JP4966908B2 - Plasma display panel and manufacturing method thereof - Google Patents

Description

  The present invention relates to a plasma display panel and a manufacturing technique thereof, and more particularly to a technique effective when applied to improvement of discharge delay of a plasma display panel.

  A plasma display panel (PDP), for example, generates a gas discharge in a discharge space called a cell in which a discharge gas such as a rare gas is enclosed, and excites a phosphor with vacuum ultraviolet rays generated at this time. This is a display panel for displaying images.

  Currently, AC (alternating current) driving PDPs that are generally commercialized are of the surface discharge type. In the surface discharge type PDP, the phosphor for color display can be arranged away from the display electrode pair in the thickness direction of the panel, thereby reducing deterioration of the phosphor characteristics due to ion bombardment (sputtering) during discharge. can do. Therefore, the surface discharge type PDP is suitable for extending the life as compared with the counter discharge type in which the paired display electrodes (referred to as X electrodes and Y electrodes) are arranged on the front substrate and the rear substrate.

  In the front substrate of the general surface discharge AC type PDP, a protective film is provided to prevent the dielectric layer covering the X and Y display electrode pairs from being deteriorated by the impact of ions during discharge. This protective film not only prevents the dielectric layer from deteriorating due to the impact of ions during discharge, but also has a function of emitting secondary electrons and causing the discharge to grow when ions collide with the protective film. .

As the protective film, a magnesium oxide (MgO) thin film is generally used because of its ion bombardment resistance and ease of secondary electron emission (see Patent Document 1).
JP 2006-147417 A

<Examination of discharge delay>
The protective film of MgO has a high secondary electron emission coefficient and is effective in reducing the discharge start voltage. However, in recent years, it has become necessary to further increase the address speed in accordance with the demand for higher definition of the PDP. As a result, improvement of the discharge delay has become a new important issue.

  That is, as the resolution of the PDP increases, the number of display lines increases. For example, the so-called full high-definition standard has 1080 display lines. In the PDP, a predetermined frame time (field) is divided into a plurality of subfields, and gradation display is performed by a combination of the number of sustain discharges (display discharges) performed in each subfield. In order to form an image, an operation (address (writing) operation) for selecting a cell to be lit is performed for each subfield. Specifically, a wall charge is formed by applying a pulse to the scan electrode and the address electrode of the selected cell to generate a discharge (address discharge). Thereafter, an operation (sustain operation) for generating a sustain discharge (display discharge) in the selected cell by applying a drive waveform to the cell group is performed. Therefore, for example, in order to perform scanning for 1080 lines (selection of discharge / non-discharge for each display line) for a subfield necessary for gradation display within a predetermined frame time, address operation time (that is, to the electrode) It is necessary to shorten the time required for generating the address discharge and forming the wall charges by applying the voltage (pulse). In other words, the higher the definition of the PDP, the greater the problem of how to reduce the discharge delay in the address operation or the like.

  Here, discharge delay is generally considered as the sum of formation delay and statistical delay. The formation delay is the time from the generation of the initial electrons generated between the electrodes to the formation of a clear discharge, and is regarded as the substantially minimum discharge time when many discharges are performed. On the other hand, the statistical delay is the time from the start of voltage application until the start of ionization until the discharge starts, and the variation in the discharge delay when the discharge is repeated many times is generally governed by this time. being called. If these discharge delays are long, the address time must be lengthened to prevent display mistakes, and the display period contributing to image formation is shortened. Therefore, it is desirable for the PDP to have a short discharge delay.

  In gas discharge, charged particles in a space (discharge space) are accelerated by an external electric field, collide with other gas molecules, and the gas molecules ionize to grow to increase the number of ionized particles. If no is supplied, the discharge does not start, and the start of discharge is delayed until charged particles are supplied. Accordingly, the discharge delay can be shortened as more priming electrons (initially charged particles) serving as discharge seeds are supplied into the discharge space.

  In Patent Document 1 described above, a technique for providing a crystalline magnesium oxide layer containing crystalline powder on an MgO film is proposed as one solution for shortening the discharge delay. According to the above-mentioned Patent Document 1, by providing a powder of magnesium oxide crystal that emits cathode luminescence light having a peak within 200 to 300 nm (especially around 235 nm), electrons are emitted by energy levels corresponding to the peak wavelength. Since it can be trapped for a long time, it is assumed that the electrons are taken out as initial electrons necessary for the start of discharge and the discharge delay is reduced. In addition, in Patent Document 1, in order to obtain a powder of MgO crystal that performs cathodoluminescence emission having a peak at a predetermined wavelength, the powder is classified and the frequency distribution of MgO crystals having a predetermined particle diameter or more is obtained. It is described that the amount of the increase is increased.

<Examination of technology for arranging a plurality of MgO crystal powders on the surface of MgO film>
However, when the present inventor has examined the configuration described in Patent Document 1, it has been found that there is a problem that it is difficult to uniformly distribute the distribution of characteristics within the PDP or the characteristics of each PDP. It was.

That is, in order to uniformly shorten the discharge delay in the plane of the PDP, it is necessary to increase the amount of the MgO crystal disposed, and the surface of the MgO film is covered with the MgO crystal. However, in this case, the surface area at which the MgO crystal is exposed to the discharge space is larger than when no MgO crystal is formed. MgO has the property of easily adsorbing impurities such as CO ₂ and H ₂ O, and the phosphor (especially a phosphor having a green emission characteristic) deteriorates due to the increased impurity as the surface area increases, resulting in a green color. Light emission becomes weak, and color unevenness (so-called red unevenness in the screen) in which the display color is increased in red becomes noticeable.

<Study of technology to reduce the amount of MgO crystal>
Therefore, as a result of studying a technique for improving the exposed area of the MgO film by reducing the amount of the MgO crystal to be deposited, the present inventor arranges the MgO crystal described in Patent Document 1, for example. We found a new problem that arises when the amount is simply reduced.

  That is, first, when there are variations in the size and number of MgO crystal particles arranged on the MgO film, MgO crystal particles adhering to the area of the discharge cell, which is the minimum light emission unit of display, vary. As a result, the amount of priming electrons supplied in the display discharge varies from cell to cell, and the light emission luminance varies from discharge cell to discharge cell. This phenomenon is referred to as granular unevenness because fine particle-like light and dark unevenness is visually recognized when the PDP is turned on, and causes a display failure of the PDP.

  Second, regarding the discharge delay, simply reducing the amount of MgO crystal disposed reduces the amount of priming electrons supplied, and as a result, the discharge delay cannot be shortened. Note that the above-mentioned Patent Document 1 describes that the amount of MgO crystal powder can be reduced by increasing the particle size distribution (frequency distribution) ratio of a crystal having a large particle size in the MgO crystal by classification. ing. However, simply performing classification cannot remove fine MgO crystal particles adhering to each MgO crystal as described in FIG. 6 or FIG. In addition, a part of the MgO crystal (particularly the top of the cube) may be damaged due to impact during classification or the like. Further, the damaged piece may adhere to the MgO film after the MgO crystal is disposed. For this reason, the orientation of the surface facing the discharge space of the MgO crystal is not uniform, and with a small amount of arrangement, priming electrons cannot be supplied sufficiently, so that the discharge delay cannot be shortened.

  Third, since a classification process is required to collect the powder of the MgO crystal that performs cathodoluminescence emission having a peak at a predetermined wavelength, the manufacturing process becomes complicated and the manufacturing efficiency decreases. is there.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique capable of improving the discharge delay of the PDP and preventing the display failure of the PDP.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  In order to solve the above-mentioned problems, the present inventors have conducted examinations and experiments. As a result, by arranging MgO crystal particles on the MgO film and setting the coverage of the MgO film to 10% or less, the red in the above-described screen is obtained. It has been found that occurrence of unevenness or increase in discharge voltage can be suppressed. Further, it has been experimentally found that the occurrence of granular unevenness can be prevented even if the amount of MgO crystal particles attached is reduced by setting the cumulative particle size distribution of MgO crystal particles to a predetermined value or less.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

  That is, the plasma display panel in one embodiment of the present invention includes a pair of substrate structures facing each other through a discharge space formed by enclosing a discharge gas, and one of the pair of substrate structures is A plurality of display electrode pairs disposed on the substrate, a dielectric layer covering the plurality of display electrode pairs, and a protective layer covering the dielectric layer. Here, the protective layer includes an MgO film stacked on the surface of the dielectric layer and a plurality of MgO crystal particles attached on the MgO film. The coverage of the surface of the MgO film is 10% or less. The cumulative 90% value of the cumulative particle size distribution of the plurality of MgO crystal particles is set to 3.98 μm or less.

  Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  That is, it is possible to improve the discharge delay of the PDP and prevent the display failure of the PDP.

  Before describing the present invention in detail, the meaning of terms in the present application will be described as follows.

  “MgO crystal single particle” means a primary particle (single particle) of a crystal composed of MgO. Accordingly, the “MgO crystal single particle” does not include secondary particles such as aggregates or aggregates in which a plurality of single particles are aggregated. On the other hand, “MgO crystal particles” are used as a general term including secondary particles such as aggregates and aggregates in which a plurality of MgO crystal single particles are aggregated in addition to MgO crystal single particles.

  The “cumulative particle size distribution” indicates a ratio of particles having a specific particle size or less to the whole. In other words, the cumulative 50% value means that particles having a particle size equal to or less than 50% occupy the whole. For example, referring to FIG. 8B, the cumulative 50% value is 1.27 μm, indicating that particles of 1.27 μm or less occupy 50% of the total.

  In the following embodiments, when it is necessary for the sake of convenience, the description will be divided into a plurality of sections or embodiments. However, unless otherwise specified, they are not irrelevant to each other. There are some or all of the modifications, details, supplementary explanations, and the like.

  Also, components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof is omitted in principle. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<1. Basic structure of PDP>
First, an example of the structure of the PDP of the present embodiment will be described with reference to FIGS. 1 and 2 by taking an AC drive type three-electrode surface discharge type PDP for color display as an example. FIG. 1 is an enlarged perspective view of an essential part of an enlarged PDP according to the present embodiment, and FIG. 2 is an essential part showing the surface state of a protective layer by inverting the front substrate structure shown in FIG. It is an expansion perspective view.

  In FIG. 1, the PDP 1 has a front substrate structure 11 and a rear substrate structure 12 which are a pair of substrate structures facing each other via a discharge space 24 formed by enclosing a discharge gas.

  The front substrate structure 11 includes a plurality of display electrode pairs X and Y electrodes 15 disposed on a front substrate (first substrate) 13, a dielectric layer 17 covering these display electrode pairs, And a protective layer 18 covering the dielectric layer. Further, as shown in FIG. 2, the protective layer 18 includes a MgO (magnesium oxide) film 18a stacked on the surface of the dielectric layer 17, and a plurality of MgO crystal particles 18b attached on the MgO film 18a. .

  The front substrate structure 11 and the back substrate structure 12 are overlapped with each other so as to face each other, and have a discharge space 24 therebetween. That is, the front substrate structure 11 and the back substrate structure 12 are disposed to face each other with the discharge space 24 interposed therebetween.

  The front substrate structure 11 has a first surface 13a serving as a display surface of the PDP 1, and includes a front substrate 13 which is a glass substrate, for example. A plurality of X electrodes (display electrodes) 14 and display electrodes (scanning electrodes) 15 that are display electrodes of the PDP 1 are formed on the surface (inner surface) opposite to the first surface 13 a of the front substrate 13. ing.

  The X electrode 14 and the Y electrode 15 constitute a pair of display electrodes for performing a sustain discharge (display discharge), and are alternately arranged so as to extend in a strip shape along the row direction DX, for example. The pair of X electrode 14 and Y electrode 15 form a display line in the row direction DX in the PDP 1. In FIG. 1, two pairs of the X electrode 14 and the Y electrode 15 are shown in an enlarged manner. However, the PDP 1 has a plurality of X electrodes 14 and Y electrodes 15 according to the number of display lines. Yes.

The X electrode 14 and the Y electrode 15 are generally composed of, for example, an X transparent electrode 14a and a Y transparent electrode 15a made of a transparent electrode material such as ITO (Indium Tin Oxide) or SnO ₂ , for example, Ag, Au, Al, An X bus electrode 14b and a Y bus electrode 15b made of Cu, Cr, or a stacked body thereof (for example, a stacked body of Cr / Cu / Cr) are formed.

  The X transparent electrode 14a and the Y transparent electrode 15a mainly contribute to the sustain discharge, and the light transmittance is higher than that of the X bus electrode 14b and the Y bus electrode 15b so that the light emission of the phosphor can be observed from the front substrate 13 side. high. On the other hand, the X bus electrode 14b and the Y bus electrode 15b use a metal material having a lower resistance than the X transparent electrode 14a and the Y transparent electrode 15a in order to pass a driving current with a low resistance.

  The step of forming the display electrode pair (X electrode 14 and Y electrode 15) on one surface of the front substrate (first substrate) 13 (the surface located on the opposite side of the first surface 13a) is performed as follows, for example. . That is, by using a thick film forming technique such as screen printing for transparent electrode materials, Ag, and Au, and by using a thin film forming technique such as a vapor deposition method and a sputtering method and an etching technique for other metals, It can be formed with a predetermined number, thickness, width and interval.

  In FIG. 1, the X transparent electrode 14a and the Y transparent electrode 15a extend in a strip shape, but the electrode structures of the X transparent electrode 14a and the Y transparent electrode 15a are not limited thereto. For example, in order to stabilize sustain discharge and improve discharge efficiency, the position where the shortest distance between the pair of electrodes (referred to as a discharge gap) overlaps with the X bus electrode 14b and the Y bus electrode 15b so as to approach the cell. It is good also as a structure which forms a protrusion part in the direction which respectively opposes. Also, various modifications such as a straight shape, a T-shape or a ladder shape can be used for the shape of the protruding portion. Further, the electrode structure of the X electrode 14 and the Y electrode 15 is not limited to the shape shown in FIG. 1. For example, these display electrode pairs are arranged at equal intervals, and the adjacent X electrode 14 and Y electrode 15 are arranged. A structure called a so-called ALIS (Alternate Lighting of Surface Method) in which all the gaps become display lines may be adopted.

These electrodes (X electrodes 14, Y electrodes 15) is mainly covered by the configured dielectric layers 17 of a glass material such as SiO _2. The step of forming the dielectric layer 17 so as to cover the display electrode pair is performed as follows, for example. That is, the dielectric layer 17 is formed by, for example, applying a frit paste mainly composed of a low melting point glass powder on the front substrate 13 by a screen printing method and baking it. In addition, a sheet-like dielectric sheet called a so-called green sheet can be attached and fired. Alternatively, it may be formed by depositing SiO ₂ film by a plasma CVD method.

  A protective layer 18 is formed on the inner surface side of the dielectric layer 17 to protect the dielectric layer 17 from impact caused by ion collision caused by discharge (mainly sustain discharge) during display. Therefore, the protective layer 18 is formed so as to cover the surface of the dielectric layer 17. The detailed structure and function of the protective layer 18 and details of the process of forming the protective layer 18 on the surface of the dielectric layer 17 will be described later.

  On the other hand, the back substrate structure 12 has a back substrate 19 which is, for example, a glass substrate. A plurality of address electrodes 20 are formed on the surface (inner surface) of the back substrate 19 facing the front substrate structure 11. Each address electrode 20 is formed so as to extend along a column direction DY intersecting (substantially orthogonal to) the direction in which the X electrode 14 and the Y electrode 15 extend. The address electrodes 20 are arranged with a predetermined arrangement interval so as to be substantially parallel to each other.

  The material constituting the address electrode 20 is, for example, Ag, Au, Al, Cu, Cr, or a laminated body thereof (for example, a laminated body of Cr / Cu / Cr), similar to the X bus electrode 14b and the Y bus electrode 15b. Etc. can be used. Further, by using a thick film forming technique or a thin film forming technique such as a vapor deposition method or a sputtering method and an etching technique according to the material used for the address electrode 20, it can be formed with a predetermined number, thickness, width and interval. it can.

  The address electrode 20 and the Y electrode 15 formed on the front substrate structure 11 constitute an electrode pair for performing address discharge, which is discharge for selecting lighting / non-lighting of the cell 25. That is, the Y electrode 15 has both a function as a sustain discharge electrode and a function as an address discharge electrode (scanning electrode).

  The address electrode 20 is covered with a dielectric layer 21. The dielectric layer 21 can be formed using the same material and the same method as the dielectric layer 17 on the front substrate 13. A plurality of partition walls 22 extending in the thickness direction of the back substrate structure 12 are formed on the dielectric layer 21. The barrier ribs 22 are formed to extend in a line along the column direction DY in which the address electrodes 20 extend. The front substrate structure 11 and the rear substrate structure 12 are fixed in a state where the surface on which the protective layer 18 is formed and the surface on which the partition wall 22 is formed are opposed to each other. A position on the plane of the partition wall 22 is disposed between the adjacent address electrodes 20. By disposing the barrier ribs 22 between the adjacent address electrodes 20, a discharge space 24 for dividing the surface of the dielectric layer 21 in the column direction DY corresponding to the position of each address electrode is formed. In addition to the line shape shown in FIG. 1, various modifications such as a meander shape, a lattice shape, or a ladder shape can be applied to the shape of the partition wall 22.

  The step of forming the partition wall 22 can be formed by a sand blast method, a photo etching method, or the like. For example, in the sandblasting method, a frit paste made of a low melting glass frit, a binder resin, a solvent or the like is applied on the dielectric layer 21 and dried, and then a cutting mask having an opening of a partition pattern is formed on the frit paste layer. It is formed by spraying cutting particles in the provided state, cutting the frit paste layer exposed at the opening of the mask, and further firing. In the photo-etching method, instead of cutting with cutting particles, a photosensitive resin is used as the binder resin, and it is formed by baking after exposure and development using a mask.

  Phosphors that generate red (R), green (G), and blue (B) visible light on the upper surface of the dielectric layer 21 on the address electrodes 20 and the side surfaces of the barrier ribs 22 when excited by vacuum ultraviolet rays. 23r, 23g, and 23b are formed at predetermined positions, respectively. The step of forming the phosphors 23r, 23g, and 23b in the region partitioned by the barrier ribs 22 is performed as follows, for example. First, phosphor pastes containing phosphor powders having emission characteristics of respective colors, a binder resin, and a solvent are prepared. This phosphor paste is formed by applying the phosphor paste in a discharge space partitioned by barrier ribs by a method using screen printing or a dispenser, and repeating this for each color, followed by firing.

  The phosphors 23r, 23g, and 23b can also be formed by a photolithography technique using a sheet-like phosphor layer material (so-called green sheet) containing phosphor powder, a photosensitive material, and a binder resin. In this case, a phosphor sheet of each color is formed between the corresponding barrier ribs 22 by applying a sheet of a predetermined color to the entire display area on the substrate, performing exposure and development, and repeating this for each color. Can do.

  Each discharge space 24 is filled with a gas such as a rare gas called a discharge gas at a predetermined pressure. As the discharge gas, for example, a mixed gas such as Xe-Ne whose Xe partial pressure ratio is adjusted to several percent to several tens percent can be used.

  The PDP 1 can be obtained by assembling the surface of the front substrate 13 on which the display electrode pair is formed and the rear substrate 19 so as to face each other with the discharge space 24 therebetween. In this assembling process, the alignment process between the front substrate 13 and the back substrate 19 is performed, and the outer peripheral portion between each substrate (the front substrate 13 and the back substrate 19) is sealed using, for example, a low melting glass material called a seal frit. A sealing process, a process of exhausting the gas remaining in the internal space of the PDP 1 and filling a discharge gas, and the like.

  In the PDP 1, one cell 25 is configured corresponding to the intersection of the pair of X electrode 14, Y electrode 15, and address electrode 20. That is, the cell 25 is formed at each intersection of the display electrode pair (a pair of the X electrode 14 and the Y electrode 15) and the address electrode 20. The plane area of the cell 25 is defined by the arrangement interval of the pair of X electrodes 14 and Y electrodes 15 and the arrangement interval of the partition walls 22. Each cell 25 is formed with one of a red phosphor 23r, a green phosphor 23g, and a blue phosphor 23b.

  A set of R, G, and B cells 25 constitutes a pixel. That is, each of the phosphors 23r, 23g, and 23b is a light emitting element of the PDP 1, and is excited by vacuum ultraviolet rays having a predetermined wavelength generated by the sustain discharge, and visible light of each color of red (R), green (G), and blue (B). Is emitted.

  Although FIG. 1 shows an example in which the address electrode 20 is formed on the back substrate structure 12, the address electrode 20 can also be formed on the front substrate structure 11. In this case, the dielectric layer 17 shown in FIG. 1 has a multi-layer structure, and the display electrode pair is covered with the first dielectric layer, and between the first dielectric layer and the second dielectric layer. The address electrode 20 can be formed.

<2. Detailed structure and function of protective layer>
Next, the detailed structure and function of the protective layer 18 shown in FIGS. 1 and 2 will be described with reference to FIGS. FIG. 3 is an explanatory diagram for explaining a particle size distribution model of MgO crystal particles. 4 and 5 are diagrams showing an example of the MgO crystal particles shown in FIG. 2. FIG. 4 is a perspective view showing the MgO crystal single particles, and FIG. 5 shows the side surfaces of the three MgO crystal single particles in close contact. It is explanatory drawing which shows the aggregate which aggregated. FIG. 6 is an enlarged cross-sectional view showing the microscopic relationship between the MgO film and MgO crystal particles shown in FIG. Moreover, FIG. 7 is explanatory drawing for demonstrating the embodiment of the especially preferable crushing method in the crushing process for preparing the MgO crystal particle shown in FIGS. Moreover, FIG. 8 is explanatory drawing which shows the cumulative particle size distribution of the MgO crystal particle for every crushing method in the crushing process for preparing the MgO crystal particle shown in FIGS. 10 and 11 are enlarged cross-sectional views showing the microscopic relationship between an MgO film and MgO crystal particles, which are comparative examples for the present embodiment.

  In FIG. 2, the protective layer 18 includes an MgO film 18a stacked on the surface of the dielectric layer 17, and a plurality of MgO crystal particles 18b attached on the MgO film 18a.

<2-1. MgO film>
The MgO film 18a has a (111) oriented surface on the surface facing the discharge space 24 (see FIG. 1). The protective layer 18 is required to have a function of preventing the dielectric layer 17 from being deteriorated by the impact of ions during discharge and a function of promoting the growth and maintenance of the discharge by emitting secondary electrons. For this reason, MgO having a high secondary electron emission coefficient is used for the protective layer 18, and in particular, a secondary surface that is higher than when the (100) surface is used by setting the surface facing the discharge space 24 as the (111) surface. An electron emission coefficient is obtained. The PDP 1 can improve the secondary electron emission coefficient by setting the surface of the MgO film 18a facing the discharge space 24 as the (111) plane, so that the discharge voltage can be reduced. That is, the PDP 1 can reduce power consumption. Although the orientation of the surface of the MgO film 18a mainly has the (111) plane, the embodiment in which the surface of the MgO film 18a includes an orientation plane other than the (111) plane is not excluded.

  Further, although the MgO film 18a is composed of MgO as a main component, an additive (for example, CaO or the like) for improving the spatter resistance and the secondary electron emission coefficient can be added thereto. In this case, the spatter resistance or secondary electron emission coefficient of the protective layer 18 can be further improved.

  The step of forming the MgO film 18a can be formed by a thin film process known in the art such as an electron beam evaporation method or a sputtering method.

<2-2. MgO crystal particles>
<2-2-1. About discharge delay ＞
Next, the MgO crystal particles 18b may be made of only MgO, but may contain a small amount of another component (for example, flux residue) to the extent that the crystal structure is not affected.

  The MgO crystal particles 18b have a function of supplying more priming electrons (initially charged particles), which become a seed of discharge when performing address discharge or display discharge, to the discharge space 24. That is, the priming electrons in the discharge space 24 can be increased by attaching the plurality of MgO crystal particles 18b on the MgO film 18a. When the priming electrons in the discharge space 24 increase, it is possible to shorten the time from when the voltage for discharge is applied until the discharge is started. For example, in the case of address discharge, it is possible to shorten the time from when a voltage is applied between the address electrode 20 and the Y electrode 15 shown in FIG. The discharge delay in can be shortened.

  When the arrangement amount of the MgO crystal particles 18b, that is, the adhesion amount of the MgO crystal particles 18b on the surface of the MgO film 18a is increased, the supply amount of priming electrons in the discharge space 24 increases.

<2-2-2. Problems and solutions by attaching MgO crystal particles>
However, according to the study of the present inventor, if the amount of MgO crystal particles 18b is excessively increased, the display color of the PDP 1 becomes abnormal. That is, when the MgO crystal particles 18b are attached, the surface area at which the MgO crystal particles 18b are exposed to the discharge space is larger than when the MgO crystal particles 18b are not attached. MgO has the property of easily adsorbing impurities such as CO ₂ and H ₂ O, and the phosphor (especially a phosphor having a green emission characteristic) deteriorates due to the increased impurity as the surface area increases, resulting in a green color. Light emission becomes weak, and color unevenness (so-called red unevenness in the screen) that increases redness in the display color may occur. When the adhesion amount of the MgO crystal particles 18b is small, this phenomenon is so small that it can be ignored effectively, but this phenomenon increases as the adhesion amount increases. As a result of the present inventors experimentally examining this critical point, this phenomenon becomes particularly significant when the coverage of the MgO film 18a exceeds 10%.

  It has also been found that the discharge voltage increases when the amount of MgO crystal particles 18b attached is excessively large. This is presumably because the amount of secondary electron emission decreases when the surface of the MgO film 18a is covered with the MgO crystal particles 18b.

  Therefore, in the present embodiment, the adhesion amount of the MgO crystal particles 18b is reduced, and the coverage of the MgO film 18a is set to 10% or less. Here, the “coverage” means the area of the MgO crystal particles 18b relative to the area of the underlying MgO film 18a when observed in a direction perpendicular to the surface of the MgO film 18a in which the MgO crystal particles 18b are dispersed. It is a ratio. In the present embodiment, the coverage was measured for each of a plurality of measurement points in a square field of view of 0.6 mm × 0.6 mm, for example, 10 measurement points were measured linearly at 10 mm intervals. The reason why the visual field range was a 0.6 mm × 0.6 mm square was set to be a particularly preferable range from the relationship between the cumulative particle size distribution of MgO crystal particles and the measurement accuracy of the coverage. Further, the number of measurement points and the measurement interval are not particularly limited, but it is preferable to measure at least 10 measurement points in order to improve accuracy.

  The PDP 1 according to the present embodiment has a coverage of 10% or less in all the visual field ranges described above. Further, the coverage is 10% or less in all the cells 25 of the PDP 1. Therefore, in the PDP 1 according to the present embodiment, the MgO crystal particles 18b are substantially uniformly distributed.

  Thus, by reducing the adhesion amount of the MgO crystal particles 18b so that the coverage is 10% or less in all the cells 25 of the PDP 1, the display color abnormality (red unevenness) of the PDP 1 can be suppressed. Was confirmed experimentally (details will be described later).

  In addition, it was confirmed that an increase in discharge voltage can be suppressed as compared with the case where the MgO crystal particles 18b are not attached. This is presumably because the secondary electron emission amount from the MgO film 18a can be secured by setting the coverage to 10% or less.

<2-2-3. New problems and solutions by reducing the amount of adhesion-1>
By the way, when the adhesion amount of the MgO crystal particles 18b is reduced, the uniformity of the dispersed state of the MgO crystal particles 18b on the surface of the MgO film 18a becomes a problem. When the size and number of the MgO crystal particles 18b vary, the amount of the MgO crystal particles 18b adhering per area of the cell 25 (see FIG. 1), which is the minimum light emission unit of display, varies. For this reason, the following problems occur from the viewpoint of display reliability of the PDP 1. That is, the supply amount of the priming electrons in the display discharge differs for each cell 25, and the light emission for each cell 25 varies. That is, when the PDP 1 is turned on, fine particulate light-dark unevenness (granular unevenness) is visually recognized. In particular, the MgO crystal particle 18b having a large particle size has a large influence on the variation in light emission of each cell 25 because the supply amount of the priming particle per particle is large.

  Further, when the amount of the MgO crystal particles 18b adhering per area of the cell 25 varies, the coverage of the MgO film 18a (the coverage within the visual field range described above) also varies. As a result, the distribution of the discharge voltage is not uniform for each cell 25, which causes the generation of the cell 25 having a locally high required discharge voltage. Also in this regard, the MgO crystal particles 18b having a large particle size cause a large increase in the coverage of the MgO film 18a, and thus have a great influence on the increase in discharge voltage.

  Therefore, as a result of experiments and studies on the uniformity of the dispersed state of the MgO crystal particles 18b by the present inventor, the cumulative 90% value of the cumulative particle size distribution of the plurality of MgO crystal particles is set to 3.98 μm or less. It has been found that the occurrence of unevenness can be prevented.

  Here, the reason why the cumulative flow rate distribution of the MgO crystal particles 18b is defined by the cumulative 90% value will be described. In order to prevent granular unevenness, it is important how to eliminate the MgO crystal particles 18b having a large particle diameter as described above. As an index indicating the particle size distribution of the MgO crystal particles 18b, the cumulative particle size distribution includes a cumulative 50% value, a cumulative 10% value, and the like. There are also the mode diameter of the frequency distribution (the range of the particle diameter having the highest abundance ratio) and the average particle diameter. However, in the case of the particle size distribution as shown in FIG. 3, for example, the cumulative 50% value, mode diameter, or average particle size is the same in the particle size distribution curves (a) and (b), but the granular unevenness is The amount of the MgO crystal particles 18b having a large particle size that needs to be specifically excluded for prevention is greatly different. On the other hand, if the cumulative flow rate distribution of the MgO crystal particles 18b is defined by a cumulative 90% value, the amount of the MgO crystal particles 18b having a large particle size can be made a certain ratio or less.

  By regulating the upper limit of the cumulative 90% value in this way, it is possible to eliminate MgO crystal particles 18b having an extremely large particle diameter that causes granular unevenness, and thus it is possible to prevent or suppress granular unevenness. Further, the discharge voltage can be prevented from increasing by eliminating particles having a large particle size that cause the coverage rate to increase.

  Further, for example, when the MgO crystal particles 18b are dispersed and distributed by the spray method, the MgO crystal particles 18b or aggregates 18c having excessively large particle diameters are heavier than other particles, and thus are difficult to scatter. For this reason, the uniformity of the dispersed state of the MgO crystal particles 18b decreases. That is, in this embodiment, by setting the cumulative 90% value to 3.98 μm or less, MgO crystal particles 18b or aggregates 18c having excessively large particle diameters can be excluded. For this reason, since the uniformity of the dispersed state of the MgO crystal particles 18b is improved, it is possible to prevent the appearance of granular unevenness.

  Incidentally, the MgO crystal single particles 18b1 constituting the MgO crystal particles 18b adhering to the MgO film 18a have a cubic shape as shown in FIG. 4, but for example, as shown in FIG. ) Cubic MgO crystal single particles 18b1 may be included. Although FIG. 2 shows a state in which the aggregate 18c is included, the aggregate 18c may not be included, and all of the particles adhering to the MgO film 18a may be single-particle MgO crystal single particles 18b1.

  When the MgO crystal particles 18b attached to the MgO film 18a are single particles (MgO crystal single particles 18b1) that do not include the aggregate 18c, the cumulative 90% value of the MgO crystal single particles 18b1 is 3.98 μm or less. This is a necessary condition for preventing the granular unevenness, but when the aggregate 18c is included, the particle diameter of each MgO crystal single particle 18b1 constituting the aggregate 18c is further reduced. When the particle diameter of each MgO crystal single particle 18b1 as a single particle increases, the particle diameter of each MgO crystal particle 18b tends to vary. However, by forming the structure including the aggregate 18c, the aggregate 18c is aggregated. By controlling the degree, the accumulated particle size distribution can be kept within a predetermined range. Therefore, for example, as shown in FIG. 5, it is more preferable to have a structure including an aggregate 18c in which MgO crystal single particles 18b1 are aggregated. The condition that the cumulative 90% value is 3.98 μm or more is the value of the cumulative particle size distribution when the aggregate 18c is regarded as one particle when the aggregate 18c is included.

  The cumulative particle size distribution of the MgO crystal particles 18b can be obtained using a laser diffraction particle size distribution meter. In this laser diffraction type particle size distribution form, each MgO crystal particle 18b (when the aggregate 18c is included, the aggregate 18c is regarded as one particle) is regarded as a sphere, and the particle size of each sphere particle is measured. Can do.

<2-2-4. New problem and solution 2 by reducing the amount of adhesion-2>
In the present embodiment, since the amount of MgO crystal particles 18b is reduced, it is not possible to sufficiently supply priming electrons simply by reducing the amount of MgO crystal particles 18b, resulting in a short discharge delay. You may not be able to. That is, the MgO crystal particle 18b needs to have a cumulative 90% cumulative value of 3.98 μm or less in order to prevent granular unevenness. It turned out to be necessary.

  As a result of investigation by the present inventor, by arranging the orientation of the surface of each MgO crystal particle 18b facing the discharge space 24 so as to be aligned with the (100) plane, the discharge delay is reduced even if the amount of MgO crystal particle 18b is reduced. It was found that can be shortened. Here, “alignment is aligned” means that the normal directions of the crystal planes of the MgO crystal particles 18b are coincident with each other. If the directions are coincident, the MgO crystal particles 18b are You may rotate around the normal. Further, “the orientation of the surface facing the discharge space 24 is aligned in the (100) plane” means that the surface facing each discharge space 24 among the surfaces of each MgO crystal particle 18b, that is, facing the MgO film 18a. It means that the orientation of the surface located on the opposite side of the surface is aligned in the (100) plane.

  Whether or not the orientations of the plurality of MgO crystal particles 18b are aligned (that is, the degree of orientation uniformity) depends on the signal intensity of the (200) plane in X-ray diffraction (XRD) and (111). Judgment can be made based on the ratio to the signal strength of the surface. The (200) plane is equivalent to the (100) plane, and the signal on the (200) plane is strong when the orientations of the plurality of MgO crystal particles 18b are aligned, and the orientations of the plurality of MgO crystal particles 18b are aligned. If not, it becomes very weak. On the other hand, the signal on the (111) plane is mainly a signal from the MgO film 18a, and hardly depends on whether the orientations of the plurality of MgO crystal particles 18b are aligned. Therefore, the value of {(200) plane signal intensity / (111) plane signal intensity} is an index indicating whether or not the orientations of the faces of the plurality of MgO crystal particles 18b facing the discharge space 24 are aligned. Specifically, the X-ray diffraction signal intensity measurement of the (200) plane per 1 μm thickness of the MgO film is performed, and the value after normalization according to the signal intensity ratio between the (111) plane and the (200) plane , And the (111) plane X-ray diffraction signal intensity value, and if the normalized (200) plane value is equal to or greater than the (111) plane value, the discharge delay is shortened. can do. Note that normalization is based on the (111) plane, taking into account that when the abundance ratio between the (111) plane and the (200) plane is 1/1, the measured signal intensity ratio is 11.6 / 100. Is obtained by multiplying the actually measured signal intensity of the (200) plane by 0.116.

  Next, specific means for aligning the orientations of the MgO crystal particles 18b in the present embodiment will be described. First, the MgO crystal single particle 18b1 which is a single particle constituting the MgO crystal particle 18b of the present embodiment has a cubic shape as shown in FIG. The MgO crystal single particle 18b1 is a cubic crystal surrounded by a (100) crystal plane, and all the crystal planes are equivalent in physical and chemical properties. Accordingly, each surface of the cubic MgO crystal single particle 18b1 is a (100) plane. One surface of the MgO crystal single particle 18b1 is in opposed contact with the surface of the MgO film 18a. By making one surface of the cubic MgO crystal single particle 18b1 in contact with the surface of the MgO film 18a, the normal direction of the opposite surface can be made uniform. That is, the orientation of the surface facing the discharge space 24 in the plurality of MgO crystal particles 18b can be made uniform in the (100) plane. Each MgO crystal single particle 18b1 has a cubic shape. For example, as shown in FIG. 5, a plurality of (three in FIG. 5) cubic MgO crystal single particles 18b1 are closely aggregated and aggregated. A collection 18c may be included. In this case, one surface of the aggregate 18c is opposed to the surface of the MgO film 18a. However, since each MgO crystal single particle 18b1 constituting the aggregate 18c is a cube, it faces the opposite surface (that is, the discharge space 24). The (100) plane is aligned. In this way, the amount of adhesion of the MgO crystal particles 18b is reduced by aligning the orientation of the surface of the MgO crystal particles 18b facing the discharge space 24 (the coverage of the MgO film 18a is 10% or less). It has also been experimentally found that the discharge delay can be shortened (details will be described later). Although FIG. 2 shows a state in which the aggregate 18c is included, the aggregate 18c may not be included, and all of the particles adhering to the MgO film 18a may be single-particle MgO crystal single particles 18b1.

  Further, by bringing one surface of the cube of the MgO crystal single particle 18b1 into contact with the surface of the MgO film 18a, the contact between the surface of the MgO film 18a and the MgO single crystal becomes stable surface contact. It is possible to suppress the problem of partial characteristic change due to separation or scattering of the particles 18b.

  Next, the particle diameter of each MgO crystal particle 18b is preferably set to the following particle diameter. The surface of the MgO film 18a formed by, for example, electron beam evaporation, which is the base of the MgO crystal particle 18b, has microscopic irregularities of a columnar crystal structure having a top as shown in FIG. There is a fine gap 26 between them. The head-to-top interval W1 of the columnar crystals is, for example, about 0.05 μm. Therefore, when the particle size is smaller than twice the parietal interval W1 of the columnar crystals (less than 0.1 μm) as in the MgO crystal particle 30 which is a comparative example to the present embodiment shown in FIG. 26, the MgO film 18a may not be opposed to each other. In this case, even when the MgO crystal particle 30 has a cubic shape, the MgO film 18a is not opposed to the MgO film 18a. Therefore, the orientation of the surface facing the discharge space 24 is not the (100) plane and the orientation is not uniform. Moreover, as shown in FIG. 11, even if it has MgO crystal particles 31 having a grain size that is twice or more the columnar interval W1 of the columnar crystals, it is smaller than twice the interval (1 to less than 0.1 μm). If the MgO crystal particles 30 having a particle size are included, the MgO crystal particles 30 sandwiched between the gaps 26 become a factor that inhibits the opposing contact between the MgO crystal particles 31 and the MgO film 18a.

  On the other hand, the MgO crystal particles 18b of the present embodiment do not include or have a small amount of particles having a particle diameter smaller than twice the parietal interval W1 (less than 0.1 μm). Therefore, as shown in FIG. 6, the surface of the underlying MgO film 18a can be regarded as substantially flat, which is convenient for aligning the orientation. In order to align the orientation, it is more preferable that no particle having a particle size (0.1 μm or less) smaller than twice the parietal interval W1 is included. However, after X-ray diffraction is performed as described above, If the value of the (200) plane after conversion is equal to or greater than the value of the (111) plane, the discharge delay can be shortened. Therefore, if it falls within this range, it is more than twice the parietal interval W1. Even if particles having a small particle size (0.1 μm or less) are contained, the discharge delay can be improved.

  From this point of view, when the present inventor conducted an experiment on a preferable particle diameter of the MgO crystal particles 18b, it was found that it can be expressed by a cumulative particle size distribution. That is, when the cumulative 10% value in the cumulative particle size distribution of the plurality of MgO crystal particles 18b is 0.77 μm or more, the orientation of each MgO crystal particle 18b is particularly easy to align on the (100) plane, and the MgO crystal particles 18b The cumulative particle size distribution can be determined using a laser diffraction particle size distribution meter. In this laser diffraction type particle size distribution form, each MgO crystal particle 18b (when the aggregate 18c is included, the aggregate 18c is regarded as one particle) is regarded as a sphere, and the particle size of each sphere particle is measured. Can do.

  When the MgO crystal particle 18b attached to the MgO film 18a is the MgO crystal single particle 18b1 that does not include the aggregate 18c, the cumulative 10% value of the MgO crystal single particle 18b1 is 0.77 μm or more. Although it is particularly preferable for the purpose of alignment, when the aggregate 18c is included, the particle diameter of each MgO crystal single particle 18b1 constituting the aggregate 18c may be smaller. As described in the section <2-2-3> above, by adopting a structure including the aggregate 18c, the aggregate 18c can be obtained even when the particle diameter of each MgO crystal particle 18b is smaller than a predetermined particle diameter. By controlling the degree of aggregation, the cumulative particle size distribution can be kept within a predetermined range. Therefore, from the viewpoint of aligning the orientation, for example, as shown in FIG. 5, a structure including an aggregate 18c in which MgO crystal particles 18b are aggregated is more preferable. The condition that the cumulative 10% value is 0.77 μm or more is the value of the cumulative particle size distribution when the aggregate 18c is regarded as one particle when the aggregate 18c is included. However, even when the aggregate 18c is included, if the particle diameter of each MgO crystal particle 18b constituting the aggregate 18c is excessively small, it becomes an inhibiting factor for aligning the orientation as described above. Therefore, it is preferable to reduce the number of particles having a particle size (0.1 μm or less) smaller than twice the vertex distance W1 shown in FIG. From this point of view, when the present inventor examined, if the cumulative particle size distribution of the single particles of each MgO crystal single particle 18b1 contained in the aggregate 18c is 0.59 μm or more in terms of a cumulative 10% value, 0.1 μm or less. It was found that MgO crystal particles 18b having a particle size of almost no exist, and the alignment can be made particularly easy.

  Here, the reason why the cumulative flow rate distribution of the MgO crystal particles 18b is defined by the cumulative 10% value is as follows. That is, in order to align the orientation in the (100) plane, it is important to eliminate the MgO crystal particles 18b having a small particle diameter. This is because, in order to effectively eliminate the MgO crystal particles 18b having a small particle diameter, it is particularly effective to define the cumulative 10% value.

<2-3. Step of forming protective layer>
The step of forming the protective layer 18 on the surface of the dielectric layer 17 shown in FIGS. 1 and 2 includes the step of preparing MgO crystal particles 18b, the step of forming the MgO film 18a on the surface of the dielectric layer 17, A step of attaching a plurality of MgO crystal particles 18b to the surface of the MgO film 18a so that the coverage of the MgO film 18a is 10% or less. Each step will be described in detail below. The step of forming the MgO film 18a on the surface of the dielectric layer 17 is formed by a thin film process known in the art such as an electron beam evaporation method or a sputtering method as described above. Detailed description will be omitted.

<2-3-1. Step of preparing MgO crystal particles>
As a method for preparing MgO crystal particles to be attached to the surface of the MgO film 18a, a method of manufacturing by a vapor phase method is known. However, the MgO crystal particles 18b of the present embodiment are particularly preferably prepared by the following method.

  That is, it is prepared by mixing the MgO seed crystal obtained by the vapor phase method and the flux (flux that promotes melting of the MgO seed crystal) and then firing, and crushing the obtained fired product. Since the MgO seed crystal obtained by the vapor phase method has a small particle size and a large variation in particle size, it is difficult to align the orientation even if the MgO seed crystal itself is scattered on the MgO film 18a. On the other hand, the MgO crystal particles 18b prepared by the above method have a relatively large particle size (compared to the MgO seed crystal) and can suppress variations in particle size. Accordingly, when the MgO crystal particles 18b are dispersed on the MgO film 18a, the cumulative particle size distribution of the MgO crystal particles 18b is easily kept within the above-described predetermined range, so that the orientation is easily aligned.

  Preparation of MgO seed crystals by the vapor phase method is, for example, the method described in JP-A No. 2004-182521, “Materials” November 1987, Vol. 36, No. 410, pages 1157 to 1161. It can be carried out by the method described in “Synthesis and Properties of Magnesia Powder by Gas Phase Method”. Moreover, you may purchase the MgO seed crystal produced by the vapor phase method from Ube Materials Corporation.

  The flux is a reaction accelerator that promotes melting of the MgO seed crystal. For example, a magnesium halide (magnesium fluoride or the like) can be used. The amount of flux added can be, for example, 0.001 to 0.1 wt%.

  Further, the firing of the mixture of the MgO seed crystal and the flux (flux) is performed at 1000 to 1700 ° C. for 1 to 5 hours, for example. The particle diameter of the obtained MgO crystal particles 18b increases in proportion to the firing temperature, firing time, or amount of flux added. Further, the smaller the particle size of the MgO seed crystal, the faster the crystal growth rate during firing. For this reason, the dispersion | variation in the particle size of the MgO crystal particle 18b obtained in proportion to baking temperature, baking time, and the addition amount of a flux becomes small. Accordingly, the firing temperature, time, and flux addition amount are appropriately set so that the cumulative particle size distribution of the MgO crystal particles 18b is within the above-described predetermined range. Further, for example, fine MgO crystal particles 30 as shown in FIG. 11 may adhere to the surface of the MgO seed crystal. If the MgO seed crystal is melted as described above, the MgO seed crystal may be used. At the same time, since the fine MgO crystal particles 30 are also melted, the fine MgO crystal particles 30 can be prevented or suppressed from adhering to the resulting MgO crystal particles 18b. Therefore, the MgO crystal particles 18b obtained by this method have extremely small particle adhesion, and the particle size of each single particle is larger than that of the MgO seed crystal. Specifically, if the MgO crystal particles 18b are prepared by this method, the cumulative particle size distribution of the obtained single particles of each MgO crystal single particle 18b1 is 0.59 μm or more with a cumulative 10% value.

  Since the fired product is obtained as a lump 18d in which a large number of MgO crystal single particles 18b1 are aggregated, the lump 18d is crushed in advance before adhering to the MgO film 18a. Further, even when not mixed and fired with the flux as described above, the MgO crystal particles 18b are likely to agglomerate due to adsorption of moisture or the like, so that it is necessary to disintegrate them. The crushing method is not particularly limited as long as the shape and the cumulative particle size distribution of the MgO crystal particles 18b are within the predetermined range described above, but crushing by the following method is particularly preferable.

  That is, for example, as shown in FIG. 7, a lump 18d such as a fired product is dispersed in a solvent (dispersion medium) to form a first slurry 18e, and an orifice (restriction hole) is applied while pressurizing the first slurry 18e. ) Crush by passing 27. When the lump 18d such as a baked product is a very large lump, it is previously made a small lump before being dispersed in a solvent. This small lump is obtained, for example, by putting the fired product in a mortar and grinding it with a pestle. However, when the mortar is ground until the above-described predetermined cumulative particle size distribution is reached, a part of the cubic MgO crystal single particle 18b1 is easily lost. Therefore, at this stage, as a pretreatment of the crushing step described below, the cubic MgO crystal single particles 18b1 are agglomerated to such an extent that no defects are generated.

  Next, a lump 18d such as a fired product is dispersed in a solvent to form a first slurry 18e. The dispersion medium (solvent) of the first slurry 18e is not particularly limited, but a compound having a highly polar molecular structure such as a hydroxyl group, a carbonyl group, or a nitrile group and not changing the crystal structure of the MgO crystal particle 18b is preferable. Alcohols such as propanol (isopropyl alcohol, IPA) are particularly preferred. The concentration of the MgO crystal particles 18b in the slurry is, for example, 0.01-2 wt%. If it is within this concentration range, the second slurry 18f after pulverization should be used as it is (for example, continuously) when the spray method is used to disperse and distribute the MgO crystal particles 18b on the MgO film 18a. Can do.

  Next, as the crushing step, the first slurry 18e in which the lump 18d is dispersed in the solvent is sent in the direction indicated by the arrow 28 in the drawing by the liquid feeding pressure of the pump (high pressure pump) P of the crushing device, and the first The slurry 18e is crushed by passing through the orifice 27 while being pressurized. The lump 18d, which is an aggregate of MgO crystal particles 18b in the first slurry 18e, is crushed by the shearing force generated when passing through the orifice 27 while being pressurized to obtain the second slurry 18f. As the pump P, for example, a plunger pump or the like can be used. In addition, the hole diameter and the hole shape of the orifice 27 can be appropriately adjusted according to the shearing force that needs to be generated when the first slurry 18e passes. In FIG. 7, as an example of the crushing device, the flow path of the first slurry 18 e that is a fluid is divided into a plurality (two in FIG. 7), and the flow paths are joined before being connected to the orifice 27. Shows how. In this case, the lump 18d included in the first slurry 18e may collide when flowing into the orifice 27, and may be crushed by this impact.

  As such a crushing device, for example, a atomizer “Nanomizer (registered trademark)” manufactured by Yoshida Kikai Kogyo Co., Ltd. can be used. According to this method, since it crushes without using the media which grinds an aggregate, it can prevent mixing of the foreign material in a crushing process. In addition, the degree of aggregation (aggregation degree) can be controlled by adjusting the number of times of passage through the orifice 27 or the liquid feeding pressure. Moreover, since the load (shearing force) applied to the aggregate can also be controlled, it is possible to prevent or suppress the cubic-shaped defects of the MgO crystal particles 18b.

  The cumulative particle size distribution of the MgO crystal particles 18b in the second slurry 18f after pulverization preferably has a cumulative 10% value of 0.77 μm or more. The cumulative 90% value is preferably 3.98 μm or less. This is because the cumulative particle size distribution of the plurality of MgO crystal particles 18b with the MgO crystal particles 18b attached to the surface of the MgO film 18a falls within the predetermined range.

  The above method is most preferable from the viewpoint of the shape retention of the cubic shape of the MgO crystal single particles 18b1, but there is also a method using a ball mill as another method for crushing the fired product. When crushing using a ball mill, as an example, crushing can be done using zirconia. In this case, the degree of aggregation can be controlled by changing the amount of boulder and the processing time. However, when pulverizing with a ball mill, it becomes a pulverization method using media (spheroids). Therefore, when excessively pulverized, not only the aggregation of secondary particles (that is, lump 18d) is unraveled, The primary particles (MgO crystal single particles 18b1) may be damaged. For example, there is a concern that it does not become a cubic shape. In addition, even when pulverizing with a ball mill, the first slurry 18e described above is prepared, and the mass 18d of MgO crystal particles 18b contained in the first slurry 18e is crushed similarly. It is.

  FIG. 8 shows a cumulative particle size distribution when the first slurry 18e described above is processed by a ball mill or an atomizer. The particle size distribution curves of (A), (B), and (C) shown in FIG. 8 are obtained when (A) is processed with a ball mill, (B) is when crushing is performed three times with a atomizer, (C) has shown about the case where a crushing process is performed once with the atomization apparatus. Those treated with the ball mill tend to have a smaller cumulative flow rate distribution than those treated with the atomizer. In (A), it has been crushed to a state that does not include the aggregate 18c (that is, a state that becomes single-particle MgO crystal particles 18b), and in (B) and (C), the state includes the aggregate 18c. Yes. When these are compared, the cumulative flow rate distribution values in the order of (A), (B), and (C) are all high in the cumulative 10% value, the cumulative 50% value, and the cumulative 90% value.

  Further, regarding the cumulative 10% value, it was 0.60 μm in (A), 0.77 μm in (B), and 0.94 μm in (C). That is, in the present embodiment, the result of (A) is that the MgO seed crystal is not used as it is as the MgO crystal particle 18b, but by adding a flux and firing, the cumulative particle size of the MgO crystal particle 18b as a single particle is obtained. This shows that the distribution can be 0.59 μm or more with a cumulative 10% value. The cumulative 90% value was 1.68 μm in (A), 2.93 μm in (B), and 3.84 μm in (C). That is, in (B) and (C), it can be seen that at least some of the MgO crystal particles 18b aggregate to form an aggregate 18c. The results of (B) and (C) are obtained by a method of crushing the mass 18d by passing the orifice 27 while pressurizing the first slurry 18e without using a medium as in the case of the atomizer. It shows that the aggregation state of the plurality of MgO crystal single particles 18b1 can be controlled to fall within a predetermined cumulative particle size distribution.

<2-3-2. Step of attaching a plurality of MgO crystal particles to the surface of the MgO film>
The method of attaching the plurality of MgO crystal particles 18b to the surface of the MgO film 18a is not particularly limited as long as the MgO crystal particles 18b can be uniformly dispersed (including the aggregate 18c; hereinafter the same in this section). The spray method described below is particularly preferable in that the MgO crystal particles 18b can be uniformly dispersed.

  In the spray method, a slurry in which MgO crystal particles 18b are dispersed (for example, the second slurry 18f after pulverization described in <2-3-1>) is discharged from a spray device called a spray gun and attached. As the spray gun, a so-called two-fluid air atomizing system that atomizes and discharges the second slurry 18f and air into a two-liquefied state can be used.

  The concentration of the MgO crystal particles 18b in the slurry is 0.01 to 2 wt%. At this time, the size of the droplets of the atomized second slurry 18f can be adjusted by adjusting the pressure of the air (atomization pressure) for atomizing the second slurry 18f. Therefore, reaggregation of the MgO crystal particles 18b in the droplets or adhesion failure to the MgO film 18a can be prevented. The MgO crystal particles 18b can be attached to the entire surface or a part of the MgO film 18a.

  In the present embodiment, the cumulative particle size distribution of the MgO crystal particles 18b is adjusted within a predetermined range as described in the section <2-2-3> and <2-2-4>. Each droplet is uniformly dispersed with the MgO crystal particles 18b. As a result, it is possible to deposit uniformly with a coverage of 10% or less over the entire visual field range on the surface of the MgO film 18a.

<3. Effect verification experiment>
Next, in order to verify the effect of each configuration in the PDP 1 of the present embodiment described above, the result of a verification experiment performed by the present inventor will be described. FIG. 9 is an explanatory diagram showing the results of the effect verification experiment of the present embodiment.

  In the effect verification experiment shown in FIG. 9, a PDP having a cumulative particle size distribution in which the cumulative particle size distribution 90% value of the MgO crystal particles 18b is 1.67 μm (sample 1) to 6.14 μm (sample 10) is produced. The effect of the configuration described in the present embodiment was verified by comparing the delay and uneven brightness (granular unevenness) in the screen at the time of lighting. In FIG. 9, “D90” represents a cumulative 90% value in each sample, and its unit is μm. “D50” and “D10” respectively represent a cumulative 50% value and a cumulative 10% value in each sample, and the unit is μm. Hereinafter, conditions for preparing Samples 1 to 10 will be described in order.

<3-1. Preparation conditions of MgO crystal particles>
The method for preparing the MgO crystal particles 18b is as follows. First, 48 ppm of MgF2 (manufactured by Furuuchi Chemical Co., Ltd., purity: 99.99%) was added as a flux to an MgO seed crystal (trade name: vapor phase high purity ultrafine magnesia (2000A), manufactured by Ube Materials Corporation). . This was mixed and ground by grinding with a mortar and pestle. Next, the raw material after mixing and pulverization was fired in the air at a firing time of 1 hour and a temperature of 1450 ° C. to obtain a fired product of MgO crystal particles 18b. Next, the fired product obtained using a mortar and pestle was crushed into a lump 18d.

  Part of the obtained mass 18d is mixed with IPA (manufactured by Kanto Chemical Co., Ltd., for electronic industry), and pulverized using a zirconia ball ball mill until the aggregate 18c is eliminated, and there is no aggregation. A slurry (different from the second slurry 18f in that the aggregate 18c is not included) was obtained. In Sample 1 shown in FIG. 9, the slurry processed by this ball mill was distributed and distributed to the MgO film 18a to produce a PDP.

  Moreover, after another part of the obtained lump 18d was mixed with IPA, the agglomeration was controlled by changing the number of treatments using a pulverizer (that is, the cumulative 90% value with respect to the state where no agglomerate was present). To obtain a second slurry 18f.

  With respect to the obtained MgO crystal particles 18b, a cumulative particle size distribution was determined using a laser diffraction particle size distribution meter (model: LA-300, manufactured by Horiba, Ltd.). The obtained results are shown in FIG.

<3-2. Conditions for dispersion distribution to MgO film>
Next, the surface of the MgO film 18a was spray-coated with a second slurry 18f whose aggregation was controlled using a coating spray gun, and the MgO crystal particles 18b were adhered to the surface of the MgO film 18a. The spray gun used was a two-fluid air atomization system. The concentration of MgO crystal particles 18b in the second slurry 18f was set to 0.6 wt%, and the atomization pressure applied to the spray gun was set to 180 kPa. The MgO crystal particles 18b were attached so that the density of the MgO crystal particles 18b was 0.1 g per m ² .

<3-3. Other manufacturing conditions for PDP>
Other manufacturing conditions of the PDPs of Samples 1 to 10 shown in FIG. 9 are as follows. As shown in FIG. 1, a display electrode pair (X electrode 14 and Y electrode 15), a dielectric layer 17, and a protective layer 18 (MgO film 18a and a plurality of aligned alignments deposited thereon are formed on a front substrate 13 made of glass. The front-side substrate structure 11 was produced by forming the MgO crystal particles 18b). In addition, the back-side substrate structure 12 was fabricated by forming the address electrodes 20, the dielectric layers 21, the barrier ribs 22, and the phosphors 23 on the back substrate 19 made of glass. Next, the front side substrate structure 11 and the back side substrate structure 12 were overlapped and the peripheral edge portion was sealed with a sealing material to produce a panel having an airtight discharge space inside. Next, after the discharge space 24 was evacuated, a discharge gas was enclosed to complete the PDP.

The conditions of each substrate structure are as follows.
(Front side substrate structure 11)
Width of X and Y transparent electrodes 14a and 15a: 270 μm
Width of X and Y bus electrodes 14b and 15b: 95 μm
Discharge gap width: 100 μm
Dielectric layer 17: formed by coating and firing a low-melting glass paste, thickness: 30 μm
MgO film 18a: MgO film by electron beam evaporation, thickness: 1.1 μm
(Back side substrate structure 12)
Address electrode 20 width: 70 μm
Dielectric layer 21: formed by applying and baking a low-melting glass paste, thickness: 10 μm
The thickness of each phosphor 23 just above the address electrode 20: 20 μm
Partition 22 height: 140 μm Top width: 50 μm
Partition pitch 22: 360 μm
Discharge gas: Ne96% -Xe4%, 500 Torr.

<3-4. Lighting test and evaluation>
Next, a lighting test was performed on each manufactured PDP, and the coverage of the MgO film 18a, presence or absence of red unevenness, discharge voltage, granular unevenness, discharge delay, and X-ray diffraction signal intensity measurement were evaluated. The results of the lighting test are shown in FIG.

  First, the coverage, the presence / absence of red unevenness, and the evaluation results of the discharge voltage will be described. In the measurement of the coverage, the visual field range was divided and the coverage was measured at 10 measurement points. In Samples 1 to 10, the coverage of the MgO film 18a was 10% or less at all the measurement points. Moreover, what was called an aging process for 8 hours was performed about each PDP, and the red nonuniformity mentioned above was confirmed visually, but the red nonuniformity was not able to be confirmed about all the samples 1-10. In the case where the phosphor 23 is deteriorated due to the impurities, if the aging process is performed for about 8 hours, the unevenness of red becomes obvious. Therefore, in the samples 1 to 10 shown in FIG. 9, the coverage of the MgO film 18a is 10% or less. Thus, it is considered that the appearance of red unevenness could be prevented. Although not shown in FIG. 9, a PDP in which the MgO crystal particles 18b are not attached to the surface of the MgO film 18a was also prepared, and the discharge voltage of this PDP and each PDP of Samples 1 to 10 was measured. There was no increase. Therefore, it is considered that samples 1 to 10 shown in FIG. 9 were able to prevent the discharge voltage from increasing by setting the coverage of the MgO film 18a to 10% or less.

  Next, the evaluation result of light and dark unevenness (granular unevenness) will be described. The test for granular unevenness is performed by visual observation, and a sample in which the unevenness is not visually recognized (that is, not manifested) is marked with ◯, and a sample that has been visually recognized (realized) is marked with ×. As shown in FIG. 9, the granular unevenness was visually recognized in the samples 8 to 10 in which the cumulative 90% value of the MgO crystal particles 18b was 4.04 μm or more as shown in FIG. 9. On the other hand, no granular unevenness was observed in any of Samples 1 to 7 having a size of 3.98 μm or less. From this result, it was experimentally verified that it is possible to prevent the appearance of granular unevenness by setting the cumulative 90% value of the MgO crystal particles 18b to 3.98 μm or less.

  In addition, according to the present embodiment, the cumulative particle size distribution of the MgO crystal particles 18b can be kept within a predetermined range without adding a new process such as classification of the MgO crystal particles 18b. Can be suppressed. In the present embodiment, the step of crushing the lump 18d in the first slurry 18e is included, but the single crystal of MgO has high cohesiveness. For example, the MgO seed crystal described above is converted into the MgO crystal. Even if it is used as particles as it is, it is necessary to crush the aggregates by some method, so even if this step is carried out, the production steps are not particularly increased.

  Next, the evaluation result of the discharge delay will be described. In the discharge delay test, a voltage was applied to the address electrode 20, and the time from when the voltage was applied until when the discharge was actually started was measured. The time until the start of discharge was measured 1000 times, and the evaluation method evaluated the time required for 95% or more of the 1000 measured data to start discharging (the value of the cumulative discharge success probability being 95%). Regarding the determination of whether or not the discharge delay has been improved, the sample with the cumulative discharge success probability of 95% is less than 1.1 μm, and the value with the cumulative discharge success probability of 95% is 1.1 μm or more. Each sample is marked with a cross. The reason why the threshold for determining the improvement effect of the discharge delay is 1.1 μm is as follows. That is, it was determined in consideration of the case where the PDP 1 is adapted to the full high-definition standard. Specifically, in a PDP 1 conforming to the full high-definition standard, when considering a case where one field (16.7 milliseconds) is divided into 10 subfields and driven in a progressive manner, the time per subfield is about 1.7 milliseconds. It is. Since 1080 address discharge scans are performed within this time, the discharge delay in the address discharge needs to be at least 1.6 μsec (1.7 msec / 1080 times). In addition, since it is necessary to perform a sustain discharge and an initializing discharge (so-called reset discharge) within one subfield, 1.1 μsec is set as a threshold in consideration of the time required for these.

  In FIG. 9, neither Sample 1 nor Sample 2 in which the cumulative 10% value of MgO crystal particles 18b was 0.69 μm or less confirmed the effect of improving the discharge delay. On the other hand, all of Samples 3 to 10 having a thickness of 0.77 μm or more could improve the discharge delay.

  As a result of measuring the X-ray diffraction signal intensity for each sample and performing the above-described normalization, the samples 1 and 2 both have an X-ray diffraction signal intensity on the (111) plane per 1 μm thickness of the MgO film 18a. It was less than 1 times. On the other hand, in Samples 3 to 10, all were equal to or greater than the same size. From this result, it can be seen that by setting the cumulative 10% value of MgO crystal particles 18b to 0.77 μm or more, the orientation of each MgO crystal particle 18b can be aligned in the (100) plane, and as a result, the discharge delay can be improved. It was. In addition, the degree of alignment can be determined by measuring the X-ray diffraction signal intensity, and {(200) plane signal intensity / (111) plane signal intensity} after the above-described normalization is performed. It has been found that the discharge delay is improved when the value of is equal to or greater than 1.

  Samples 2 to 10 each include the aggregate 18c of the MgO crystal single particles 18b1 shown in the sample 1, and the ones with varying degrees of aggregation are used. Therefore, if the cumulative particle size distribution of each MgO crystal single particle 18b1 contained in the aggregate 18c in Samples 2 to 10 is 0.59 μm or more in terms of a cumulative 10% value, the degree of aggregation is controlled to control the aggregation. It has been experimentally verified that the discharge delay can be improved by setting the cumulative 10% value of the MgO crystal particles 18b including the aggregates 18c to 0.77 μm or more.

  In the configuration including the aggregate 18c, the cumulative particle size distribution of the single particles of the MgO crystal single particles 18b1 constituting the aggregate 18c is even smaller than this, and the cumulative 10% value is 0.59 μm or more. It has been found that the discharge delay can be improved because the orientation of the surface facing the discharge space 24 can be made uniform in the (100) plane.

<3-5. Related Experiments>
Next, as a related experiment, a test for confirming the uniformity of the dispersed state of the MgO crystal particles 18b was performed. As an index indicating the uniformity of the dispersed state of the MgO crystal particles 18b, a value obtained by dividing three times the standard deviation of the coverage of the MgO film 18a by the average value of the coverage is used. It has been found that when this value exceeds 20%, granular unevenness becomes obvious due to variation in coverage. Here, the “standard deviation” means the standard deviation of the coverage estimated based on the sample of the coverage for each measurement visual field. The reason why “a value obtained by dividing three times the standard deviation of the coverage ratio of the MgO film 18a by the average value of the coverage ratio” as an index is as follows. That is, assuming that the distribution of the coverage is a normal distribution and assuming that the standard deviation is σ, the average value +/− 3σ includes 99.73% of all data, and thus the variation in the measured value is increased. It was expressed as 3σ. For comparison, 3σ was divided by the average value for the purpose of expressing the extent of variation with respect to the average value.

  When a value obtained by dividing three times the standard deviation of the coverage of the MgO film 18a by the average value of the coverage was measured, it was confirmed that all the samples 3 to 7 were 20% or less. That is, according to the present embodiment, by setting the cumulative 10% value of the MgO crystal particles 18b to 0.77 μm or more and the cumulative 90% value to 3.98 μm or less, each cell 25 (see FIG. 1). The variation in the cumulative particle size distribution of can be reduced.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  The present invention relates to a plasma display panel used in, for example, a display device such as a personal computer or a workstation, a flat-screen television receiver, or a plasma display device used as a device for displaying advertisements or information. Can be widely applied.

It is a principal part expansion assembly perspective view which expands and shows the principal part of PDP which is one embodiment of this invention. It is a principal part expansion perspective view which reverses the upper and lower sides of the front substrate structure shown in FIG. 1, and shows the surface state of a protective layer. It is explanatory drawing for demonstrating the particle size distribution model of MgO crystal particle. It is a figure which shows an example of the MgO crystal particle shown in FIG. 2, Comprising: It is a perspective view which shows a MgO crystal single particle. It is a figure which shows an example of the MgO crystal particle shown in FIG. 2, Comprising: It is explanatory drawing which shows the aggregate which the side surface of three MgO crystal single particles adhered and aggregated. FIG. 3 is an enlarged sectional view showing a microscopic relationship between the MgO film and MgO crystal particles shown in FIG. 2. It is explanatory drawing for demonstrating an example of the embodiment of the crushing method in the crushing process for preparing the MgO crystal particle shown in FIGS. It is explanatory drawing which shows the cumulative particle size distribution of the MgO crystal particle for every crushing method in the crushing process for preparing the MgO crystal particle shown in FIGS. It is explanatory drawing which shows the result of the effect verification experiment of one embodiment of this invention. It is an expanded sectional view which shows the microscopic relationship of the MgO film | membrane and MgO crystal particle which is a comparative example with respect to one embodiment of this invention. It is an expanded sectional view which shows the microscopic relationship of the MgO film | membrane and MgO crystal particle which is another comparative example with respect to one embodiment of this invention.

Explanation of symbols

1 PDP (Plasma Display Panel)
11 Front substrate structure (first substrate structure)
12 Back substrate structure (second substrate structure)
13 Front substrate (first substrate)
13a First surface (surface)
14 X electrode (display electrode)
14a X transparent electrode 14b X bus electrode 15 Y electrode (display electrode)
15a Y transparent electrode 15b Y bus electrode 17 Dielectric layer 18 Protective layer 18a MgO films 18b, 30, 31 MgO crystal particles 18b1 MgO crystal single particles 18c Aggregates 18d Agglomerates 18e First slurry 18f Second slurry 19 Back substrate (Second board)
20 address electrode 21 dielectric layer 22 partition walls 23, 23r, 23g, 23b phosphor 24 discharge space 25 cell 26 gap 27 orifice (throttle hole)
28 Arrow W1 Vertical distance

Claims (9)

A pair of substrate structures facing each other via a discharge space formed by enclosing a discharge gas, wherein one of the pair of substrate structures includes a plurality of display electrode pairs disposed on a substrate; a dielectric layer covering the display electrode pairs, a plasma display panel which have a protective layer covering the dielectric layer,
The protective layer includes a MgO (magnesium oxide) film laminated on the surface of the dielectric layer, and a plurality of MgO crystal particles dispersedly arranged on the MgO film in a region corresponding to all cells of the plasma display panel And
The coverage of the surface of the MgO film with the plurality of MgO crystal particles is 10% or less,
A plasma display panel, which comprises a cumulative 90% value of the cumulative particle size distribution of the plurality of MgO crystal particles less 3.98Myuemu. The plasma display panel according to claim 1, wherein
A plasma display panel, wherein a cumulative 10% value of a cumulative particle size distribution of the plurality of MgO crystal particles is 0.77 μm or more . The plasma display panel according to claim 1 or 2,
The plasma display panel, wherein the plurality of MgO crystal particles include an aggregate obtained by aggregating a plurality of MgO crystal single particles. In the plasma display panel according to any one of claims 1 to 3,
The plurality of MgO crystal particles are obtained by mixing a MgO seed crystal obtained by a vapor phase method and a flux that promotes melting of the MgO seed crystal, firing the mixture, and crushing the obtained fired product. A plasma display panel characterized by that. The plasma display panel according to claim 4, wherein
The baked product is crushed by dispersing the baked product in a solvent to form a slurry, and crushing the baked product by passing through an orifice while pressing the slurry. Forming a display electrode pair on one surface of the first substrate;
Forming a dielectric layer so as to cover the display electrode pair;
A method of manufacturing a PDP of the chromatic and forming a protective layer on the surface of the dielectric layer,
In the step of forming the protective layer,
Preparing a plurality of MgO crystal particles;
Forming a MgO (magnesium oxide) film on the surface of the dielectric layer;
The plurality of MgO crystal particles are dispersedly arranged on the surface of the MgO film in a region corresponding to all cells of the plasma display panel so that the coverage of the MgO film with the plurality of MgO crystal particles is 10% or less. It contains a step,
Before SL more of MgO crystal grains cumulative particle size distribution 10% accumulated value of 0.77μm or more, a manufacturing method of a plasma display panel, characterized by the following 3.98μm cumulative 90% value. In the manufacturing method of the plasma display panel of Claim 6,
The method for manufacturing a plasma display panel, wherein the plurality of MgO crystal particles include an aggregate in which a plurality of MgO crystal single particles are aggregated. In the manufacturing method of the plasma display panel of Claim 6 or Claim 7,
In the step of preparing the plurality of MgO crystal particles,
A plasma display panel comprising a step of mixing an MgO seed crystal obtained by a vapor phase method and a flux that promotes melting of the MgO seed crystal, followed by firing and crushing the obtained fired product. Manufacturing method. In the manufacturing method of the plasma display panel of Claim 8,
The method for producing a plasma display panel is characterized in that the baked product is crushed by dispersing the baked product in a solvent to form a slurry and passing the orifice through the slurry while pressurizing the slurry.

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