JP2008133390A - Pyrophosphoric acid alkaline earth metal salt phosphor, fluorescent lamp and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color liquid crystal display having high luminance and wide color reproduction range, a blue light-emitting phosphor for the liquid crystal display and a fluorescent lamp using the phosphor. <P>SOLUTION: The pyrophosphoric acid alkaline earth metal salt phosphor is represented by the general formula: (Sr<SB>1-a-b-c</SB>Ca<SB>a</SB>M<SB>b</SB>Eu<SB>c</SB>)<SB>2</SB>P<SB>2</SB>O<SB>7</SB>(wherein M is at least one kind of element selected from Mg, Ba and Zn; 0<a≤0.4, 0≤b≤0.4, 0<a+b≤0.4 and 0.001≤c≤0.1). The alkaline earth metal pyrophosphoric acid salt phosphor has an emission peak wavelength which is close to a peak wavelength of transmittance curve of a blue color filter and the phosphor has a narrow half-width of ≤45 nm. The color liquid crystal display having high luminance and wide color reproduction range can be provided by combining back light using the phosphor as a blue light-emitting phosphor with a color filter. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an alkaline earth metal pyrophosphate phosphor, a fluorescent lamp, and a liquid crystal display device, and more particularly to a color liquid crystal display device having high luminance and a wide color reproduction range.

  Liquid crystal display devices are used in personal computers and televisions, and are widely used from conventional monochrome display to color display. A color liquid crystal display device is a liquid crystal display device that uses blue, green, and red minute pixels formed by dividing the screen in a grid pattern as the smallest unit that constitutes a display image, and controls the brightness to display the color. is there. This color liquid crystal display device uses a liquid crystal element as an optical shutter, and combines this with a white light source backlight and a color filter that transmits blue, green, or red light in units of pixels. An image is displayed. The color liquid crystal display device is required to have the same characteristics as the current color CRT, and is required to have a high luminance and a wide color reproduction range.

A cold-cathode fluorescent lamp that can be easily made into a thin tube is mainly used as a backlight of a white light source, and a three-wavelength phosphor has been conventionally used as a phosphor for a cold-cathode fluorescent lamp. For example, Y ₂ O ₃ : Eu, YVO ₄ : Eu or the like is used as the red light emitting phosphor, and LaPO ₄ : Ce, Tb, Zn ₂ SiO ₄ : Mn or the like is used as the green light emitting phosphor. The blue emitting a phosphor _{(Sr, Ca) 10 (PO} 4) 6 Cl 2: Eu, Sr 10 (PO 4) 6 Cl 2: Eu, Sr 2 P 2 O 7: Sn, Ba 2 P 2 O _{7: Ti, BaMg 2 Al 16} O 27: Eu and the like are used. However, a color liquid crystal display device combining a backlight using these blue light emitting phosphors and a color filter does not satisfy both luminance and color reproduction range.

  Since the brightness and color reproduction range of a color liquid crystal display device are determined by the emission spectrum of the backlight and the transmittance curve of the color filter, the peak wavelength of the emission spectrum of the blue light emitting phosphor is the peak wavelength of the transmittance curve of the blue color filter. The closer the brightness is, the higher the luminance of the color liquid crystal display device is, and the narrower the half-value width of the emission spectrum of the blue light emitting phosphor is, the higher the color purity of the blue region is and the wider the color reproduction range of the color liquid crystal display device. Therefore, as the blue light emitting phosphor for backlight of the color liquid crystal display device, the peak wavelength of the transmittance curve of the blue color filter is near 460 nm as shown in FIG. However, the conventional blue light emitting phosphor does not satisfy both of them.

A color liquid crystal display device excellent in luminance and color reproducibility is disclosed in Japanese Patent Laid-Open No. 9-97017, etc., but is not sufficient, and further improvement in characteristics is desired.
JP-A-9-97017

  The present invention has been made to solve such problems. An object of the present invention is to provide a color liquid crystal display device having high luminance and a wide color reproduction range, and further to providing a blue light emitting phosphor for the liquid crystal display device and a fluorescent lamp using the same. is there.

  In order to achieve the above object, the present inventors have made extensive studies, and as a result, combined a backlight using a alkaline earth metal pyrophosphate phosphor having a specific composition as a blue light emitting phosphor and a color filter. The color liquid crystal display device has been newly found to have a high luminance and a wide color reproduction range, and has completed the present invention.

(1) The alkaline earth metal pyrophosphate phosphor of the present invention is characterized in that the general formula is represented by the following formula.
_{(Sr 1-a-b-} c Ca a M b Eu c) 2 P 2 O 7
(Where M is at least one element selected from Mg, Ba and Zn, 0 <a ≦ 0.4, 0 ≦ b ≦ 0.4, 0 <a + b ≦ 0.4, 0.001 ≦ c ≦ 0.1)

(2) The alkaline earth metal pyrophosphate phosphor of the present invention is the alkaline earth metal pyrophosphate phosphor according to (1), wherein the peak wavelength of the emission spectrum is in the range of 425 to 440 nm, The half width is 45 nm or less.

(3) 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 alkaline earth metal pyrophosphate phosphor described in (1) or (2).

(4) The fluorescent lamp of the present invention is the fluorescent lamp described in (3), wherein the fluorescent lamp is a cold cathode fluorescent lamp.

(5) The liquid crystal display device of the present invention is a combination of an optical shutter using liquid crystal, a backlight of a white light source, and a color filter that is provided for each pixel and transmits blue, green, or red light. In the liquid crystal display device configured as described above, the backlight is the fluorescent lamp described in (3) or (4).

  Since the peak wavelength of the emission spectrum of the phosphor of the present invention is in the range of 425 to 440 nm and is close to the peak wavelength of the transmittance curve of the blue color filter, the luminance of the color liquid crystal display device is improved. Further, since the half width of the emission spectrum of the phosphor of the present invention is as narrow as 45 nm or less, the color purity of the blue region is increased and the color reproduction range of the color liquid crystal display device is expanded. By combining a backlight using the phosphor of the present invention as a blue light emitting phosphor and a color filter, a color liquid crystal display device having high luminance and a wide color reproduction range can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiment described below exemplifies an alkaline earth metal pyrophosphate phosphor, a fluorescent lamp, and a liquid crystal display device for embodying the technical idea of the present invention. The metal pyrophosphate phosphors, fluorescent lamps and liquid crystal display devices are not specified as follows.

  Here, a method for producing an alkaline earth metal pyrophosphate phosphor according to an embodiment of the present invention will be described in detail. As a phosphor material, a strontium compound, a calcium compound, a compound of at least one element selected from magnesium, barium and zinc, a europium compound, and a phosphate are weighed according to the target phosphor composition. Then, a flux is further added to these raw materials and mixed. After filling this raw material mixture into a crucible, it is put in a furnace and fired at 1000 to 1400 ° C. in a reducing atmosphere. After cooling, the fired product is wet-dispersed and then separated and dried to obtain the alkaline earth metal pyrophosphate phosphor of the present invention.

  As the strontium compound, the calcium compound, the compound of at least one element selected from magnesium, barium and zinc, and the europium compound, an oxide or a compound that becomes an oxide by thermal decomposition is preferably used. For example, a compound which decomposes at a high temperature and becomes an oxide such as carbonate, hydroxide, nitrate, oxalate is preferable. Further, a coprecipitate containing all or part of the elements constituting the phosphor or an oxide obtained by calcining these can be used. As for phosphates, alkaline earth metal phosphates and ammonium phosphates are preferably used. After mixing these phosphor raw materials with a ball mill, a V-type mixer, etc., they are filled in a crucible such as alumina, quartz, silicon carbide, etc. It is preferable to bake for 12 hours. When the firing temperature is lower than 1000 ° C., the reaction does not proceed.

  Next, a cold cathode fluorescent lamp is produced using the alkaline earth metal pyrophosphate 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 warm air through the glass tube, followed by baking, exhausting, attaching a filament, and attaching a base to obtain a cold cathode fluorescent lamp.

  FIG. 2 shows an example of the cold cathode fluorescent lamp of the present invention. A phosphor layer 12 composed 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 the 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.

  FIG. 3 is a cross-sectional view showing an example of the color liquid crystal display device of the present invention. The backlight unit 21 is provided with a white cold cathode fluorescent lamp as a light source 23, and the light is emitted to the liquid crystal panel side by a light guide plate or the like. An alignment sheet 24 is attached to the front surface of the backlight unit 21 to adjust the direction of the emitted light, and light perpendicular to the liquid crystal panel 22 is introduced from the backlight unit 21. The liquid crystal panel 22 includes a transparent electrode 25 and a TFT for driving a liquid crystal 25, a transparent electrode 26 facing the transparent electrode 26, a color filter 27, a liquid crystal layer 28 sandwiched between the transparent electrodes, and a TFT control circuit 30. , TFT, liquid crystal layer, and color filter exist corresponding to each display pixel. The voltage applied to the liquid crystal layer 28 of each display pixel is determined by the TFT, and the phase of the liquid crystal layer changes to change the light transmittance. The transmitted light is selectively transmitted through the color filter 27 only in a specific wavelength range. In this way, each display pixel displays a specific color with a specific intensity, and the set is recognized as an image of the color liquid crystal display device.

  FIG. 4 is a bird's eye view showing an example of the color liquid crystal display device of the present invention. As shown in the figure, the TFT control circuit 34 consists of two systems, a circuit that processes information in the vertical direction of the screen and a circuit that processes information in the horizontal direction, and the sum of their outputs is the voltage applied to each display pixel. Become.

Next, the characteristics of the alkaline earth metal pyrophosphate phosphor of the present invention will be described with reference to the drawings. Figure 5, is obtained by changing the amount of Ca _{(Sr 0.99-a Ca a Eu} 0.01) 2 P 2 O 7 phosphors for in Example 3, the Ca amount emission peak wavelength (nm) (a Value). Here, the emission peak wavelength is a wavelength indicating the maximum emission intensity in the emission spectrum when the phosphor is excited by ultraviolet rays at 254 nm. From this figure, the emission peak wavelength of the phosphor shifts to the longer wavelength side as the Ca content (a value) increases, but the rate of shift decreases when exceeding a = 0.1, and 0 <a ≦ 0. In the range of 4, the peak wavelength is found to be in the range of 425 to 440 nm. Thus, the phosphor of the present invention shifts the emission peak wavelength to the longer wavelength side by addition of Ca and approaches the peak wavelength (near 460 nm) of the transmittance curve of the blue color filter. The conventional color liquid crystal display device is improved in luminance. The Ca amount (a value) of the phosphor of the present invention is preferably in the range of 0 <a ≦ 0.4, and more preferably in the range of 0.025 ≦ a ≦ 0.4. In this range, a high-luminance color liquid crystal display device can be obtained.

  FIG. 6 shows the relationship between the full width at half maximum (nm) and the Ca content (a value) for the phosphor. Here, the full width at half maximum is the difference in wavelength at which the emission intensity is ½ of the maximum emission intensity in the emission spectrum when the phosphor is excited with 254 nm ultraviolet light. From this figure, the phosphor of the present invention has a slightly expanded half-value width due to the addition of Ca. However, when the Ca content (a value) is in the range of 0 <a ≦ 0.4, the half-value width of the emission spectrum is as narrow as 45 nm or less. It turns out that purity is high.

FIG. 7 shows the emission peak wavelength (nm) and the amount of Eu (c) for the (Sr _0.8-c Ca _0.2 Eu _c ) ₂ P ₂ O ₇ phosphor obtained by changing the amount of Eu in Example 1. Value). From this figure, the emission peak wavelength of the phosphor shifts to the longer wavelength side as the Eu amount (c value) increases, but the shift ratio decreases when c = 0.02 is exceeded, and 0.001 ≦ c ≦ It can be seen that the peak wavelength is in the range of 425 to 440 nm in the range of 0.1. The Eu amount (c value) of the phosphor of the present invention is preferably in the range of 0.001 ≦ c ≦ 0.1, and more preferably in the range of 0.01 ≦ c ≦ 0.05. In this range, a high-luminance color liquid crystal display device can be obtained.

  FIG. 8 shows the relationship between the full width at half maximum (nm) and the Eu amount (c value) for the phosphor. From this figure, it can be seen that the phosphor of the present invention has a narrow half-width of the emission spectrum of 45 nm or less and high color purity when the Eu amount (c value) is in the range of 0.001 ≦ c ≦ 0.1.

  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]
<Phosphor>
As raw materials, 1.56 mol of SrCO _3, 0.40 mol of CaCO ₃ , 0.02 mol of Eu ₂ O ₃ and 2.0 mol of (NH ₄ ) ₂ HPO ₄ were mixed with a ball mill, and this raw material mixture was charged into an alumina crucible and reduced. Baking at 1200 ° C. for 6 hours in an atmosphere (2% H ₂ / N ₂ ). After cooling, it is subjected to a dispersion treatment, passed through a wet sieve, dehydrated and dried, and further passed through a dry sieve to obtain a (Sr _0.78 Ca _0.2 Eu _0.02 ) ₂ P ₂ O ₇ phosphor. FIG. 9 shows an emission spectrum of this phosphor when excited with 254 nm ultraviolet rays. From this figure, it can be seen that the emission peak wavelength is 434 nm, the half width is 35 nm, and the phosphor emits blue light.

<Single color fluorescent lamp>
The phosphor thus obtained and the binder are added to a nitrocellulose / butyl acetate solution and mixed to prepare a phosphor coating 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, dried through warm air, and baked at 580 ° C. for 15 minutes to form a fluorescent film. Then, according to a normal method, exhaust, electrode mounting, and attachment of a base are performed to obtain a monochromatic cold cathode fluorescent lamp that emits blue light. The emission spectrum of this monochromatic fluorescent lamp is shown in FIG.

<White fluorescent lamp>
Next, the alkaline earth metal pyrophosphate phosphor emitting blue light, the BaMgAl ₁₀ O ₁₇ : Eu, Mn green light emitting phosphor, and the Y ₂ O ₃ : Eu red light emitting phosphor in a weight ratio of blue: green: Mix at a ratio of 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. Then, according to a normal method, exhaust, electrode mounting, and attachment of a base are performed to obtain a white cold cathode fluorescent lamp. The emission spectrum of this white fluorescent lamp is shown in FIG.
The measurement results of the alkaline earth metal pyrophosphate phosphor, single color fluorescent lamp, and white fluorescent lamp are shown in Table 1, Table 2, and Table 3, respectively.

[Examples 2 to 12]
Alkaline earth metal in the same manner as in Example 1 except that CaCO ₃ and Eu ₂ O ₃ among the phosphor raw materials are mixed in amounts corresponding to the Ca amount (a value) and Eu amount (c value) in Table 1. A pyrophosphate phosphor is prepared.

[Comparative Example 1]
Alkaline earth metal pyrophosphate in the same manner as in Example 1 except that CaCO ₃ is not added among the phosphor raw materials and Eu ₂ O ₃ is mixed in an amount corresponding to the Eu amount (c value) in Table 1. A phosphor is prepared. FIG. 9 shows an emission spectrum of this phosphor when excited with 254 nm ultraviolet rays.

For the alkaline earth metal pyrophosphate phosphors obtained in Examples 1 to 12 and Comparative Example 1, Table 1 shows the Ca amount (a value), Eu amount (c value), and the Y value by the XYZ color system. The Z value, the chromaticity coordinates x · y, and the emission peak wavelength and half width when excited with 254 nm ultraviolet rays are shown. The light emission characteristic values in this table were measured using a Hamamatsu Photonics spectrophotometer after irradiating the phosphor with 254 nm ultraviolet light using a low-pressure mercury lamp manufactured by Hamamatsu Photonics. The Z value indicates a relative value when the Y value and the Z value of the (Sr _0.662 Ca _0.327 Eu _0.011 ) ₁₀ (PO ₄ ) ₆ Cl ₂ phosphor are 100%, respectively. For comparison, the comparative example 2 shows a (Ba _0.743 Ti _0.257 ) ₂ P ₂ O ₇ phosphor as a conventionally known Ba ₂ P ₂ O ₇ : Ti phosphor for comparison. It was. From this table, it can be seen that the phosphors of the examples of the present invention have an emission spectrum peak wavelength in the range of 425 to 440 nm and a half width of 45 nm or less. In addition, the phosphor of the example of the present invention has a very narrow half-value width and a small value of the chromaticity coordinates x · y compared to the Ba ₂ P ₂ O ₇ : Ti phosphor of the conventional comparative example 2. It can be seen that the color purity is high.

  As described above, a color liquid crystal display device having high luminance and a wide color reproduction range can be provided by combining a backlight using the phosphor of the present invention as a blue light emitting phosphor and a color filter. .

It is a figure which shows the transmittance | permeability curve of a color filter. It is a figure which shows an example of the cold cathode fluorescent lamp of this invention. It is sectional drawing which shows an example of the color liquid crystal display device of this invention. It is a bird's-eye view which shows an example of the color liquid crystal display device of this invention. It is a figure which shows the relationship between the light emission peak wavelength (nm) and Ca amount (a value) of the fluorescent substance of this invention. It is a figure which shows the relationship between the half value width (nm) of the fluorescent substance of this invention, and Ca content (a value). It is a figure which shows the relationship between the light emission peak wavelength (nm) and Eu amount (c value) of the fluorescent substance of this invention. It is a figure which shows the relationship between the half value width (nm) and Eu amount (c value) of the fluorescent substance of this invention. It is a figure which shows the emission spectrum of the fluorescent substance of Example 1 and Comparative Example 1. It is a figure which shows the emission spectrum of the monochromatic fluorescent lamp of Example 1 and Comparative Example 2. It is a figure which shows the emission spectrum of the white fluorescent lamp of Example 1.

Explanation of symbols

1 Blue color filter transmittance curve
2 Green color filter transmittance curve
3 Transmission curve of red color filter
11 Translucent airtight container
12 Phosphor layer
13 Discharge medium
14a, 14b electrode
21 Backlight unit
22 LCD panel
23 Light source
24 Oriented sheet
25 Transparent electrode / TFT
26 Transparent electrode
27 Color filter
28 Liquid crystal layer
29 Glass plate
30 TFT control circuit
31 Backlight unit
32 LCD panel
33 Light source
34 TFT control circuit

Claims (5)

An alkaline earth metal pyrophosphate phosphor, wherein the general formula is represented by the following formula:
_{(Sr 1-a-b-} c Ca a M b Eu c) 2 P 2 O 7
(Where M is at least one element selected from Mg, Ba and Zn, 0 <a ≦ 0.4, 0 ≦ b ≦ 0.4, 0 <a + b ≦ 0.4, 0.001 ≦ c ≦ 0.1)   2. The alkaline earth metal pyrophosphate phosphor according to claim 1, wherein the peak wavelength of the emission spectrum is in the range of 425 to 440 nm and the half width is 45 nm or less.   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 alkaline earth metal pyrophosphate phosphor according to claim 1.   The fluorescent lamp according to claim 3, wherein the fluorescent lamp is a cold cathode fluorescent lamp.   In the liquid crystal display device configured by combining an optical shutter using liquid crystal, a backlight of a white light source, and a color filter that is provided for each pixel and transmits blue, green, or red light. 5. A liquid crystal display device, wherein the light is a fluorescent lamp according to claim 3 or 4.

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