JP2011048918A - Plasma display panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain a PDP (plasma display panel) allowing low-voltage driving with les luminance reduction. <P>SOLUTION: A first substrate 2 of the PDP includes a substrate 3; a display electrode 6 formed on the substrate 3; a dielectric layer 8 formed to cover the display electrode 6; and a protective film 9 formed on the dielectric layer 8 and exposed to a discharge space. The protective film 9 contains two oxides of a magnesium oxide, a calcium oxide, a strontium oxide and a barium oxide. In the protective film 9, a peak is present at a diffraction angle, between a diffraction angle at which a peak generates when only one oxide of two oxides is analyzed in X-ray diffraction analysis on a specific azimuth surface and a diffraction angle at which a peak generates, when only the other oxide is analyzed. The protective film 9 is formed, such that the percentage content of one of two oxides which is larger in molecular weight than the other is gradually reduced from the discharge space side, down to at least a predetermined depth. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a plasma display panel used for a display device or the like.

  A plasma display panel (hereinafter referred to as a PDP) can realize a high definition and a large screen, and thus a 100-inch class television or the like has been commercialized. In recent years, PDP has been applied to high-definition televisions that have more than twice the number of scanning lines compared to the conventional NTSC system. In response to energy problems, efforts to further reduce power consumption and environmental issues There is also a growing demand for PDPs that do not contain lead components in consideration of the above.

  A PDP basically includes a front plate and a back plate. The front plate is a glass substrate of sodium borosilicate glass produced by the float process, a display electrode composed of a striped transparent electrode and a bus electrode formed on one main surface of the glass substrate, A dielectric layer that covers the display electrode and functions as a capacitor, and a protective film that includes magnesium oxide (MgO) formed on the dielectric layer.

  On the other hand, the back plate is a glass substrate, stripe-shaped address electrodes formed on one main surface thereof, a base dielectric layer covering the address electrodes, a partition formed on the base dielectric layer, The phosphor layer is formed between the barrier ribs and emits red, green and blue light.

  The front plate and the back plate are hermetically sealed with their electrode forming surfaces facing each other, and a discharge gas of neon (Ne) -xenon (Xe) is sealed at a pressure of 400 Torr to 600 Torr in a discharge space partitioned by a partition wall. ing. PDP discharges by selectively applying a video signal voltage to the display electrodes, and the ultraviolet rays generated by the discharge excite each color phosphor layer to emit red, green, and blue light, thereby realizing color image display is doing.

  In addition, such a PDP driving method includes an initialization period in which wall charges are adjusted so that writing is easy, a writing period in which writing discharge is performed according to an input image signal, and a discharge space in which writing is performed. A driving method having a sustain period in which display is performed by generating a sustain discharge is generally used. A period (subfield) obtained by combining these periods is repeated a plurality of times within a period (one field) corresponding to one frame of an image, thereby performing PDP gradation display.

  In such a PDP, the role of the protective film formed on the dielectric layer of the front plate is to protect the dielectric layer from ion bombardment due to discharge and to emit initial electrons for generating address discharge. In this case, secondary electrons are emitted during discharge to promote discharge.

  As a conventional technique, a technique for suppressing a discharge voltage by changing a material of a protective film and improving secondary electron emission characteristics is disclosed (for example, Patent Document 1).

JP 2003-1773738 A

  However, the conventional protective film has a problem that it does not realize the property of suppressing gas adsorption (hereinafter also referred to as gas adsorbing property) while maintaining high secondary electron emission capability. Of the protective films of the prior art, materials with high secondary electron emission ability have poor gas adsorption (gas is easily adsorbed), and materials with good gas adsorption (difficult to adsorb gas) have secondary electron emission ability. Low.

  In response to this problem, the inventors have invented a new PDP. In the protective film of this PDP, in the X-ray diffraction analysis for a specific orientation plane, a diffraction angle at which a peak is generated when one oxide simple substance of the two oxides is analyzed, and the other oxide simple substance are analyzed. It is characterized in that there is a peak at a diffraction angle between the diffraction angle at which the peak sometimes occurs. According to such a configuration, the secondary electron emission characteristics in the protective layer can be improved and low voltage driving can be realized. In general, when the Xe gas partial pressure of the discharge gas is increased in order to increase the luminance, the discharge start voltage is increased. However, high luminance and low voltage driving can be realized by using the protective film described above and a discharge gas having a large Xe gas partial pressure.

  As a result of further research on the PDP, the present inventors have found a problem that the luminance decreases as the discharge time elapses. For example, when the protective film is a complex oxide composed of magnesium oxide and calcium oxide, the sputtering rate for neon (Ne) in the discharge gas is higher for magnesium oxide than for calcium oxide. For example, as shown in FIG. Over time, the content of calcium oxide on the surface of the protective film increases according to the amount sputtered. Usually, the discharge center portion is most sputtered, so that the discharge center portion has the highest calcium oxide concentration. As a result, the discharge width decreases as the discharge time elapses, causing a decrease in luminance. In general, the smaller the molecular weight, the higher the sputtering rate.

  The present invention has been made in view of such a problem, and an object of the present invention is to realize a PDP that can be driven at a low voltage and has little reduction in luminance.

In order to achieve the above object, a PDP of the present invention includes a first substrate and a second substrate disposed to face the first substrate, and the gap is between the first substrate and the second substrate. A PDP having a discharge space filled with a discharge gas,
The first substrate is
A substrate,
Display electrodes formed on the substrate;
A dielectric layer formed to cover the display electrode;
A protective film formed on the dielectric layer and exposed to the discharge space;
The second substrate is
An address electrode formed in a direction crossing the direction of the display electrode;
Partition walls that partition the discharge space,
The protective film includes two oxides of magnesium oxide, calcium oxide, strontium oxide, and barium oxide,
In the X-ray diffraction analysis of the specific orientation plane, the protective film has a diffraction angle at which a peak is generated when one oxide simple substance of the two oxides is analyzed, and when the other oxide simple substance is analyzed. There is a peak at a diffraction angle between the diffraction angle at which the peak occurs,
The protective film is formed such that the content of the oxide having the larger molecular weight of the two oxides decreases in order from the discharge space side to at least a predetermined depth.

  According to such a configuration, the secondary electron emission characteristics in the protective film can be improved, low voltage driving can be realized, and the composition of the protective film surface hardly changes, so that high luminance, low voltage driving, and high luminance maintenance ratio are achieved. PDP can be realized.

  According to the present invention, it is possible to realize a PDP that can be driven at a low voltage with high luminance display performance and that has little reduction in luminance.

The perspective view which shows the structure of PDP in embodiment of this invention Sectional drawing which shows the structure of the front plate of the PDP The figure which shows the X-ray-diffraction result in the protective film of the PDP The figure which shows an example of the CaO density | concentration after 1000-hour discharge of the protective film which consists of MgO-CaO complex oxides

[Embodiment 1]
(Configuration of PDP)
Hereinafter, a PDP according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view showing the structure of a PDP according to an embodiment of the present invention. The basic structure of the PDP is the same as that of a general AC surface discharge type PDP. As shown in FIG. 1, the PDP 1 has a front plate 2 made of a front glass substrate 3 and a back plate 10 made of a back glass substrate 11 facing each other, and its outer peripheral portion is sealed with a glass frit or the like. The material is hermetically sealed. The discharge space 16 inside the sealed PDP 1 is filled with a discharge gas such as Xe and Ne at a pressure of 400 Torr to 600 Torr.

  On the front glass substrate 3 of the front plate 2, a pair of strip-shaped display electrodes 6 each composed of the scanning electrodes 4 and the sustain electrodes 5 and a plurality of black stripes (light shielding layers) 7 are arranged in parallel to each other. A dielectric layer 8 is formed on the front glass substrate 3 so as to cover the display electrodes 6 and the light-shielding layer 7 and retain a charge, thereby functioning as a capacitor. A protective film 9 is further formed thereon. .

  On the back glass substrate 11 of the back plate 10, a plurality of strip-like address electrodes 12 are arranged in parallel to each other in a direction orthogonal to the direction of the scanning electrodes 4 and the sustain electrodes 5 of the front plate 2, The dielectric layer 13 is covered. Further, a partition wall 14 having a predetermined height is formed on the base dielectric layer 13 between the address electrodes 12 to divide the discharge space 16. In each groove between the barrier ribs 14, a phosphor layer 15 that emits red, green, and blue light by ultraviolet rays is sequentially formed. A discharge space is formed at a position where the scan electrode 4 and the sustain electrode 5 intersect with the address electrode 12, and a discharge space having red, green, and blue phosphor layers 15 arranged in the direction of the display electrode 6 is used for color display. Become a pixel.

FIG. 2 is a cross-sectional view showing the configuration of the front plate 2 of the PDP 1 in the embodiment of the present invention, and FIG. 2 is shown upside down from FIG. As shown in FIG. 2, a display electrode 6 and a light shielding layer 7 including scanning electrodes 4 and sustain electrodes 5 are formed in a pattern on a front glass substrate 3 manufactured by a float method or the like. Scan electrode 4 and sustain electrode 5 are made of transparent electrodes 4a and 5a made of indium tin oxide (ITO), tin oxide (SnO ₂ ), and the like, and metal bus electrodes 4b and 5b formed on transparent electrodes 4a and 5a, respectively. It is comprised by. The metal bus electrodes 4b and 5b are used for the purpose of imparting conductivity in the longitudinal direction of the transparent electrodes 4a and 5a, and are formed of a conductive material whose main component is a material such as silver (Ag).

  The dielectric layer 8 includes a first dielectric layer 81 provided on the front glass substrate 3 so as to cover the transparent electrodes 4a and 5a, the metal bus electrodes 4b and 5b, and the light shielding layer 7, and a first dielectric. The second dielectric layer 82 formed on the layer 81 has at least two layers, and the protective film 9 is further formed on the second dielectric layer 82.

  The protective film 9 is formed of a plurality of layers. Here, a case of two layers will be described. The protective film 9 includes a first protective film 91a formed on the second dielectric layer 82 of the dielectric layer 8, and a second protective film 91b formed on the first protective film 91a. Aggregated particles 92 in which a plurality of magnesium oxide (MgO) crystal particles 92 a are aggregated adhere to the protective film 9. Here, the first protective films 91a and 91b are formed of a metal oxide composed of magnesium oxide and calcium oxide. In the X-ray diffraction analysis on the surface of the protective film 9, the metal oxide is between the diffraction angle at which the peak of magnesium oxide alone occurs and the diffraction angle at which the peak of calcium oxide alone in the same orientation as the peak of magnesium oxide alone is generated. There is a peak. The second protective film 91b has a higher calcium oxide content than the first protective film 91a. Note that the first protective film 91a may be magnesium oxide containing no calcium oxide. When the protective film 9 has only one layer, calcium oxide has a lower sputtering rate with respect to Xe. Therefore, as the discharge time elapses, the calcium oxide concentration at the discharge center of the protective film 9 increases, and within the discharge area of the protective film 9. As a result, the discharge width is reduced, resulting in a decrease in discharge luminance. However, if the calcium oxide concentration of the protective film 9 decreases as the dielectric side decreases as in the present embodiment, the sputtering progresses even if the calcium oxide concentration in the region where the sputtering progresses increases as the discharge time elapses. Since a region having a low calcium oxide concentration is reached from the region, the difference in the calcium oxide concentration in the discharge area of the protective film 9 is reduced, and as a result, a decrease in discharge width can be prevented and a decrease in luminance can be suppressed. .

(PDP manufacturing method)
Next, a method for manufacturing such a PDP 1 will be described.

  First, the scan electrode 4, the sustain electrode 5, and the light shielding layer 7 are formed on the front glass substrate 3. Transparent electrodes 4a and 5a and metal bus electrodes 4b and 5b constituting scan electrode 4 and sustain electrode 5 are formed by patterning using a photolithography method or the like. The transparent electrodes 4a and 5a are formed using a thin film process or the like, and the metal bus electrodes 4b and 5b are solidified by baking a paste containing a silver (Ag) material at a predetermined temperature. Similarly, the light shielding layer 7 is also formed by screen printing a paste containing a black pigment or by forming a black pigment on the entire surface of the glass substrate and then patterning and baking using a photolithography method.

  Next, a dielectric paste is applied on the front glass substrate 3 by a die coating method or the like so as to cover the scan electrode 4, the sustain electrode 5, and the light shielding layer 7, thereby forming a dielectric paste (dielectric material) layer. After the dielectric paste is applied, the surface of the applied dielectric paste is leveled by leaving it to stand for a predetermined time, so that a flat surface is obtained. Thereafter, the dielectric paste layer is formed by baking and solidifying the dielectric paste layer to cover the scan electrode 4, the sustain electrode 5, and the light shielding layer 7. The dielectric paste is a paint containing a dielectric material such as glass powder, a binder and a solvent.

  Next, a protective film 9 is formed on the dielectric layer 8.

  In the present embodiment, the protective film 9 is composed of a first protective film 91a formed on the dielectric layer 8, and a second protective film 91b formed on the first protective film 91a, and Each is formed of a metal oxide containing magnesium oxide and calcium oxide. And it forms with the thin film film-forming method using the pellet of the independent material of magnesium oxide (MgO) and calcium oxide (CaO), and the pellet which mixed those materials. As a thin film forming method, a known method such as an electron beam evaporation method, a sputtering method, or an ion plating method can be applied. As an example, 1 Pa is considered as the upper limit of the pressure that can actually be taken in the sputtering method and 0.1 Pa in the electron beam evaporation method, which is an example of the evaporation method.

  Further, as the atmosphere during the formation of the first protective film 91a and the second protective film 91b, the atmosphere during the film formation is adjusted in a sealed state shut off from the outside in order to prevent moisture adhesion and adsorption of impurities. Thus, a protective film made of a metal oxide having predetermined electron emission characteristics can be formed.

  Next, the aggregated particles 92 of the magnesium oxide (MgO) crystal particles 92a formed on the protective film 9 will be described. These crystal particles 92a can be manufactured by any one of the following vapor phase synthesis method or precursor baking method.

  In the gas phase synthesis method, a magnesium metal material having a purity of 99.9% or more is heated in an atmosphere filled with an inert gas, and a small amount of oxygen is introduced into the atmosphere to directly oxidize magnesium, thereby oxidizing the material. Magnesium (MgO) crystal particles 92a can be produced.

On the other hand, in the precursor firing method, the crystal particles 92a can be produced by the following method. In the precursor firing method, a magnesium oxide (MgO) precursor is uniformly fired at a high temperature of 700 ° C. or higher, and this is gradually cooled to obtain magnesium oxide (MgO) crystal particles 92a. Examples of the precursor include magnesium alkoxide (Mg (OR) ₂ ), magnesium acetylacetone (Mg (acac) ₂ ), magnesium hydroxide (Mg (OH) ₂ ), magnesium carbonate (MgCO ₂ ), and magnesium chloride (MgCl ₂ ). ), Magnesium sulfate (MgSO ₄ ), magnesium nitrate (Mg (NO ₃ ) ₂ ), or magnesium oxalate (MgC ₂ O ₄ ) can be selected. Depending on the selected compound, it may usually take the form of a hydrate, but such a hydrate may be used.

  These compounds are adjusted so that the purity of magnesium oxide (MgO) obtained after calcination is 99.95% or more, preferably 99.98% or more. If these compounds contain a certain amount or more of various impurity elements such as alkali metals, B, Si, Fe, and Al, unnecessary interparticle adhesion and sintering occur during heat treatment, and highly crystalline magnesium oxide ( This is because it is difficult to obtain MgO) crystal particles. For this reason, it is necessary to adjust the precursor in advance by removing the impurity element.

  The magnesium oxide (MgO) crystal particles 92a obtained by any of the above methods are dispersed in a solvent, and the dispersion is dispersed and dispersed on the surface of the protective film 9 by spraying, screen printing, electrostatic coating, or the like. Let Thereafter, the solvent is removed through a drying / firing process, and the magnesium oxide (MgO) crystal particles 92 a can be fixed on the surface of the protective film 9.

  Through such a series of steps, predetermined components (scanning electrode 4, sustaining electrode 5, light shielding layer 7, dielectric layer 8, and protective film 9) are formed on front glass substrate 3, and front plate 2 is completed.

  On the other hand, the back plate 10 is formed as follows. First, the structure for the address electrode 12 is formed by a method of screen printing a paste containing silver (Ag) material on the rear glass substrate 11 or a method of patterning using a photolithography method after forming a metal film on the entire surface. A material layer to be a material is formed. Thereafter, the address electrode 12 is formed by firing at a predetermined temperature. Next, a dielectric paste is applied on the rear glass substrate 11 on which the address electrodes 12 are formed by a die coating method or the like so as to cover the address electrodes 12 to form a dielectric paste layer. Thereafter, the base dielectric layer 13 is formed by firing the dielectric paste layer. The dielectric paste is a paint containing a dielectric material such as glass powder, a binder and a solvent.

  Next, a partition wall forming paste containing a partition wall material is applied on the base dielectric layer 13 and patterned into a predetermined shape to form a partition wall material layer. Then, the partition 14 is formed by baking at a predetermined temperature. Here, as a method of patterning the partition wall paste applied on the base dielectric layer 13, a photolithography method or a sand blast method can be used. Then, the phosphor layer 15 is formed by applying and baking a phosphor paste containing a phosphor material on the base dielectric layer 13 between the adjacent barrier ribs 14 and on the side surfaces of the barrier ribs 14. Through the above steps, the back plate 10 having predetermined components on the back glass substrate 11 is completed.

  A front plate 2 and a rear plate 10 having predetermined constituent members are arranged so as to face each other so that the scanning electrodes 4 and the address electrodes 12 are orthogonal to each other, and the periphery thereof is sealed with a glass frit, and xenon (Xe ) And neon (Ne) and the like are enclosed, and the PDP 1 is completed.

Here, the first dielectric layer 81 and the second dielectric layer 82 constituting the dielectric layer 8 of the front plate 2 will be described in detail. The dielectric material of the first dielectric layer 81 is composed of the following material composition. That is, 20 wt% to 40 wt% of bismuth oxide (Bi ₂ O ₃ ), 0.5 wt% to 12 wt.% Of at least one selected from calcium oxide (CaO), strontium oxide (SrO), and barium oxide (BaO). Contains 0.1% by weight to 7% by weight of at least one selected from molybdenum oxide (MoO ₃ ), tungsten oxide (WO ₃ ), cerium oxide (CeO ₂ ), and manganese dioxide (MnO ₂ ). .

In place of molybdenum oxide (MoO ₃ ), tungsten oxide (WO ₃ ), cerium oxide (CeO ₂ ), manganese dioxide (MnO ₂ ), copper oxide (CuO), chromium oxide (Cr ₂ O ₃ ), cobalt oxide At least one selected from (Co ₂ O ₃ ), vanadium oxide (V ₂ O ₇ ), and antimony oxide (Sb ₂ O ₃ ) may be contained in an amount of 0.1 wt% to 7 wt%.

Further, as components other than the above, zinc oxide (ZnO) is 0 wt% to 40 wt%, boron oxide (B ₂ O ₃ ) is 0 wt% to 35 wt%, and silicon oxide (SiO ₂ ) is 0 wt% to A material composition that does not contain a lead component, such as 15 wt% and aluminum oxide (Al ₂ O ₃ ) 0 wt% to 10 wt% may be included.

  A dielectric material powder is produced by pulverizing a dielectric material composed of these composition components with a wet jet mill or a ball mill so as to have a particle size of 0.5 μm to 2.5 μm. Next, 55 wt% to 70 wt% of the dielectric material powder and 30 wt% to 45 wt% of the binder component are well kneaded with three rolls to paste for the first dielectric layer 81 for die coating or printing. Is made.

  The binder component is ethyl cellulose, terpineol containing 1% to 20% by weight of acrylic resin, or butyl carbitol acetate. In the paste, dioctyl phthalate, dibutyl phthalate, triphenyl phosphate, and tributyl phosphate are added as plasticizers as needed, and glycerol monooleate, sorbitan sesquioleate, and homogenol (Kao Corporation) as dispersants. The printing property may be improved as a paste by adding a phosphate ester of an alkyl allyl group, etc.

  Next, using this first dielectric layer paste, the front glass substrate 3 is printed by a die coat method or a screen printing method so as to cover the display electrode 6 and dried, and then slightly higher than the softening point of the dielectric material. The first dielectric layer 81 is formed by firing at a temperature of 575 ° C. to 590 ° C.

Next, the second dielectric layer 82 will be described. The dielectric material of the second dielectric layer 82 is composed of the following material composition. That is, bismuth oxide (Bi ₂ O ₃ ) is 11 wt% to 20 wt%, and at least one selected from calcium oxide (CaO), strontium oxide (SrO), and barium oxide (BaO) is 1.6 wt%. It contains ˜21 wt%, and contains 0.1 wt% to 7 wt% of at least one selected from molybdenum oxide (MoO ₃ ), tungsten oxide (WO ₃ ), and cerium oxide (CeO ₂ ).

In place of molybdenum oxide (MoO ₃ ), tungsten oxide (WO ₃ ), and cerium oxide (CeO ₂ ), copper oxide (CuO), chromium oxide (Cr ₂ O ₃ ), cobalt oxide (Co ₂ O ₃ ), At least one selected from vanadium oxide (V ₂ O ₇ ), antimony oxide (Sb ₂ O ₃ ), and manganese oxide (MnO ₂ ) may be contained in an amount of 0.1 wt% to 7 wt%.

Further, as components other than the above, zinc oxide (ZnO) is 0 wt% to 40 wt%, boron oxide (B ₂ O ₃ ) is 0 wt% to 35 wt%, and silicon oxide (SiO ₂ ) is 0 wt% to A material composition that does not contain a lead component, such as 15 wt% and aluminum oxide (Al ₂ O ₃ ) 0 wt% to 10 wt% may be included.

  A dielectric material powder is produced by pulverizing a dielectric material composed of these composition components with a wet jet mill or a ball mill so as to have a particle size of 0.5 μm to 2.5 μm. Next, 55 wt% to 70 wt% of the dielectric material powder and 30 wt% to 45 wt% of the binder component are well kneaded with three rolls to obtain a second dielectric layer paste for die coating or printing. Make it. The binder component is ethyl cellulose, terpineol containing 1% to 20% by weight of acrylic resin, or butyl carbitol acetate. In addition, dioctyl phthalate, dibutyl phthalate, triphenyl phosphate and tributyl phosphate are added to the paste as needed, and glycerol monooleate, sorbitan sesquioleate, homogenol (Kao Corporation) as a dispersant. The printability may be improved by adding a phosphoric ester of an alkyl allyl group or the like.

  Next, using this second dielectric layer paste, printing is performed on the first dielectric layer 81 by screen printing or die coating, followed by drying, and then a temperature slightly higher than the softening point of the dielectric material is 550 ° C. Bake at 590 ° C.

The film thickness of the dielectric layer 8 is preferably set to 41 μm or less in total of the first dielectric layer 81 and the second dielectric layer 82 in order to ensure visible light transmittance. The first dielectric layer 81 has a bismuth oxide (Bi ₂ O ₃ ) content of the second dielectric layer 82 in order to suppress the reaction of the metal bus electrodes 4b and 5b with silver (Ag). It is more than the content of (Bi ₂ O ₃ ) and is 20 wt% to 40 wt%. Therefore, since the visible light transmittance of the first dielectric layer 81 is lower than the visible light transmittance of the second dielectric layer 82, the film thickness of the first dielectric layer 81 is set to the film thickness of the second dielectric layer 82. It is thinner.

The second dielectric layer 82 is less likely to be colored when the content of bismuth oxide (Bi ₂ O ₃ ) is 11 wt% or less, but bubbles are likely to be generated in the second dielectric layer 82. Therefore, it is not preferable. On the other hand, if the content exceeds 40% by weight, coloration tends to occur, and the transmittance decreases.

  In addition, the smaller the film thickness of the dielectric layer 8, the more remarkable the effect of improving the luminance and reducing the discharge voltage. Therefore, it is desirable to set the film thickness as small as possible within the range where the withstand voltage does not decrease. From such a viewpoint, in the embodiment of the present invention, the thickness of the dielectric layer 8 is set to 41 μm or less, the first dielectric layer 81 is set to 5 μm to 15 μm, and the second dielectric layer 82 is set to 20 μm to 36 μm. Yes.

  The PDP manufactured in this way has little coloring phenomenon (yellowing) of the front glass substrate 3 even when an Ag material is used for the display electrode 6, and there is no generation of bubbles in the dielectric layer 8. It has been confirmed that the dielectric layer 8 excellent in withstand voltage performance is realized.

Next, in the PDP according to the embodiment of the present invention, the reason why yellowing and generation of bubbles in the first dielectric layer 81 are suppressed by these dielectric materials will be considered. That is, by adding molybdenum oxide (MoO ₃ ) or tungsten oxide (WO ₃ ) to dielectric glass containing bismuth oxide (Bi ₂ O ₃ ), Ag ₂ MoO ₄ , Ag ₂ Mo ₂ O ₇ , Ag ₂ are added. It is known that compounds such as Mo ₄ O ₁₃ , Ag ₂ WO ₄ , Ag ₂ W ₂ O ₇ , and Ag ₂ W ₄ O ₁₃ are easily formed at a low temperature of 580 ° C. or lower. In the present embodiment, since the firing temperature of the dielectric layer 8 is 550 ° C. to 590 ° C., silver ions (Ag ⁺ ) diffused into the dielectric layer 8 during firing are molybdenum oxide in the dielectric layer 8. It reacts with (MoO), tungsten oxide (WO), cerium oxide (CeO ₂ ), and manganese oxide (MnO ₂ ) to produce a stable compound and stabilize it. That is, since silver ions (Ag ⁺ ) are stabilized without being reduced, they do not aggregate to form a colloid. Therefore, the stabilization of silver ions (Ag ⁺ ) reduces the generation of oxygen accompanying the colloidalization of silver (Ag), thereby reducing the generation of bubbles in the dielectric layer 8.

On the other hand, in order to make these effects effective, in a dielectric glass containing bismuth oxide (Bi ₂ O ₃ ), molybdenum oxide (MoO ₃ ), tungsten oxide (WO ₃ ), cerium oxide (CeO ₂ ), oxidation The content of manganese (MnO ₂ ) is preferably 0.1% by weight or more, more preferably 0.1% by weight or more and 7% by weight or less. In particular, when the amount is less than 0.1% by weight, the effect of suppressing yellowing is small.

  That is, the dielectric layer 8 of the PDP in the embodiment of the present invention suppresses the yellowing phenomenon and the generation of bubbles in the first dielectric layer 81 in contact with the metal bus electrodes 4b and 5b made of Ag material. High light transmittance is realized by the second dielectric layer 82 provided on the layer 81. As a result, it is possible to realize a PDP having a high transmittance with very few bubbles and yellowing as the entire dielectric layer 8.

(Details of protective film)
Next, the detail of the protective film 9 in this Embodiment is demonstrated.

  In the present embodiment, the first protective film 91a and the second protective film 91b are made of metal oxide formed by electron beam evaporation using magnesium oxide (MgO) and calcium oxide (CaO) as raw materials. Yes. Further, the protective film 9 includes a diffraction angle at which a peak occurs when analyzing magnesium oxide (MgO) alone in X-ray diffraction analysis, and calcium oxide (CaO) alone having the same orientation as the peak of magnesium oxide (MgO) alone. There is a peak between the diffraction angle at which the peak occurs when analyzed.

  FIG. 3 shows the results of X-ray diffraction analysis of the first protective film 91a or the second protective film 91b and the results of X-ray diffraction analysis of magnesium oxide (MgO) and calcium oxide (CaO) alone in this embodiment. FIG.

  In FIG. 3, the horizontal axis represents the Bragg diffraction angle (2θ), and the vertical axis represents the intensity of the X-ray diffraction wave. The unit of the diffraction angle is shown in degrees when one round is 360 degrees, and the intensity is shown in an arbitrary unit. In the figure, each crystal orientation plane is shown in parentheses. As shown in FIG. 3, taking the (111) plane of the crystal orientation as an example, the diffraction angle of calcium oxide (CaO) alone has a peak at 32.2 degrees, and the magnesium oxide (MgO) alone It can be seen that the diffraction angle has a peak at 36.9 degrees.

  Similarly, in the crystal orientation plane (200) plane, calcium oxide (CaO) simple substance has a peak at 37.3 degrees, and magnesium oxide (MgO) simple substance has a peak at 42.8 degrees. .

  On the other hand, an X-ray diffraction result of the protective film 9 in the present embodiment formed by a thin film deposition method using pellets of a single material of magnesium oxide (MgO) or calcium oxide (CaO) or a pellet obtained by mixing these materials. These are the points A and B in FIG.

  That is, the X-ray diffraction results of the metal oxides constituting the first protective film 91a or the second protective film 91b according to the embodiment of the present invention show that the diffraction angles of the single crystals are each in the crystal orientation plane (111) plane. There is a peak at a diffraction angle of 36.1 degrees, which is the point A between, and on the crystal orientation plane (200), there is a peak at a diffraction angle of 41.1 degrees, which is the point B between the single diffraction angles. is doing.

  Note that the crystal orientation planes of the first protective film 91a and the second protective film 91b are determined by the film forming conditions and the ratio of magnesium oxide (MgO) and calcium oxide (CaO). In this form, there is a peak between the peaks of each single material.

  The energy level of the metal oxide having such characteristics also exists between magnesium oxide (MgO) and calcium oxide (CaO). As a result, the protective film 9 exhibits better secondary electron emission characteristics compared to magnesium oxide (MgO) alone. Then, the discharge sustaining voltage is lowered. Therefore, particularly when the partial pressure of xenon (Xe) as the discharge gas is increased in order to increase the luminance, it is possible to reduce the discharge voltage and realize a low-voltage and high-luminance PDP.

  For example, when a mixed gas of xenon (Xe) and neon (Ne) is used as the discharge gas, the luminance increases by about 30% when the partial pressure of xenon (Xe) is changed from 10% to 15%. However, when the protective film 9 made of magnesium oxide (MgO) alone is used, the discharge sustaining voltage is simultaneously increased by about 10%. On the other hand, in the present embodiment, by using the protective film 9 having the above-described characteristics, the discharge sustaining voltage can be reduced by about 10%.

  When the discharge gas is all xenon (Xe), that is, when the partial pressure of xenon (Xe) is 100%, the luminance increases by about 180%, but at the same time, the discharge sustaining voltage increases by about 35%. Exceeding normal operating voltage range. However, when the protective film 9 in the present embodiment is used, the sustaining voltage can be reduced by about 20%. Therefore, the discharge sustain voltage within the normal operation range can be obtained. As a result, a high-luminance and low-voltage driven PDP can be realized.

  Note that the reason why the protective film 9 in this embodiment can reduce the sustaining voltage is considered to be due to the band structure of each metal oxide.

  That is, the depth from the vacuum level of the valence band of calcium oxide (CaO) exists in a shallower region than that of magnesium oxide (MgO). Therefore, when driving the PDP, the number of electrons emitted by the Auger effect when the electrons present at the energy level of calcium oxide (CaO) transition to the ground state of the xenon (Xe) ion is magnesium oxide (MgO ) Is expected to increase compared to

  In addition, the protective film 9 in the present embodiment is composed mainly of magnesium oxide (MgO) and calcium oxide (CaO), and in X-ray diffraction analysis, the main component magnesium oxide (MgO) is oxidized and oxidized. A peak exists between the diffraction angles of calcium (CaO) alone.

  Regarding the energy level of the metal oxide film, it has a synthesized property of magnesium oxide (MgO) and calcium oxide (CaO). Therefore, the energy level of the protective film 9 also exists between magnesium oxide (MgO) and calcium oxide (CaO) alone, and the amount of energy acquired by other electrons due to the Auger effect is released beyond the vacuum level. Sufficient amount. As a result, the protective film 9 can exhibit better secondary electron emission characteristics as compared with magnesium oxide (MgO) alone, and as a result, the discharge sustaining voltage can be reduced.

  In addition, when calcium oxide (CaO) single-piece | unit was used as the protective film, since reaction was high, calcium oxide was easy to react with an impurity, and had the subject that electron emission performance fell for it. However, as described in this embodiment, the metal oxide structure of magnesium oxide (MgO) and calcium oxide (CaO) can reduce the reactivity and solve these problems.

  Furthermore, each layer of the protective film 9 in the present embodiment is mainly composed of calcium oxide (CaO) and magnesium oxide (MgO), and in the X-ray diffraction analysis, the main component magnesium oxide (MgO) Since a peak exists between the diffraction angles of calcium oxide (CaO) alone, it is formed with a crystal structure with few impurities and oxygen deficiency. Therefore, excessive emission of electrons during driving of the PDP is suppressed, and in addition to the effect of achieving both low voltage driving and secondary electron emission performance, the effect of moderate electron retention characteristics is also exhibited. This charge retention characteristic is particularly effective for retaining wall charges stored during the initialization period and preventing write defects during the write period to perform reliable write discharge.

(Experimental result)
Next, a description will be given of the results of an experiment conducted to confirm the effect of the CaO content difference between the first protective film 91a and the second protective film 91b in the present embodiment.

Example 1
As the first protective film 91a, a mixed pellet of MgO and CaO having a molar ratio of MgO: CaO = 0.95: 0.05 is evaporated by an electron beam to form an Mg _0.95 Ca _0.05 O film of 500 nm as the protective film 91b. Formed to a thickness. Thereafter, the hearth of the electron beam evaporation apparatus is moved, and a mixed pellet of MgO and CaO having a molar ratio of MgO: CaO = 0.85: 0.15 is evaporated with an electron beam to form a protective film 91b with Mg _0.85 Ca _0.15 O. A film was formed to 300 nm to complete the front plate. During the formation of the first protective film 91a and the second protective film 92b, 100 sccm of oxygen was introduced into the vapor deposition chamber, and the pressure in the vapor deposition chamber was 0.04 Pa. The substrate temperature at the time of forming the first protective film 91a and the second protective film 92b was 300 ° C. The front plate and the back plate were sealed with frit glass, and a mixed gas of Ne 10% and Xe 90% was sealed at a pressure of 50 kPa in the internal discharge space to produce a PDP.

(Example 2)
As the first protective film 91a, MgO was used and CaO was not included. Otherwise, a PDP was produced in the same manner as in Example 1 above.

(Comparative Example 1)
The protective film 9 is a single layer, and a mixed pellet of MgO and CaO having a molar ratio of MgO: CaO = 0.85: 0.15 is evaporated by an electron beam to form an Mg _0.85 Ca _0.15 O film at 800 nm. Formed to complete the front plate. Otherwise, a PDP was produced in the same manner as in Example 1 above.

(Evaluation)
The PDPs produced in Examples 1 and 2 and Comparative Example 1 were continuously lit for 8000 hours by applying the same discharge sustaining voltage (rectangular waves of 200 V and 100 kHz), and then the luminance change rate was measured. . The rate of change in discharge luminance was the ratio of the luminance after continuous lighting to the luminance before continuous lighting described above. Thereafter, the PDP is cleaved, a small piece in the center of the front plate is cut out, and the calcium oxide content in the discharge area of the protective film 9 of the cut out piece is measured by X-ray photoelectron spectroscopy (Quantera SXM manufactured by ULVAC-PHI Co., Ltd.) The value of the ratio (maximum value / minimum value) of the concentration (maximum value) of the portion where the calcium oxide concentration in the discharge area becomes maximum and the concentration (minimum value) of the portion where the calcium oxide concentration becomes minimum was obtained. The measurement results are shown in Table 1.

  As is apparent from the results in Table 1, if the calcium oxide concentration of the protective film 9 is reduced toward the dielectric as in Examples 1 and 2, the calcium oxide concentration in the region where sputtering progressed as the discharge time elapsed. However, the difference in calcium oxide concentration in the discharge area of the protective film was reduced in the region where the sputtering progressed, so that the decrease in luminance could be suppressed. In addition, the inventors analyzed the reason why the decrease in luminance was large in Comparative Example 1. Then, it was found that the discharge width was reduced as compared with Examples 1 and 2. Specifically, it was found that the value of the flowing current was smaller in Comparative Example 1 than in Examples 1 and 2 with respect to the applied pulse voltage. The inventors speculate that the decrease in luminance is due to the decrease in the discharge width.

[Other Embodiments]
The present invention is not limited to the above-described embodiment, and various modifications and changes can be made without departing from the spirit of the present invention.

(1)
In the above-described embodiment, the protective film 9 is formed from magnesium oxide and calcium oxide. However, the present invention is not limited to this, and the protective film may include any two oxides of magnesium oxide, calcium oxide, strontium oxide, and barium oxide. At this time, in the X-ray diffraction analysis of the specific orientation plane, the protective film was analyzed for the diffraction angle at which a peak was generated when one of the two oxides was analyzed and the other oxide alone. If the peak exists at a diffraction angle between the diffraction angle at which the peak sometimes occurs, the sustaining voltage can be lowered as in the embodiment.

  Further, at this time, when the protective film is formed so that the content of the oxide having the larger molecular weight of the two oxides decreases in order from the discharge space side to at least a predetermined depth, As in the embodiment, it is possible to suppress a decrease in luminance due to sputtering.

(2)
In the above-described embodiment, the protective film 9 is composed of a plurality of layers 91a and 91b, and the content of calcium oxide in the second protective film 91b on the discharge space side is the same as that of the first protective film 91a on the dielectric layer side. It was set as the structure larger than the content rate of a calcium oxide. However, the protective film 9 may not have a plurality of layers, but may have a configuration in which the content of calcium oxide is sequentially reduced from the discharge space side to at least a predetermined depth. The predetermined depth may be a depth considered to be exposed to the discharge space by sputtering, and can be determined as appropriate according to the specifications of the PDP.

[Features of the embodiment]
Characteristic parts in the above embodiment are listed below. In addition, the invention included in the said embodiment is not limited to the following. In addition, what was described in parentheses after each configuration is a specific example of each configuration described to help understanding of the features. Each configuration is not limited to these specific examples. In addition, in order to obtain the effects described for each feature, configurations other than the described features may be modified or deleted.

(C1)
A first substrate (front plate 2); and a second substrate (back plate 10) disposed opposite to the first substrate (front plate 2), the first substrate (front plate 2) and the second substrate. A plasma display panel (1) in which a discharge space (16) filled with a discharge gas is formed between a substrate (back plate 10) and
The first substrate (front plate 2) is
A substrate (front glass substrate 3);
Display electrodes (6) formed on the substrate (front plate 2);
A dielectric layer (8) formed to cover the display electrode (6);
A protective film (9) formed on the dielectric layer (8) and exposed to the discharge space;
The second substrate (back plate 10) is
An address electrode (12) formed in a direction crossing the direction of the display electrode (6);
Partition walls (14) partitioning the discharge space (16),
The protective film (9) includes two oxides of magnesium oxide, calcium oxide, strontium oxide, and barium oxide,
In the X-ray diffraction analysis of the specific orientation plane, the protective film has a diffraction angle at which a peak is generated when one oxide simple substance of the two oxides is analyzed, and when the other oxide simple substance is analyzed. There is a peak at a diffraction angle between the diffraction angle at which the peak occurs,
The protective film is formed such that the content of the oxide having the larger molecular weight of the two oxides decreases in order from the discharge space side to at least a predetermined depth.
(Effect) A PDP that can be driven at a low voltage and has a small decrease in luminance can be realized.

(C2)
A plasma display panel according to C1,
The protective film includes a plurality of layers, and the content of the layer on the discharge space side is larger than the content of the layer on the dielectric layer side.
(Effect) It is easy to form the protective film so that the content ratio of the oxide having the larger molecular weight of the two oxides sequentially decreases from the discharge space side to at least a predetermined depth. .

  As described above, the present invention is useful for realizing a PDP with low power consumption and high luminance maintenance rate.

1 PDP
2 Front plate 3 Front glass substrate 4 Scan electrode 4a, 5a Transparent electrode 4b, 5b Metal bus electrode 5 Sustain electrode 6 Display electrode 7 Black stripe (light shielding layer)
8 Dielectric layer 9 Protective film 10 Back plate 11 Back glass substrate 12 Address electrode 13 Base dielectric layer 14 Partition 15 Phosphor layer 16 Discharge space 81 First dielectric layer 82 Second dielectric layer 91a First protective film 91b Second protective film

Claims (2)

A plasma display panel, comprising: a first substrate; and a second substrate disposed opposite to the first substrate, wherein a discharge space filled with a discharge gas is formed between the first substrate and the second substrate. Because
The first substrate is
A substrate,
Display electrodes formed on the substrate;
A dielectric layer formed to cover the display electrode;
A protective film formed on the dielectric layer and exposed to the discharge space;
The second substrate is
An address electrode formed in a direction crossing the direction of the display electrode;
Partition walls that partition the discharge space,
The protective film includes two oxides of magnesium oxide, calcium oxide, strontium oxide, and barium oxide,
In the X-ray diffraction analysis of the specific orientation plane, the protective film has a diffraction angle at which a peak is generated when one oxide simple substance of the two oxides is analyzed, and when the other oxide simple substance is analyzed. There is a peak at a diffraction angle between the diffraction angle at which the peak occurs,
The protective film is formed such that the content of the oxide having the larger molecular weight of the two oxides decreases in order from the discharge space side to at least a predetermined depth.
Plasma display panel. The protective film is composed of a plurality of layers, and the content of the layer on the discharge space side is larger than the content of the layer on the dielectric layer side,
The plasma display panel according to claim 1.

Images