaphosphate and a hydroxide is obtained.

[Example 15]
Prepared in the same manner as in Example 1 except that 18.7 ml of a solution adjusted to 0.3 mol / l using dysprosium nitrate pentahydrate instead of yttrium nitrate.n hydrate was added. An SCA phosphor coated with dysprosium metaphosphate and hydroxide is obtained.

[Example 16]
A lutetium nitrate was prepared in the same manner as in Example 1 except that 18.7 ml of a solution adjusted to 0.3 mol / l using lutetium nitrate.n hydrate instead of yttrium nitrate.n hydrate was added. An SCA phosphor coated with a metaphosphate and a hydroxide is obtained.

[Example 17]
A scandium was prepared in the same manner as in Example 1 except that 18.7 ml of a solution adjusted to 0.3 mol / l using scandium nitrate · n hydrate instead of yttrium nitrate · n hydrate was added. An SCA phosphor coated with a metaphosphate and a hydroxide is obtained.

[Example 18]
Using yttrium nitrate n hydrate (Soegawa Riken, purity 99.99%), except that 1.9 ml of a solution adjusted to 0.3 mol / l was added, it was prepared in the same manner as in Example 1, An SCA phosphor coated with yttrium metaphosphate and hydroxide is obtained.

[Example 19]
Using yttrium nitrate n hydrate (manufactured by Soegawa Rikagaku, purity 99.99%), it was prepared in the same manner as in Example 1 except that 3.8 ml of a solution adjusted to 0.3 mol / l was added. An SCA phosphor coated with yttrium metaphosphate and hydroxide is obtained.

[Example 20]
Using yttrium nitrate n hydrate (manufactured by Soekawa Rikagaku, purity 99.99%), it was prepared in the same manner as in Example 1 except that 5.6 ml of a solution adjusted to 0.3 mol / l was added. An SCA phosphor coated with yttrium metaphosphate and hydroxide is obtained.

[Example 21]
Using yttrium nitrate n hydrate (manufactured by Soekawa Riken, purity 99.99%), except that 18.7 ml of a solution adjusted to 0.3 mol / l was added, prepared in the same manner as in Example 1, An SCA phosphor coated with yttrium metaphosphate and hydroxide is obtained.

[Example 22]
Using yttrium nitrate.n hydrate (Soegawa Riken, purity 99.99%), prepared in the same manner as in Example 1 except that 26.2 ml of a solution adjusted to 0.3 mol / l was added, An SCA phosphor coated with yttrium metaphosphate and hydroxide is obtained.

[Example 23]
Using a solution adjusted to 1.7 wt% using potassium hydroxide (manufactured by Kanto Chemical Co., Ltd.) and adjusting the pH to 8.0, it was prepared in the same manner as in Example 21, and yttrium metaphosphate and water were used. An oxide-coated SCA phosphor is obtained.

[Example 24]
Prepared in the same manner as in Example 21 except that 6.8 ml (0.5 times that in Example 1) of a solution adjusted to 2.25 wt% using sodium hexametaphosphate (manufactured by Kanto Chemical Co., Ltd., deer grade) was added dropwise. An SCA phosphor coated with yttrium metaphosphate and hydroxide is obtained.

[Example 25]
Prepared in the same manner as in Example 21 except that 20.3 ml (1.5 times as much as Example 1) of a solution adjusted to 2.25 wt% using sodium hexametaphosphate (manufactured by Kanto Chemical Co., Ltd., deer grade) was added dropwise. An SCA phosphor coated with yttrium metaphosphate and hydroxide is obtained.

[Example 26]
A yttrium metaphosphate prepared in the same manner as in Example 1 except that 13.5 ml of a solution adjusted to 2.25 wt% using sodium metaphosphate having a polymerization degree of 31 (manufactured by Yoneyama Chemical Co., Ltd., Super) was added dropwise. A hydroxide-coated SCA phosphor is obtained.

[Comparative Example 1]
An SCA phosphor that is not coated with a surface treatment substance is prepared.

[Comparative Example 2]
100 g of SCA phosphor is placed in 200 ml of pure water and suspended. 18.7 ml of a solution adjusted to 0.3 mol / l using yttrium nitrate.n hydrate (manufactured by Soekawa Riken, purity 99.99%) is added. Further, 13.5 ml of a solution adjusted to a concentration of 2.25% using orthophosphoric acid is added dropwise. Thereafter, the pH is adjusted to 9.5 using a solution adjusted to 1.7 wt% using potassium hydroxide (manufactured by Kanto Chemical Co., Ltd., special grade). After completion of the dropwise addition, washing, draining, drying and sieving are performed sufficiently to obtain an SCA phosphor coated with yttrium orthophosphate and hydroxide.

[Comparative Example 3]
100 g of SCA phosphor is placed in 200 ml of pure water and suspended. 18.7 ml of a solution adjusted to 0.3 mol / l using yttrium nitrate.n hydrate (manufactured by Soekawa Riken, purity 99.99%) is added. Further, 13.5 ml of a solution adjusted to a concentration of 2.25% using sodium pyrophosphate is added dropwise. Thereafter, the pH is adjusted to 9.5 using a solution adjusted to 1.7 wt% using potassium hydroxide (manufactured by Kanto Chemical Co., Ltd., special grade). After completion of dropping, washing, draining, drying, and sieving are performed to obtain an SCA phosphor coated with yttrium pyrophosphate and hydroxide.

  For the SCA phosphors coated with the surface treatment materials obtained in Examples 1 to 26 and Comparative Examples 1 to 3, the coating amount of the surface treatment material (in terms of rare earth elements) is shown in Table 1. From this table, it can be seen that in the phosphors of the examples of the present invention, the coating amount of the surface treatment substance is in the range of 0.1 to 20 mol% in terms of the amount of rare earth elements with respect to the phosphor. Moreover, a white cold cathode fluorescent lamp is produced using these phosphors as follows.

The SCA phosphor emitting blue light, (Ba _0.9 Eu _0.1 ) (Mg _0.9 Mn _0.1 ) Al ₁₀ O ₁₇ green light emitting phosphor, and (Y _0.9 Eu _0.1 ) ₂ The O ₃ red light emitting phosphor is mixed in a weight ratio of blue: green: red = 50: 20: 30. This mixed phosphor and binder are added to a nitrocellulose / butyl acetate solution and mixed to prepare a phosphor-coated slurry. This is poured into a glass tube having a tube diameter of 3 mm and a length of 400 mm, applied to the inner surface thereof, dried through warm air, and baked at 560 ° C. for 3 minutes to form a fluorescent film. Thereafter, exhaust and electrodes are attached according to a normal method to obtain a white cold cathode fluorescent lamp.

  For the white cold cathode fluorescent lamp thus obtained, the initial luminous flux (%) (relative value), the luminous flux maintenance factor (%) when lit for 100 hours, the change amount Δx of chromaticity x, and the change amount Δy of chromaticity y. The results are shown in Table 1. From this table, it can be seen that all of the fluorescent lamps of the embodiment of the present invention have a luminous flux maintenance factor of 97% or more when lit for 100 hours, which is higher than that of the fluorescent lamp of the comparative example. In addition, the fluorescent lamps of the examples of the present invention have Δx and Δy in the ranges of Δx ≦ + 0.0040 and Δy ≦ + 0.010, respectively, which are smaller than the fluorescent lamps of the comparative examples and have little change over time in chromaticity. I understand that.

  Next, for the white cold cathode fluorescent lamps of Example 1 and Comparative Example 1, the tube end color difference immediately after lighting is measured as follows. That is, the emission color was measured at positions of 30 mm, 200 mm, and 370 mm from one end of the fluorescent lamp, and the difference in emission color between the tube end portion (30 mm, 370 mm) and the central portion (200 mm) was determined. From this table, it can be seen that the fluorescent lamp of Example 1 of the present invention has less tube end color difference than the fluorescent lamp of Comparative Example 1.

  As described above, according to the present invention, it is possible to obtain a fluorescent lamp that suppresses the color difference at the tube end when the lamp is turned on, has a high lamp luminous flux maintenance factor, and has little change over time in lamp chromaticity. It can be suitably used for a light source such as a backlight.

It is a figure which shows an example of the cold cathode fluorescent lamp of this invention. It is a figure which shows the relationship between Y amount (mol%) of the surface treatment substance of the fluorescent substance of this invention, and the initial luminous flux (%) of a cold cathode fluorescent lamp. It is a figure which shows the relationship between Y amount (mol%) of the surface treatment substance of the fluorescent substance of this invention, and the luminous flux maintenance factor (%) of a cold cathode fluorescent lamp. It is a figure which shows the relationship between Y amount (mol%) of the surface treatment substance of the fluorescent substance of this invention, and variation | change_quantity (DELTA) x of chromaticity x of a cold cathode fluorescent lamp. It is a figure which shows the relationship between Y amount (mol%) of the surface treatment substance of the fluorescent substance of this invention, and variation | change_quantity (DELTA) y of chromaticity y of a cold cathode fluorescent lamp. It is a figure which shows the relationship between pH value and the initial luminous flux (%) of a cold cathode fluorescent lamp. It is a figure which shows the relationship between pH value and the luminous flux maintenance factor (%) of a cold cathode fluorescent lamp. It is a figure which shows the relationship between pH value and variation | change_quantity (DELTA) x of chromaticity x of a cold cathode fluorescent lamp. It is a figure which shows the relationship between pH value and the variation | change_quantity (DELTA) y of chromaticity y of a cold cathode fluorescent lamp.

Explanation of symbols

11 Translucent airtight container
12 Phosphor layer
13 Discharge medium
14a, 14b electrode

Claims (5)

  1. A phosphor characterized in that the surface of a phosphor particle is coated with a surface treatment substance containing a rare earth metaphosphate and a rare earth hydroxide.   The rare earth element constituting the rare earth metaphosphate and the rare earth hydroxide is at least one element selected from the group consisting of Y, La, Ce, Gd, Eu, Tb, Dy, Lu, and Sc. The phosphor according to claim 1, wherein the phosphor is present.   3. The phosphor according to claim 1, wherein a coating amount of the surface treatment substance is in a range of 0.1 to 20 mol% in terms of a rare earth element amount with respect to the phosphor.   In a fluorescent lamp comprising a translucent airtight container, a phosphor layer formed in the translucent airtight container, a discharge medium enclosed in the translucent airtight container, and an electrode, the phosphor layer is A fluorescent lamp comprising the phosphor according to claim 1.   The fluorescent lamp according to claim 4, wherein the fluorescent lamp is a cold cathode fluorescent lamp.

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