JP3442973B2 - Plasma display panel - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma display panel (PDP) and a phosphor suitable for use in various displays such as PDP.

[0002]

2. Description of the Related Art Plasma display panel (PDP)
Since the screen can be made larger and thinner, it is attracting attention as a flat panel display that can replace a cathode ray tube (CRT).

The surface discharge type AC PDP has a back substrate having barrier ribs defining discharge cells, an address electrode and a phosphor layer, a transparent electrode extending in a direction orthogonal to the address electrode, a transparent dielectric layer and a protective layer. And a front substrate having. The phosphor layer has red (R), green (G), and
It is formed by applying a paste of phosphor powder that emits blue (B) light by screen printing and drying. The thickness of these phosphor layers is set to about 20 μm. A mixed gas of He-Xe, Ne-Xe, etc. is sealed in the discharge cell formed between the rear substrate and the front substrate. In this PDP, surface discharge is caused in the vicinity of the front substrate in the discharge cell, and the fluorescent substance is excited by the ultraviolet rays generated from the discharge gas to emit visible light.

Conventionally, the phosphor layer of the PDP is formed by using a phosphor manufactured by a firing method using a flux. The shape of the phosphor particles obtained by this method is a polyhedron. When a paste is prepared using such a phosphor, the dispersibility of the phosphor particles is poor and the phosphor particles tend to aggregate. Therefore, when the phosphor layer is formed by applying the paste, cavities are formed inside the phosphor layer and unevenness is generated on the surface of the phosphor layer. Therefore, the phosphor layer becomes thicker and the discharge space of the cell becomes narrower, so that the ultraviolet rays for exciting the phosphor are reduced and the brightness is lowered. Also,
Since the irregularities on the surface of the phosphor layer diffusely reflect the emitted light, the loss of light increases, the brightness decreases, and the brightness varies. Actually, the brightness of the current PDP is 0.8 [lm / W] in overall efficiency, which is darker than that of a CRT that shows a brightness of 1.7 [lm / W].

Up to now, in order to increase the brightness of the PDP,
(1) Forming a phosphor layer composed of phosphor particles having a particle diameter of 1.5 μm or less; (2) gradually increasing the thickness of the phosphor layer toward the front side; (3) forming the phosphor layer A white reflecting layer made of titanium oxide is provided below; and the like. However, these methods essentially solve the problem that the brightness decreases due to the narrowing of the discharge space due to the increase in the thickness of the phosphor layer and the irregular reflection of light emission due to the unevenness of the surface of the phosphor layer. is not. As mentioned above,
PDPs are required to have improved brightness.

Further, the PDP has a slow response speed, and there is a problem that an afterimage occurs when a moving image is displayed. In particular, Zn ₂ SiO ₄ : Mn, which is often used as a green phosphor, has a long light emission life and thus tends to cause a green afterimage. Therefore, it is required for the PDP to reduce the occurrence of an afterimage.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a plasma display panel which has high brightness and is less likely to cause an afterimage. Another object of the present invention is to provide a phosphor having high quantum efficiency and short emission life, which contributes to high performance of the display.

[0008]

A plasma display panel according to the present invention comprises a rear substrate having barrier ribs defining discharge cells, address electrodes and a phosphor layer, a transparent electrode extending in a direction orthogonal to the address electrodes and a transparent dielectric. A plasma display panel having a front substrate having a body layer and a protective layer, causing a discharge in a discharge cell formed between the rear substrate and the front substrate, and exciting a phosphor to emit light.
The phosphor particles forming the phosphor layer have an average particle size of 0.
1 to 5 μm, ratio of major axis to minor axis is 1.0 to 1.5, particles
Surface irregularities are 5% or less of the particle size, and adhere to the particle surface
Ultra fine particles of 0.01% by weight or less and micro resonance
It is characterized by showing a vessel effect .

Another plasma display panel of the present invention includes a back substrate having barrier ribs for defining discharge cells, address electrodes and a phosphor layer, a transparent electrode extending in a direction orthogonal to the address electrode, a transparent dielectric layer and protection. A plasma display panel having a front substrate having a layer and causing a discharge in a discharge cell formed between the rear substrate and the front substrate to excite the phosphor to emit light. The phosphor particles to be used have an average particle diameter of 0.1 to 5 μm,
The ratio of the maximum and the minimum curvature is 1.5 or less, the irregularity of the particle surface
Is 5% or less of the particle size, ultrafine particles that adhere to the particle surface
Is 0.01% by weight or less and exhibits a microresonator effect.
And wherein the nest.

[0010]

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the structure of a surface discharge type AC plasma display panel according to the present invention will be described with reference to FIG. As shown in FIG. 1, this PDP has a front substrate 1 and a rear substrate 2. On the back substrate 2, partition walls 3 are provided in parallel in stripes so as to define the discharge cells in stripes. Partition 3
A stripe-shaped address electrode 4 is formed in each discharge cell defined by. Further, a phosphor layer 5 is formed on the surface of the back substrate 2, the address electrodes 4 and the barrier ribs 3 of each discharge cell. Each of these phosphor layers 5 contains a red phosphor, a green phosphor or a blue phosphor. On the front substrate 1, stripe-shaped transparent electrodes 6 extending in a direction orthogonal to the address electrodes 4 and bus electrodes 7 overlapping the transparent electrodes 6 to reduce the electric resistance thereof are formed. The surface of the front substrate 1 is covered with a transparent dielectric layer 8 and a protective layer 9. The protective layer 9 is made of MgO, for example, and has a function of improving discharge characteristics. The front substrate 1 is placed on the rear substrate 2 and sealed. A mixed gas of He—Xe, Ne—Xe, etc. is sealed in the discharge cell formed between the rear substrate 2 and the front substrate 1.

The surface discharge type AC PDP operates as follows. When a surface discharge is generated near the front substrate in the discharge cell, the discharge gas mainly has wavelengths of 147 nm and 172 nm.
It emits vacuum ultraviolet rays (VUV). The phosphor in the phosphor layer is excited by vacuum ultraviolet rays and emits visible light when returning to the ground state.

In the present invention, examples of the phosphors used in the phosphor layer include, but are not limited to, the followings. As the red phosphor, Y ₂
O ₃ : Eu, (Y, Gd) ₂ O ₃ : Eu, Y ₂ SiO
_{5: Eu, YBO 3: Eu} , (Y, Gd) BO 3: E
u, GdBO ₃ : Eu, ScBO ₃ : Eu, or the like is used.

As the green phosphor, BaAl ₁₂ O ₁₉ : M
n, YBO ₃ : Tb, Zn ₂ SiO ₄ : Mn, etc. are used. As a blue phosphor, BaMgAl ₁₄ O ₂₃ : E
u ²⁺ , CaWO ₄ : Pb, Y ₂ SiO ₅ : Ce, etc. are used.

In the present invention, as the phosphor particles forming the phosphor layer, transparent spherical phosphor particles having substantially no or substantially a protrusion such as an edge on the surface and having a spherical shape or a shape close to that of a spherical shape are used. . Specifically, the phosphor particles have an average particle diameter of 0.1 to 5 μm, preferably 0.5 to 1
μm, and the ratio of major axis to minor axis is 1.0 to 1.5. The average particle size of the phosphor particles is 0.1 μm
If it is less than 5 μm, the brightness of the phosphor screen becomes small. The ratio of the major axis (maximum diameter) and the minor axis (minimum diameter) of each phosphor particle, that is, the aspect ratio, is in the range of 1.0 to 1.5, preferably 1.0 to 1.2, 1.0
The range of -1.1 is more preferable. When the aspect ratio of the phosphor particles exceeds 1.5, unevenness is likely to occur on the surface when the phosphor layer is formed by coating.

When a paste is prepared using the spherical phosphor as described above, the dispersibility of the phosphor particles is good, the particles do not agglomerate with each other, and the viscosity of the paste becomes low. When such a paste is applied to form the phosphor layer, there are few cavities inside the phosphor layer, and it is possible to form a uniformly smooth surface without unevenness. Therefore, the packing density is 50 to
It can be as high as 65%. As a result, it is possible to prevent diffuse reflection of light emitted from the phosphor, prevent light loss, and improve the brightness of the PDP. Further, if the surface of the phosphor layer becomes smooth, the discharge space becomes wider, which is also advantageous in improving the brightness.

The spherical phosphor as described above can be produced, for example, by melting raw material phosphor particles in thermal plasma and quenching them. A method for producing a spherical phosphor by thermal plasma is disclosed in, for example, Japanese Patent Application Laid-Open No. 8-109375. Alternatively, a spherical phosphor can be produced by plasma spraying.

For a PDP which is required to have particularly high luminous efficiency and luminous color accuracy, the chromaticity coordinates (x, y), which is an index of whiteness, is 0.31≤x≤0.33 0.31 It is preferable to use a spherical phosphor with ≦ y ≦ 0.33. Since the phosphor having chromaticity coordinates in the above range has a small body color, it is possible to avoid a decrease in luminous efficiency and an influence on color development. Further, the light reflectance of the spherical phosphor is preferably 95% or more.

In order to form a phosphor layer using the spherical phosphor as described above, phosphor powder of each color is mixed with a binder solution composed of, for example, polyvinyl alcohol, n-butyl alcohol, ethylene glycol and water. Using the prepared paste, it is applied by a method such as screen printing.

The phosphor layer preferably has a variation of 25% or less, more preferably 20% or less, between the film thickness at the position 20 μm from the upper end of the partition wall and the film thickness at the center position of the address electrode. This means that the thickness of the phosphor layer is almost uniform. This is for uniformly irradiating the phosphor layer with ultraviolet rays. When the variation in the thickness of the phosphor layer is large, some phosphor particles are behind the other phosphor particles and are not irradiated with ultraviolet rays. The use of the spherical phosphor is also advantageous for making the film thickness of the phosphor layer uniform.

In order to efficiently radiate the light emitted from the phosphor to the outside, it is effective to provide a visible light reflecting layer between the phosphor layer and the rear substrate and the partition. In order to increase the reflection of the emitted light, it is preferable to form a visible light reflection layer on substantially the entire surface between the phosphor layer and the back substrate, address electrodes and partition walls. Examples of the substance that reflects visible light include MgO, α-Al ₂ O ₃ , MgAl ₂ O ₄ , and 3A.
l ₂ O ₃ · 5SiO ₂ or 2MgO · 2Al ₂ O ₃ ·
5SiO ₂ particles may be mentioned, with MgO being particularly preferred.
The average particle size of such a substance is preferably 10 to 200 nm. The particles in the above particle size range can efficiently scatter visible light. Further, these substances have better electron emission characteristics than TiO ₂ used for the known white reflective layer, and contribute not only to the visible light reflective layer but also to facilitating discharge. The thickness of the visible light reflection layer is preferably 0.1 to 5 μm, and more preferably 0.1 to 5 μm.
˜1 μm is more preferred. If the film thickness is less than 0.1 μm, the effect of reflecting visible light cannot be obtained, and if it exceeds 5 μm, the discharge space becomes narrow and the brightness decreases.

FIG. 2 shows a cross-sectional view of a PDP in which a visible light reflection layer 11 is formed on the back substrate 2, the address electrodes 4 and the partition walls 3 and a phosphor layer 5 is formed thereon. In the present invention, if the phosphor layer is formed by using the spherical phosphor exhibiting the microresonator effect, the quantum efficiency of the phosphor, which is usually said to be 30 to 80%, can be improved, and the brightness of the PDP is improved. can do. The microresonator effect is Garrett
Is the first phenomenon observed with CaF ₂ : Sm crystal spheres of about 100 μm. When light is incident on this crystal sphere, they repeatedly undergo total internal reflection inside the crystal sphere and are confined.
As a result, we observed that it causes laser oscillation (C.
G. Garrett et al., Phys. Rev. 124, 1807 (1961)). The microresonator effect is based on other material systems, such as Nile red doped polystyrene transparent microspheres of about 40 μm,
It has also been observed in Nd ³⁺ doped fluoride glass spheres of about 100 μm. Further, it has been observed that the Eu chelate compound shortens the emission lifetime of Eu due to an increase in transition probability due to the microresonator effect. However, there has been no case where the micro-cavity effect has been observed in general crystalline rare earth phosphors.

Microresonator effect
Phenomenon exhibiting spering Gallery Mode) is the following phenomenon. FIG. 4A shows the frequency dependence of the density of states of the light spontaneously emitted from the phosphor. Figure 4
(B) shows the frequency dependence of the state density of the light emitted when the light is three-dimensionally confined inside the phosphor microspheres. In FIG. 4B, it can be seen that light of a certain wavelength is enhanced. As shown in FIG. 4 (c), when light is confined in a sphere, light interference / resonance occurs, and the resonance wavelength matches the emission wavelength of the phosphor, compared to spontaneous emission light. It shows that light with extremely high intensity and short emission life is emitted.

In order to confine light in the microsphere phosphor, the spherical phosphor preferably has a particle size of 0.1 to 20 μm. The microresonator effect is unlikely to occur with a spherical phosphor having a particle size smaller than 0.1 μm. Further, when applied to PDP, the spherical phosphor preferably has a particle size of 0.1 to 5 μm. When the particle size exceeds 5 μm, unevenness is likely to occur on the surface when the phosphor layer is formed by coating.

The performance as a microresonator can be evaluated by the Q value which is a factor representing loss. The higher the Q value, the smaller the loss, and the lower the Q value, the larger the loss. For example, in the case of a Fabry-Perot resonator consisting of two flat plate mirrors, the Q value is about 5000. In the case of an optical resonator formed by fine processing of semiconductors, the Q value is 100 to
It is about 5,000. In this case, the Q value depends on the processing accuracy. In a resonator composed of microspheres, the accuracy of the sphere corresponds to the processing accuracy, and the Q value increases as it approaches the true sphere. That is, the smaller the surface of the spherical phosphor is, such as unevenness or foreign matter, which obstructs the path of light, the higher the resonator effect.

Specifically, the ratio of the maximum and the minimum curvature of the phosphor particles is 1.5 or less, and the closer to 1, the more preferable. When the ratio of the maximum curvature to the minimum curvature exceeds 1.5, the microcavity effect cannot be obtained because of the presence of edges and bumps on the surface of the particles. Moreover, it is preferable that the surface irregularities of the phosphor particles are within 5% of the particle diameter of each particle. A method of calculating the unevenness on the surface of the phosphor particles will be described with reference to FIG. That is, when the radius of the sphere covering the largest area of the surface of the phosphor particles is R and the radius of the sphere passing through the apex of the largest unevenness is R ′, the unevenness ratio is (R ′ / R−1) × Given at 100. Furthermore, it is preferable that the amount of ultrafine particles attached to the surface of the phosphor particles is 0.01% by weight or less. The microresonator satisfying such conditions exhibits a Q value of 1000 to 10 ⁵ .

When the phosphor powder is viewed as an aggregate of microspheres, it is preferable that the phosphor powder has a sharp particle size distribution. Specifically, in the particle size distribution, the fluctuation between the 80% D value and the 50% D value and the fluctuation between the 50% D value and the 20% D value are both 2.
It is preferably 0% or less. The particle size distribution is measured with a particle size distribution measuring instrument such as Microtrac after the phosphor is dispersed in water and stirred for 5 minutes or more. In this case, the particle size is measured on a number basis. For example, 50% D indicates the particle size when the integrated value from the smaller particle size is 50%.

With the phosphor powder having a sharp particle size distribution as described above, it is possible to obtain uniform and high-luminance light emission as a whole. On the other hand, the phosphor powder having a wide particle size distribution weakens the effect of enhancing the brightness.

The true spherical fluorescent substance exhibiting the above-mentioned micro-resonator effect is obtained by melting the raw fluorescent substance particles in the thermal plasma and rapidly cooling them to make them spherical, and then making the obtained spherical fluorescent substance water or ethanol. It can be prepared by dispersing the above in an ultrasonic wave, applying ultrasonic waves, and further heat treating at an appropriate temperature.

Since the spherical fluorescent substance exhibiting the microresonator effect has high quantum efficiency, the thickness of the fluorescent substance layer formed by using it can be reduced. The average thickness of the phosphor layer is preferably 3 times or less the average particle size of the phosphor particles.
FIG. 6 shows the phosphor layer 5 having a thickness that is about twice the average particle diameter of the phosphor particles 10. By reducing the thickness of the phosphor layer, the discharge space can be widened and the intensity of vacuum ultraviolet rays emitted from the discharge gas can be increased.

An ultraviolet reflecting layer made of a substance that reflects vacuum ultraviolet rays may be provided between the phosphor layer and the rear substrate and the partition. When the ultraviolet reflection layer is provided, the fluorescent substance can be excited from the back and side faces to efficiently emit light. Therefore, it contributes to the improvement of the excitation light density required for expressing the microresonator effect. Materials that reflect vacuum ultraviolet rays include MgF ₂ , LiF, and CaF.
₂ , fluorides such as YF ₃ may be mentioned. The average particle size of the fluoride particles is preferably about 0.5 to 1 μm. Such fluoride particles have high secondary electron emission ability,
It also shows the effect of lowering the discharge voltage. Further, a metal thin film having a high reflectance in the VUV range such as Ir may be used as the ultraviolet ray reflecting layer.

FIG. 3 shows a cross-sectional view of a PDP in which an ultraviolet reflection layer 12 is formed on the back substrate 2, the address electrodes 4 and the partition walls 3 and a phosphor layer 5 is formed thereon. The above-described microresonator effect can be obtained even with a phosphor other than the phosphors already exemplified, and can be applied to a display other than the PDP. Suitable phosphors for producing the microresonator effect include Al ₂ O ₃ : Cr, BeAl ₂ O ₄ : Cr, InB.
O ₃ : Eu, Tb, (Y, Gd) BO ₃ : Eu, YA
_{G: Nd, YF 3: Pr} , YGdF 4: Pr, Y 2 O
A crystal doped with a rare earth element or a transition metal element such as ₃ : Eu, Y ₂ O ₃ : Pr, Y ₂ O ₂ S: Eu is suitable. A phosphor doped with a rare earth element is suitable for use in a display.

These phosphors also have an average particle size of 0.1 to 2
0 μm, the unevenness of the particle surface is 5% or less with respect to the particle diameter, and the ultrafine particles adhering to the particle surface are 0.01% by weight or less,
Regarding the particle size distribution, it is preferable that the variation between the 80% D value and the 50% D value and the variation between the 50% D value and the 20% D value are both 20% or less.

[0034]

EXAMPLES Examples of the present invention will be described below. Comparative Example 1, Example 1a and Example 1b The AC type PDP shown in FIG. 1 was manufactured as follows.

A front substrate on which transparent electrodes, bus electrodes, a transparent dielectric layer and a protective layer were formed, and a back substrate on which address electrodes and partition walls were formed were prepared. The phosphor layer was formed as follows. Each phosphor powder was mixed with a binder solution prepared by adding n-butyl alcohol and ethylene glycol to a 10% aqueous solution of polyvinyl alcohol having a saponification degree of 88% to prepare a phosphor paste. Then, the phosphor paste was applied to predetermined cells on the back substrate by screen printing and dried to form phosphor layers of each color.

Further, the front substrate was placed on the rear substrate on which the phosphor layer was formed and sealed, and a mixed gas of xenon, helium and neon was sealed in the discharge cell so as to have a pressure of 500 Torr to manufacture a PDP. .

Comparative Example 1 All of the red phosphor Y ₂ O ₃ : Eu and the green phosphor BaAl ₁₂ O ₁₉ : Mn obtained by the flux firing method were used.
A blue phosphor BaMgAl ₁₄ O ₂₃ : Eu ²⁺ was used. The average particle size of each of these phosphors was 3 μm.

Example 1a The three phosphor powders of Comparative Example 1 were each subjected to thermal plasma treatment. As a result, the obtained red phosphor Y ₂ O ₃ : Eu had an average particle size of 0.9 μm, a ratio of major axis to minor axis of 1.05,
The green phosphor BaAl ₁₂ O ₁₉ : Mn has an average particle size of 1.2 μm.
m, ratio of major axis to minor axis is 1.10, blue phosphor BaMg
Al ₁₄ O ₂₃ : Eu ²⁺ had an average particle diameter of 1.0 μm and a ratio of major axis to minor axis of 1.10. A phosphor layer was formed using these three kinds of phosphors. The thickness of the phosphor layer was 20 μm at a position 20 μm from the upper end of the partition wall and 24 μm at the center position of the address electrode.

Example 1b Prior to forming the phosphor layer, a visible light reflecting layer was formed as follows. MgO having an average particle size of 10 nm was mixed with the above binder solution to prepare a paste. This paste was applied to the surface of each cell of the back substrate by screen printing and dried to form a visible light reflection layer having a film thickness of 1 μm. Then, in the same manner as in Example 1a, each of the three types of phosphor paste was applied to a predetermined cell on the back substrate,
It dried and formed the fluorescent substance layer of each color.

Table 1 shows the results of measuring the brightness of each color of the PDPs manufactured in Comparative Example 1, Example 1a and Example 1b. This table shows the luminance obtained in Comparative Example 1 as 10
It represents a relative luminance of 0.

Since spherical phosphors are used in Examples 1a and 1b, the brightness is improved as compared with Comparative Example 1. In Example 1b, since the visible light reflection layer made of MgO particles was formed, the brightness was improved as compared with Example 1a.

[0042]

[Table 1]

Comparative Example 2, Example 2a and Example 2b PDPs were manufactured in the same manner as above. Comparative Example 2 Red phosphor (Y, Gd) ₂ O ₃ : Eu, green phosphor Zn ₂ SiO ₅ obtained by the flux firing method.
: Mn and a blue phosphor BaMgAl ₁₄ O ₂₃ : Eu ²⁺ were used. The average particle size of each of these phosphors was 2 μm. A phosphor layer was formed using these three kinds of phosphors. The thickness of the phosphor layer is 20 μm at the position 20 μm from the upper end of the partition wall, and 30 at the center position of the address electrode.
μm, which was non-uniform.

Example 2a Each of the three types of phosphor powders of Comparative Example 2 was subjected to thermal plasma treatment to be spherical. After that, the obtained phosphor powder is dispersed in water, ultrasonically cleaned for 15 minutes, and then dried.
It heat-processed at 000 degreeC for 1 hour.

FIG. 7 shows an SEM photograph of (Y, Gd) ₂ O ₃ : Eu phosphor particles. There is no unevenness on the surface of the particles,
No adhesion of ultrafine particles was observed. The phosphor particles had an average particle diameter of 2 μm. The other phosphor particles also had similar shapes.

A phosphor layer was formed using these three kinds of phosphors. The thickness of the phosphor layer was 20 μm at a position 20 μm from the upper end of the partition wall and 22 μm at the center position of the address electrode.

Example 2b Before forming the phosphor layer, an ultraviolet reflecting layer was formed as follows. MgF ₂ particles having an average particle size of 1 μm were mixed with a binder solution to prepare a paste. This paste was applied to the surface of each cell of the back substrate by screen printing and dried to form an ultraviolet reflective layer having a film thickness of 3 μm. Then, in the same manner as in Example 2a, three types of phosphor pastes were applied to predetermined cells of the back substrate and dried to form phosphor layers of each color. At this time, the average thickness of the phosphor layer was set to 6 μm.

Table 2 shows the results of measuring the white luminance of the PDPs produced in Comparative Example 2, Example 2a and Example 2b. This table shows the white luminance obtained in Comparative Example 2 as 1.
The relative luminance is set to 00.

In Examples 2a and 2b, the brightness was improved as compared with Comparative Example 1. In particular, in Example 2b, since the phosphor layer is thin and has a wide discharge space, the brightness is further improved. Further, a green afterimage was observed in Comparative Example 2 and Example 2a, but no green afterimage was observed in Example 2b.

[0050]

[Table 2]

Comparative Example 3, Example 3a and Example 3b The brightness and fluorescence lifetime of the microsphere phosphor were evaluated as follows. The measuring method will be described with reference to FIG.

The phosphor particles 10 are dispersed on the glass plate 21. The photomultiplier 22 is installed at a position 10 cm above the phosphor particles 10. A filter 23 is installed on the front surface of the photomultiplier 22. On the other hand, an optical fiber 25 connected to a flash lamp 24 is arranged below the glass plate 21 to irradiate the phosphor particles 10 with light. Then, the light emitted from the phosphor particles 10 is detected by the photomultiplier 22, the signal is converted into a voltage, and the voltage is output to the oscilloscope 26.

The brightness and fluorescence lifetime of the microsphere phosphor were evaluated as follows. Photomultiplier 22
The peak value of the signal was used as the brightness. Further, afterglow generated after stopping the irradiation of light was measured, and the time when the brightness reached a signal value of 10% of the peak value was defined as the fluorescence lifetime.
The measurement is performed on, for example, 50 phosphor particles,
Calculate the average value.

Comparative Example 3 Commercially available Al ₂ O ₃ and Cr ₂ O ₃ were weighed in a molar ratio of 1: 0.1 and mixed in a ball mill for 1 hour. This mixture was put into a crucible and baked in an electric furnace at 1300 ° C. for 1 hour to prepare an Al ₂ O ₃ : Cr phosphor.

The phosphor particles thus obtained had a polyhedral shape. The particle size distribution of the phosphor powder has a 50% D value of 4
μm, 20% D value was 2 μm, and 80% D value was 7 μm. Example 3a The Al ₂ O ₃ : Cr phosphor obtained in Comparative Example 3 was subjected to thermal plasma treatment in an Ar atmosphere at a frequency of 14 MHz and a plate power of 5 kW. After the thermal plasma treatment, the powder taken out is dispersed in ethanol and placed in an ultrasonic cleaner,
Ultrasonic cleaning was performed for 30 minutes. Then, the powder was taken out, dried, and heat-treated at 1000 ° C. for 1 hour.

No unevenness or foreign matter was found on the surface of the obtained particles. The diameter of the phosphor particles was uniform everywhere in one particle, and averaged 5 μm. The amount of ultrafine particles adhering to the surface was 0.001% by weight.

Example 3b The Al ₂ O ₃ : Cr phosphor obtained in Example 3a was classified as follows. Water was placed in a 500 mL beaker, and 10 g of phosphor powder was added. While stirring with a stirrer, ultrasonic waves were applied for 30 minutes to disperse. The phosphor dispersion liquid was gently poured into a 10 L graduated cylinder containing water. After leaving still for 30 minutes, the liquid in the range of 3 L to 6 L was sucked up by a graduated cylinder and taken out by a rubber tube. This liquid was dried to obtain a phosphor powder.

The particle size distribution of the phosphor powder thus obtained has a 50% D value of 5 μm and a 20% D value of 4.1 μm.
The 0% D value was 5.9 μm. Comparative Example 3, Example 3a
Table 3 shows the results of measuring the brightness and the fluorescence lifetime of the phosphor of Example 3b by the method described above. In these measurements, a filter that transmits light having a wavelength of 650 nm or more was used. The brightness is shown as a relative value with the brightness of Comparative Example 3 as 100. The phosphors of Example 3a and Example 3b are brighter and have shorter fluorescence lifetime than the phosphor of Comparative Example 3.

[0059]

[Table 3]

Comparative Example 4 and Example 4 The brightness and fluorescence lifetime of the Y ₂ O ₃ : Eu phosphor were evaluated in the same manner as in the above example.

Comparative Example 4 A commercially available Y ₂ O ₃ : Eu phosphor was used. Example 4 A commercially available Y ₂ O ₃ : Eu phosphor was subjected to thermal plasma treatment under a condition of a frequency of 5 MHz and a plate power of 20 kW in an Ar atmosphere. After the thermal plasma treatment, the powder taken out was dispersed in ethanol, placed in an ultrasonic cleaner and ultrasonically cleaned for 30 minutes. The powder was taken out, dried, and heat-treated at 1000 ° C. for 1 hour.

No unevenness or foreign matter was observed on the surface of the obtained particles. The diameter of the phosphor particles was uniform everywhere in one particle, and averaged 4 μm. The amount of fine particles adhering to the surface was 0.001% by weight.

Table 3 shows the results of measuring the brightness and the fluorescence lifetime of the phosphors of Comparative Example 4 and Example 3b by the methods described above. In these measurements, wavelength 590
A filter that transmits light having a wavelength of nm or more was used. The brightness is shown as a relative value with the brightness of Comparative Example 4 as 100. The phosphor of Example 4 is brighter and has a shorter fluorescence lifetime than the phosphor of Comparative Example 4.

[0064]

[Table 4]

[0065]

As described above in detail, according to the present invention, it is possible to provide a plasma display panel which has high luminance and is less likely to cause an afterimage. Further, it is possible to provide a phosphor that has a high quantum efficiency and a short emission life and contributes to high performance of the display.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing the structure of a surface discharge type AC plasma display panel according to the present invention.

FIG. 2 is a sectional view of a PDP provided with a visible light reflection layer.

FIG. 3 is a cross-sectional view of a PDP provided with an ultraviolet reflective layer.

FIG. 4 is a diagram showing frequency dependence of density of states when spontaneous emission or a microresonator effect occurs.

FIG. 5 is a diagram showing a method for calculating irregularities on the surface of phosphor particles.

FIG. 6 is a diagram showing a phosphor layer having a thickness twice the average particle diameter of phosphor particles.

FIG. 7 is an SEM photograph of the phosphor particles obtained in Example 2a.

FIG. 8 is a diagram showing a configuration of an apparatus for measuring the brightness and the lifetime of fluorescence of phosphor particles.

[Explanation of symbols]

1 ... Front substrate 2 ... Rear substrate 3 ... Partition 4 ... Address electrode 5 ... Phosphor layer 6 ... Transparent electrode 7 ... Bus electrode 8 ... Transparent dielectric layer 9 ... Protective layer 10 ... Phosphor particles 11 ... Visible light reflective layer 12 ... Ultraviolet reflective layer 21 ... Glass plate 22 ... Photomultiplier 23 ... Filter 24 ... Flash lamp 25 ... Optical fiber 26 ... Oscilloscope

Continuation of the front page (72) Inventor Albesar / Keiko 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Toshiba Research & Development Center Co., Ltd. (56) Reference JP-A-8-134443 (JP, A) JP-A 8-109375 (JP, A) JP-A-8-92554 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 11/02 C09K 11/08 H01J 17/02

Claims (7)

(57) [Claims] 1. A back substrate having barrier ribs defining discharge cells, an address electrode and a phosphor layer, and a front substrate having a transparent electrode extending in a direction orthogonal to the address electrode, a transparent dielectric layer and a protective layer. In the plasma display panel, which has a discharge in a discharge cell formed between the rear substrate and the front substrate and excites the phosphor to emit light, the phosphor particles forming the phosphor layer are average particles. Diameter is 0.1
˜5 μm, ratio of major axis to minor axis is 1.0 to 1.5, particle table
5% or less of surface irregularities adhere to the particle surface
Ultra fine particles of 0.01% by weight or less and a microresonator
A plasma display panel characterized by showing effects . 2. The plasma display panel according to claim 1, wherein the variation between the thickness of the phosphor layer at a position 20 μm away from the upper end of the partition wall and the thickness of the phosphor layer at the center position of the address electrode is 25% or less. . 3. A back substrate having barrier ribs defining discharge cells, address electrodes and a phosphor layer, and a front substrate having transparent electrodes extending in a direction orthogonal to the address electrodes, a transparent dielectric layer and a protective layer. In the plasma display panel, which has a discharge in a discharge cell formed between the rear substrate and the front substrate and excites the phosphor to emit light, the phosphor particles forming the phosphor layer are average particles. Diameter 0.1
~ 5 μm, ratio of maximum and minimum curvature is 1.5 or less, particles
Surface irregularities are 5% or less of the particle size, and adhere to the particle surface
Ultra fine particles of 0.01% by weight or less and micro resonance
Plasma display panel characterized by exhibiting a container effect . 4. The plasma display panel according to claim 3, wherein the average thickness of the phosphor layer is 3 times or less the average particle size of the phosphor particles. 5. The plasma display panel according to claim 3, further comprising a reflective layer between the phosphor layer, the back substrate and the partition. 6. The reflective layer comprises MgO, α-Al ₂ O ₃ , Mg
Al ₂ O ₄ , 3Al ₂ O ₃ .5SiO ₂ or 2MgO.2
Al ₂ O ₃ .5SiO ₂ , MgF ₂ , LiF, CaF ₂ , Y
The plasma display panel according to claim 5, comprising a substance that reflects visible light or ultraviolet light selected from the group consisting of F ₃ and Ir. 7. The particle size distribution of the phosphor particles is
Variation between 80% D value and 50% D value and 50% D value and 2
The variation with 0% D value is 20% or less in all cases.
Or the plasma display panel described in 3.