JP2005149835A - Plasma display panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To materialize a PDP having high luminescent efficiency and a long life, by lowering the driving voltage of the PDP when N<SB>2</SB>is added to a filler gas. <P>SOLUTION: This plasma display panel is provided with: a first substrate; a second substrate facing the first substrate; a first electrode formed on the side of the first substrate, which faces the second substrate; a second electrode formed on the side of the second substrate, which faces the first substrate; a first dielectric layer formed so as to cover the first electrode; a second dielectric layer formed so as to cover the second electrode; a protective layer formed so as to cover the first dielectric layer; and a discharge space filled with the filler gas, which is formed between the protective layer and the second dielectric layer. The protective layer is made of ZnO, and the filler gas contains N<SB>2</SB>. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a plasma display panel (hereinafter referred to as PDP), and more particularly to a PDP capable of high-efficiency discharge.

  PDP has features such as easy screen enlargement, good display quality, and wide viewing angle compared to liquid crystal display, and can be thinned, so it can be made large, such as a wall-mounted display. It has come to be used as a display device.

  An outline of the operating principle of the PDP is that a rare gas is excited by causing discharge in a discharge space in which a sealed gas made of a rare gas, for example, called a display cell is sealed, and phosphors are generated by ultraviolet rays generated by the optical transition thereof. And visible light from the phosphor is used for display light emission.

  FIG. 1A schematically shows a cross-sectional view of one display cell having a structure of a conventional alternating current (AC) drive type PDP, and FIG. Show. FIG. 2 is a perspective view of an AC drive type color PDP 100 in which a plurality of the display cells shown in FIGS. 1A and 1B are arranged.

  Referring to FIGS. 1A, 1B, and 2, in the PDP 100, a front plate 101 made of a glass substrate and a back plate 105 are arranged to face each other with a discharge space 110 interposed therebetween. A display electrode 102 is disposed on the front plate 101 on the side facing the back plate 105. The display electrode 102 is covered with a dielectric layer 103 made of, for example, lead oxide glass, and the like. The dielectric layer 103 is covered with a protective film 104 made of MgO. The display electrode 102 is configured by arranging a pair of band-like scanning electrodes and sustaining electrodes in parallel with each other.

  On the other hand, a plurality of strip-shaped data electrodes 106 orthogonal to the display electrode 102 are provided on the back plate 105 on the side facing the front plate 101, and the plurality of data electrodes 106 are parallel to each other. And each data electrode 106 is covered by a dielectric layer 107.

  Further, a partition wall 108 for separating the plurality of data electrodes 106 and forming a discharge space 110 is provided on the dielectric layer 107. Further, a phosphor layer 109 is formed from the dielectric layer 107 on the data electrode 106 to the side surface of the partition wall 108. The PDP 100 shown in FIG. 3 has a structure in which, for example, red, green, and blue phosphors 109 are sequentially arranged with the partition wall 108 interposed therebetween in order to enable color display.

  Filled gas is sealed in the discharge space 110, and the sealed gas is composed of a mixed gas of at least one of He, Ne, Kr and Ar and Xe, for example.

  In the PDP 100 having such a structure, the dielectric layers 103 and 107 are provided for accumulating charges generated by applying a voltage to the display electrode 102 and the data electrode 106.

  The protective film 104 is provided in order to reduce the discharge voltage and prevent the dielectric layer 103 from being destroyed by collision of ions generated by the discharge. As the protective film 104, an MgO film is generally used.

  The operating principle of the PDP 100 is as follows. First, the reset discharge of the display electrode 102 (between the scan electrode and the sustain electrode) is performed in the discharge space 110 of all the cells, the wall charge state is made the same, and then the scan electrode of the display electrode 102 is scanned. At the same time, a voltage is selectively applied to the data electrode 106 to cause an address discharge in the discharge space 110.

  As a result, wall charges are selectively formed on the display electrode 102. Therefore, when a discharge sustain voltage is next applied to the display electrode 102, it is possible to control whether or not a discharge is generated in the discharge space 110. Depending on the number of sustain discharges in the discharge space 110, an image can be obtained. An image can be displayed by controlling display gradation.

  However, in recent years, high performance PDPs are required to have higher brightness and higher definition, and in order to achieve higher brightness and higher definition, it is necessary to increase the luminous efficiency of the PDP. .

  In addition, since the lifetime of the PDP is determined by the deterioration of the phosphor, it is necessary to reduce the deterioration of the phosphor as much as possible and to extend the lifetime of the PDP.

As described above, as an attempt to increase the light emission efficiency of the PDP and further extend the life of the PDP, it has been proposed to use N ₂ instead of Xe as a gas used for ultraviolet excitation in the sealed gas. (For example, refer nonpatent literature 1-nonpatent literature 3.)
TV Society Technical Report, Yokozawa, ED474, pp.69-74 (1979) IEICE General Conference, Ueda et al., C-9-2 KCChoi et al, SID Int. Symp. Dig. Tech. Papers, pp432-435, VOL. VIII, May2002

However, when N ₂ is added to the sealed gas of the PDP, there has been a problem that the drive voltage increases. In particular, as the partial pressure of N ₂ is increased in the sealed gas, the driving voltage tends to increase, and there is a problem that the power consumption and cost of the driving circuit increase. N ₂ is contained in the sealed gas of the PDP. It was difficult to add.

  Therefore, an object of the present invention is to solve the above problems.

A specific problem of the present invention is to realize a PDP having a long lifetime by making it possible to reduce the driving voltage of the PDP when N ₂ is added to the sealed gas, increasing the light emission efficiency.

In the present invention, in order to solve the above-described problem, the first substrate, the second substrate facing the first substrate, and the first substrate on the side facing the second substrate are formed. A first electrode; a second electrode formed on a side of the second substrate facing the first substrate; and a first dielectric layer formed to cover the first electrode A second dielectric layer formed so as to cover the second electrode, a protective film formed so as to cover the first dielectric layer, the protective film, and the second dielectric A plasma display panel comprising a discharge space formed between layers and encapsulated with an encapsulated gas, wherein the protective film is made of ZnO, and the encapsulated gas contains N _2. Was used.

According to the present invention, by using a film made of ZnO as the protective film of the plasma display panel, secondary electrons are easily emitted from the surface of the protective film, and the discharge start voltage can be lowered. Therefore, it is possible to add N ₂ gas to the sealed gas, and it is possible to realize a PDP with high luminous efficiency, little damage to the phosphor and long life.

Further, when the ratio of the partial pressure of N _{2 to} the total pressure of the sealed gas is 2% or more, the luminous efficiency is increased and the effect of suppressing the driving voltage is particularly increased as compared with the conventional case. Is preferable.

  Further, if the hexagonal c-axis of the ZnO crystal of the protective film grows perpendicularly to the substrate and is preferentially oriented in the (0001) plane, the sputtering film has resistance to sputtering in the discharge space. Is preferable.

According to the present invention, it is possible to reduce the driving voltage of the PDP when N ₂ is added to the PDP sealing gas, and the luminous efficiency is high, and the damage to the phosphor is reduced and the PDP has a longer life. Can be realized.

  Next, embodiments of the present invention will be described with reference to the drawings.

  Next, embodiments of the present invention will be described below with reference to the drawings.

  FIG. 3A schematically shows a cross-sectional view of one display cell of the structure of the AC drive type PDP according to the first embodiment of the present invention, and FIG. The figure is shown. FIG. 4 is a perspective view of an AC drive type color PDP 10 in which a plurality of the display cells shown in FIGS. 4A and 4B are arranged.

  3A, 3B and 4, in the PDP 10, the front plate 11 and the back plate 15 made of a glass substrate are arranged to face each other with the discharge space 20 in between. A display electrode 12 is disposed on the front plate 11 on the side facing the back plate 15, and the display electrode 12 is covered with a dielectric layer 13 made of, for example, lead oxide glass. The dielectric layer 13 is covered with a protective film 14 made of ZnO. The display electrode 12 is configured by arranging a pair of strip-like scan electrodes and sustain electrodes in parallel with each other.

  A plurality of strip-shaped data electrodes 16 orthogonal to the display electrodes 12 are provided on the back plate 15 on the side facing the front plate 11, and the plurality of data electrodes 16 are parallel to each other. The data electrodes 16 are arranged and covered with a dielectric layer 17.

  Further, a partition wall 18 for separating the plurality of data electrodes 16 and forming the discharge space 20 is provided on the dielectric layer 17 substantially in parallel with the data electrode 16. A phosphor layer 19 is formed from the dielectric layer 17 on the data electrode 16 to the side surface of the partition wall 18. The PDP 10 shown in FIG. 5 has a structure in which, for example, red, green, and blue phosphors 19 are sequentially arranged with the partition wall 18 interposed therebetween in order to enable color display.

  In the PDP 10, the dielectric layers 13 and 17 are provided for accumulating charges generated by applying a voltage to the display electrode 12 and the data electrode 16.

  FIG. 4 shows a shape in which three display cells are combined as an example, but the number of display cells is arbitrary, and actually a PDP that is a large display device by combining a larger number of display cells. Form.

  The operation principle of the PDP 10 is as follows. First, the reset discharge of the display electrode 12 (between the scan electrode and the sustain electrode) is performed in the discharge space 20 of all the cells, the wall charge state is made the same, and then the scan electrode of the display electrode 12 is scanned. At the same time, a voltage is selectively applied to the data electrode 16 to cause an address discharge in the discharge space 20.

  As a result, wall charges are selectively formed on the display electrode 12. Therefore, when a discharge sustain voltage is next applied to the display electrode 12, it is possible to control whether or not a discharge occurs in the discharge space 20, and depending on the number of sustain discharges in the discharge space 20, An image can be displayed by controlling display gradation.

In this embodiment, the sealed gas sealed in the discharge space 11 is composed of a mixed gas of at least one of He, Ne, Ar, Kr and Xe and N ₂ , for example. The luminous efficiency of the PDP greatly depends on the enclosed gas. For example, increasing the N ₂ mixing ratio of the enclosed gas or the ratio of the partial pressure of N _{2 to} the total pressure of the enclosed gas improves the luminous efficiency. Higher brightness and higher definition. Furthermore, the lifetime of the phosphor is also increased, and the lifetime of the PDP can be increased.

Thus, it is thought that the effect that the luminous efficiency is improved by adding N ₂ to the sealed gas and the lifetime of the phosphor is extended is because the excitation wavelength of N ₂ is long. For example, a table comparing Xe added to a conventional PDP sealing gas with N ₂ excitation wavelength, phosphor excitation energy, and energy conversion efficiency according to this example is shown below.

上記のように、例えば従来用いられていたＸｅの場合、励起波長が１４７ｎｍと短く、エネルギーが高いために、蛍光体による紫外線から可視光へのエネルギー変換効率が低くなってしまう。そのため、蛍光体に与えるダメージも大きく、長期間にわたる使用においては焼き付などを生じる場合があった。

As described above, for example, in the case of Xe conventionally used, since the excitation wavelength is as short as 147 nm and the energy is high, the energy conversion efficiency from ultraviolet rays to visible light by the phosphor is lowered. Therefore, the damage given to the phosphor is large, and there are cases where seizure or the like occurs when used over a long period of time.

On the other hand, when N _{2 according} to the present embodiment is used, since the excitation wavelength has a strong emission spectrum at 340 to 450 nm centered at 337 nm, the energy conversion efficiency from ultraviolet light to visible light is high, and Xe is Since it is 2.3 times that used, and visible light emission can be obtained efficiently, the light emission efficiency can be improved.

Further, the damage given to the phosphor during the discharge is smaller as the energy of the ultraviolet rays applied to the phosphor is lower, and therefore the life tends to be longer. N ₂ is less than that when Xe is used. When it is used, the ultraviolet energy is 1 / 2.3, that is, about 43%. When N ₂ is used, it is possible to realize a life that is twice or more that of the prior art.

However, when N ₂ is added to the sealed gas, conventionally, since the discharge start voltage increases and the drive voltage increases, it has been very difficult to use N ₂ as the sealed gas. Therefore, the inventor of the present invention uses a layer made of ZnO for the protective film 14, thereby lowering the discharge start voltage, lowering the driving voltage of the PDP, and using N ₂ as the sealing gas. I found it possible.

In this embodiment, the display electrode 12 is covered with the protective film 14 made of ZnO, and the protective film 14 faces the discharge space 20.
The discharge characteristics in the discharge space 20, the discharge start voltage, and the like are such that secondary electrons emitted from the surface of the protective film 14 are easily emitted when ions or excited particles of the sealed gas enter the protective film 14. It depends greatly on the size.

  ZnO used in this example is considered to have such a characteristic that secondary electrons are easily emitted because the band gap is small. Therefore, the effect of reducing the drive voltage by lowering the discharge start voltage. It is thought to play.

In addition, when ZnO is used for the protective film and N ₂ is added to the sealing gas, the electron affinity of ZnO may be reduced due to the interaction between ZnO and N ₂ , which causes a decrease in the discharge start voltage. It is speculated that it may be one of the following.

In particular, when the partial pressure of N _{2 in} the sealed gas is increased, the effect of suppressing the increase in driving voltage is increased, and the ratio of the partial pressure of N ₂ to the total pressure is increased as will be described later with reference to FIG. By setting it to 2% or more, the effect becomes effective, and the luminous efficiency also increases.

  Further, the protective film 14 is sputtered due to collision of ions formed when a discharge occurs in the discharge space 20, and the surface of the protective film 14 is scraped by sputter etching.

  Therefore, in order to prolong the life or maintenance cycle of the PDP due to damage due to sputtering of the protective film 14, the sputtering resistance of the protective film 14 is increased, that is, the speed at which the protective film 14 is sputter etched. It is important to reduce the size.

  As a result of experiments, the inventors of the present invention have shown that when forming a ZnO film constituting the protective film 14, the hexagonal c-axis of the ZnO crystal grows perpendicularly to the plane on which the ZnO film is formed. It was found that when the ZnO film was formed so as to be preferentially oriented in the (0001) plane with the above-described orientation, the sputtering resistance of the ZnO film was high.

  Therefore, the hexagonal c-axis of the ZnO crystal of the ZnO film as the protective film 14 is oriented so that it grows perpendicular to the surface on which the ZnO film is formed, and the ZnO film is preferentially oriented on the (0001) plane. By forming in this way, the speed at which the protective film 14 of the PDP 10 is sputter-etched is reduced, and the life of the PDP 10 can be extended.

  Next, a method for manufacturing the PDP 10 shown in FIGS. 3A and 3B and FIG. 4 will be described. However, in the following text, the same reference numerals are used for the parts described above, and detailed description is omitted.

  First, a transparent conductive film and a laminated film made of chromium (Cr) / copper (Cu) / Cr (chromium) are formed on the front plate 11 made of a glass substrate by a sputtering method.

  Next, the transparent conductive film and the laminated film are formed into a strip-like pattern with a thickness of 170 μm and the laminated film of 55 μm, respectively, using a photolithography technique, and the display electrode 12 is obtained.

  Next, a low melting point glass paste is printed on the front plate 11 on which the display electrodes 12 are formed, dried, and then baked to form the dielectric layer 3 having a thickness of about 20 μm. .

  Next, the protective film 14 made of ZnO is formed to have a thickness of 0.8 μm by using an RF magnetron sputtering method so as to cover the dielectric layer 3. In addition to the RF magnetron sputtering method, a method such as MBE (Molecular Beam Epitaxy), CVD (Chemical Vapor Deposition), PLD (Pulsed Laser Deposition) or the like is used as a method for forming the protective film 14. Can be used.

  Further, as described above, in order to increase the sputtering resistance of the protective film 14, the c-axis orientation in which the hexagonal c-axis of the ZnO crystal grows perpendicularly to the substrate is preferentially grown. Therefore, sputtering vapor deposition is performed, for example, under the conditions of a sputtering pressure of 1 to 10 Pa, an oxygen concentration of 10 to 50% in a mixed gas of Ar and oxygen, a substrate temperature of 150 to 500 ° C., and a vapor deposition rate of 1.0 μm / hr.

  Next, a photosensitive silver paste is formed in a strip pattern using a photolithography technique at a desired position on the back plate 15 made of a glass substrate, thereby forming the data electrode 16 made of silver. The dielectric layer 17 was formed so as to cover the data electrode 16.

Further, the barrier rib 8 having a width of 60 μm and a height of 130 μm was formed on the dielectric layer 17, and the phosphor 19 was applied on the surfaces of the barrier rib 18 and the dielectric layer 17. Wherein the phosphor 9, for example, a red light emitter _{((Y x Gd 1-x} ) BO 3: Eu 3+), green light-emitting body (BaAl ₁₂ O _19: Mn) and blue emitter (BaMgAl ₁₄ O _23: Eu ²⁺ ).

Next, the front plate 11 and the back plate 15 are bonded together so that the display electrode 12 and the data electrode 16 are orthogonal to each other, the periphery is sealed with glass frit, and the discharge space 20 is exhausted. An enclosed gas obtained by adding N ₂ gas to the Ne—Xe mixed gas is enclosed in the discharge space 20 so that the pressure becomes 5 kPa to 70 kPa. In this case, the partial pressure of N ₂ is set to 2% or more with respect to the total pressure of the sealed gas.

Next, FIG. 5 shows the result of measuring the discharge start voltage of the PDP when the ratio of the partial pressure of N _{2 to} the total pressure of the sealed gas is increased in the PDP 10.

  In the measurement, a 20 kHz rectangular pulse (duty = 20%) of 0 (V) and Vs (V) was alternately applied to a pair of electrodes for AC discharge, and a voltage at which discharge was started was measured. In the measurement, the experiment was performed by applying a voltage 20 seconds after the discharge was stopped by lowering the voltage.

  For comparison, the measurement result of the voltage in the case where 0.8 μm of a conventionally used MgO film is formed on the protective film 14 is also shown. In this case, the total pressure of the sealed gas was 67 kPa. Note that the driving voltage of the PDP strongly depends on the discharge start voltage in the discharge space, and the rate of increase / decrease in the discharge start voltage indicates the rate of increase / decrease in the drive voltage of the PDP.

Referring to FIG. 5, when a film made of ZnO is used for the protective film 14 in this embodiment, the discharge start voltage is lower than when a film made of MgO is used for the protective film 14. I understand that. In particular, when the ratio of the partial pressure of N _{2 to} the total pressure of the sealed gas is set to 2% or more, the effect of suppressing the discharge start voltage is increased. When the partial pressure of N ₂ is increased, ZnO is used. The effect of suppressing the discharge start voltage is increased, and the luminous efficiency is also increased. In order to obtain such an effect, the total pressure of the sealed gas is preferably in the range of 5 kPa to 70 kPa.

  In this embodiment, the case where ZnO is used for the protective film 14 has been described. However, the effect of the present invention is not limited to this, and for example, a trace amount of metals such as Cu, Mn, and Li is included. Even when a ZnO-based compound is used for the protective film 14, the same effects as described in the present embodiment can be obtained.

  Furthermore, although an example of an AC drive type PDP has been shown in the present embodiment, the present embodiment is not limited to the AC drive type. For example, in the DC drive type or the AC / DC hybrid drive type, a cathode or By using ZnO as the protective film covering the anode, it is possible to obtain the same effect as described in this embodiment, and it is possible to realize a PDP with a low driving voltage, high efficiency and a long life.

According to the present invention, when N ₂ is added to the PDP sealing gas, the driving voltage of the PDP can be lowered, the luminous efficiency is high, and the phosphor is less damaged by ultraviolet rays, so that the lifetime is increased. It is possible to realize a long PDP.

(A) is a schematic cross-sectional view of one display cell having a conventional PDP structure, and (B) is a cross-sectional view taken along the line AA. FIG. 2 is a cross-sectional perspective view of a conventional AC drive type color PDP in which a plurality of display cells of FIG. 1 are arranged. (A) is a schematic cross-sectional view of one display cell of the structure of the PDP of the present invention, and (B) is a cross-sectional view taken along the line BB. FIG. 4 is a cross-sectional perspective view of an AC drive type color PDP of the present invention in which a plurality of the display cells of FIG. 3 are arranged. A N ₂ partial pressure dependence of the measurement results of the discharge starting voltage in accordance with an embodiment of the present invention.

Explanation of symbols

10,100 PDP
11, 111 Front plate 12, 102 Display electrode 13, 103 Dielectric layer 14, 104 Protective film 16, 106 Data electrode 17, 107 Dielectric layer 18, 108 Bulkhead 19, 109 Phosphor 20, 110 Discharge space

Claims (3)

A first substrate;
A second substrate facing the first substrate;
A first electrode formed on a side of the first substrate facing the second substrate;
A second electrode formed on a side of the second substrate facing the first substrate;
A first dielectric layer formed to cover the first electrode;
A second dielectric layer formed to cover the second electrode;
A protective film formed to cover the first dielectric layer;
A plasma display panel provided with a discharge space formed between the protective film and the second dielectric layer and filled with a sealing gas,
The plasma display panel according to claim 1, wherein the protective film is made of ZnO, and the sealed gas contains N ₂ . The plasma display panel of claim 1, wherein the ratio of the partial pressure of N ₂ to the total pressure of the sealed gas is 2% or more.   3. The plasma display panel according to claim 1, wherein a hexagonal c-axis of the ZnO crystal of the protective film grows perpendicularly to the substrate and is preferentially oriented in the (0001) plane.

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