WO2012117665A1

WO2012117665A1 - Plasma display panel

Info

Publication number: WO2012117665A1
Application number: PCT/JP2012/000666
Authority: WO
Inventors: 上野　巌; 卓司辻田; 幸弘森田; 貴仁中山; 章伸岩本
Original assignee: パナソニック株式会社
Priority date: 2011-03-03
Filing date: 2012-02-01
Publication date: 2012-09-07
Also published as: JP2012185916A

Abstract

A plasma display panel is provided with a front plate and a back plate positioned so as to face the front plate. The front plate contains a display electrode, a dielectric layer for covering the display electrode, and a protective layer for covering the dielectric layer. The protective layer includes MgO, and a compound of Ca, O, and at least one element selected from a group consisting of V, Mn, Co, Ni, Cu, Mo and W.

Description

Plasma display panel

The technology disclosed herein relates to a plasma display panel used for a display device or the like.

One function of a protective layer of a plasma display panel (hereinafter referred to as PDP) is to emit electrons for generating discharge.

The driving voltage can be lowered by using a material having a high secondary electron emission capability for the protective layer. For this reason, it is known to use magnesium oxide (MgO) and calcium oxide (CaO) having a higher secondary electron emission capability for the protective layer (for example, see Patent Document 1).

JP 2010-080388 A

The PDP includes a front plate and a back plate disposed to face the front plate. The front plate includes a display electrode, a dielectric layer that covers the display electrode, and a protective layer that covers the dielectric layer. The protective layer includes MgO, at least one element selected from the group consisting of V, Mn, Co, Ni, Cu, Mo, and W, and a compound of Ca and O.

FIG. 1 is a perspective view illustrating a schematic structure of a PDP according to an embodiment. FIG. 2 is a schematic sectional view showing the structure of the protective layer according to the first embodiment. FIG. 3 is a schematic cross-sectional view showing the structure of the protective layer according to the second embodiment. FIG. 4 is a schematic cross-sectional view showing the structure of the protective layer according to the third embodiment. FIG. 5 is an enlarged view of a part of the protective layer shown in FIG.

[1. Configuration of PDP1]
The PDP 1 of the present embodiment is an AC surface discharge type PDP. As shown in FIG. 1, the PDP 1 has a structure in which a front plate 2 including a front glass substrate 5 and the like and a back plate 3 including a back glass substrate 11 and the like face each other. The outer peripheral portions of the front plate 2 and the back plate 3 are hermetically sealed with a sealing material made of glass frit or the like. The discharge space 15 inside the sealed PDP 1 is filled with discharge gas such as Ne (neon) and Xe (xenon) at a pressure of 55 kPa to 80 kPa.

The front plate 2 has display electrodes 8 including scan electrodes 6 and sustain electrodes 7 formed on the front glass substrate 5. Further, the front plate 2 includes a dielectric layer 9 that covers the display electrode 8 and a protective layer 10 that covers the dielectric layer 9. For example, the scan electrode 6 and the sustain electrode 7 have a structure in which the

bus electrodes

6b and 7b are stacked on the

transparent electrodes

6a and 7a. The front plate 2 may be provided with black stripes. Further, the

transparent electrodes

6 a and 7 a may be omitted from the scan electrode 6 and the sustain electrode 7.

The back plate 3 has a plurality of address electrodes 12 formed on the back glass substrate 11. The address electrode 12 is arranged in a direction orthogonal to the display electrode 8. Further, the back plate 3 includes a base dielectric layer 13 that covers the address electrodes 12 and a partition wall 4 that is formed at a position corresponding to the space between the address electrodes 12 on the base dielectric layer 13. Further, the back plate 3 includes

phosphor layers

14R, 14G, and 14B formed between adjacent barrier ribs 4.

A discharge cell is formed at a position where the display electrode 8 and the address electrode 12 intersect. The discharge cell performs color display using a phosphor layer 14R that emits red light, a phosphor layer 14G that emits green light, and a phosphor layer 14B that emits blue light.

[2. Manufacturing method of PDP1]
[2-1. Manufacturing method of front plate 2]
Scan electrode 6 and sustain electrode 7 are formed on front glass substrate 5 by photolithography. Specifically, first,

transparent electrodes

6 a and 7 a are formed on the front glass substrate 5. The

transparent electrodes

6a and 7a are obtained by patterning an ITO (Indium Tin Oxide) film. The

bus electrodes

6b and 7b contain silver (Ag) for ensuring conductivity. The

bus electrodes

6b and 7b may have a laminated structure of a black electrode containing a black pigment for improving the contrast of the image display surface and a metal electrode for ensuring conductivity.

As the material for the

bus electrodes

6b and 7b, an electrode paste containing silver (Ag), a glass frit for binding silver, a photosensitive resin, a solvent, and the like is used. First, an electrode paste is applied to the front glass substrate 5 by a screen printing method or the like. Next, the solvent in the electrode paste is removed by a drying furnace. Next, the electrode paste is exposed through a photomask having a predetermined pattern.

Next, the electrode paste is developed to form a bus electrode pattern. Finally, the bus electrode pattern is fired at a predetermined temperature in a firing furnace. That is, the photosensitive resin in the electrode pattern is removed. Further, the glass frit in the electrode pattern is melted. The molten glass frit is vitrified again after firing.

Bus electrodes

6b and 7b are formed by the above process. In addition to the method of screen printing the electrode paste, a sputtering method, a vapor deposition method, or the like can be used.

A main gap is formed in a relatively narrow region between the transparent electrode 6a and the transparent electrode 7a. The main gap is a region where sustain discharge occurs in the PDP 1. An interpixel gap is formed in a relatively wide area between the transparent electrode 6a and the transparent electrode 7a. The sustain discharge generated in the main gap expands with time. However, the sustain discharge does not extend to the interpixel gap. That is, the discharge region is a region between the bus electrode 6b and the bus electrode 7b with the main gap interposed therebetween.

Next, the dielectric layer 9 is formed. As a material for the dielectric layer 9, a dielectric paste containing a dielectric glass frit, a resin, a solvent, and the like is used. First, a dielectric paste is applied on the front glass substrate 5 by a die coating method or the like so as to cover the display electrode 8 with a predetermined thickness. Next, the solvent in the dielectric paste is removed by a drying furnace. Finally, the dielectric paste is fired at a predetermined temperature in a firing furnace. That is, the resin in the dielectric paste is removed. Further, the dielectric glass frit is melted. The molten dielectric glass frit is vitrified again after firing. Through the above steps, the dielectric layer 9 is formed. Here, besides the method of die coating the dielectric paste, a screen printing method, a spin coating method, or the like can be used. Alternatively, a film that becomes the dielectric layer 9 can be formed by a CVD (Chemical Vapor Deposition) method or the like without using a dielectric paste.

Next, the protective layer 10 is formed on the dielectric layer 9. Details of the protective layer 10 will be described later.

The front plate 2 is completed through the above steps.

[2-2. Manufacturing method of back plate 3]
Address electrodes 12 are formed on the rear glass substrate 11 by photolithography. As an address electrode material, silver (Ag) for securing conductivity, glass frit for binding silver, a photosensitive resin, a solvent, and the like are used. First, the address electrode paste is applied on the rear glass substrate 11 with a predetermined thickness by screen printing or the like. Next, the solvent in the address electrode paste is removed by a drying furnace. Next, the address electrode paste is exposed through a photomask having a predetermined pattern. Next, the address electrode paste is developed to form an address electrode pattern. Finally, the address electrode pattern is fired at a predetermined temperature in a firing furnace. That is, the photosensitive resin in the address electrode pattern is removed. Further, the glass frit in the address electrode pattern is melted. The molten glass frit is vitrified again after firing. The address electrode 12 is formed by the above process. Here, besides the method of screen printing the address electrode paste, a sputtering method, a vapor deposition method, or the like can be used.

Next, the base dielectric layer 13 is formed. As a material for the base dielectric layer 13, a base dielectric paste containing a dielectric glass frit, a resin, a solvent, and the like is used. First, a base dielectric paste is applied by a screen printing method or the like so as to cover the address electrodes 12 on the rear glass substrate 11 on which the address electrodes 12 are formed with a predetermined thickness. Next, the solvent in the base dielectric paste is removed by a drying furnace. Finally, the base dielectric paste is fired at a predetermined temperature in a firing furnace. That is, the resin in the base dielectric paste is removed. Further, the dielectric glass frit is melted. The molten dielectric glass frit is vitrified again after firing. Through the above steps, the base dielectric layer 13 is formed. Here, other than the method of screen printing the base dielectric paste, a die coating method, a spin coating method, or the like can be used. Further, a film that becomes the base dielectric layer 13 can be formed by CVD (Chemical Vapor Deposition) method or the like without using the base dielectric paste.

Next, the partition walls 4 are formed by photolithography. As a material for the partition 4, a partition paste including a filler, a glass frit for binding the filler, a photosensitive resin, a solvent, and the like is used. First, the barrier rib paste is applied on the underlying dielectric layer 13 with a predetermined thickness by a die coating method or the like. Next, the solvent in the partition wall paste is removed by a drying furnace. Next, the barrier rib paste is exposed through a photomask having a predetermined pattern. Next, the barrier rib paste is developed to form a barrier rib pattern. Finally, the partition pattern is fired at a predetermined temperature in a firing furnace. That is, the photosensitive resin in the partition pattern is removed. Further, the glass frit in the partition wall pattern is melted. The molten glass frit is vitrified again after firing. The partition 4 is formed by the above process. Here, in addition to the photolithography method, a sandblast method or the like can be used.

Next, the phosphor layers 14R, 14G, and 14B are formed. As a material of the phosphor layers 14R, 14G, and 14B, a phosphor paste containing phosphor particles, a binder, a solvent, and the like is used. First, a phosphor paste is applied on the underlying dielectric layer 13 between adjacent barrier ribs 4 and on the side surfaces of the barrier ribs 4 by a dispensing method or the like. Next, the solvent in the phosphor paste is removed by a drying furnace. Finally, the phosphor paste is fired at a predetermined temperature in a firing furnace. That is, the resin in the phosphor paste is removed. The phosphor layers 14R, 14G, and 14B are formed by the above steps. Here, in addition to the dispensing method, a screen printing method or the like can be used.

The back plate 3 is completed through the above steps.

[2-3. Assembly method of front plate 2 and rear plate 3]
First, a sealing material (not shown) is formed around the back plate 3 by a dispensing method. As a material for the sealing material (not shown), a sealing paste containing glass frit, a binder, a solvent, and the like is used. Next, the solvent in the sealing paste is removed by a drying furnace. Next, the front plate 2 and the back plate 3 are arranged to face each other so that the display electrodes 8 and the address electrodes 12 are orthogonal to each other. Next, the periphery of the front plate 2 and the back plate 3 is sealed with glass frit. Finally, a discharge gas containing Ne, Xe or the like is enclosed in the discharge space 15.

[3. Details of Protective Layer 10]
Conventionally, a protective layer containing CaO has the following problems. CaO is chemically unstable compared to MgO. CaO easily reacts with carbon dioxide or moisture in the air, and changes to calcium carbonate (CaCo ₃ ) or calcium hydroxide (Ca (OH) ₂ ). When CaCo ₃ or Ca (OH) ₂ is formed, the secondary electron emission ability of the protective layer is lowered. That is, it is a problem that the driving voltage of the PDP cannot be lowered.

[3-1. First form]
As shown in FIG. 2, in the protective layer 10 of the first form, metal oxide particles 92 are attached on the base layer 91 formed on the dielectric layer 9. As an example, the underlayer 91 is a mixed film of MgO and CaO. As an example, the metal oxide particles 92 are CaMoO ₄ particles.

[3-1-1. Method for Forming Underlayer 91]
For example, the underlayer 91 is formed by an EB (Electron Beam) vapor deposition apparatus. The material is a pellet obtained by sintering single crystal MgO and single crystal CaO. The pellet may further contain Al, Si, or the like as impurities. First, an electron beam is irradiated to the pellet arrange | positioned in the film-forming chamber of EB vapor deposition apparatus. The pellets that have received the energy of the electron beam evaporate. The evaporated MgO and CaO adhere to the dielectric layer 9 of the front glass substrate 5 arranged in the film forming chamber. MgO and CaO deposited on the dielectric layer 9 form a mixed film of MgO and CaO. The mixed film of MgO and CaO covers the dielectric layer 9. The film thickness of the mixed film of MgO and CaO is adjusted so as to be within a predetermined range depending on the intensity of the electron beam, the pressure in the film forming chamber, and the like.

In addition, the concentration of CaO in the base layer 91 is appropriately set in the range of 5 mol% to 40 mol%.

Further, the base layer 91 uses a film containing a metal oxide such as strontium oxide (SrO), barium oxide (BaO), and aluminum oxide (Al ₂ O ₃ ) in addition to the mixed film of MgO and CaO. Can do. A film containing a plurality of types of metal oxides can also be used.

[3-1-2. Method of attaching metal oxide particles 92]
As an example, the metal oxide particles 92 are attached by a slit coater and a drying device.

The slit coater includes a table, a coating head, a table drive system, a laser displacement meter, and the like. The material is a solution in which CaMoO ₄ particles having an average particle diameter of 0.7 to 1.5 μm are dispersed in a diluting solvent at a concentration of 5% by volume. The average particle diameter is a volume cumulative average diameter (D50). In addition, a laser diffraction particle size distribution measuring device MT-3300 (manufactured by Nikkiso Co., Ltd.) was used for measuring the average particle size.

The diluting solvent is, for example, a mixed solvent of 95% by volume of 3-methyl-3-methoxybutanol and 5.0% by volume of α-terpineol. The viscosity of the solution was adjusted to 10 mPa · s. First, the front glass substrate 5 is installed on the table of the slit coater. The front glass substrate 5 is fixed by vacuum chucking on a table. A distance (gap) between the coating head of the slit coater and the front glass substrate 5 is measured by a laser displacement meter or the like. For example, the height of the coating head is adjusted so as to maintain a distance of 100 μm. Furthermore, the coating head moves at a constant speed of 50 mm / s, for example. The solution sent from the solution tank to the coating head is uniformly coated on the front glass substrate 5 so as to have a film thickness of 15 μm. A coating film in which CaMoO ₄ particles are dispersed in a diluent solvent is formed on the base layer 91. CaMoO ₄ particles settle in the coating. The precipitated CaMoO ₄ particles adhere to the base layer 91.

Next, the front glass substrate 5 is transferred to a drying device. As an example, the drying apparatus includes a vacuum chamber, a heater, a table, a vacuum pump, a pressure gauge, and the like. The front glass substrate 5 is placed on a table in a vacuum chamber at atmospheric pressure that is previously maintained at a predetermined temperature by a heater. Thereafter, the vacuum pump exhausts the inside of the vacuum chamber to a predetermined pressure. As the pressure inside the vacuum chamber drops, the diluted solvent is desorbed from the coating film.

As an example, in this embodiment, the vacuum chamber temperature is 70 ° C. to 100 ° C., the pressure is 0.1 Pa to 10 Pa, and the treatment time is 5 min. By the above process, the CaMoO ₄ particles have a coverage ratio of 0.1 to 10% in terms of the area ratio with the base layer 91.

The coverage is the ratio of the area a where the metal oxide particles 92 are adhered in the area of one discharge cell as a ratio of the area b of one discharge cell. That is, it is calculated by the formula of coverage (%) = a / b × 100. As a measuring method, for example, an area corresponding to one discharge cell divided by the barrier ribs 4 is imaged by a camera. Next, the captured image is trimmed to the size of one cell of x × y. Next, the trimmed image is binarized into black and white data. Next, the area a of the black area by the metal oxide particles 92 is obtained based on the binarized data. Finally, the coverage is calculated by the formula a / b × 100.

In addition, since this drying conditions are fluctuate | varied also with the kind of dilution solvent used, the film thickness of a coating film, etc., it can change suitably.

In addition to the slit coater, a screen printing method, a spray method, a spin coating method, a die coating method, or the like can be used to attach the metal oxide particles 92. An organic resin or the like may be added to the dilution solvent. By adding an organic resin, the viscosity of the solution can be increased. When an organic resin is added, it is preferable to add a baking step in order to remove the organic resin.

[3-1-3. Method for Producing Metal Oxide Particle 92]
As an example, a method for producing CaMoO ₄ particles will be described. First, CaCO ₃ powder and molybdenum oxide (MoO ₃ ) powder are mixed. The concentration of the MoO ₃ powder in the mixed powder is appropriately adjusted in the range of 0.5 mol% or more and 10 mol% or less. Next, the mixed powder is fired. The firing temperature is preferably 900 ° C. or higher and 1200 ° C. or lower. The atmosphere during firing is preferably an inert gas such as nitrogen. The top keeping time during firing is preferably about 1 hour.

Note that at least one oxide selected from the group consisting of SrO and BaO can be used instead of CaO. Further, instead of MoO ₃ , oxidation of at least one element selected from the group consisting of vanadium (V), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu) and tungsten (W) Can be used.

That is, at least one element selected from the group consisting of V, Mn, Co, Ni, Cu and W can be used instead of Mo in CaMoO ₄ .

[3-2. Second form]
As shown in FIG. 3, the protective layer 10 of the second form is dotted with metal oxides 95 in the base material 94 formed on the dielectric layer 9. As an example, the base material 94 is a mixed film of MgO and CaO. The metal oxide 95 is CaMoO ₄ as an example.

[3-2-1. Method of forming base material 94 and metal oxide 95]
As an example, the base material 94 and the metal oxide 95 are formed by an EB (Electron Beam) vapor deposition apparatus. The material of the base material 94 is a mixed pellet obtained by sintering single crystal MgO and single crystal CaO. As an example, the material of the metal oxide 95 is CaMoO ₄ pellets. The concentration of CaO in the mixed pellets and CaMoO ₄ pellets is appropriately adjusted in the range of 5 mol% to 40 mol%. The concentration of CaMoO ₄ in the mixed pellets and CaMoO ₄ pellets is appropriately adjusted in the range of 0.5 mol% or more and 10 mol% or less. Al, Si, or the like may be further added to the mixed pellet as impurities.

Incidentally, CaMoO ₄ pellets by sintering CaMoO ₄ particles produced by the method described above is manufactured.

First, an electron beam is irradiated to the mixed pellet and CaMoO ₄ pellet arranged in the film forming chamber of the EB vapor deposition apparatus. The mixed pellets and CaMoO ₄ pellets subjected to the energy of the electron beam evaporate. The evaporated MgO, CaO and CaMoO ₄ adhere on the dielectric layer 9 of the front glass substrate 5 arranged in the film forming chamber. The MgO and CaO deposited on the dielectric layer 9 forms a mixed film of MgO and CaO that is the base material 94. CaMoO ₄ which is the metal oxide 95 enters the base material 94. That is, CaMoO ₄ is scattered in the base material 94. The film thickness of the mixed film of MgO and CaO interspersed with CaMoO ₄ is adjusted so as to fall within a predetermined range depending on the intensity of the electron beam, the pressure in the film forming chamber, and the like.

The base material 94 can be a film containing a metal oxide such as SrO, BaO, Al ₂ O ₃ in addition to a mixed film of MgO and CaO. A film containing a plurality of types of metal oxides can also be used.

Furthermore, at least one element selected from the group consisting of V, Mn, Co, Ni, Cu and W can be used instead of Mo in CaMoO ₄ .

[3-3. Third form]
As shown in FIGS. 4 and 5, the protective layer 10 of the third form includes a mixture of first particles 97, second particles 98, and third particles 99. As an example, the first particles 97 are MgO particles. As an example, the second particles 98 are CaO particles. The third particles 99 are CaMoO ₄ particles as an example.

[3-3-1. Method for Forming First Particle 97, Second Particle 98, and Third Particle 99]
The protective layer 10 composed of the first particles 97, the second particles 98, and the third particles 99 is formed on the dielectric layer 9 by an application method as an example. As the first particles 97, single crystal MgO particles having an average particle diameter of 10 nm to 100 nm (hereinafter referred to as nano MgO particles) are used. As the second particles 98, single crystal CaO particles having an average particle diameter of 10 nm to 100 nm (hereinafter referred to as nano CaO particles) are used. As the third particles 99, CaMoO ₄ particles having an average particle diameter of 10 nm to 100 nm (hereinafter referred to as nano CaMoO ₄ particles) are used.

Nano MgO particles are produced by a vapor phase generation method. Specifically, magnesium vapor is generated by vaporizing magnesium under high energy such as plasma or electron beam. Next, the magnesium vapor is cooled in a short time by a cooling gas (for example, argon gas) containing oxygen gas, thereby producing nano-MgO particles.

Nano CaO particles and nano CaMoO ₄ particles are produced in the same manner.

The nano-particle paste as a coating material is manufactured by kneading nano-mixed particles in which nano-MgO particles, nano-CaO particles and nano-CaMoO ₄ particles are mixed with a vehicle having a weight equivalent to that of the nano-mixed particles. . As an example, the vehicle is a mixture of 60% by weight of terpineol, 30% by weight of butyl carbitol acetate, and 10% by weight of an acrylic resin.

Next, a nanoparticle paste is applied on the dielectric layer 9 by a screen printing method or the like. The nanoparticle paste applied on the dielectric layer 9 is dried and fired to remove the vehicle. The protective layer 10 composed of nano-MgO particles, nano-CaO particles, and nano-CaMoO ₄ particles is formed by the above process.

In addition, the density | concentration of the nano CaO particle in the protective layer 10 is suitably adjusted in 5 mol% or more and 40 mol% or less. The concentration of CaMoO ₄ in the protective layer 10 is appropriately adjusted in the range of 0.5 mol% or more and 10 mol% or less.

The first particles 97 and the second particles 98 can use metal oxides such as SrO, BaO, and Al ₂ O ₃ in addition to MgO. A plurality of types of metal oxides can also be used.

Further, the third particles 99 can use at least one element selected from the group consisting of V, Mn, Co, Ni, Cu, and W instead of Mo in CaMoO ₄ .

[4. Summary]
A PDP 1 according to the present embodiment includes a front plate 2 and a back plate 3 arranged to face the front plate 2. The front plate 2 includes a display electrode 8, a dielectric layer 9 that covers the display electrode 8, and a protective layer 10 that covers the dielectric layer 9.

The protective layer 10 according to the first embodiment includes a base layer 91 and metal oxide particles 92 dispersedly disposed on the base layer 91. The metal oxide particle 92 is a compound of at least one element selected from the group consisting of V, Mn, Co, Ni, Cu, Mo, and W and Ca and O. Furthermore, the underlayer 91 preferably has at least one oxide selected from the group consisting of CaO, SrO, and BaO.

The protective layer 10 according to the second embodiment includes MgO as the base material 94 and at least one element selected from the group consisting of V, Mn, Co, Ni, Cu, Mo, and W as the metal oxide 95, and Ca and O. And a compound. Furthermore, the protective layer 10 preferably has at least one oxide selected from the group consisting of CaO, SrO and BaO in the base material 94.

The protective layer 10 of the third form includes MgO particles as the first particles 97, Ca and at least one element selected from the group consisting of V, Mn, Co, Ni, Cu, Mo, and W as the third particles. Compound particles with O. Furthermore, the protective layer 10 preferably has at least one oxide particle selected from the group consisting of CaO, SrO and BaO as the second particle 98.

According to the X-ray diffraction analysis, the peak intensity of CaCo ₃ and Ca (OH) ₂ is smaller in the protective layer 10 according to the present embodiment than in the conventional protective layer made of a mixed film of MgO and CaO. Was confirmed. That is, in the protective layer 10 according to the present embodiment, the alteration is suppressed as compared with the conventional protective layer. This is because the compound of Ca and O and at least one element selected from the group consisting of V, Mn, Co, Ni, Cu, Mo and W, which the protective layer 10 has, suppresses the alteration of calcium. This is probably because of this.

The PDP 1 having the protective layer 10 according to the present embodiment was able to reduce the sustain voltage as compared with the PDP having the conventional protective layer.

The technique disclosed here can realize a PDP capable of reducing the sustain voltage. Therefore, it is useful for a display device with a large screen.

1 PDP
2 Front plate 3 Back plate 4 Bulkhead 5 Front glass substrate 6

Scan electrode

6a, 7a

Transparent electrode

6b, 7b Bus electrode 7 Sustain electrode 8 Display electrode 9 Dielectric layer 10 Protective layer 11 Rear glass substrate 12 Address electrode 13

Base dielectric layer

14R, 14G, 14B Phosphor layer 15 Discharge space 91 Underlayer 92 Metal oxide particle 94 Base material 95 Metal oxide 97 First particle 98 Second particle 99 Third particle

Claims

A front plate,
A back plate disposed opposite to the front plate,
The front plate includes a display electrode, a dielectric layer covering the display electrode, and a protective layer covering the dielectric layer,
The protective layer includes MgO, at least one element selected from the group consisting of V, Mn, Co, Ni, Cu, Mo, and W, and a compound of Ca and O.
Plasma display panel.
The protective layer further includes at least one oxide selected from the group consisting of CaO, SrO and BaO.
The plasma display panel according to claim 1.