JP2011150909A - Plasma display panel and plasma display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain plasma display panel having high light-emitting efficiency at low power consumption. <P>SOLUTION: In the plasma display panel having a front plate forming a dielectric layer so as to cover a display electrode formed on a substrate and forming a protective layer on the dielectric layer, and a back plate oppositely arranged so as to form a discharge space on the front plate and forming a data electrode in a direction crossed with the display electrode and preparing a partition for dividing the discharge space, upon forming a base film 91 on the dielectric layer 8, the protective layer 9 is formed by making agregated particles 92 wherein crystal particles 92b with a particle diameter smaller than that of the crystal particle 92a are aggregated on the crystal particles 92a made of metal oxide, and cube-shaped crystal particles 93 made of metal oxide stick so as to be distributed over the whole surface on the base film 91. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a plasma display panel and a plasma display apparatus as display devices.

  Since plasma display panels (hereinafter referred to as PDP) can achieve high definition and large screen, 65-inch class televisions have been commercialized. In recent years, PDP has been applied to high-definition televisions having more than twice the number of scanning lines as compared with the conventional NTSC system, and PDP containing no lead component is required in consideration of environmental problems.

  A PDP basically includes a front plate and a back plate. The front plate is a glass substrate made of sodium borosilicate glass by a float method, a display electrode composed of a striped transparent electrode and a bus electrode formed on one main surface of the glass substrate, and a display electrode A dielectric layer that covers and acts as a capacitor, and a protective layer made of magnesium oxide (MgO) formed on the dielectric layer. On the other hand, the back plate is a glass substrate, stripe-shaped data electrodes formed on one main surface thereof, a base dielectric layer covering the data electrodes, a partition formed on the base dielectric layer, It is comprised with the fluorescent substance layer which light-emits each of red, green, and blue formed between the partition walls.

  The front plate and the back plate are hermetically sealed with their electrode forming surfaces facing each other, and Ne—Xe discharge gas is sealed at a pressure of 400 Torr to 600 Torr in a discharge space partitioned by a partition wall. 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 (See Patent Document 1).

JP 2003-128430 A

  In such a PDP, the protective layer formed on the dielectric layer of the front plate protects the dielectric layer from ion bombardment due to discharge, and emits initial electrons for generating address discharge. It is done. Protecting the dielectric layer from ion bombardment plays an important role in preventing an increase in discharge voltage, and emitting initial electrons for generating an address discharge is an address discharge error that causes image flickering. It is an important role to prevent.

  In order to increase the number of initial electrons emitted from the protective layer and reduce the flicker of the image, for example, an attempt has been made to add Si or Al to MgO.

  In recent years, high definition has been advanced in televisions, and a low-cost, low-power-consumption, high-brightness full HD (high definition) (1920 × 1080 pixels: progressive display) PDP is required in the market. Since the electron emission characteristics from the protective layer determine the image quality of the PDP, it is very important to control the electron emission characteristics.

  The present invention has been made in view of such problems, and an object of the present invention is to realize a PDP having high-definition and high-luminance display performance and low power consumption.

  In order to achieve the above object, a PDP according to the present invention includes a front plate in which a dielectric layer is formed so as to cover a display electrode formed on a substrate and a protective layer is formed on the dielectric layer. A plasma display panel having a back plate which is disposed so as to form a discharge space on the face plate and which has a data electrode in a direction crossing the display electrode and which has a partition wall which partitions the discharge space, The protective layer forms a base film on the dielectric layer, and on the base film, aggregated particles obtained by aggregating crystal particles having a particle size smaller than the crystal particles on crystal particles made of a metal oxide; It is characterized in that a plurality of cubic crystal particles made of metal oxide are attached so as to be distributed over the entire surface.

  Further, the plasma display device has a front plate in which a dielectric layer is formed so as to cover the display electrodes formed on the substrate and a protective layer is formed on the dielectric layer, and a discharge space is formed in the front plate. And a plasma display panel having a plurality of discharge cells, the data electrode being formed in a direction crossing the display electrode and a back plate provided with a partition wall that partitions the discharge space. For the plasma display panel, one field is composed of a plurality of subfields, and an address period for generating an address discharge for selecting a discharge cell to emit light in each subfield, and a discharge selected by the address period Plasma display for displaying light emission by providing a sustain period for generating a sustain discharge in a cell The protective layer of the plasma display panel forms a base film on the dielectric layer, and a crystal particle made of a metal oxide on the base film has a particle size smaller than the crystal particle. It is characterized in that a plurality of agglomerated particles obtained by agglomerating crystal particles having a cubic shape and cubic crystal particles made of a metal oxide are attached so as to be distributed over the entire surface.

  In PDPs, attempts have been made to improve the electron emission characteristics by mixing impurities in the protective layer. However, if the impurities are mixed in the protective layer to improve the electron emission characteristics, the surface of the protective layer is simultaneously developed. The charge is accumulated in the memory, and the decay rate at which the charge is reduced over time when used as a memory function increases. Therefore, it is necessary to take measures such as increasing the applied voltage to suppress this. As described above, the protective layer must have a high electron emission ability and a low charge decay rate as a memory function, that is, a high charge retention characteristic. There was a problem.

  The present invention provides a PDP that improves electron emission characteristics, has charge retention characteristics, and can achieve both high image quality, low cost, and low voltage, thereby achieving low power consumption, high definition, and high brightness. A PDP having display performance can be realized.

  In particular, according to the present invention, by improving the electron emission characteristics, the discharge delay characteristics in the PDP can be improved, and the sustain discharge voltage during the sustain discharge can be reduced.

The perspective view which shows the structure of PDP in embodiment of this invention Electrode arrangement of the PDP Block circuit diagram of plasma display device of the present invention Drive voltage waveform diagram of the device Sectional drawing which shows the structure of the front plate of the PDP Explanatory drawing which expands and shows the protective layer part of the PDP The schematic diagram which shows the particle structure of the surface of a protective layer in PDP by this invention Enlarged view for explaining aggregated particles in the protective layer of the PDP Characteristic diagram showing the results of cathodoluminescence measurement of crystal particles FIG. 5 is a characteristic diagram showing the results of examination of electron emission performance and Vscn lighting voltage in a PDP in the results of experiments conducted to explain the effects of the present invention FIG. 5 is a characteristic diagram showing the relationship between the lighting time of the PDP and the electron emission performance in the results of experiments conducted to explain the effects of the present invention. Enlarged view for explaining the coverage in the protective layer of the PDP FIG. 6 is a characteristic diagram showing comparison of sustain discharge voltages in the results of experiments conducted to explain the effects of the present invention. Characteristic diagram showing the relationship between crystal grain size and electron emission performance Characteristic diagram showing the relationship between the grain size of crystal grains and the incidence of partition wall breakage Process drawing which shows the process of protective layer formation in the manufacturing method of PDP by this invention

  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 Ne or Xe at a pressure of 400 Torr to 600 Torr.

  On the front glass substrate 3 of the front plate 2, a pair of strip-like display electrodes 6 made up of scanning electrodes 4 and sustain electrodes 5 and black stripes (light-shielding layers) 7 are arranged in a plurality of rows in parallel with each other. A dielectric layer 8 serving as a capacitor is formed on the front glass substrate 3 so as to cover the display electrode 6 and the light shielding layer 7, and a protective layer 9 made of magnesium oxide (MgO) is formed on the surface. Has been.

Here, the scan electrode 4 and the sustain electrode 5 are each formed by forming a bus electrode made of Ag on a transparent electrode made of a conductive metal oxide such as ITO, SnO ₂ , or ZnO.

  Further, on the rear glass substrate 11 of the rear plate 10, a plurality of data electrodes 12 made of a conductive material mainly composed of Ag parallel to each other in a direction orthogonal to the scanning electrodes 4 and the sustain electrodes 5 of the front plate 2. Are arranged in parallel to each other, and the underlying dielectric layer 13 covers them. Further, a partition wall 14 having a predetermined height is formed on the underlying dielectric layer 13 between the data electrodes 12 to divide the discharge space 16. A phosphor layer 15 that emits red, green, and blue light by ultraviolet rays is sequentially applied to the data electrode 12 in the groove between the barrier ribs 14. A discharge cell is formed at a position where the scan electrode 4 and the sustain electrode 5 intersect with the data electrode 12, and the discharge cell 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.

  In the present invention, the discharge gas sealed in the discharge space 16 is a discharge gas mixed so that the concentration of xenon is 10% or more and 30% or less in the discharge gas.

  FIG. 2 is an electrode array diagram of the PDP in the embodiment of the present invention. N scanning electrodes Y1, Y2, Y3... Yn (4 in FIG. 1) and n sustaining electrodes X1, X2, X3... Xn (5 in FIG. 1) are arranged in a row. M data electrodes D1... Dm (12 in FIG. 1) which are long in the direction are arranged. A discharge cell is formed at a portion where a pair of scan electrode Y1 and sustain electrode X1 intersects with one data electrode D1, and m × n discharge cells are formed in the discharge space. Each of these electrodes is connected to a connection terminal provided at a peripheral end portion outside the image display area of the front plate and the back plate.

  FIG. 3 is a circuit block diagram of a plasma display device using this PDP. This plasma display device includes a PDP panel 20, an image signal processing circuit 21, a data electrode drive circuit 22, a scan electrode drive circuit 23, a sustain electrode drive circuit 24, a timing generation circuit 25, and a power supply circuit (not shown). ).

  The image signal processing circuit 21 converts the image signal sig into image data for each subfield. The data electrode driving circuit 22 converts the image data for each subfield into signals corresponding to the data electrodes D1 to Dm, and drives the data electrodes D1 to Dm. The timing generation circuit 25 generates various timing signals based on the horizontal synchronization signal H and the vertical synchronization signal V, and supplies them to each drive circuit block. Scan electrode drive circuit 23 supplies drive voltage waveforms to scan electrodes SC1 to SCn based on timing signals, and sustain electrode drive circuit 24 supplies drive voltage waveforms to sustain electrodes SU1 to SUn based on timing signals.

  Next, a driving voltage waveform and its operation for driving the PDP will be described with reference to FIG. FIG. 4 is a diagram showing drive voltage waveforms applied to the respective electrodes of the PDP.

  In the plasma display device according to the present embodiment, one field is constituted by a plurality of subfields, and each subfield emits light after an initialization period in which an initializing discharge is generated in the discharge cell, and after the initializing period. An address period for generating an address discharge for selecting a discharge cell to be generated, and a sustain period for generating a sustain discharge in the discharge cell selected by the address period.

  In the initializing period of the first subfield, the data electrodes D1 to Dm and the sustain electrodes SU1 to SUn are held at 0 (V), and from the voltage Vi1 (V) that is lower than the discharge start voltage with respect to the scan electrodes SC1 to SCn. A ramp voltage that gradually increases toward the voltage Vi2 (V) exceeding the discharge start voltage is applied. Then, the first weak initializing discharge is caused in all the discharge cells, negative wall voltages are stored on scan electrodes SC1 to SCn, and positive walls on sustain electrodes SU1 to SUn and data electrodes D1 to Dm. The voltage is stored. Here, the wall voltage on the electrode refers to a voltage generated by wall charges accumulated on the dielectric layer or the phosphor layer covering the electrode.

  Thereafter, sustain electrodes SU1 to SUn are maintained at positive voltages Ve1 and Ve2 (V), and a ramp voltage that gradually decreases from voltage Vi3 (V) to voltage Vi4 (V) is applied to scan electrodes SC1 to SCn. Then, the second weak initializing discharge is caused in all the discharge cells, the wall voltage between scan electrodes SC1 to SCn and sustain electrodes SU1 to SUn is weakened, and the wall voltage on data electrodes D1 to Dm is reduced. Is also adjusted to a value suitable for the write operation.

  In the subsequent address period, scan electrodes SC1 to SCn are temporarily held at Vc (V). Next, negative scan pulse voltage Va (V) is applied to scan electrode SC1 in the first row, and data electrode Dk (k = 1 to 1) of the discharge cell to be displayed in the first row among data electrodes D1 to Dm. A positive write pulse voltage Vd (V) is applied to m). At this time, the voltage at the intersection between the data electrode Dk and the scan electrode SC1 is obtained by adding the wall voltage on the data electrode Dk and the wall voltage on the scan electrode SC1 to the externally applied voltage (Vd−Va) (V). And the discharge start voltage is exceeded. Then, an address discharge occurs between data electrode Dk and scan electrode SC1 and between sustain electrode SU1 and scan electrode SC1, and a positive wall voltage is accumulated on scan electrode SC1 of this discharge cell, and on sustain electrode SU1. And a negative wall voltage is also accumulated on the data electrode Dk.

  In this manner, an address operation is performed in which address discharge is caused in the discharge cells to be displayed in the first row and wall voltage is accumulated on each electrode. On the other hand, the voltage at the intersection of the data electrodes D1 to Dm and the scan electrode SC1 to which the address pulse voltage Vd (V) is not applied does not exceed the discharge start voltage, so that address discharge does not occur. The above address operation is sequentially performed until the discharge cell in the nth row, and the address period ends.

  In the subsequent sustain period, positive sustain pulse voltage Vs (V) is applied to scan electrodes SC1 to SCn as a first voltage, and ground potential, that is, 0 (V) is applied to sustain electrodes SU1 to SUn as a second voltage. Apply. In the discharge cell in which the address discharge has occurred at this time, the voltage between scan electrode SCi and sustain electrode SUi is the sustain pulse voltage Vs (V), the wall voltage on scan electrode SCi and the wall voltage on sustain electrode SUi. Is added and exceeds the discharge start voltage. Then, a sustain discharge occurs between scan electrode SCi and sustain electrode SUi, and the phosphor layer emits light due to the ultraviolet rays generated at this time. Then, a negative wall voltage is accumulated on scan electrode SCi, and a positive wall voltage is accumulated on sustain electrode SUi. At this time, a positive wall voltage is also accumulated on the data electrode Dk.

  In the discharge cells in which no address discharge has occurred in the address period, no sustain discharge occurs, and the wall voltage at the end of the initialization period is maintained. Subsequently, 0 (V) that is the second voltage is applied to scan electrodes SC1 to SCn, and sustain pulse voltage Vs (V) that is the first voltage is applied to sustain electrodes SU1 to SUn. Then, in the discharge cell in which the sustain discharge has occurred, the voltage between the sustain electrode SUi and the scan electrode SCi exceeds the discharge start voltage, so that the sustain discharge occurs again between the sustain electrode SUi and the scan electrode SCi, Negative wall voltage is accumulated on sustain electrode SUi, and positive wall voltage is accumulated on scan electrode SCi.

  Thereafter, similarly, by applying sustain pulses of the number corresponding to the luminance weight alternately to scan electrodes SC1 to SCn and sustain electrodes SU1 to SUn, the sustain discharge continues in the discharge cells that have caused the address discharge in the address period. Done. Thus, the maintenance operation in the maintenance period is completed.

  The operations in the initialization period, the writing period, and the sustain period after the subsequent second subfield are substantially the same as the operations in the first subfield, and thus description thereof is omitted. In the present embodiment, in subfields after the second subfield, sustain electrodes SU1 to SUn are maintained at positive voltages Ve1 and Ve2 (V), and scan electrodes SC1 to SCn are supplied with voltage Vi3 (V). By applying a ramp voltage that gradually falls toward the voltage Vi4 (V), a weak initializing discharge is driven only in the discharge cells in which the sustain discharge has occurred in the previous subfield. That is, in the first subfield, an all-cell initializing operation for generating an initializing discharge in all discharge cells is performed, and in the second and subsequent subfields, only the discharge cells that have caused a sustain discharge in the previous subfield are performed. An operation for selectively generating an initializing discharge is performed. The all-cell initializing operation and the selective initializing operation are different from the first subfield and the other subfields as in the present embodiment, and the all-cell initializing operation is the same as the first subfield. It may be performed in the initialization period in subfields other than the field, or may be performed once every several fields.

  The operation in the address period and the sustain period is the same driving method as that in the first subfield described above, but the number of sustain pulses corresponding to the luminance weighting is applied for light emission by the sustain discharge in the sustain period. Thus, driving is performed so as to control the luminance weight for each subfield.

  The present invention can improve the discharge delay characteristic in the PDP by improving the electron emission characteristic of the PDP in such a plasma display device, and can reduce the consumption by reducing the sustain discharge voltage during the sustain discharge. The present invention provides a display device having high-power and high-luminance display performance with electric power, and the configuration that characterizes the present invention will be described in detail below.

FIG. 5 is a cross-sectional view showing the configuration of the front plate 2 of the PDP 1 according to the embodiment of the present invention, which is shown upside down with respect to FIG. As shown in FIG. 5, the display electrode 6 and the light shielding layer 7 which consist of the scanning electrode 4 and the sustain electrode 5 are pattern-formed on the front glass substrate 3 manufactured by the float process etc. As shown in FIG. 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 ), etc., 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 silver (Ag) material.

  The dielectric layer 8 is provided so as to cover the transparent electrodes 4 a and 5 a, the metal bus electrodes 4 b and 5 b formed on the front glass substrate 3, and the light shielding layer 7, and further a protective layer 9 on the dielectric layer 8. Is forming.

  Next, a method for manufacturing a PDP 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. The transparent electrodes 4a and 5a and the metal bus electrodes 4b and 5b of the scan electrode 4 and the 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 desired 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 layer (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 baked and solidified to form the dielectric layer 8 that covers 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 layer 9 made of magnesium oxide (MgO) is formed on the dielectric layer 8 by a vacuum deposition method. Through the above steps, predetermined components (scanning electrode 4, sustaining electrode 5, light shielding layer 7, dielectric layer 8, and protective layer 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 data 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 forming a metal film on the entire surface and then patterning using a photolithography method. A data layer is formed by forming a material layer to be a product and firing it at a desired temperature. Next, a dielectric paste is applied on the back glass substrate 11 on which the data electrodes 12 are formed by a die coating method so as to cover the data 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 including 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 and then fired to form the partition walls 14. 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. Next, the phosphor layer 15 is formed by applying 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 and baking it. Through the above steps, the back plate 10 having predetermined components on the back glass substrate 11 is completed.

  In this way, the front plate 2 and the back plate 10 having predetermined constituent members are arranged to face each other so that the scanning electrodes 4 and the data electrodes 12 are orthogonal to each other, and the periphery thereof is sealed with a glass frit, so that a discharge space is obtained. 16 is filled with a discharge gas containing Ne, Xe or the like, thereby completing the PDP 1.

Here, the dielectric layer 8 of the front plate 2 will be described in detail. The dielectric material of the dielectric layer 8 contains 20% to 40% by weight of bismuth oxide (Bi ₂ O ₃ ) as a main component, and further includes calcium oxide (CaO), strontium oxide (SrO), and barium oxide (BaO). At least one selected from 0.5 wt% to 12 wt% selected from molybdenum oxide (MoO ₃ ), tungsten oxide (WO ₃ ), cerium oxide (CeO ₂ ), and manganese dioxide (MnO ₂ ). Is contained in a material composition that does not contain a lead component. In addition to these materials, zinc oxide (ZnO) is contained in an amount of 0 to 40% by weight, boron oxide (B ₂ O ₃ ) in an amount of 0 to 35% by weight, and silicon oxide (SiO ₂ ) in an amount of 0 to 4% by weight. It is configured by mixing a material containing no lead component such as 15% by weight and 0% by weight to 10% by weight of aluminum oxide (Al ₂ O ₃ ).

  The dielectric layer 8 is made of a dielectric material such that the film thickness is 40 μm or less and the relative dielectric constant ε is 7 or less. The effect of setting the dielectric constant ε of the dielectric layer 8 to 7 or less will be described later.

  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 that the average particle size is 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 first 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 dielectric layer paste, the front glass substrate 3 is printed by a die coating method or a screen printing method so as to cover the display electrode 6 and dried, and then the temperature is slightly higher than the softening point of the dielectric material. By baking at 575 ° C. to 590 ° C., the dielectric layer 8 is formed.

  Next, the structure and manufacturing method of the protective layer, which is a feature of the PDP according to the present invention, will be described.

  In the PDP according to the present invention, as shown in FIG. 6, the protective layer 9 forms a base film 91 made of MgO containing Al as an impurity on the dielectric layer 8, and on the base film 91. Aggregated particles 92 in which several crystal particles 92b having a smaller particle diameter than the crystal particles 92a are aggregated on MgO crystal particles 92a which are metal oxides, and cubic crystal particles 93 of MgO which are metal oxides are obtained. It is configured by being dispersed in a discrete manner and adhering a plurality so as to be uniformly distributed over the entire surface. Further, in the present invention, in the aggregated particles 92 in which several MgO crystal particles 92a and several crystal particles 92b are aggregated, the crystal particles 92a are particles having an average particle size in the range of 0.9 μm to 2 μm. The MgO crystal particles 92b having a small average particle diameter are particles having an average particle diameter in the range of 0.3 μm to 0.9 μm.

  FIG. 7 is a schematic diagram showing the actual particle structure of the surface of the protective layer 9 in the PDP according to the present invention. On the base film 91 made of MgO, the polyhedral crystal particles 92a are formed on the polyhedral crystal particles 92a of MgO. It shows that agglomerated particles 92 in which several 92b are agglomerated and MgO cubic crystal particles 93 are adhered in a discretely dispersed state. In addition, the cubic crystal particles 93 of MgO include particles having a particle size of 2000 angstroms and nanoparticles having a particle size of 100 nm or less. The cubic crystal particles 93 are aggregated, the MgO polyhedral crystal particles 92a or the polyhedral crystal particles 92b, or the aggregated particles 92 of the polyhedral crystal particles 92a and 92b are formed into a cubic MgO shape. Some of the crystal particles 93 were attached. Further, the polyhedral crystal particles 92a of MgO are produced by a liquid phase method, and the cubic crystal particles 93 of MgO are produced by a gas phase method.

  Here, as shown in FIG. 8, the agglomerated particles 92 are those in which crystal particles 92a and 92b having a predetermined primary particle size are agglomerated or necked, and are bonded with a large binding force as a solid. Rather, the primary particles form a body of aggregate due to static electricity, van der Waals force, etc., so that some or all of them become primary particles due to external stimuli such as ultrasound. It is what is combined. The particle diameter of the agglomerated particles 92 is about 1 μm, and the crystal particles 92a and 92b have a polyhedral shape having seven or more faces such as a tetrahedron and a dodecahedron. The MgO crystal particles 92a and 92b are prepared by a liquid phase method in which a MgO precursor solution such as magnesium carbonate or magnesium hydroxide is prepared and fired. Crystal particles having a shape can be obtained. The particle size can be controlled by controlling the firing temperature and firing atmosphere by this liquid phase method. Generally, the firing temperature can be selected in the range of about 700 to 1500 degrees, but the primary particle size can be controlled to about 0.3 to 2 μm by setting the firing temperature to a relatively high 1000 degrees or more. . Further, the crystal particles 92a and 92b are obtained by a liquid phase method. By obtaining the MgO precursor by heating, the primary particles are aggregated by a phenomenon called aggregation or necking in the generation process. Particles 92 can be obtained.

  On the other hand, cubic crystal particles 93 of MgO are obtained by a vapor phase method in which magnesium is heated to a boiling point or more to generate magnesium vapor and vapor phase oxidation, and the particle size is 2000 angstroms or more (measured by BET method). As a result, a crystal particle having a cubic single crystal structure and a multiple crystal structure in which the crystals are fitted to each other are obtained. For example, a method for synthesizing magnesium powder by the gas phase method is known from “Materials”, Vol. 36, No. 410, “Synthesis of Magnesia Powder by Gas Phase Method and Its Properties”.

  In addition, in the case of forming a cubic single crystal structure crystal particle having a large particle size with an average particle size of 2000 angstroms or more, a heating temperature at which magnesium vapor is generated is increased, and a flame in which magnesium and oxygen react By increasing the length of, the temperature difference between the flame and the surroundings becomes large, so that MgO crystal particles can be obtained by a gas phase method having a large particle size.

  Further, the aggregated particles 92 in which several MgO polyhedral crystal particles 92a and 92b are aggregated and the MgO cubic crystal particles 93 are excited by electron beam irradiation to emit cathodoluminescence (CL) light. When the CL emission characteristics were measured, the characteristics shown in FIG. 9 were obtained. In FIG. 9, the characteristic indicated by the thin solid line is the CL emission characteristic of the polyhedral crystal particles 92a and 92b of MgO, that is, the CL emission characteristic of the aggregated particle 92, and the characteristic indicated by the thick solid line is that of MgO. This is a characteristic of CL emission of the cubic crystal particle 93.

  As shown in FIG. 9, the aggregated particles 92 in which several MgO polyhedral crystal particles 92a and 92b are aggregated are excited by electron beam irradiation to have a wavelength region of 200 nm to 300 nm, particularly a wavelength range of 230 nm to 250 nm. The crystal grains 93 of the MgO cubic shape have a peak at the wavelength of 200 nm to 300 nm and the emission characteristics of the electron beam are not emitted. This is a characteristic of emitting CL light having a peak in a wavelength region of 400 nm to 450 nm. That is, the aggregated particles 92 in which several MgO polyhedral crystal particles 92a and 92b adhered on the base film 91 made of MgO and the cubic crystal particles 93 of MgO have the above-described CL emission. It has an energy level corresponding to the peak wavelength.

  Next, the results of experiments conducted to confirm the effect of the PDP having the protective layer according to the present invention will be described.

  First, a PDP having a protective layer having a different configuration was made as a prototype. Prototype 1 is a PDP in which only a protective layer made of MgO is formed. Prototype 2 is a PDP in which a protective layer made of MgO doped with impurities such as Al and Si is formed. Prototype 3 is made of metal on the protective layer made of MgO. The PDP, prototype 4, in which only primary particles of oxide crystal particles are dispersed and adhered, has agglomerated particles 92 in which MgO crystal particles having the same particle diameter are aggregated on an underlayer of MgO. The PDP, prototype 5, which is attached so as to be distributed almost uniformly over the entire surface, is a product of the present invention, and an MgO crystal having an average grain size in the range of 0.9 μm to 2 μm on the base film made of MgO. A polyhedral aggregated particle 92 in which MgO crystal particles 92b having a particle diameter smaller than that of the crystal particle 92a are aggregated around the particle 92a and a cubic MgO crystal particle 93 over almost the entire surface. It is a PDP attached so as to be uniformly distributed.

  The PDP having these five types of protective layer configurations was examined for its electron emission performance and charge retention performance.

  The electron emission performance is a numerical value indicating that the larger the electron emission amount, the greater the amount of electron emission. The initial electron emission amount can be measured by irradiating the surface with an ion or electron beam and measuring the amount of electron current emitted from the surface. However, it is difficult to perform non-destructive evaluation of the front plate surface of the panel. Accompany. Therefore, here, as described in Japanese Patent Application Laid-Open No. 2007-48733, a numerical value that is a measure of the probability of occurrence of discharge, called statistical delay time, is measured out of the delay time during discharge, and its reciprocal number. Is integrated into a numerical value that corresponds linearly to the amount of initial electron emission, and this numerical value is used for evaluation here. This delay time at the time of discharge means the time of discharge delay that is delayed from the rise of the pulse, and the discharge delay is the time when the initial electrons that trigger when the discharge is started are discharged from the surface of the protective layer to the discharge space. It is considered as a main factor that it is difficult to be released into the inside.

  In addition, as an indicator of the charge retention performance, a voltage value of a voltage applied to the scan electrode (hereinafter referred to as a Vscn lighting voltage) necessary for suppressing the charge emission phenomenon when manufactured as a PDP was used. That is, the lower the Vscn lighting voltage, the higher the charge retention capability. Since this can be driven at a low voltage even in the panel design of the PDP, it is possible to use components having a small withstand voltage and capacity as the power source and each electrical component. In the current product, an element having a withstand voltage of about 150 V is used as a semiconductor switching element such as a MOSFET for sequentially applying a scanning voltage to the panel, and the Vscn lighting voltage is 120 V or less in consideration of variation due to temperature. It is desirable to keep it down.

  The results of examining the electron emission performance and the charge retention performance are shown in FIG. As is apparent from FIG. 10, prototypes 4 and 5 in which aggregated particles obtained by aggregating MgO crystal particles on a base film made of MgO are dispersed and adhered so as to be distributed almost uniformly over the entire surface. In the evaluation of the charge retention performance, the Vscn lighting voltage can be set to 120 V or lower, and the electron emission performance can be obtained with a favorable characteristic of 6 or higher.

  That is, generally, the electron emission capability and the charge retention capability of the protective layer of the PDP are contradictory. For example, it is possible to improve the electron emission performance by changing the film forming conditions of the protective layer, or by forming a film by doping impurities such as Al, Si, and Ba in the protective layer. As a side effect, the Vscn lighting voltage also increases.

  In the PDP formed with the protective layer according to the present invention, it is possible to obtain an electron emission capability having characteristics of 6 or more and a charge holding capability of Vscn lighting voltage of 120 V or less. For the protective layer of the PDP in which the cell size tends to increase and the cell size tends to decrease, both the electron emission capability and the charge retention capability can be satisfied.

  Here, the result of examining the change with time of the electron emission performance of the protective layer will be described. In order to extend the life of the PDP, it is required that the electron emission performance of the protective layer does not deteriorate over time.

  FIG. 11 shows the transition of the electron emission performance with respect to the lighting time of the PDP as a result of investigating the deterioration over time of the electron emission performance of the prototypes 4 and 5 having good characteristics in FIG. As is apparent from FIG. 11, MgO having a particle size smaller than that of the crystal particles 92a is formed around the MgO crystal particles 92a having an average particle size of 0.9 μm to 2 μm on the base film made of MgO. Prototype 5 which is a product of the present invention in which polyhedral aggregated particles 92 obtained by agglomeration of crystal particles 92b and cubic MgO crystal particles 93 are attached so as to be distributed almost uniformly over the entire surface, It can be seen that the electron emission performance is less deteriorated with time than the work 4.

  The reason for this is considered to be that in Prototype 4, the ions generated by the discharge in the PDP cell impact the protective layer, causing the aggregated particles to peel off. On the other hand, in Prototype 5 of the present invention, a small particle size is obtained by agglomeration of particles having a crystal particle size smaller than the above particles around crystal particles having an average particle size in the range of 0.9 μm to 2 μm. It is considered that the crystal particles having the surface area have a large surface area, so that the adhesiveness with the base film is enhanced, and the aggregated particles are hardly peeled off by ion impact.

  In the PDP formed with the protective layer according to the present invention, it is possible to obtain an electron emission capability having characteristics of 6 or more and a charge holding capability of Vscn lighting voltage of 120 V or less. As the protective layer of PDP, which tends to increase and the cell size tends to decrease, it can satisfy both the electron emission capability and the charge retention capability, and further the deterioration of the electron emission performance over time is small, Stable image quality can be obtained.

  Here, in the PDP according to the present invention, when the aggregated particles 92 and the crystal particles 93 are deposited on the base film 91, the aggregated particles 92 and the crystal particles 93 are deposited so as to be distributed over the entire surface with a coverage of 10% to 20%. I am letting. The coverage in the present invention is the area a where the aggregated particles 92 and the crystal particles 93 adhere in the area of one discharge cell, expressed as a ratio of the area b of one discharge cell. (%) = A / b × 100. As an actual measurement method, for example, as shown in FIG. 12, an image of a region corresponding to one discharge cell divided by the barrier ribs 14 is taken by a camera, and the size of one cell of x × y is obtained. After the trimming, the captured image after binarization is binarized into black and white data, and then the area a of the black area by the MgO aggregated particles 92 is obtained based on the binarized data, and as described above, a / b × It is obtained by calculating according to the equation of 100.

  Next, in the present invention, in order to confirm the effect of the PDP having the protective layer according to the present invention in which polyhedral crystal particles and cubic crystal particles having different CL emission characteristics are adhered, FIG. 13 shows the results of manufacturing and examining the sustain discharge voltage. Prototype A is a PDP in which only agglomerated particles 92 made of MgO crystal particles 92a and 92b having a peak of CL emission in the wavelength region of 200 nm to 300 nm are dispersed and adhered on the base film 91 made of MgO. B and C are MgO polyhedrons having a particle size smaller than that of the crystal particles 92a around the crystal particles 92a having an average particle size of 0.9 μm to 2 μm on the MgO base film. The PDP according to the present invention has the aggregated particles 92 formed by agglomerating crystal particles 92b and the cubic MgO crystal particles 93 attached so as to be distributed almost uniformly over the entire surface. The prototype B and the prototype C are prototypes in which the relative dielectric constant ε of the dielectric layer 8 is changed. The prototype B has a relative dielectric constant ε of the dielectric layer 8 of about 9.7. In the prototype C, the dielectric constant 8 of the dielectric layer 8 is set to 7. The coverage is about 13%, which is 20% or less.

  As is apparent from FIG. 13, it was found that the prototypes B and C, which are the products of the present invention, can reduce the sustain discharge voltage with respect to the prototype A. That is, MgO polyhedral crystal particles 92a and 92b having a characteristic of performing CL emission having a peak in a wavelength region of 200 nm to 300 nm and CL emission having a peak in a wavelength region of 400 nm to 450 nm are performed. The PDP having the protective layer to which the characteristic MgO cubic crystal particles 93 are attached can reduce the sustain discharge voltage and can reduce the power consumption of the PDP. Furthermore, as is clear from the characteristics of the prototypes B and C, in the present invention, the sustain discharge voltage can be lowered more by reducing the relative dielectric constant ε of the dielectric layer 8, especially the inventors of the present invention. According to the experiment, it was found that the effect can be obtained more significantly by setting the relative dielectric constant ε of the dielectric layer 8 to 7 or less.

  Next, the particle size of the crystal particles used in the protective layer of the PDP according to the present invention will be described. In the following description, the particle diameter means an average particle diameter, and the average particle diameter means a volume cumulative average diameter (D50).

  FIG. 14 shows an experimental result of examining the electron emission performance by changing the particle diameter of MgO crystal particles in the protective layer according to the present invention. In FIG. 14, the particle diameter of MgO crystal particles was measured by SEM observation of the crystal particles.

  As shown in FIG. 14, it can be seen that when the particle size is reduced to about 0.3 μm, the electron emission performance is lowered, and when the particle size is approximately 0.9 μm or more, high electron emission performance is obtained.

  By the way, in order to increase the number of electrons emitted in the discharge cell, it is desirable that the number of crystal particles per unit area on the protective layer is larger. However, according to the experiments by the present inventors, the protective layer of the front plate is used. When the crystal particles are present in the part corresponding to the top of the partition wall of the back plate that is in close contact with the substrate, the top of the partition wall is damaged, and the corresponding material is placed on the phosphor. It has been found that a phenomenon that does not turn off occurs. The phenomenon of the partition wall breakage is unlikely to occur unless the crystal particles are present in the portion corresponding to the top of the partition wall. Therefore, if the number of attached crystal particles increases, the probability of the partition wall breakage increases.

  FIG. 15 is a diagram showing the results of experiments on the relationship between partition wall breakage in the PDP of the present invention by spraying the same number of crystal particles having different particle sizes per unit area.

  As is apparent from FIG. 15, when the crystal particle diameter is increased to about 2.5 μm, the probability of partition wall breakage increases rapidly. However, if the crystal particle diameter is smaller than 2.5 μm, the probability of partition wall breakage is compared. It can be seen that it can be kept small.

  Based on the above results, in the protective layer of the PDP of the present invention, it is considered desirable that the aggregated particles have a particle size of 0.9 μm or more and 2.5 μm or less. In addition, it is necessary to consider variations in manufacturing crystal grains and manufacturing variations when forming a protective layer.

  In order to take into account such factors as manufacturing variations, the result of experiments using crystal particles with different particle size distributions resulted in the use of aggregated particles with an average particle size in the range of 0.9 μm to 2 μm. It was found that the above-described effects of the present invention can be obtained stably.

  Next, a manufacturing process for forming a protective layer in the PDP according to the present invention will be described with reference to FIG.

  As shown in FIG. 16, after performing the dielectric layer forming step A1 for forming the dielectric layer 8, in the next base film vapor deposition step A2, by a vacuum vapor deposition method using a sintered body of MgO containing Al as a raw material. A base film made of MgO is formed on the dielectric layer 8.

  Thereafter, a step of discretely attaching a plurality of polyhedral crystal particles 92a and 92b and a plurality of cubic crystal particles 93 on the unfired base film formed in the base film deposition step A2 is performed. .

  In this step, first, a crystal particle paste in which polyhedral crystal particles 92a and 92b having a predetermined particle size distribution are mixed in a solvent and a crystal particle paste in which cubic crystal particles 93 are mixed in a solvent are separately prepared. Prepared, and then mixed with two types of crystal particle pastes to produce a mixed crystal particle paste in which polyhedral crystal particles 92a, 92b and crystal particles 93 are mixed in a solvent. In crystal particle paste application step A3, The mixed crystal particle paste is applied onto the base film to form a crystal particle paste film having an average film thickness of 8 μm to 20 μm. In addition, as a method for applying the crystal particle paste onto the base film, a screen printing method, a spray method, a spin coating method, a die coating method, a slit coating method, or the like can also be used.

  Here, as an example of the solvent used for preparing the crystal particle paste, the affinity with the MgO base film 91 and the crystal particles 92a, 92b, and 93 is high, and evaporation removal in the subsequent drying step A4 is easy. For example, organic solvents such as methylmethoxybutanol, terpineol, propylene glycol, and benzyl alcohol alone or a mixed solvent thereof are used, for example. The viscosity of the paste using these solvents is several mPaS to several tens mPaS.

  The substrate on which the mixed crystal particle paste is coated on the base film is immediately transferred to the drying step A4 and dried under reduced pressure. Since the crystal particle paste is rapidly dried within a few tens of seconds in the vacuum chamber, the convection of the crystal particle paste that is noticeable in heat drying does not occur. To be attached. In addition, as a drying method in this drying step A4, a heat drying method may be used according to a solvent or the like used when producing an aggregate / crystal particle paste.

  Thereafter, the unfired base film formed in the base film deposition step A2 and the crystal particle paste film formed in the crystal particle paste application step A3 for forming the crystal particle paste film and subjected to the drying step A4 are fired in the protective layer. In step A5, by simultaneously firing at a temperature of several hundred degrees to remove the solvent and resin components remaining in the crystal particle paste film, a plurality of polyhedral crystal particles 92a, 92b on the base film 91; The protective layer 9 to which the cubic crystal particles 93 are attached can be formed.

  According to this method, a plurality of crystal particles 92a and 92b and crystal particles 93 can be attached to the base film 91 so as to be uniformly distributed over the entire surface.

  In addition to such a method, a method of spraying particle groups directly with a gas or the like without using a solvent or the like, or a method of simply spraying using gravity may be used.

In the above description, MgO is taken as an example of the protective layer. However, the performance required for the base is to have high anti-spattering performance for protecting the dielectric from ion bombardment, and has a high charge retention capability. That is, the electron emission performance may not be so high. In conventional PDPs, in order to achieve both the electron emission performance above a certain level and the sputter resistance performance, a protective layer mainly composed of MgO has been formed in many cases. Since the composition is controlled predominantly by the material single crystal particles, there is no need to use MgO, and other materials having excellent impact resistance such as Al ₂ O ₃ may be used.

  In the present embodiment, the description has been made using MgO particles as single crystal particles. However, other single crystal particles also oxidize metals such as Sr, Ca, Ba, and Al, which have high electron emission performance like MgO. Since the same effect can be obtained even if crystal grains made of a material are used, the particle type is not limited to MgO.

  As described above, the present invention is useful for realizing a PDP having high-definition and high-luminance display performance and low power consumption.

1 PDP
2 Front plate 3 Front glass substrate 4 Scan electrode 5 Sustain electrode 6 Display electrode 7 Black stripe 8 Dielectric layer 9 Protective layer 91 Base film 92 Aggregated particles 92a, 92b, 93 Crystal particles 10 Back plate 11 Back glass substrate 12 Data electrode 13 Base dielectric layer 14 Partition 15 Phosphor layer 16 Discharge space

Claims (6)

A front plate in which a dielectric layer is formed so as to cover a display electrode formed on the substrate and a protective layer is formed on the dielectric layer, and the front plate is disposed so as to face each other so as to form a discharge space. A plasma display panel having a data electrode in a direction intersecting with the electrode and a back plate provided with a partition wall for partitioning the discharge space, wherein the protective layer forms a base film on the dielectric layer In addition, aggregated particles obtained by aggregating crystal particles having a smaller particle size than the crystal particles and cubic crystal particles made of the metal oxide over the entire surface are formed on the base film. A plasma display panel, wherein a plurality of the plasma display panels are attached so as to be distributed. The plasma display panel according to claim 1, wherein the aggregated particles have an average particle size in a range of 0.9 μm to 2 μm. 2. The plasma display panel according to claim 1, wherein the crystal particles constituting the agglomerated particles and the cubic crystal particles are composed of MgO crystal particles. The plasma display panel according to claim 1, wherein the crystal particles constituting the aggregated particles have a polyhedral shape. The plasma display panel according to claim 1, wherein the base film is made of MgO. A front plate in which a dielectric layer is formed so as to cover a display electrode formed on the substrate and a protective layer is formed on the dielectric layer; A plasma display panel having a data electrode in a direction intersecting with the electrode and a back plate provided with a partition wall for partitioning the discharge space, and having a plurality of discharge cells. One field is composed of a plurality of subfields, and in each subfield, an address period for generating an address discharge for selecting a discharge cell to emit light, and a sustain discharge is generated in the discharge cells selected by the address period. A plasma display apparatus for performing light emission display with a sustain period, wherein the plasma display The protective layer of the panel is formed by forming a base film on the dielectric layer and agglomerating crystal grains made of metal oxide on the base film with crystal grains having a smaller particle size than the crystal grains. A plasma display device comprising a plurality of particles and cubic crystal particles made of a metal oxide so as to be distributed over the entire surface.

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