JP2011190304A - Phosphor for plasma display panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phosphor for a PDP enhanced in the luminous efficiency of phosphor particles and the extraction efficiency of visible light, and further improved in the color purity. <P>SOLUTION: The phosphor 10 includes a core part 11 composed of oxide particles that reflects visible light and having a large reflectance, a wavelength selection layer 12 that covers the core part 11 and allows a prescribed wavelength of visible light to penetrate therethrough, and a luminescent layer 13 that covers the wavelength selection layer 12 and is excited by a vacuum ultraviolet ray to emit a visible light. According to the phosphor, the PDP excellent in the luminance, the luminous efficiency, the color reproduction range, and a contrast is achieved. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a phosphor for a plasma display panel, and more particularly to a phosphor that realizes high luminous efficiency and high contrast.

  In recent years, as a situation surrounding general household televisions including a plasma display panel (hereinafter referred to as PDP), reduction of environmental load is required, and reduction of power consumption has become an essential issue. On the other hand, in order to make full use of the advantages of PDP, it is indispensable to achieve higher contrast and a higher sense of presence.

  The PDP displays an image by converting electric energy into vacuum ultraviolet rays (peak wavelengths: 147 nm, 172 nm), and further converting into visible light (wavelengths: 380 nm to 760 nm) with a phosphor. It is. The display performance is expressed by indices such as luminance, light emission efficiency, color reproduction range, and contrast. Among them, the performance of the phosphor greatly influences the display performance. A performance index required for a phosphor for realizing low power consumption in a PDP is an improvement in luminous efficiency. As such an approach, improvement of the bulk luminance of the phosphor itself and improvement of light extraction efficiency from the phosphor layer are required. In addition, a performance index required for a phosphor to realize high contrast and high presence is expansion of a color reproduction region, and it is necessary to improve color purity of blue, green, and red.

  In general, a phosphor used in a PDP is a particle synthesized by a solid phase method or a liquid phase method, and is composed of a solid solution of a plurality of oxides. As a method for improving the luminance efficiency of such a phosphor for PDP, Patent Document 1 discloses an example in which a coating layer having a refractive index lower than the refractive index of the phosphor particles is provided on the surface of the phosphor particles. Moreover, as a method for increasing the color purity (contrast) of a phosphor for PDP, Patent Document 2 discloses an example in which a color pigment is coated on the surface of phosphor particles. Furthermore, Patent Document 3 discloses an ultrafine particle phosphor having a three-layer structure as a method for improving the luminance efficiency and color purity of the phosphor for PDP.

JP 10-125240 A International Publication No. 2009/5195 JP 2005-139389 A

  However, in the phosphor described in Patent Document 1, since the phosphor remains white, when the screen when not emitting light is black, the screen becomes white due to the reflection of external light and the contrast and color purity are reduced. There was a problem. In addition, in the phosphor described in Patent Document 2, since the phosphor of each color is coated with a color pigment corresponding to each color, a decrease in contrast (color purity) due to reflection of external light is reduced. There was a problem that the luminance was lowered.

  In addition, when the phosphor particles having a three-layer structure described in Patent Document 3 are used for PDP, there are the following problems. In other words, high-energy excitation light with wavelengths of 147 nm and 172 nm is absorbed by the coating layer, and the excitation energy arrival rate reaching the semiconductor layer as the light emitting portion is lowered. As a result, there is a problem that the brightness of the ultrafine particle phosphor is lowered. Furthermore, since the phosphor described in Patent Document 3 uses an organic material layer as an intermediate layer, it has a problem that it is easily affected by deterioration due to a thermal process.

  An object of the present invention is to solve such a problem and to provide a phosphor for PDP with improved luminous efficiency and visible light extraction efficiency of phosphor particles and further improved color purity.

  In order to achieve the above-described object, the phosphor for PDP of the present invention includes a core part that reflects visible light, a wavelength selection layer that covers the core part and transmits a predetermined wavelength of visible light, covers a wavelength selection layer, and vacuums. And a light emitting layer that emits visible light when excited by ultraviolet rays.

  According to the phosphor having such a configuration, it is possible to realize a PDP in which the luminous efficiency of the phosphor particles and the extraction efficiency of visible light are increased and the color purity is further improved.

  Furthermore, it is desirable that the core portion is made of oxide particles and that the reflectance is larger than the reflectance of the light emitting layer. According to such a configuration, there is no influence by the thermal process, and the extraction efficiency of visible light can be improved.

  Furthermore, the wavelength selection layer is made of an inorganic material, and it is desirable that visible light having a peak at 450 ± 5 nm is allowed to pass through the light emitting layer that emits blue light. According to such a configuration, the blue color purity can be improved.

  Furthermore, the wavelength selection layer is made of an inorganic material, and it is desirable that visible light having a peak at 555 ± 5 nm is allowed to pass through the light emitting layer that emits green light. According to such a configuration, the color purity of green can be improved.

  Further, the wavelength selection layer is made of an inorganic material, and it is desirable to allow visible light having a peak at 760 ± 5 nm to pass through the light emitting layer that emits red light. According to such a configuration, the color purity of red can be improved.

  As described above, according to the phosphor for PDP of the present invention, it is possible to realize a PDP having improved luminous efficiency and visible light extraction efficiency of phosphor particles and further improved color purity.

It is sectional drawing which shows the structure of the fluorescent substance for PDP in embodiment. It is a figure which shows the synthesis | combination process of the fluorescent substance for PDP in embodiment. It is sectional drawing which shows the discharge cell of PDP.

  Hereinafter, an embodiment of a PDP phosphor according to the present invention will be described in detail with reference to the drawings.

(Embodiment)
Hereinafter, the configuration of the phosphor for PDP in the embodiment, the principle of light emission, the material of each functional layer, the synthesis process, and the effect will be described in this order. FIG. 1 is a cross-sectional view illustrating a configuration of a phosphor for PDP in the embodiment. As shown in FIG. 1, the phosphor 10 includes a core portion 11 that reflects visible light, a wavelength selection layer 12 that covers the core portion 11 and transmits a predetermined wavelength of visible light, covers the wavelength selection layer 12, and is formed by vacuum ultraviolet rays. It is comprised by the light emitting layer 13 which emits visible light by being excited.

  The principle of light emission in the phosphor 10 configured as described above will be described. The emission colors extracted from the phosphor 10 used as a PDP application must be red, green, and blue. The layer that determines the emission color is the light emitting layer 13 that is the outermost surface layer. The light emitting layer 13 is composed of a host crystal that absorbs vacuum ultraviolet light that is excitation light and transmits it to the light emission center, and a light emission center that converts the transmitted excitation energy into visible light that is the three primary colors.

  The light emitted from the phosphor 10 includes three types of light emitted from the light-emitting layer 13, 15 and external light reflected light 16. These light emission 14 is used for high luminous efficiency and high color purity. , 15 and the external light reflected light 16 are important to take out efficiently.

  First, the light emission 14 extracted directly from the light emitting layer 13 will be described. Vacuum ultraviolet rays (peak wavelengths of 147 nm and 172 nm) generated by the discharge in the PDP discharge cell excite the outermost light emitting layer 13 of the phosphor 10. Vacuum ultraviolet rays are high in energy and are rapidly absorbed after entering the light-emitting layer 13 and greatly attenuated when entering about several tens of nanometers. In the process, vacuum ultraviolet rays are absorbed by the base material forming the light emitting layer 13 and transmitted to the emission center. Then, the light is converted into visible light at the light emission center, and light emission 14 is emitted from the surface of the light emitting layer 13 of the phosphor 10.

  Next, light emission 15 from the light emitting layer 13 toward the inside of the phosphor 10 will be described. The light emission 15 directed inward from the light emitting layer 13 first transmits only a predetermined wavelength band in the wavelength selection layer 12. At the same time as passing through the wavelength selection layer 12, only a predetermined wavelength band having good color purity is extracted. The light emission 15 selected in this way reaches the innermost core portion 11 and is reflected, and at the same time, the traveling direction is converted to the outside. Then, the light again passes through the wavelength selection layer 12 and the light emitting layer 13 and is taken out from the phosphor 10. Therefore, since the light emission 15 passes through a predetermined wavelength band in the wavelength selection layer 12, the color purity is very good, and the light emission 15 is superimposed on the light emission 14 and extracted from the phosphor 10. As a result, the color purity and luminous efficiency of the entire light emission can be increased.

  Next, the external light reflected light 16 will be described. When outside light is incident, part of the light is reflected by the light emitting layer 13 and extracted. This is not particularly different from the conventional external light reflection. However, a part of the light passes through the light emitting layer 13 and is selected in a predetermined wavelength band in the wavelength selection layer 12, is reflected by the core portion 11, and is taken out to the outside. Therefore, since the external light reflected light 16 passes through a predetermined wavelength band in the wavelength selection layer 12, the color purity is very good, and it is superimposed on the light emission 14 and 15 and taken out from the phosphor 10. As a result, the color purity and luminous efficiency of the entire light emission can be further increased.

  Thus, according to the phosphor 10 in the embodiment, it is possible to improve the light extraction efficiency, contrast, and color purity. Further, the reflectance can be increased without making the phosphor 10 small particles.

Next, details of the functions and materials of the core portion 11, the wavelength selection layer 12, and the light emitting layer 13 that constitute the phosphor 10 will be described. The core portion 11 has a function of converting the light emission 15 emitted from the light emitting layer 13 to the inside or the external light reflected light 16 in the outward direction of the phosphor 10. The material is preferably a chemically stable material, and is preferably a metal oxide whose reflectance is at least greater than that of the light emitting layer 13. From such a point, it is desirable that the material contains at least one oxide selected from Al ₂ O ₃ , TiO ₂ , BaTiO ₃ , MoO ₃ , and WO ₃ . The particle diameter is not particularly specified but is preferably 0.5 μm or less.

  The core portion 11 has a function of converting the light emission 15 emitted from the light emitting layer 13 toward the core portion 11 or the external light reflected light 16 in the direction of the light emitting layer 13, and a visible light wavelength including 380 nm to 760 nm. It has a function of reflecting the area. By doing in this way, luminous efficiency can be improved.

Further, the wavelength selection layer 12 has a function of selecting a predetermined wavelength band of the light emission 15 emitted from the light emitting layer 13 to the inner shell side of the phosphor 10 or the external light reflected light 16 and allowing the light to pass through the core portion 11. Have. As a result, it has a function of improving the color purity of emitted light that has passed through the wavelength selection layer 12. The material of the wavelength selection layer 12 is preferably an inorganic material rather than an organic material because it is exposed to a high temperature process when the outermost light emitting layer 13 of the phosphor 10 is formed. For example, it is desirable to use Fe ₂ O ₃ for red, CoO—ZnO—MgO for green, and CoO.2Al ₂ O _{3 for} blue.

  The wavelength selection layer 12 transmits visible light having a peak at 760 ± 5 nm to the red light emitting layer 13 and passes visible light having a peak at 555 ± 5 nm to the green light emitting layer 13. Further, visible light having a peak at 450 ± 5 nm is allowed to pass through the light emitting layer 13 emitting blue light. In addition, each half width is made smaller than the half width of light emission of the light emitting layer 13. By doing in this way, the color purity of red, green, and blue can be improved, respectively.

  The light emitting layer 13 has a function of converting vacuum ultraviolet excitation light generated by discharge into desired visible light. The light emitting layer 13 is composed of a base crystal that has a function of absorbing vacuum ultraviolet rays and efficiently transmitting energy to the light emission center, and a light emission center that converts the transmitted energy into visible light. Vacuum ultraviolet has a wavelength band having peaks at 147 nm and 172 nm. Visible light is the three primary colors of red, green and blue light, and has respective peak wavelengths around 760 nm, 550 nm and 450 nm.

As the material constituting the light emitting layer 13, YBO ₃ : Eu, (Y, Gd) (P, V) O ₄ : Eu, or a mixture thereof is used for red, and Zn ₂ SiO is used for green. ₄ : Mn, BaMgAl ₁₀ O ₁₇ : Mn, (Y, Gd) ₃ Al ₅ O ₁₂ : Tb, (Y, Gd) ₃ Al ₅ O ₁₂ : Ce, (Y, Gd) Al ₃ (BO ₃ ) ₄ : Tb or a mixture thereof is used. For blue, BaAlMg ₁₀ O ₁₇ : Eu or the like is used. These materials are not limited to the above materials as long as they are three primary color phosphors having a peak at the above wavelength.

  Next, a synthesis process for producing such a phosphor 10 will be described. FIG. 2 is a diagram illustrating a process for synthesizing the phosphor for PDP in the embodiment. The synthesis process is roughly the step S1 for synthesizing the innermost core part 11 of the phosphor 10, the step S2 for synthesizing and synthesizing the wavelength selective layer 12 as an intermediate layer on the core part 11, and the outermost surface layer. Step S3 for covering and synthesizing the light emitting layer 13 is configured.

First, step S1 will be described. In step S1, an object is to synthesize the core part 11. For example, the case where the material of the core part 11 is made of Al ₂ O ₃ will be described as an example. A 0.2 molar aqueous solution of alumina nitrate is prepared and supplied from the supply pipe 20 to the tank 22 of the atomizer 21. The atomizer 21 is vibrated at a frequency of about 60 Hz, and the droplets 23 of the Al ₂ O ₃ aqueous solution are filled in the atomizer 21. On the other hand, the carrier gas is fed from the supply pipe 24 in order to sequentially feed the droplets 23 after the next process. N ₂ is used as the carrier gas. The carrier gas is not limited to N ₂ as long as it does not cause interaction with the raw material.

The droplets 23 are continuously sent to the firing furnace 25 with a carrier gas. The temperature of the firing furnace 25 is set to 1500 ° C. While the droplets 23 pass through the firing furnace 25, the water is evaporated, and Al ₂ O ₃ fine particles of about 0.5 μm close to a true sphere can be synthesized. The particle diameter can be adjusted by the frequency at which the atomizer 21 is vibrated, the concentration of the aqueous solution of the starting material, the PH concentration, and the like. The crystallinity of the synthesized fine particles can be adjusted by adjusting the pH concentration of the aqueous solution, the temperature rise temperature of the firing furnace 25, or the holding temperature thereof.

  The core part 11 synthesized in step S1 is carried by the carrier gas, passes through the supply pipe 26, and is continuously conveyed to step S2. In step S <b> 2, the core portion 11 is covered with a wavelength selection layer 12 that is an intermediate layer of the phosphor 10.

  In step S2, the material of the phosphor 10 that emits red light will be described as an example. For example, 0.02 mol of ferric nitrate aqueous solution is supplied to the atomizer 28 through the supply pipe 27. In the same manner as in step S 1, a droplet 29 of ferric nitrate aqueous solution is generated in the atomizer 28, and the atomizer 28 is filled with the atmosphere of the droplet 29. Then, the core portion 11 synthesized in step S1 is passed through the droplet 29.

As a result, the ferric nitrate solution droplet 29 can be adhered to the surface of the core portion 11. Thereafter, the wavelength selection layer 12 made of iron oxide (Fe ₂ O ₃ ) can be formed on the surface of the core portion 11 by continuously passing through the firing furnace 30. The holding temperature of the firing furnace 30 is 1400 ° C., and is desirably lower than the firing temperature when the core portion 11 is formed. The film thickness and film density of the wavelength selection layer 12 can be adjusted by the vibration frequency of the atomizer 28, the concentration of the aqueous solution of the starting material, the PH concentration, and the like. The crystallinity of the wavelength selection layer 12 can be adjusted by adjusting the pH concentration of the aqueous solution, the temperature rise temperature of the firing furnace 30, the holding temperature, and the like.

  The core part 11 covered with the wavelength selection layer 12 in step S2 is carried by the carrier gas, passes through the supply pipe 31, and is continuously carried to step S3. In step S <b> 3, the light emitting layer 13 is further coated on the wavelength selection layer 12.

The material of the phosphor 10 that emits red light in the step S3 will be described as an example. When the light emitting layer 13 is formed of YBO ₃ : Eu, a mixed aqueous solution of yttrium nitrate, boric acid and europium nitrate is used as a raw material. These mixed aqueous solutions are supplied from the supply pipe 32 to the atomizer 33. As in step S1 and step S2, the atomizer 33 is filled with these aqueous solution droplets 34. Then, the core portion 11 covered with the wavelength selection layer 12 synthesized in step S2 passes through the atmosphere of the droplet 34.

  As a result, droplets 34 of these mixed aqueous solutions can be attached to the surface of the wavelength selection layer 12. Thereafter, the light emitting layer 13 of yttrium, borate, and europium can be formed on the surface of the wavelength selection layer 12 by continuously passing through the firing furnace 35. The holding temperature of the firing furnace 35 is 1100 ° C., and is desirably lower than the firing temperature when the wavelength selection layer 12 is formed. The film thickness and film density of the light emitting layer 13 can be adjusted by the vibration frequency of the atomizer 33, the concentration of the aqueous solution of the starting material, the PH concentration, and the like. The crystallinity of the light emitting layer 13 can be adjusted by adjusting the PH concentration of the aqueous solution, the temperature rise temperature of the firing furnace 35, the holding temperature, and the like.

  In this way, the phosphor 10 that emits red light can be synthesized through the path from step S1 to step S3. Similarly, phosphors 10 emitting green light and blue light can be synthesized. Finally, the particle size distribution of the phosphor 10 is adjusted by passing through a filter 36 for classification.

  The above synthesis process is a basic process. For example, a gas modification type may be changed during firing, a reducing atmosphere may be used, or a surface modification process may be added for the purpose of suppressing surface deterioration.

  A red phosphor, a green phosphor, and a blue phosphor were produced by the above synthesis process, and a PDP for a full high-definition television having a screen size of 42 inches was produced. FIG. 3 is a cross-sectional view showing a discharge cell of such a PDP 50. As shown in FIG. A front substrate 52 on which the row electrodes 51 are formed and a rear substrate 54 to which the address electrodes 53 are attached are arranged opposite to each other. On the rear substrate 54, a base dielectric layer 55 is formed so as to cover the address electrodes 53, and a partition wall 57 is formed on the base dielectric layer 55 so as to partition discharge spaces 56 serving as discharge cells. On the side face of the partition wall 57 and the base dielectric layer 55 of the discharge space 56, a phosphor layer 58 is formed by laminating the phosphor 10 described above. In the phosphor layer 58, a red phosphor layer, a green phosphor layer, and a blue phosphor layer are formed in order for each address electrode 53 corresponding to each color discharge cell.

  The phosphor layer 58 is formed by applying and baking the above-described phosphor 10 by a printing method or the like.

  A PDP 50 in which the material of the phosphor 10 was changed was produced, evaluated for lighting, and its brightness and contrast were measured. The results are shown in Table 1.

  Table 1 shows a case where phosphors 10 having a core part 11, a wavelength selection layer 12, and a light emitting layer 13 and having different material compositions are used as Examples 1 to 4 in the embodiment. As an example 1, a case where a phosphor without a conventional core 11 and wavelength selection layer 12 is used is shown. Note that the luminance and contrast are shown as relative values, assuming that the luminance or contrast of Comparative Example 1 is 1.

  From Table 1, the brightness | luminance and contrast of PDP50 using the fluorescent substance of Examples 1-4 in an embodiment can be made higher than PDP using the conventional fluorescent substance.

  As described above, according to the phosphor for PDP of the present invention, visible light extraction efficiency and color purity (contrast) can be greatly improved, and it is useful for an image display device using PDP.

DESCRIPTION OF SYMBOLS 10 Fluorescent substance 11 Core part 12 Wavelength selection layer 13 Light emitting layer 14,15 Light emission 16 External light reflected light 20,24,26,27,31,32 Supply pipe 21,28,33 Atomizer 22 Tank 23,29,34 Droplet 25, 30, 35 Firing furnace 36 Filter 50 PDP
51 Row electrode 52 Front substrate 53 Address electrode 54 Rear substrate 55 Base dielectric layer 56 Discharge space 57 Bulkhead 58 Phosphor layer

Claims (5)

A core part that reflects visible light, a wavelength selection layer that covers the core part and transmits a predetermined wavelength of the visible light, and a light emitting layer that covers the wavelength selection layer and emits visible light when excited by vacuum ultraviolet rays A phosphor for a plasma display panel. The phosphor for a plasma display panel according to claim 1, wherein the core part is made of oxide particles and has a reflectance higher than that of the light emitting layer. 2. The plasma display panel according to claim 1, wherein the wavelength selection layer is made of an inorganic material and allows visible light having a peak at 450 ± 5 nm to pass through the light emitting layer emitting blue light. Phosphor. 2. The plasma display panel according to claim 1, wherein the wavelength selection layer is made of an inorganic material, and allows visible light having a peak at 555 ± 5 nm to pass through the light emitting layer that emits green light. Phosphor. 2. The plasma display panel according to claim 1, wherein the wavelength selection layer is made of an inorganic material and allows visible light having a peak at 760 ± 5 nm to pass through the light emitting layer that emits red light. Phosphor.

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