JPH08293262A - Plasma display panel - Google Patents

Abstract

PURPOSE: To enhance brightness by making a lower layer part on the back of a discharge space more solid than an upper layer part on the front side, in phosphor layers which are provided on the back of the discharge space sandwiched between a pair of substrates and which are made to emit light by a discharge. CONSTITUTION: Display electrodes X, Y, a dielectric layer 17, a protective film 18, a discharge space 30, a phosphor layer 28, and an address electrode A are sequentially arranged between glass substrates 11, 21. Stripes of partitions 29 are provided between the electrodes A to divide the discharge space 30 into unit emission areas. In the case of full-color display, three color phosphor layers 28 for red, green, and blue cover the upper surfaces of the electrodes A and the side faces of the partitions 29, and the light emitted from the layers and transmitted through the substrate 11 serves for displaying. A lower layer 281 on the back of the layers 28 uses phosphor particles with smaller diameters than those used in an upper layer 282 on the front side, so that the lower layer 281 is more solid than the upper layer 282. Therefore, a part of ultraviolet radiation passing through the upper layer 282 is reflected by the lower layer 281 and thereby the upper layer 282 is excited, so the efficiency for utilizing exciting energy for displaying is increased, resulting in enhanced brightness.

Description

Detailed Description of the Invention

The present invention relates to a plasma display panel (PDP) having a phosphor layer inside. PDP is
It is a self-luminous display device capable of high-speed display, and is attracting attention as a large-screen display means for high-definition video. Under such circumstances, a PDP with higher brightness is desired.

[0002]

2. Description of the Related Art A PDP is a display panel having a structure in which a pair of substrates (usually glass substrates) facing each other across a discharge space are used as a base. In the PDP, by providing the phosphor layer of the ultraviolet excitation type inside, it is possible to display a color different from the emission color of the discharge gas. For full color display,
Phosphor layers of three colors of R (red), G (green) and B (blue) are provided.

Generally, the phosphor layer is formed on the back side of the discharge space,
That is, it is arranged on the inner surface of the substrate on the back side. As a result, the surface layer portion of the phosphor layer having high excitation efficiency faces the front substrate, and the light emission of the surface layer portion is efficiently used for display.

In order to form such a phosphor layer, there is a method in which a phosphor paste containing phosphor particles of a predetermined emission color as a main component is sequentially applied for each color by a screen printing method and dried and then collectively baked. Widely used.

Conventionally, phosphor particles having a substantially constant size have been used as a material for the phosphor layer, and a phosphor layer having a uniform layer structure has been formed.

[0006]

The light emitted in the deep layer portion (the portion far from the discharge space) in the phosphor layer is less likely to be emitted to the front side than the light emitted in the surface layer portion. Therefore, in the conventional homogeneous phosphor layer, the phosphor particles in the deep layer are not effectively used for display, which is disadvantageous in terms of brightness.

When the phosphor layer is also used for accumulating wall charges, it is desirable that the phosphor layer be dense. However, if phosphor particles with a small particle size are used to obtain a dense layer,
There is also a problem that the brightness is lowered and the life is shortened as compared with the case of using phosphor particles having a large particle size.
This is because phosphor particles having a small particle size have a large proportion of the outer skin portion that does not contribute to light emission per unit volume, and moreover, deterioration due to ion bombardment is likely to proceed.

The present invention has been made in view of the above problems, and an object thereof is to improve luminance.

[0009]

A PDP according to the invention of claim 1
Is a PDP having a phosphor layer on the back side of the discharge space sandwiched between a pair of substrates, the phosphor layer emitting light by a discharge generated in the discharge space, and a lower layer portion of the phosphor layer on the back side of the discharge space. However, compared with the upper layer portion on the front side, it is more densely configured.

In the PDP of the second aspect of the present invention, the phosphor layer is composed of a lower layer on the back side with respect to the discharge space and an upper layer on the front side, the lower layer being the first phosphor particles and the upper layer being the above-mentioned. The second phosphor particles are larger than the phosphor particles.

In the PDP of the third aspect of the present invention, the phosphor layer is composed of a large number of phosphor particles stacked on the substrate on the back side, and the particle diameter of the phosphor particles is farther from the discharge space. It has a small grain size distribution in the thickness direction.

A PDP according to a fourth aspect of the present invention has an electrode that covers the discharge space with the phosphor layer.

[0013]

The excitation energy incident from the discharge space excites the upper layer of the phosphor layer to emit light. Of the light emitted in the upper layer portion, the light traveling toward the front side becomes display light. Part of the excitation energy that has entered the discharge space and passed through the upper layer portion is reflected by the dense lower layer portion to excite the upper layer portion. Light emitted from the upper layer portion is more likely to be emitted to the front surface side than in the lower layer portion, so that the utilization efficiency of excitation energy for display is increased.

[0014]

1 is an exploded perspective view showing the basic structure of a PDP 1 according to a first embodiment. The PDP 1 is a surface discharge type PDP having a three-electrode structure in which a pair of display electrodes X and Y and an address electrode A correspond to a unit light emitting area EU of matrix display, and is classified as a reflection type according to the arrangement form of phosphors. It is called.

The display electrodes X and Y for surface discharge are provided on the inner surface of the glass substrate 11 on the front side, and are covered in the discharge space 30 by a dielectric layer 17 made of low melting point glass. On the surface of the dielectric layer 17, a protective film 18 made of MgO having a large secondary electron emission coefficient and having a thickness of about several thousand Å is formed.
Is provided. Since the display electrodes X and Y are arranged on the front side of the discharge space 30, a wide transparent conductive film made of a nesa film or the like is used in order to widen the surface discharge and minimize the shielding of the display light. 41 and a narrow metal film (bus electrode) 42 that complements its conductivity.

On the other hand, the address electrode A has a unit light emitting region E.
The electrodes for selectively emitting U are arranged on the rear glass substrate 21 at a constant pitch (for example, 220 μm) so as to be orthogonal to the display electrodes X and Y.

Stripe-shaped partition walls 29 having a height of about 140 μm are provided between the address electrodes A.
As a result, the discharge space 30 moves in the line direction (display electrodes X,
The unit light emitting area EU is partitioned in the Y extension direction), and the gap size of the discharge space 30 is defined.

The upper surface of the address electrode A and the partition wall 2
A phosphor layer 28 of three primary colors of R, G, B having a layer structure described later so as to cover the inner wall surface on the back side including the side surface of 9
Is provided. The phosphor layer 28 of each color emits light when excited by the ultraviolet rays emitted by the discharge gas in the discharge space 30 during surface discharge. Of the light emitted from the phosphor layer 28, the light that passes through the glass substrate 11 on the front side and is emitted to the outside becomes display light. One pixel in PDP1
EG is composed of three unit light emitting regions (sub-pixels) EU of R, G and B, and full color display is possible by combining R, G and B.

FIG. 2 is a partial sectional view of the PDP 1 of FIG. 1, FIG.
FIG. 3 is a schematic diagram of a layer structure of the phosphor layer 28. The phosphor layer 28 of the PDP 1 has a two-layer structure including a lower layer 281 and an upper layer 282. The lower layer 281 on the back side with respect to the discharge space 30 is a layer having a thickness of about 15 μm in which a large number of phosphor particles p1 having a particle size of about 2 μm are stacked as shown in FIG. 3, and is different from the upper layer 282 on the front side with respect to the discharge space 30. It is precise. The upper layer 282 has a large number of phosphor particles p2 having a particle size of, for example, about 5 μm, which are larger than the phosphor particles p1.
Is a layer having a thickness of about 15 μm.

The phosphor layer 28 having such a layer structure can be formed by a thick film method. That is, the phosphor paste containing the phosphor particles p1 as a main component is applied to a predetermined position of the glass substrate 21 after the address electrodes A and the partition walls 29 are provided using a screen mask. Subsequently, a phosphor paste containing phosphor particles p2 as a main component is applied in an overlapping manner. Then, after being left to stand at room temperature (10 minutes) and heat-treated at about 100 ° C. (30 minutes) to be dried, each phosphor paste layer is collectively baked at a temperature of about 450 ° C.

In the PDP 1, since the lower layer 281 of the phosphor layer 28 is dense, ultraviolet rays (excitation energy) attempting to pass through the phosphor layer 28 are reflected by the lower layer 281 and the phosphor particles p2 of the upper layer 282 are absorbed. To excite. That is, a large amount of ultraviolet rays enter the phosphor particles p2 not only from the front side but also from the back side. Light emitted from the upper layer 282 by a distance closer to the discharge space 30 is more likely to be emitted to the front side than the lower layer 281, so that the excitation of the upper layer 282 is more effective than the excitation of the lower layer 281 in the amount of light emission contributing to display. The utilization efficiency of ultraviolet rays is high. Further, the lower layer 281 also reflects visible light traveling from the upper layer 282 to the back side. From these, the brightness is higher than when the phosphor layer 28 is uniform in the thickness direction, that is, when the phosphor particles p1 and p2 have the same particle diameter.

FIG. 4 is a partial sectional view of the PDP 2 of the second embodiment, and FIG. 5 is a schematic view of the layer structure of the phosphor layer 28b of FIG. The PDP 2 is a surface discharge PDP having the same structure as the above-mentioned PDP 1 except for the layer structure of the phosphor layer 28b.

The phosphor layer 28b of the PDP 2 is also the lower layer 281.
It is a layer having a two-layer structure composed of b and an upper layer 282b. The total thickness of the phosphor layer 28b is about 30 μm. As shown in FIG. 5, the lower layer 281b is mainly composed of small-sized (particle size is, for example, about 2 μm) phosphor particles p1. On the other hand, the upper layer 282b is mainly composed of large-sized (particle diameter is, for example, about 5 μm) phosphor particles p2. Lower layer 281
The boundary between b and the upper layer 282b is not clear, and large-sized phosphor particles p2 may be mixed in the lower layer 281b and small-sized phosphor particles p1 may be mixed in the upper layer 282b.

The phosphor layer 28b having such a layer structure can be formed by the following procedure. First, the phosphor particles p1
And phosphor particles p2 are added to the binder at an appropriate ratio (for example, the same weight ratio) to prepare a phosphor paste.
The phosphor paste is screen-printed to form barrier ribs 2.
The coating is carried out between 9 and the glass substrate 21 is fixedly arranged immediately with the coating surface facing downward. At this time, the phosphor paste is diluted with a solvent in advance, and the viscosity of the phosphor paste is adjusted so that the phosphor paste has a fluidity that does not cause dripping and barely maintains the coating state due to surface tension.

The phosphor paste is slowly dried with the coated surface facing downward. Inside the phosphor paste during drying, the large-sized phosphor particles p2 are replaced by the small-sized phosphor particles p.
1. The particles settle faster than 1, and the phosphor particles p1 and the phosphor particles p2
And are roughly separated and deposited. After that, the dried phosphor paste is fired to obtain the phosphor layer 28b.

In the PDP 2, as in the PDP 1 described above, the upper layer 28 is formed by the reflection of the ultraviolet rays on the lower layer 281b.
Since 2b is efficiently excited, it is possible to increase the brightness of the display.

FIG. 6 is a partial sectional view of the PDP 3 of the third embodiment, and FIG. 7 is a schematic view of the layer structure of the phosphor layer 28c of FIG. The PDP 3 is also a three-sided discharge PDP similar to the PDPs 1 and 2 described above.

The phosphor layer 28c of the PDP 3 is a layer having a single layer structure of phosphor particles p of various sizes and having a thickness of about 30 μm. However, the particle size distribution of the phosphor particles p is not irregular, and the phosphor layer 28c schematically shows the discharge space 3
The particle size distribution in the thickness direction is such that the particle size becomes smaller as it goes away from 0. That is, the lower layer portion 281c and the upper layer portion 282 are bordered by an arbitrary position (for example, the center) in the thickness direction.
When divided into c and c, the arithmetic mean value of the particle diameters of the phosphor particles p constituting the lower layer portion 281c on the back side with respect to the discharge space 30 is the arithmetic mean value of the particle diameters of the phosphor particles p constituting the upper layer portion 282c. Smaller than.

The phosphor layer 28c having such a layered structure is mainly composed of a phosphor particle group having a substantially wide particle size range, for example, a phosphor powder having an average particle size of 5 μm and a standard deviation of 1.8. It can be formed by using a phosphor paste and utilizing the difference in the sedimentation speed depending on the particle size, as in the case of the PDP 2 described above.

Also in the PDP 3, since the lower layer portion 281c is denser than the upper layer portion 282c, the PDP described above is used.
Similar to 1 and 2, the phosphor layer 28c is efficiently excited by the reflection of the ultraviolet rays on the lower layer portion 281c. Therefore, high-luminance display can be realized.

In order to confirm the effect of the above embodiment, PD
Prototypes P1, 2, 3 were made. Further, as a comparative example, a PDP having the same structure as PDP 1 was produced except that the phosphor layer 28 was a homogeneous layer composed of phosphor particles having a constant particle diameter. However, in order to improve the accuracy of the experiment, the phosphor (Y, G
d) BO ₃ : Eu alone is used, and all unit emission regions EU are used.
The luminescent color of was designated as R. Then, the luminance on the outer surface of the glass substrate 11 was measured using a luminance meter. The results are summarized in Table 1 together with the forming conditions.

[0032]

[Table 1]

As shown in Table 1, according to the present invention, 20 to 3
It is possible to improve the brightness by 0%. In addition, PDP1
It is considered that the brightness of PDP2 is lower than that of PDP2 because the small-sized phosphor particles p2 are mixed in the upper layer 282b.
It is considered that the brightness of PDP3 is higher than that of PDP2 because there are a small amount of phosphor particles p larger than the phosphor particles p2 in the uppermost part of the phosphor layer 28c.

In the above-mentioned embodiment, the AC drive type surface discharge type PDPs 1 to 3 are exemplified, but the present invention can be applied to the DC drive type PDP 4 shown in FIG. 8, for example. In the PDP 4 of FIG. 8, a pair of display electrodes X and Y
, Are arranged on the glass substrates 11 and 21 so as to be orthogonal to each other. The display electrodes X and Y are the discharge space 30.
Exposed to each other, and a counter discharge occurs between the substrates each time a drive voltage is applied. The phosphor layer 28 is composed of a lower layer 281 and an upper layer 282 similarly to the PDP 1, and is provided by overprinting on the glass substrate 21 on the back side so as to expose the display electrodes Y.

The brightness of the PDP 4 having such a structure is 200.
It was cd / m ² . Further, instead of the phosphor layer 28, P
As with DP2, 2
When a phosphor layer having a layered structure is provided, the brightness is 170 cd.
/ M ² . On the other hand, when a uniform phosphor layer composed of phosphor particles having a constant particle diameter was provided as in the conventional case, the brightness was 140 cd / m ² . That is, according to the dense phosphor layers 28 and 28b on the back side of the discharge space 30,
It was confirmed that it was effective in improving the brightness even in DC driving.

According to the embodiments of FIGS. 1 to 7 described above, the phosphor layers 28, 28 in which the address electrode A has a dense portion.
Since it is covered with b and 28c, the wall discharge can be used to generate the address discharge.

[0037]

According to the inventions of claims 1 to 4,
The excitation energy is significantly reflected by the lower layer portion of the phosphor layer, and the excitation efficiency of the upper layer portion where the emitted light is easily emitted to the front surface side is increased, so that the amount of light emission effective for display is increased and the brightness is increased.

According to the fourth aspect of the invention, it is possible to drive the phosphor layer positively as a dielectric layer without impairing the brightness and the life.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a basic structure of a PDP of a first embodiment.

FIG. 2 is a partial cross-sectional view of the PDP of FIG.

FIG. 3 is a schematic diagram of a layer structure of the phosphor layer of FIG.

FIG. 4 is a partial sectional view of a PDP according to a second embodiment.

5 is a schematic diagram of a layer structure of the phosphor layer of FIG.

FIG. 6 is a partial sectional view of a PDP according to a third embodiment.

FIG. 7 is a schematic view of a layer structure of the phosphor layer of FIG.

FIG. 8 is a partial cross-sectional view of the PDP of the fourth embodiment.

[Explanation of symbols]

 1 PDP (Plasma Display Panel) 2 PDP (Plasma Display Panel) 3 PDP (Plasma Display Panel) 4 PDP (Plasma Display Panel) 11 Glass Substrate (Substrate) 21 Glass Substrate (Substrate) 28, 28b, 28c Phosphor Layer 30 Discharge Space 281,281b Lower layer (lower layer portion) 281c Lower layer portion 282,282b Upper layer (upper layer portion) 282c Upper layer portion p Phosphor particle p1 Phosphor particle (first phosphor particle) p2 Phosphor particle (second phosphor particle) A Address electrode (electrode)

Claims (4)

[Claims] 1. A plasma display panel having a phosphor layer on the back side of a discharge space sandwiched between a pair of substrates, the phosphor layer emitting light by a discharge generated in the discharge space, wherein the phosphor layer is the discharge layer. A plasma display panel, wherein a lower layer portion on the back side of the space has a denser layer structure than an upper layer portion on the front side. 2. The phosphor layer comprises a lower layer on the back side and an upper layer on the front side with respect to the discharge space, and the lower layer is a first layer.
The plasma display panel according to claim 1, wherein the plasma display panel is made of phosphor particles, and the upper layer is made of second phosphor particles larger than the phosphor particles. 3. The phosphor layer is composed of a large number of phosphor particles stacked on the substrate on the back side, and the particle size of the phosphor particles becomes smaller as the distance from the discharge space becomes smaller. The plasma display panel according to claim 1, which has a distribution. 4. The plasma display panel according to claim 1, further comprising an electrode that covers the discharge space with the phosphor layer.