JPH06310037A - Dielectric composition and plasma display panel - Google Patents

Abstract

PURPOSE:To provide a plasma display panel having good characteristic at the low cost, and to provide a dielectric composition that can be effectively used for the panel. CONSTITUTION:An oxide crystal containing at least one element chosen among Be, Mg, Ca, Sr, Ba, Sc, Y, Th and lanthanide element, is prepared. In the case of average particle size (d) as measured according to a light transmittance method, and of an average particle size D as calculated from a specific surface area, d/D is no greater than 7, while (d) is 15-60vol% of the powder of 0.5-10mum, and softening point of the oxide glass is lower than the melting point of the oxide crystal. The powder of 100vol% containing 40-85 vol% of the powder of average particle size (d) of 0.5-10mum is kneaded with a liquid vehicle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric composition and a plasma display panel using the same.

[0002]

2. Description of the Related Art Plasma display panels (hereinafter referred to as P
The electrodes (abbreviated as DP) whose electrodes are covered with a dielectric material to cause discharge on the surface include display discharge for sustaining the discharge in an alternating current, priming ions by selective discharge or discharge for removing charges on the surface of the dielectric material. There are known so-called trigger discharges and the like for ensuring the above.

Since the following problems are common, an AC PDP used as a display discharge will be described. This PDP is
It has high brightness and long life because it has a memory function in discharge characteristics and has been developed with excellent discharge surface material.

Although various methods are known for constructing a PDP, in order to make it thin, many of them employ a hermetically sealed container for discharge gas in which the front and rear plates facing each other are sealed with seal glass. To be done. Low-priced soda lime glass is used for both front and back plates.

In a PDP having a large number of fine display cells capable of displaying an image, a square cell array in which display cells and electrodes can be easily formed is usually adopted. A cell is formed at a portion where the line-shaped row and column electrodes intersect each other with a space therebetween, so that a large number of cells can be independently selected. Such a selection electrode is composed of two electrode groups.

In the AC type, the pair of display discharge electrodes are covered with a dielectric. This display discharge electrode can also be used as a selection electrode. Further, the display discharge electrode may not have a selection function, and a selection electrode called a writing electrode may be separately formed. The write electrode can be used as either a coated or exposed electrode. These combinations are arbitrary. In addition, a plurality of electrodes not used for selection are usually commonly connected.

There are two types of display, one that utilizes the visible emission of discharge gas (monochromatic PDP) and the other that makes the phosphor emit visible light by the ultraviolet rays generated by discharge (color PDP).

An example of a partial schematic sectional view of such a general color PDP is shown in FIG. On the back plate BP, a pair of display discharge electrodes SX and SY are formed in a line shape in the vertical direction. The electrode material is, for example, A1 and is formed using a thin film technique or the like. SX is also used as a selection electrode and is independent, but SY is connected in common because it is used only for sustain of discharge. The display discharge electrode is covered with a coating dielectric. The covering dielectric DL is composed of a dielectric layer (for example, a glass layer formed by thick film printing) for covering the electrodes and a protective layer (for example, MgO or the like deposited by vapor deposition) thereon. There is.

On the front glass plate FG, write electrodes W, which are the other select electrodes, are formed in a line shape parallel to each other, and these are covered with phosphors PH of respective colors.
The writing electrode is formed of an ink such as Ag, and the phosphor is a powder ink of each color, and is formed by applying a thick film technique.

A partition wall PW is formed between the front plate and the back plate to secure a discharge space, regulate the distance between electrodes, and prevent erroneous discharge. It is a display cell CL. The partition wall is formed by using, for example, glass ink.

The above-mentioned structure is a general type which is classified as a three-phase electrode, surface discharge type and transmission type color PDP.

The characteristics required for the coated dielectric are as follows. (1) To cover the electrodes closely. (2) The dielectric capacitance is uniform in many cells. (3) The surface is smooth because the discharge characteristics are uniform. (4) The surface is made of a protective material. (5) Select a surface material that lowers the driving voltage.

Oxide glass (hereinafter simply referred to as glass) material is preferably used for the above (1) to (3).
A film can be easily formed by using glass powder, and a dense, smooth, and homogeneous coated dielectric can be formed by melting glass. As for (4) and (5), a sufficient amount of a general glass material has not been obtained, so a specific material is formed on the surface. As a forming method, thin film technology such as vapor deposition and sputtering is adopted. However, the thin-film technology has the drawbacks of expensive equipment and poor mass productivity.

Therefore, a method of using a protective material in powder form that can be driven at a low voltage has been studied. That is, the protective material powder is used alone, or a small amount of a fixing material such as glass is used together. In this method, the thick film technology can be applied, so that the cost is low, and the low voltage and the protection characteristics are successfully satisfied. However, since the surface state of the protective layer is not sufficient, the discharge characteristics vary widely. Therefore, there is a drawback that manufacturing conditions and drive circuits are limited.

As described above, in the conventional PDP, the characteristics and the price are not satisfied in the formation of the coating dielectric.

[0016]

SUMMARY OF THE INVENTION The present invention has been made in view of these problems of the prior art, and an object thereof is to provide a PDP having excellent characteristics at a low cost and a dielectric composition useful for the PDP. And

[0017]

The above object of the present invention is achieved by the following dielectric composition and PDP.

That is, according to the present invention, Be, Mg, Ca,
An oxide crystal containing at least one element selected from the elements Sr, Ba, Sc, Y, Th and lanthanide,
Assuming that the average particle diameter d measured by the light transmission method and the average particle diameter D calculated from the specific surface area are d / D of 7 or less and d of 0.5 to 10 μm, 15 to 60 vol% of powder, An oxide glass having a softening point lower than the melting point of the oxide crystal, a powder having an average particle diameter d of 0.5 to 10 μm and a total of 100 vol% including 40 to 85 vol% of the powder was kneaded together with a liquid vehicle. It is a characteristic dielectric composition.

Further, according to the present invention, a back plate and a front glass plate are sealed around each other to form a discharge gas container, and a plurality of display cells having a display area of 0.2 mm ² or less are formed in the container. In a PDP in which a discharge electrode coated with a dielectric is formed in each cell, at least the surface of the coated dielectric on which discharge occurs is Be, Mg, Ca, Sr, Ba,
Oxide crystal powder 15-60v containing at least one element selected from Sc, Y, Th and lanthanide elements
ol% is dispersed in oxide glass to form a protective layer, and the surface roughness R _{MAX of the} protective layer is 1.5 μm or less.

The present invention will be described in more detail below. Since the PDP of the present invention is the same as the conventional one except for the surface protective layer of the dielectric covering the discharge electrode, other constitutions, materials, forming techniques and the like can be used. In addition, the average particle diameter used in the following description is obtained by the light transmission method as d,
What is calculated from the specific surface area is represented as D.

First, the dielectric composition of the present invention will be described. The thickness of the coating dielectric is about 20 to 60 μm in view of the amount of charges accumulated on the surface and the reliability of insulation. Glass, which is easy to be densely coated, is preferred, but a protective layer is formed on at least the surface of the dielectric. This is because there is not enough glass alone. The protective layer in the present invention is formed of a mixture of a protective material and glass. Although the forming method is arbitrary, thick film technology is convenient, and the thickness of the protective layer is preferably 1 to 20 μm which can be easily achieved by the thick film technology. Even if it is less than 1 μm, there is no problem in protection characteristics,
It becomes difficult to form a uniform film.

Ink-like compositions are formed for thick film technology applications. As a liquid vehicle for this purpose, each cellulose such as methyl and ethyl, an acrylic resin or the like is pine oil,
Butyl carbitol, butyl carbitol acetate,
A general one dissolved in a solvent such as cellosolve can be used. 30-60 parts by weight of the vehicle may be kneaded with 100 parts by weight of the total powder. In the experiment described later, such a composition was used to construct the PDP shown in FIG.
Of course, the entire dielectric can be formed with this composition.

Protective materials include Be, Mg, Ca, S
An oxide crystal powder containing at least one element selected from r, Ba, Sc, Y, Th and lanthanide elements is used. Oxides of the above elements are known to be excellent in low voltage driving and protection characteristics. Here, the lanthanide element means La, Ce, Pr, Nd, Pm, Sm, Eu, and G.
d, Tb, Dy, Ho, Er, Tm, Yb and Lu. The oxide is a single element such as MgO, Y ₂ O ₃ or La.
₂ O ₃ or the like or a complex element such as MgO / Al ₂ O ₃ can be used. Also, a plurality of oxides may be mixed.

A protective material having a d of 0.5 to 10 μm is used. If it is less than 0.5 μm, the amount of glass that reacts with glass in a molten state increases, which is not preferable in terms of characteristics. 10 μm
If it is larger than the above range, the unevenness on the surface of the dielectric becomes large, and it becomes difficult to perform fine patterning and thin film formation, which is not preferable.

In order to avoid unnecessary reaction between the protective material and the glass, the softening point of the glass is selected to be lower than the melting point of the protective material. If there is a difference of 1000 ° C. or more, the amount of the protective material dissolved is small. Of course, it is also necessary that the softening point does not deform the panel substrate when the protective layer is formed. Further, the thermal expansion coefficients of the protective layer and the dielectric layer are designed close to those of the substrate material to be fixed. Since the selection range of the glass is wide, it is possible to easily select the glass having the above characteristics, and many examples such as B ₂ O ₃ —ZnO and SiO ₂ —B ₂ O ₃ —PbO system can be exemplified.

The d of the glass is 0.5 to 10 μm.
When the glass is less than 0.5 μm, it is difficult to remove bubbles in the protective layer when the glass is melted, and the bubbles deteriorate the characteristics of PDP. If it is larger than 10 μm, unevenness is likely to occur and a thin film cannot be formed.

The ratio of the protective material to the glass is 15 in the protective material.
It is about 60 vol%. If it is less than 15 vol%, it cannot be driven at a low voltage, and the protective properties are not sufficient, which is especially true of a protective material having a small particle size. If it exceeds 60 vol%, a dense and smooth film cannot be formed.

The characteristics of the protective layer are evaluated mainly by the discharge sustaining voltage V
s and the operation margin Vm. It is preferable that Vs is a voltage immediately before the discharge is extinguished by gradually decreasing the voltage of the discharge generated at the discharge start voltage Vf or higher.
The Vs and Vf vary in each display cell, but the drive voltage is set during this period. Therefore, the minimum Vf and the maximum Vs
The difference Vm of Vm must be positive. Vm is an index of uniformity and represents an allowable tolerance. That is, the larger the Vm, the easier the manufacturing.

Now, Vs changes depending on the type and pressure of the discharge gas, the distance between the electrodes, etc., but changes in the protective layer on the discharge surface when other conditions are constant. The results of this comparative experiment are shown in FIG. In each of the following figures, the point A is formed by the conventional thin film technology.

The horizontal axis of FIG. 2 represents the vol% of the protective material in the glass and the protective material of the dielectric ink used for forming the protective layer. Protective material and its d / D are constant (12),
The same glass is used. As can be seen from the curve in which d of the protective material is changed, Vs has a minimum value, which decreases as d or the protective material ratio increases. This is because Vs generally decreases as the number of protective materials increases, but if the amount is too large, cracks or voids occur in the protective layer and the characteristics deteriorate.

When d is less than 0.5 μm, the minimum value becomes unclear, but this is because the protective material is largely dissolved in the glass, and bubbles are entrained or voids are generated in a small amount. When d is larger than 10 μm, the amount of change in Vs is small.

The above tendency is the same for powders having different D, and it can be seen from FIG. 2 that it is preferable to design the protective layer so that Vs is minimized.

Next, the relationship between Vm and the surface roughness of the protective layer is shown in FIG.
Shown in. Vm decreases as the number of display cells increases and as the area decreases, but it is particularly sensitive to the area. It can be seen from FIG. 3 that Vm decreases as R _MAX increases. In addition, the smaller the cell area S, the faster Vm decreases with R _MAX . A cell with an area of 0.2 mm ² or less is useful for a high-definition PDP, and R _MAX is 1.5
It is preferably not more than μm, and more preferably not more than 0.8 μm.

As described above, in the protective layer formed by mixing the glass and the protective material, the composition having the minimum Vs is preferable. When the surface roughness is measured in the vicinity of such a composition, R _MAX
Was found to be proportional to d of the protective material used. Usually, the cheapest powder obtained by the pulverization method has a d / D of 10
That is all. With the powder of d / D = 12 used in FIG. 2, a relationship of approximately R _MAX = 1/4 dμm is obtained. That is, d
The smaller V is, the better Vm is, but this is the worse direction from Vs.

The surface roughness is also related to the particle size distribution and shape of the powder, and this is the essence of the present invention. In the present invention, d / D is used to define the distribution and shape,
A value of 7 or less is adopted. The smaller this value, the closer the powder shape is to a sphere, and the sharper the particle size distribution. When d / D is 12, 7, and 5, the surface roughness R _MAX of the protective layer having a composition that minimizes each Vs is about 1 / 4d, 1 / 6d, 1/7.
It was dμm. That is, if d / D is reduced, R _MAX
Therefore, Vm can be increased and Vm can be increased.

When d / D is made small, a good effect is also given to Vs. Experimental results showing this are shown in FIG.

This FIG. 4 is similar to FIG. 2, except that d of protective material powder is kept constant at 2 μm and d / D is changed. As can be seen from FIG. 4, the minimum value of Vs becomes smaller as d / D becomes smaller, and at the same time, the ratio of the protective material that gives it becomes larger. This tendency is the same even when d changes.

If d / D is reduced as described above, Vs
It can be seen that the Vm characteristics can be improved at the same time. d /
The minimum value of D is theoretically 1, but at this time, the powder is a perfect spherical shape having the same size. Clearly, such powders are expensive. Therefore, in reality, powder having d / D of 7 or less is selected.

The powder having d / D of 7 or less in the particle size range in the present invention cannot be obtained by the pulverization method as described above. However, it can be mass-produced by the following method.

(1) A method of spraying a liquid raw material. a) Melt and spray the protective material at high temperature. b) The fine protective material is dispersed in a liquid (eg water), sprayed to form granules and then heated and sintered. At this time, a caking material such as a resin is generally added to the liquid to stabilize the granules. Further, the material may be used in a sol state having a caking property.

(2) Dissolve the powder having a large d / D. The powder having a large d / D is generally angular. When this is dissolved, sharp corners with high solubility are quickly dissolved and become round. Examples of the treatment liquid include acids, alkalis, glass and the like.

(3) Utilizing crystal growth. Various crystal growth methods are known, and the powder obtained thereby generally forms a polyhedron. These d / D values are generally 7 or less.

As the protective material, after heat treatment,
The form of the compound to be used may be selected, which is a commonly used method.

The above experimental results are not exact because they vary depending on the production technical factors such as the kneading state of the protective material and glass, the state of the applied protective layer, and the firing schedule. However, it tends to be obtained by making the above factors constant, and can be appropriately determined by a simple experiment.

The preferred embodiments and procedures of the present invention are summarized below. (1) Regarding protective material: a) d / D is 7 or less in order to improve Vs and Vm. The smaller, the better, but the price is taken into consideration when deciding.

B) The particle size is 0.5 to 10 μm. Vm
If you select a large one within the allowable range of
s can be reduced, driving load is reduced, and the ratio of the protective material can be increased, so that the protective property is also good. More preferably, it is 2 to 5 μm.

(2) Regarding glass: a) In order to make the mixing with the protective material uniform, it is preferable that d / D is small, but it is not particularly limited because it has little influence on the characteristics.

B) The particle size is 0.5 to 10 μm, more preferably 2 to 5 μm, and it is desirable that the particle size be the same as that of the protective material powder.

(3) Regarding mixing of protective material and glass: a) The minimum value of Vs is obtained by changing the mixing ratio. Since there is an experimental error, ± 10 vol% of the ratio giving the minimum value is preferable. Specifically, the protective material is 15 to 60 vol.
%, And more preferably 30 to 45 vol%. At this time, even if a simple thick film technique is applied, a protective layer having R _{MAX of} 1.5 μm or less can be obtained.

[0050]

EXAMPLES The present invention will be described in more detail below with reference to examples.

Example As the protective material, a powder obtained by treating pulverized powder of molten MgO with an aqueous hydrochloric acid solution and dissolving a part of the powder was used. The d / D of this powder was 6, and the d was 4 μm. Further, as glass, it has a softening point of 490 ° C. and has a SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —Ba content.
The O-PbO type was used. Average particle size d of this glass
Is about 4 μm. PD by changing the ratio of protective material and glass
When the Vs of P was measured, it was 165V, which was the minimum value at 45 vol% of the protective material. Therefore, this ratio was used as the dielectric composition.

A total of 100 parts by weight of the protective material and glass powder was kneaded together with 45 parts by weight of a liquid vehicle in which 10 wt% of ethyl cellulose was dissolved in butyl carbitol acetate to prepare a dielectric composition. The PDP shown in FIG. 1 was prepared, and this protective layer was formed from the above dielectric composition. The firing is 560 ° C. and the thickness is 8 μm. The total dielectric thickness was 50 μm. The cell shape of the PDP is rectangular, the pitch is 0.66 mm in length, 0.22 mm in width, and the cell area is about 0.1 mm ² . The number of cells is 640 vertical and 1920 horizontal
Met. A general method was adopted for the forming method and the like. The Vm of the completed PDP was 30V, and the R _MAX of the protective layer was 0.6 μm.

Comparative Example A crushed powder of molten MgO was used as it was as a protective material.
The d / D of this powder was 11, and the d was 8 μm. Also,
The same glass as that used in the example was used. When the Vs of the PDP was measured while changing the ratio of the protective material and the glass, the minimum value was 180 V at 30 vol% of the protective material. Therefore, this ratio was adopted as the dielectric composition.

Using this protective material and glass, a PDP was prepared by the same method as in the example. Completed PD
The Vm of P was 5 V, and the protective layer R _MAX was 2 μm.

As can be seen from the above examples and comparative examples, when the dielectric composition of the present invention is used, the PDP having good characteristics is obtained.
Is obtained.

[0056]

From the above description, the present invention has the following effects. (1) A dielectric composition useful for a PDP can be obtained by an ordinary simple method only by selecting materials having specific properties and their ratio. (2) By using the above dielectric composition, a PDP protective layer having excellent characteristics can be formed by a simple thick film technique.

[Brief description of drawings]

FIG. 1 is a partial schematic sectional view showing an example of a PDP.

FIG. 2 is a graph showing the relationship between the discharge sustaining voltage Vs and the protective material ratio.

FIG. 3 Surface roughness R _{MAX of} protective layer and operating margin Vm
A graph showing the relationship with.

FIG. 4 is a graph showing the relationship between the discharge sustaining voltage Vs and the protective material ratio.

[Explanation of symbols]

FG: front glass plate, BP: rear plate, PW: partition wall, S
X, SY: display discharge electrode, W: writing electrode, DL: coating dielectric, PH: phosphor, CL: display cell.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Tatsumasa Yokoi, 1-3-1, Noritake Shinmachi, Nishi-ku, Nagoya, Aichi Prefecture No. 36 Noritake Company Limited Limited (72) Hideyuki Asai 3-chome, Noritake Shincho, Nishi-ku, Aichi Prefecture No. 1-36 Noritake Company Limited (72) Inventor Naoya Kikuchi Noritake Shinmachi 3-chome, Nishiku, Nagoya-shi, Aichi Prefecture 1-36 Noritake Company Limited Limited (72) Inventor Ryuji Nakano Noritake Shin-cho, Nishi-ku, Nagoya Aichi Prefecture No. 1-336 Noritake Company Limited (72) Inventor Masaaki Ito No. 1-36 Noritake Shinmachi, Nishi-ku, Nagoya, Aichi Prefecture Noritake Company Limited Limited

Claims (2)

[Claims] 1. Be, Mg, Ca, Sr, Ba, Sc,
When the average particle size d measured by the light transmission method and the average particle size D calculated from the specific surface area are oxide crystals containing at least one element selected from Y, Th and lanthanide elements, d / D Is 7 or less and d is 0.5 to 10 μm, and the powder is 15 to 60 vol%, and the oxide glass has a softening point lower than the melting point of the oxide crystal, and the average particle diameter d is 0.5 to 10 μm.
A dielectric composition, characterized in that a total of 100 vol% powder including 40 to 85 vol% of m powder is kneaded with a liquid vehicle. 2. A discharge gas container having a back plate and a front glass plate sealed around the periphery thereof, and a display area of 0.
In a plasma display panel in which a plurality of display cells each having a size of ² mm ² or less are formed, and a discharge electrode coated with a dielectric is formed in each cell, at least the surface of the coated dielectric where discharge is generated is Be, Mg, Ca, Sr,
Oxide crystal powder 15 containing at least one element selected from Ba, Sc, Y, Th and lanthanide elements
A plasma display panel, wherein 60 vol% is dispersed in an oxide glass to form a protective layer, and the surface roughness R _{MAX of the} protective layer is 1.5 μm or less.