JPH0963482A - Formation method for phosphor layer in pdp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a PDP having a phosphor layer with higher luminance by forming a phosphor layer using a phosphor of a specific composition in manufacturing a plasma display panel(PDP). SOLUTION: Display electrodes X, Y which are the electrodes for plane discharge are provided inside a glass substrate 11 in the front side and coated with a dielectric layer 17 in relation to a discharge space 30. A protection film 18 which is composed of MgO of large secondary electron emission coefficient and has the thickness of several thousands A is provided on the surface of the dielectric layer 17. Because the display electrodes X, Y are arranged in the front side of the discharge space 30, a plane discharge is set to the wide range and the shield of the display light is set to the minimum so that they are constituted of a broad-width transparent conductive film 41 composed of Nesa film, etc., and a narrow metal film 42 for compensating its conductivity. Paste for forming a phosphor layer is an aggregate of phosphor particles formed by mixing the primary particles and the secondary particles, and the phosphor particles having such particle size distribution that 50% grain size and the primary particle size are substantially coincided with each other are used.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a PDP (Plasma Displ
ay Panel: a method for forming a phosphor layer for manufacturing a plasma display panel.

A PDP is a thin display device capable of high-speed display and has been attracting attention as a large color display device for high definition. As the PDP market expands, the technology for producing high quality PDPs becomes more important.

[0003]

2. Description of the Related Art A PDP is a display panel having a structure in which a pair of substrates (usually glass plates) facing each other across a discharge space are used as a base. In the PDP, by providing an ultraviolet excitation type phosphor layer in the discharge space, it is possible to display a color different from the emission color of the discharge gas.

The PDP for full-color display is R
It has phosphor layers of three colors (red), G (green), and B (blue). Usually, these phosphor layers are formed by a method in which a phosphor paste containing powdery phosphor particles as a main component is sequentially applied on a substrate for each color by a screen printing method, and dried and then collectively baked. To be done. A method (precipitation method) of applying a suspension in which phosphor particles are dispersed and depositing the phosphor particles by sedimentation is also known.

Conventionally, in the formation of the phosphor layer of each color, as the phosphor particles, a bare fluorescent material having a primary particle diameter of about several μm or a thin fluorescent material of MgO to enhance secondary electron emission is used. Membrane-coated microcapsule phosphors have been used. For example, (Y, Gd) BO ₃ : Eu is used as the R fluorescent substance, Zn ₂ SiO ₄ : Mn or BaAl ₁₂ O ₁₉ : Mn is used as the G fluorescent substance, and 3 (Ba , Mg) O ・ 8
Al ₂ O ₃ : Eu was used.

[0006]

The brightness of the PDP depends not only on the material (composition) of the fluorescent substance of each color but also on the formation state (film quality) of the fluorescent substance layer.

An object of the present invention is to obtain a phosphor layer having a better film quality for enhancing brightness.

[0008]

Generally, a powder of a fluorescent substance (a group of phosphor particles) which is a material of a phosphor layer is composed of a primary particle and a secondary particle in which a plurality of primary particles are integrated. It is a mixture. Small pieces of crushed primary particles are also mixed.

When a large amount of large secondary particles are mixed, voids are generated in the phosphor layer, and the amount of light emission is reduced accordingly.
The thickness unevenness of the layer is also likely to occur. That is, ideally, a phosphor layer composed of only primary particles having a constant particle size is desirable. However, in reality, it is inevitable that the particle size of the powder varies.

Therefore, as a result of forming a phosphor layer using various powders having different particle size distributions and measuring the brightness thereof, it is found that a specific particle size distribution is more advantageous in terms of brightness than other distributions. Do you get it.

The method of the invention of claim 1 is a set of phosphor particles in which primary particles and secondary particles are mixed in the production of a PDP having a phosphor layer in a facing gap of a pair of substrates.
A group of phosphor particles having a particle size distribution in which the 50% particle size and the primary particle size are substantially the same are attached to one of the substrates to form the phosphor layer.

By using a phosphor particle group having a particle size distribution in which the 50% particle size and the primary particle size are the same, the ideal state (1
It is possible to obtain a phosphor layer having a film quality close to that of a secondary particle only).

The 50% particle size is the particle size Dp when particles having a particle size Dp or less account for 50% of the total mass (or number of particles) of the particle group. This can be calculated, for example, by measuring the number and size of particles by an electric resistance method (coulter counter method), and calculating from the particle size distribution of the particle group obtained thereby.

The primary particle diameter (also referred to as single particle diameter) Dm is
It can be measured, for example, by an air permeation method at a stage immediately after the fluorescent substance is generated by crystal growth or the like.
That is, air can be passed through the sample layer filled with the powder, and it can be obtained from the relationship between the pressure drop Δp and the flow velocity Q / t at that time based on the equation (1).

[0015]

[Equation 1]

[0016]

1 is a block diagram of a PDP 1 to which the present invention is applied.
FIG. 2 is an exploded perspective view of the main part of FIG. 2, and FIG. 2 is a diagram showing an example of the particle size distribution of phosphor particles.

The PDP 1 is a surface discharge 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 region EU of matrix display, and is classified according to the arrangement form of phosphors. It is called a reflective type.

The display electrodes X and Y are electrodes for surface discharge, are provided on the inner surface of the glass substrate 11 on the front side, and are covered with the dielectric layer 17 in the discharge space 30. 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 provided. The display electrodes X and Y are connected to the discharge space 3
Since it is arranged on the front side of 0, the wide transparent conductive film 41 made of a nesa film or the like and the narrow metal that supplements the conductivity thereof are formed in order to widen the surface discharge and minimize the shielding of the display light. It is composed of a film (bus electrode) 42.

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

A stripe-shaped partition 29 having a height of about 200 μm is provided between each address electrode 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
To cover the inner wall surface on the back side including the side surface of 9,
R, G, B phosphor layers 28R, 28G, 28B of respective colors
(Hereinafter, it is referred to as a phosphor layer 28 when it is not necessary to distinguish the colors.). 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.

In the PDP 1, one picture element (pixel) E
Three unit light emitting areas (subpixels) where G is R, G, and B
It is made up of EU and is capable of full-color display by combining R, G, and B.

In manufacturing the PDP 1 having the above structure,
After the address electrode A and the partition 29 are provided on the glass substrate 21, the phosphor layer 28 is formed by using, for example, a screen printing method.

That is, the phosphor paste in which the phosphor particles and the vehicle are mixed is sequentially applied one by one using a screen mask so as to be dropped between the partition walls 29.
At this time, in order to make the coating amount of each sub-pixel uniform,
The phosphor paste is extruded from the screen mask so as to almost completely fill the gaps between the partition walls 29. As the vehicle, a mixture of a cellulose-based or acrylic-based thickener resin and an alcohol-based or ester-based organic solvent is used. Further, the content of the phosphor particles is set to 10 to 50% by weight.

Then, the phosphor pastes of three colors are dried and fired at a temperature of 500 to 600.degree. As a result, the volume of the phosphor paste decreases as the vehicle evaporates, and a phosphor layer 28 with a thickness of 20 to 30 μm that covers the inner wall surface on the back side and a void that becomes the discharge space 30 are formed.

Now, when preparing the phosphor paste,
A phosphor particle group (powder) having a particle size distribution as shown in FIG. 2 in which the 50% particle diameter and the primary particle diameter are substantially the same is mixed with a vehicle as a phosphor material, and the phosphor particles are dispersed in the vehicle. Let The secondary particles may be removed by sieving immediately before mixing. By using the phosphor particle group having a particle size distribution in which the 50% particle diameter and the primary particle diameter are the same, it is possible to obtain the phosphor layer 28 having a film quality close to the state of only the primary particles.

Next, the primary particle size will be described. In the case of a particle state of a fluorescent substance that emits light when excited by ultraviolet rays, the larger the particle size, the higher the emission brightness in the range of about 1 to 20 μm. This is because phosphor particles having a small particle size have a relatively large proportion of the outer skin portion that does not contribute to light emission per unit volume.

However, when a large number of phosphor particles are stacked in a PDP, the above tendency does not apply. That is, the larger the individual phosphor particles are, the larger the emission brightness of the phosphor layer 28 is not always. This is because the larger the particle size of each phosphor particle, the smaller the number of particles per unit volume of the phosphor layer 28 and the lower the density of the layer.

When the phosphor particles are regarded as spheres having a radius of r, the number n of particles per unit volume V is inversely proportional to the cube of r (n∝V / r ³ ). On the other hand, the brightness i of each phosphor particle is approximately proportional to r although it is an empirical rule. Therefore, assuming that each particle is uniformly excited, the brightness I per unit volume V of the phosphor layer 28 is the product of the brightness i of the particle and the number n of particles (I = i × n), and r It is inversely proportional to the square of (I∝V / r ² ). That is, the smaller the particle size of the phosphor particles, the higher the brightness of the PDP. PD
In P1, in terms of the thickness of the phosphor layer 28, the phosphor particles preferably have a particle size of 3 μm or less. However, in reality, it is difficult to produce high-quality phosphor particles (primary particles) of 1 μm or less. If the primary particles are crushed by a crushing treatment to reduce the particle size, the crystallinity may be deteriorated and the light emission rate may be lowered.

Table 1 shows the relationship between the particle size distribution and the brightness when the primary particle size is 3 μm. Samples 1 to 5 in Table 1
Are all blue 3 (Ba, Mg) O.8Al ₂ O ₃ :
It is a powder of Eu. Further, in Table 1, the brightness of the powder state and the brightness of the phosphor layer are standardized with the value of Sample 5 being 100.

[0031]

[Table 1]

As is clear from Table 1, the powder brightness is 50.
Although the% particle size is larger (that is, the larger the number of large secondary particles is), the brightness of the phosphor layer is higher as the 50% particle size is closer to the primary particle size. The same applies to the green and red fluorescent substances.

[0033]

According to the invention of claim 1, when a phosphor layer is formed using a phosphor having a specific composition, a phosphor layer having higher brightness can be obtained.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a main part of a PDP to which the present invention is applied.

FIG. 2 is a diagram showing an example of a particle size distribution of phosphor particles.

[Explanation of symbols]

 1 PDP 11,21 Glass Substrate (Substrate) 28R, 28G, 28B Phosphor Layer

Claims (1)

[Claims] 1. When manufacturing a PDP having a phosphor layer in a gap between a pair of substrates facing each other, it is a set of phosphor particles in which primary particles and secondary particles are mixed, and the particle size distribution is 50% particle size. A method of forming a phosphor layer in a PDP, characterized in that a group of phosphor particles having a distribution in which the primary particle diameter and the primary particle diameter are substantially the same are attached to one of the substrates to form the phosphor layer. .