JP2007214067A - Plasma display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma display device provided with a protection membrane in which less impurities are adsorbed compared with a conventional one by improving the quality of the protection membrane. <P>SOLUTION: A PDP has, as a protection membrane 8, a structure in which at least one kind of rare gas atoms selected from He, Ne, Ar, Kr, Xe, and Rn is dispersed in the range of 10 ppm to 1,000 ppm against MgO that becomes a base material. By this, quality of the protection membrane is improved, and by promoting high densification of the membrane and promoting reduction of adsorbates, a more stable discharge performance can be obtained compared with a conventional constitution, and simpler calcination process becomes possible resulting in the realization of cost saving of the PDP. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a plasma display device (hereinafter referred to as “PDP”) using radiation from a gas discharge.

  PDP, which is a display that uses the discharge light emission phenomenon, is arranged so that two glass substrates with predetermined electrodes formed on each surface face each other and keep a predetermined distance by partition walls And the peripheral part of both glass substrates has the basic structure sealed with the low melting glass. A phosphor is disposed on the side wall surface of the partition wall and on the surface of the glass substrate. A discharge gas, for example, a mixed gas of xenon (Xe) and neon (Ne) is sealed in the discharge space formed between the two glass substrates. The discharge gas is discharged by appropriately controlling the voltage applied to the electrode, and the phosphor formed in the PDP is excited by ultraviolet rays generated by the discharge. Visible light emission from the phosphor is observed as a PDP issuance display.

  The PDP, which is a display that uses the discharge light emission phenomenon, has a DC type (DC type) with a metal electrode exposed in the discharge space and an AC type (AC type) with a metal electrode covered with a dielectric due to its electrode structure. ). In particular, in the AC type PDP, a magnesium oxide (MgO) film is formed on the dielectric as a protective film for the dielectric.

  The MgO film (protective film) functions as a protective film to prevent (a) the above dielectric layer and electrode from being directly exposed to plasma and being damaged by ion collisions. When a discharge voltage is applied between the electrodes, the function of emitting secondary electrons for gas discharge (secondary electron emission effect), and (c) the case where there is no MgO film by accumulating wall charges It has a function of emitting electrons with a lower voltage, that is, a function of reducing the discharge voltage.

  As the protective film, a magnesium oxide film having a thickness of about several hundreds of nanometers formed by using a deposition method such as vapor deposition has been mainly used. This magnesium oxide film usually adsorbs moisture, carbon dioxide, oxygen, hydrogen, hydrocarbons, etc., and affects the initial discharge characteristics, and is released as an impurity gas in the sealed gas during PDP operation, There is concern that PDP operating conditions may be adversely affected.

In the current PDP manufacturing process, the inside of the panel is exhausted before the discharge gas is filled. The gas that cannot be removed in the exhaust process remains as an impurity gas after the product is completed. At this time, moisture and carbon dioxide adsorbed by the protective film are particularly difficult to desorb, and it is necessary to exhaust at a high temperature for a long time. This long exhaust process is often the rate limiting process for the entire line. Further, exhaust at a high temperature also affects other members, and there are limitations on the heating time and temperature. In order to avoid such adsorption of impurities, it is necessary to increase the density of magnesium oxide itself to reduce the number of impurity adsorption sites (see, for example, Patent Document 1).
JP 2002-260535 A JP 2003-303547 A JP 2004-103398 A

  A protective film in an AC type PDP is required to have a high secondary electron emission ability and a high sputtering resistance. In the PDP manufacturing process, the adsorbed gas components on the protective film, particularly moisture and carbon dioxide, are removed and the protective film is activated, but it is also necessary that this removal be easy. Since the conventional protective film has a large amount of impurities adsorbed, there is a problem that a large amount of moisture and carbon dioxide remain even after firing. As a result, it has been pointed out that the discharge characteristics of the panel are deteriorated. In addition, since the impurity gas is released from the protective film during use, the discharge characteristics are not stable. For this reason, in order to improve exhaust integrity, it is necessary to take measures such as increasing the heating temperature and extending the exhaust time, leading to an increase in manufacturing costs.

  The present invention was made to solve the above-described problems of the prior art, and in order to provide a protective film for a PDP electrode with a small amount of adsorbed impurities, the discharge stability with an increased protective film density is provided. It is to provide an excellent PDP.

  The gist of the present invention for achieving the above object is as follows.

  In the plasma display panel having a front plate on which display electrodes are wired and a back plate on which address electrodes are wired, and displaying an image by discharging in a fine discharge space formed in a gap between both substrates, A protective film made of a metal oxide film covering a dielectric layer provided on the face plate is provided, and the protective film is made of a material that suppresses adsorption of impurities.

  The relationship between the physical properties of the protective film and the PDP characteristics is closely linked, and the film with a large amount of residual impurity gases such as moisture, carbon dioxide, and hydrocarbons after the heating and exhausting process has a high operating voltage as a panel, and The operating voltage fluctuates greatly during use and is inferior in stability.

  Conventionally, an oxide film mainly composed of magnesium oxide has been used as a protective film, and a film thickness of about several hundreds of nanometers has been formed by an electron beam evaporation method or the like. The protective film formed by such a method has a large amount of adsorbed gas, and high heating temperature and long time heating are necessary in order to reduce residual impurity gas in the heating and exhausting process.

  Therefore, the present inventors have formed a dense protective film by adding a rare gas atom to the magnesium oxide protective film using a sputtering method or an ion plating method in addition to the conventional electron beam evaporation method. Therefore, it was found that the adsorption of impurities in the film was very small, and the present invention was achieved. The amount of the rare gas added is in the range of 10 ppm to 1000 ppm. The rare gas element is selected from at least one of He, Ne, Ar, Kr, Xe, and Rn. Further, the protective film is a magnesium oxide film. Further, this protective film has a refractive index of 1.65 to 1.70.

  With these configurations, a protective film for an electrode of a plasma display device with a small amount of adsorbed moisture is formed, and a plasma display device with excellent discharge stability can be provided. Specifically, the amount of water absorbed per 1 mm3 of the protective film detected when the protective film of the present invention is left in an atmosphere of 25 ° C and 80% to 85% humidity for 100 hours and then heated to 500 ° C by TDS. The protective film has an ion current value of 3 × 10 −6 or less, an ion current value of carbon dioxide of 1 × 10 −6 or less, and an ion current value of C3H5 of 3 × 10 −8 or less. In addition, the magnesium oxide film to which rare gas atoms are added within the above concentration range has good crystallinity, and as a result, the orientation is improved, and the crystal plane parallel to the substrate surface is mainly (111), ( 200) or (220).

  The present invention has a structure in which a rare gas atom of 10 ppm to 1000 ppm is added to a base material made of a metal oxide in a protective layer of a plasma display device. A protective film is provided. Oxygen vacancies that occur during film formation are less likely to occur due to the addition of a rare gas element, and good crystallinity is obtained and densified. As a result, a film with few impurity adsorption sites is formed. The magnesium oxide protective film having such a configuration is denser and less adsorbing impurities than a single magnesium oxide protective film, and can simplify the heating and exhausting process. As a result, it is possible to obtain a plasma display panel that is low in cost, low in operating voltage, and excellent in discharge characteristic stability.

<Embodiment>
FIG. 1 is a conceptual cross-sectional view showing a discharge cell structure which is a discharge unit of a conventional surface discharge AC type PDP. As shown in FIG. 1, as electrodes on the front plate 2 of the discharge cell 50, transparent electrode pairs (not shown) are patterned on the surface of the glass substrate 10 in a wide stripe pattern with a discharge gap interposed therebetween. Pairs are formed, bus electrodes for lowering electrical resistance are formed on each narrow width, and scan electrodes 5 and sustain electrodes 6 are arranged. A dielectric layer 7 and a protective film 8 are sequentially laminated so as to cover these electrode pairs. The dielectric layer 7 is made of a low melting point glass and has a current limiting function peculiar to the AC type PDP. The protective film 8 protects the electrode surface and efficiently emits secondary electrons to lower the discharge start voltage. Further, as a material for the protective film 8, a metal oxide MgO (magnesium oxide), which is an electrically insulating material having a large secondary electron emission coefficient γ, high sputtering resistance and optical transparency, is widely used. .

  On the other hand, a data electrode 12 for writing image data is formed on the glass substrate 11 of the back plate 3 so as to intersect the pair of display electrodes 4 of the front plate 2 in a direction orthogonal to the data electrode 12 and the glass substrate. 11 A dielectric layer 13 on the back side is laminated with low melting point glass so as to cover at least a part of the surface. On the dielectric layer 13 at the boundary with an adjacent discharge cell (not shown), a partition wall 14 having a predetermined height is formed in a rib shape in a pattern such as a cross-beam shape (not shown) using low melting point glass, and further a dielectric. The phosphor layer 15 is applied and baked and disposed on the surface of the body layer 13 (requires a boundary line between 13 and 14 in FIG. 1) and the side surface of the partition wall 14. As the phosphor layer 15, phosphors emitting three colors of red, green, and blue are used in the corresponding discharge cells.

  The front plate 2 and the back plate 3 are processed so that their processing surfaces are opposed to each other, and the scan electrode 5, the sustain electrode 6, and the data electrode 12 are arranged and sealed so as to be substantially orthogonal to each other. After the impurity gas is exhausted, a rare gas xenon / neon or Xe (xenon) mixed gas such as xenon / helium is sealed and sealed at about several tens of kPa.

  As a surface discharge type electrode matrix structure, a plurality of discharge cells 50 as discharge units having a three-electrode structure in which data electrodes for selecting discharge cells are arranged so as to intersect with display electrodes are arranged in a matrix. The plasma display panel is completed, and furthermore, although not shown, a plasma display device is completed by including a drive circuit for driving in a matrix form and a control circuit for controlling these in the periphery.

  In the AC type PDP, (1) an initialization period in which all display cells are initialized, (2) each discharge cell is addressed, and a display state corresponding to input data is selected and input to each discharge cell. The data is written and displayed by a driving method having a data writing period and (3) a sustain discharge period for causing the discharge cells in the display state to emit light.

  After all the display cells are initialized in the initialization period (1), the data electrode 12 on the back plate 3 and the scanning electrode 5 on the front plate 2 are placed in the data write period (2). In addition, a data voltage is applied to input write data, and wall charges are formed on the surface of the protective film 8 of the front plate 2 facing the data voltage. In the sustain discharge period of (3) above, a sustain discharge voltage pulse, for example, a rectangular wave voltage of about 200 V is applied to each of the scan electrode 5 and the sustain electrode 6 of the display electrode 4 forming a pair in the discharge cell in which the wall charges exist. They are applied so that the phases are different from each other. That is, by applying an alternating voltage between the electrode pair, a pulse discharge is generated every time the voltage polarity changes in the discharge cell which is a display cell in which the display state is written. Due to this sustain discharge, the display light is emitted from the excited xenon atom in the discharge space by a resonance line of 147 nm, from the excited xenon molecule by a molecular beam mainly composed of 173 nm, and then by the phosphor having the ultraviolet radiation provided on the back plate 3. It is obtained by converting into visible radiation at layer 15. In the discharge cell of the non-display cell in which the wall charge is not written in the protective film 8, the sustain discharge does not occur and the display state is black. Note that the display pixel unit of the AC type PDP is usually composed of discharge cells, which are three display discharge units each provided with red, green and blue light emitting phosphor layers.

(About protective film)
According to the protective film of the present invention having a small amount of adsorption of moisture, carbon dioxide and hydrocarbon, the film density of the protective film is increased, and as a result, the release of impurity gas from the protective film during use is reduced and stable. Discharge can be obtained and a long-life panel having excellent sputter resistance can be provided.

  When the amount of rare gas added is smaller than the above range, a film deficient in oxygen as usual is formed, the crystallinity is deteriorated, and the density of the film itself is also reduced. End up. On the other hand, when the amount of rare gas added is larger than the above range, oxygen vacancies can be prevented, but lattice distortion occurs due to excessive penetration of rare gas atoms into magnesium oxide, resulting in an increase in defects. A dense film cannot be obtained, resulting in an increase in impurity adsorption sites.

  In addition, the protective film containing a rare gas element within the above range mainly has a crystal plane parallel to the substrate surface (111), (200), or (220). By having such an orientation, impurity adsorption sites such as lattice defects and crystal grain boundaries are reduced. Therefore, it is desirable that the protective film has an orientation. Further, since the film is densified, the sputter resistance is improved, and the panel has a long life.

In order to obtain a film exhibiting the characteristics of the present invention, it is necessary to devise such as optimization of each film forming condition. As a specific example, when the electron beam evaporation method is used, the substrate is heated to 100 ° C. to 300 ° C. by a heater in the vapor deposition chamber, and the chamber is kept until the degree of vacuum becomes 1 × 10 ⁻⁴ to 1 × 10 ⁻⁷ Pa. Then, Ar gas is introduced while adjusting the degree of vacuum to 6 × 10−1 Pa, and a film forming method is used in which a high frequency of 13.56 MHz is applied by a high frequency power source to generate a discharge.

  The protective film for the PDP according to the present invention is not particularly limited to a film forming method as long as a protective film having a predetermined structure as an object of the present invention, that is, a rare gas element added in an amount of 10 to 1000 ppm can be obtained. For example, an electron beam evaporation method, a sputtering method, an ion plating method, or the like can be used.

(Example)
Examples of the protective film having the above structure will be described below. Magnesium oxide grains were used as the film raw material, and a protective film (protective film 1) in which 300 ppm of Ar was added from magnesium oxide by the above film forming method was formed. As a comparative example, a protective film (comparative example) to which no rare gas element was added was formed. In each experiment, a front plate formed under the respective conditions was used to make a panel, and then cut into 10 mm × 10 mm pieces.

FIG. 2 shows the relationship between each example and the refractive index. For film density and refractive index,
n = (1-p) nν + pns
(N: refractive index of the film, nν: refractive index of the space material (usually air), ns: bulk refractive index (using single crystal values), p: film density)
It is known that there is a relationship.

  According to this formula, it can be said that the higher the refractive index, the denser the film. Therefore, the protective film 1 having a high refractive index can form a dense film, and has the characteristics of improving the sputtering resistance.

  In the protective film having a refractive index in the range of 1.65 to 1.7, moderate crystallinity is maintained as described above, and impurity adsorption can be suppressed.

  As shown in FIG. 2, it can be seen that the protective film 1 has a refractive index of 1.66 and has high density and high crystallinity.

  Regarding the concentration of Ar atoms, even if Ar is added, if the concentration measured by SIMS quantitative analysis is 10 ppm or less, the effect of addition hardly appears, and conversely if it is 1000 ppm or more, the crystallinity of the protective layer decreases, On the contrary, the film density is lowered, which is not preferable. In the conventional film, the Ar content is less than 10 ppm, and it is known that a good film cannot be obtained.

FIG. 3 shows the results of determining the release characteristics of moisture, carbon dioxide and hydrocarbons from the membrane by TDS. In this experiment, the protective film of each example is the amount of moisture and carbon dioxide detected when the panel cut pieces are left in an atmosphere of 25 ° C. and 80% to 85% humidity for 100 hours and then heated to 500 ° C. by TDS. The amount of desorbed gas of C ₃ H ₅ was investigated as a representative of the hydrocarbon gas. From the figure, when compared in the range of 60 ° C to 500 ° C, the amount of desorbed gas in the protective film 1 is 63%, carbon dioxide is 41%, and C ₃ H ₅ is 28% compared to the comparative example. It was confirmed. In addition, the ionic current value of water per 1 mm3 of protective film is 2.5 × 10 ^-6 , the ionic current value of carbon dioxide is 6.9 × 10 ^-7 , and the ionic current value of C ₃ H _{5 in} the same temperature range of protective film 1 Was 1.4 × 10 ^-8 , all within the specified range. Thus, since the protective film 1 with few adsorption sites has less adsorption of impurities than the comparative example, stable discharge characteristics can be obtained, the sealing exhaust process can be simplified, cost reduction, and high reliability. Can contribute greatly.

FIG. 4 shows the Mg _2p spectrum of XPS measurement in each example. As test conditions, measurement was performed with an X-ray source of Al-Kα ray, a beam diameter of 100 μm, and a pass energy of 69 eV. In each example, a protective film was used in which the produced panel was cleaved and allowed to stand in the atmosphere for about 2 minutes. The main peak value of the protective film 1 and for that the value of the ratio (H / I) of the half width (H) is 2.9 × 10 ^-4 (I), a protective film 2, 5.8 × 10- ^4, It was confirmed that the protective film 1 was within a predetermined range, and a highly pure magnesium oxide film was obtained. In this example, Ar was used as a rare gas element. However, since it exhibits the same behavior as Ar if it is inactive, the same effect can be obtained in other rare gases (He, Ne, Kr, Xe, Rn). Is obtained.

  The gas discharge display panel of the present invention can be used for a display device using a PDP used in, for example, a transportation facility, public facility, or home television device.

Cross-sectional view of an AC type PDP according to an embodiment of the present invention Diagram showing data on refractive index of protective film Diagram showing impurity desorption spectrum from protective film Diagram showing Mg2p spectrum obtained from XPS measurement

Explanation of symbols

2 Front plate 3 Back plate 7, 13 Dielectric layer 8 Protective film 10, 11 Glass substrate 12 Data electrode 14 Partition 15 Phosphor layer 50 Discharge cell 51 Discharge space 5 Scan electrode 6 Sustain electrode

Claims (8)

A first substrate having a pair of display electrodes disposed on a main surface; and a second substrate disposed to face the main surface of the first substrate, wherein the first substrate and the second substrate In a plasma display device that displays an image by gas discharge in a space formed between a substrate and a substrate,
A plasma display device, wherein a protective film made of a metal oxide is formed on the main surface of the first substrate, and the protective film contains a rare gas. 2. The plasma display device according to claim 1, wherein the amount of rare gas added to the protective film is in a range of 10 to 1000 ppm. The plasma display device according to claim 1, wherein the protective film is made of a metal oxide containing magnesium oxide as a main component. The plasma display device according to claim 1, wherein the protective film contains magnesium oxide as a main component and contains at least one kind of rare gas selected from He, Ne, Ar, Kr, Xe, and Rn. 2. The plasma display device according to claim 1, wherein a crystal orientation parallel to the substrate surface of the protective film is mainly (111), (200) or (220). 2. The plasma display device according to claim 1, wherein the protective film has a refractive index of 1.65 to 1.7. When the protective film is left in an atmosphere at 25 ° C. and a humidity of 80% to 85% for 100 hours and then heated to 500 ° C. by TDS, the ionic current value of water per 1 mm ^{3 of the} protective film detected is 3 × 10 ^{− 2.} The plasma display device according to claim 1, wherein the ion current value of carbon dioxide is 1 × 10 ⁻⁶ or less, and the ion current value of C ₃ H ₅ is 3 × 10 ⁻⁸ or less. 2. The ratio of the main peak value (I) of the Mg _2P spectrum to its half-value width (H) (H / I) in the XPS measurement of the protective film is in the range of 2.5 to 3.5 × 10 ^−4. The plasma display device described in 1.

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