KR100412087B1 - Plasma display panel having a double protective layer - Google Patents

Abstract

The present invention relates to a plasma display panel which can simultaneously improve discharge start voltage and long life characteristics. In the plasma display panel of the present invention, two substrates face each other with a predetermined gap, and an inert gas is enclosed in the gap. And a plasma display panel in which a discharge sustaining electrode, a dielectric layer, and a protective film are sequentially stacked on a surface of at least one of the substrates in contact with an inert gas, wherein the protective film comprises: a first protective layer made of a secondary electron emission material; And a second protective layer made of a covalent metal oxide in contact with the inert gas.

Description

Plasma display panel having a double protective layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma display panel (PDP), and more particularly, to a plasma display panel capable of simultaneously improving discharge start voltage and long life characteristics.

A general plasma display panel is an apparatus for forming an image by light emission by plasma discharge or phosphors excited by plasma discharge. The plasma display panel is characterized by easy large screen, excellent display quality, and fast response speed. . In addition, since it can be thinned, it is also attracting attention as a wall-mounted display with a liquid crystal display (LCD).

Plasma display panels are classified into surface discharge type and opposite type according to the arrangement of electrodes, and are classified into AC type, DC type, or hybrid type according to whether the electrode is exposed. .

1 is a cross-sectional view of a general surface discharge type AC plasma display panel. The plasma display panel includes a back substrate 10, a first electrode 11 which is an address electrode formed on the back substrate 10, and a dielectric layer 12 formed on the back substrate 10 on which the first electrode 11 is formed. And a plurality of partitions 13 formed on the dielectric layer 12 to maintain a discharge distance, prevent electro-optical crosstalk between cells, and accommodate the phosphor 14.

In addition, a protective film 19 is formed below the dielectric layer 18. The protective film 19 increases the lifespan by preventing sputtering of the dielectric layer 18 by gas ions during discharge and starts discharge by secondary electron emission. It serves to lower the voltage. A low discharge start voltage is preferable because not only a stable discharge can be obtained but also the life of an electrode becomes long. The space between the protective film 19 and the phosphor layer 14 is filled with an inert gas.

In addition, a second electrode 16 which is a discharge sustaining electrode is formed under the front substrate 15 of the plasma display panel. In some cases, the color filter layer 17 may be formed under the second electrode 16. The second electrode or color filter layer 17 is covered by a dielectric layer 18, which serves to accumulate charge generated when a voltage is applied to the second electrode.

Referring to Figure 1 will be described the operation principle of the plasma display panel. First, a voltage corresponding to the discharge sustain voltage is applied between the second electrodes 17 to accumulate charge in the dielectric layer 18. Subsequently, when a voltage corresponding to the discharge start voltage is applied to the first electrode 11, an inert gas is separated into electrons and ions by a glow discharge, and the plasma is formed. The phosphor develops. Thereafter, the inert gas is discharged and the phosphor is colored by only applying a voltage corresponding to the discharge holding voltage to the second electrode 17 by the charge accumulated in the dielectric layer 18, thereby forming an image.

The discharge start voltage of the plasma display panel largely depends on the amount of secondary electrons emitted from the protective film 19. That is, ions generated by ionizing the inert gas collide with the protective film and enter the inside, and the protective film receives ion's kinetic energy and releases secondary electrons to promote ionization again. Therefore, in order to lower the discharge start voltage, the secondary electron emission amount of the protective film must be large.

As described above, examples of materials capable of lowering the discharge start voltage include complex oxides such as SrO + CaO, BaO + CaO, SrBaO, MgSrO, or CaSrO, and in particular, it is known that the initial discharge characteristics are excellent. . However, the compound has a low oxygen content and is chemically unstable and thus deliquescent. Therefore, since the compound easily reacts with moisture when exposed to air, the plasma display panel employing these compounds has a poor lifespan.

On the other hand, MgO having excellent secondary electron emission characteristics is also widely used as a protective film forming material. That is, when the temperature is changed or the oxygen concentration flowing during the deposition of MgO is changed, the protective film deposited at room temperature or the protective film deposited when the oxygen concentration is low contains impurities of metallic magnesium due to lack of oxygen in the film. The level is generated, and as a result, the discharge voltage is reduced. However, MgO also has a problem that the oxygen content is low, so when adsorbed in the air to adsorb moisture, not only shorten the life but also unstable, so that the discharge time is long and the discharge maintenance voltage is changed.

Accordingly, an object of the present invention is to provide a plasma display panel having a protective film capable of simultaneously improving discharge start voltage and long life characteristics.

1 is a cross-sectional view showing the structure of a general surface discharge plasma display.

2 and 3 are X-ray diffraction graphs of the MgO protective film according to the comparative example.

<Explanation of symbols for the main parts of the drawings>

10 ... back substrate 11 ... first electrode

12, 18 ... dielectric layer 13 ... bulkhead

14 ... phosphor layer 15 ... front substrate

16. Second electrode 17 ... Color filter layer

19 ... Shield

In the present invention to achieve the above technical problem,

Two substrates face each other with a predetermined gap, in which an inert gas is enclosed, and a plasma display panel in which discharge sustaining electrodes, a dielectric layer, and a protective film are sequentially stacked on a surface of at least one of the substrates in contact with the inert gas. The plasma display panel of claim 1, wherein the protective layer includes a first protective layer made of a secondary electron emission material, and a second protective layer made of a covalent metal oxide in contact with the inert gas.

The covalent metal compound is preferably at least one metal compound selected from the group consisting of MgF ₂ , La ₂ O ₃ , Gd ₂ O ₃ and LaB ₆ .

It is preferable that the thickness of a said 2nd protective layer is 50-500 kPa.

The secondary electron-emitting material is preferably at least one oxide selected from the group consisting of MgO, SrO, CaO, BaO, MgSrO, CaSrO and SrBaO.

The protective film forming compound is basically required to have excellent secondary electron emission characteristics in order to lower the discharge start voltage. However, since a protective film deposited with a complex oxide such as SrO + CaO, BaO + CaO, SrBaO, MgSrO, or CaSrO or MgO is deficient in oxygen in the membrane, when it comes into contact with air immediately after deposition, water is adsorbed to undergo a hydrolysis reaction. Done. As a result, there is a problem that the aging of the panel performance is severe and the life of the panel is shortened rapidly.

Accordingly, the present invention forms a protective film having a double structure, which includes a first protective layer formed of a material having excellent secondary electron emission characteristics but low oxygen content, and having a deliquescent property, and a second protective layer that is less affected by moisture. By trying to solve the above problems.

The second protective layer forming material which is less sensitive to the influence of moisture is preferably a metal oxide having strong covalent bonds, and specifically, for example, MgF ₂ , La ₂ O ₃ , Gd ₂ O _3, and LaB ₆ . They are low deliquescent and prevent damage to the first protective layer made of the secondary electron emission material. In addition, they also have the advantage of shortening the activation time of the PDP panel and preventing generation of impurities in the panel. If the surface layer is formed using a covalent material, the contamination is minimal since it interferes with the adsorption of polar molecules such as moisture.

The thickness of the second passivation layer is preferably about 50 to 500 mV. If the thickness of the second protective layer is 50 mV or less, it is not sufficient to sufficiently cover the surface of the protective film. It is difficult to use the characteristic of a protective film with a large secondary electron emission coefficient of a lower layer. In other words, it is difficult to meet the initial conditions in the circuit after commercialization because such properties are available after a certain amount of covalent compound in the surface layer is removed.

On the other hand, in the manufacture of the plasma display panel according to the present invention, it is preferable to deposit the lower protective layer for secondary electron emission in an oxygen-free or low oxygen atmosphere. This is because when deposited in a low oxygen atmosphere, secondary electron emission is facilitated by generation of a new energy level by incompletely oxidized ions.

The low oxygen atmosphere refers to a state in which the oxygen component is low in the valence ratio among the components of the protective film that is released after the deposition. As a specific example, at present, the ratio of oxygen to Mg of MgO is 1: 1.1, but using a low oxygen process, the ratio of oxygen to Mg can be 1: 1 or less. Here, the atomic ratio of oxygen to metal ions is 1: 1 or less.

On the other hand, the present invention is not limited to the surface-discharge AC plasma display panel as described above, it can be applied to the protective film of the opposing, direct-discharge plasma display panel.

Hereinafter, the present invention will be described in detail with reference to the following examples, but the present invention is not limited to the following examples.

Example 1

E-beam (equipment capable of continuous deposition including sputter) was deposited MgO of 5000 ~ 10000Å, and 100Å MgF ₂ was deposited in the next chamber. The amount of oxygen flowed during deposition was 0-100 sccm. At this time, the deposition vacuum and the deposition rate were as follows.

Initial vacuum degree: 4 × 10 ^-7 torr,

Substrate Temperature: 200 ℃

O ₂ partial pressure during deposition: 5.2 × 10 ^-2 torr,

Deposition rate: about 30 μs / sec

MgO single crystal pellets of purity 99.9% were used as the deposition material, and the film thickness was measured after deposition. The next layer was deposited for 25 seconds to 250 seconds with a deposition rate of 2 kW / sec. The PDP top plate thus deposited was sealed with the bottom plate and exhausted to manufacture a plasma display panel (PDP).

Example 2

E-beam (equipment capable of continuous deposition including a sputter) was deposited to 5,000 ~ 10,0001 MgO, and 200Å Gd ₂ O ₃ was deposited. The amount of oxygen flowed during deposition was 0 to 100 sccm. At this time, the deposition vacuum and the deposition rate were as follows.

Initial vacuum degree: 4 × 10 ^-7 torr

Substrate temperature: 200 ℃

O ₂ partial pressure during deposition: 5.3 × 10 ^-2 torr

Deposition rate: about 30 μs / sec

MgO single crystal pellets of purity 99.9% were used as the deposition material, and the film thickness was measured after deposition. The next layer was deposited for 25 seconds to 250 seconds with a deposition rate of 2 ms / sec. The PDP top plate thus deposited was sealed with the bottom plate and exhausted to manufacture a plasma display panel (PDP).

The double protective films of Examples 1 and 2 were observed to have a change in crystallinity by X-ray diffraction, resulting in insignificant change in nodule over time.

Comparative Example 1

Without using a double protective film, MgO was deposited as a protective film under the same conditions as above, and the change in film quality was compared as follows. Deposition using 100sccm, 0sccm and the crystallinity change was observed with time. 2 and 3 are the results of X-ray diffraction analysis with time when left in a nitrogen atmosphere and water containing moisture, respectively, the size of the peak (111, 200, 222) decreases over time You can see it disappear. Therefore, it can be seen that the NgO film without the double protective film rapidly loses its crystallinity with time regardless of moisture content in the air.

As described above, the plasma display panel according to the present invention reduces the discharge start voltage due to the first protective layer made of the secondary electron emission material and at the same time the second protective layer made of the covalent metal oxide is protected by the first protective layer. The lifetime can be increased by preventing moisture adsorption of the layer and the resulting surface damage. In addition, the plasma display panel according to the present invention also has the advantage that the generation of impurity gas is suppressed and the PDP activation time is also shortened.

Claims (4)

Two substrates face each other with a predetermined gap, in which an inert gas is enclosed, and a plasma display panel in which discharge sustaining electrodes, a dielectric layer, and a protective film are sequentially stacked on a surface of at least one of the substrates in contact with the inert gas. The protective film of claim 1, wherein the protective film includes a first protective layer made of a secondary electron emission material, and a second protective layer made of a covalent metal compound in contact with the inert gas, wherein the covalent metal compound is MgF ₂ ,; At least one metal oxide selected from the group consisting of La ₂ O ₃ , Gd ₂ O _3, and LaB ₆ . delete The plasma display panel of claim 1, wherein the second protective layer has a thickness of about 50 to about 500 microseconds. The plasma display panel of claim 1, wherein the secondary electron emission material is at least one oxide selected from the group consisting of MgO, SrO, CaO, BaO, MgSrO, CaSrO, and SrBaO.