JP2007012436A - Plasma display panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a PDP in which a discharge voltage is suppressed and which has an excellent luminous efficiency. <P>SOLUTION: The plasma display panel has a first substrate in which a first electrode, a dielectric layer covering the first electrode, and a protection film covering the dielectric layer are formed, and a second substrate in which a second electrode and a phosphor layer are formed, arranged facing each other interposing a discharge space filled with a filling gas containing Xe. The protection film contains X atomic% of SrO (provided that 5≤X<100), and the ratio of partial pressure of Xe against the total pressure of the filling gas is Y% (provided that 10≤Y≤50). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a plasma display panel (hereinafter referred to as PDP (Plasma Display Panel)), and more particularly to a plasma display panel having a protective film containing a metal oxide.

  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.

  The outline of the operation principle of PDP is called a display cell, which excites rare gas particles (atoms / molecules) by causing discharge in a discharge space filled with a rare gas filled gas, for example, by optical transition. The phosphor is excited by the generated ultraviolet light, and visible light from the phosphor is used for display light emission.

  The general structure of a conventional PDP has a structure in which electrodes are provided on two substrates disposed so as to face each other, and the discharge space is formed between these electrodes. The electrodes formed so as to face each other across the discharge space are called display electrodes and data electrodes, for example, and each of the display electrodes and the data electrodes has a structure covered with a dielectric layer. is doing.

  For example, a phosphor layer is formed on a dielectric layer covering the data electrode, and is an element that determines the color of a pixel when the PDP emits light. On the other hand, a protective film is formed on the dielectric layer covering the display electrode, and the dielectric layer is protected from damage due to sputtering.

  In this case, the discharge characteristics of the discharge space are greatly affected by the protective film facing the discharge space, particularly when the secondary electron gain of the protective film is high, that is, when secondary electrons are more likely to be emitted. It has been found that the discharge voltage in the discharge space decreases, and therefore, MgO having a relatively high secondary electron gain is generally used for the protective film. In order to further lower the discharge voltage, various materials have been proposed as a material constituting the protective film.

In the case where the discharge voltage is lowered by using the protective film material, generally, a method for improving the light emission efficiency, that is, for improving the efficiency can be considered. Among the protective film materials that have been reported so far, there have been reported materials that have a higher secondary electron gain than conventional MgO and can lower the discharge voltage (for example, patents). Reference 1).
T.shinoda etal, IEEE Trans. Electron Device, Vol.ED-26, No. 8, August 1979

  However, when these materials for reducing the discharge voltage are used, there is a problem that the light emission efficiency is lowered, and there is a concern that the light emission efficiency is lower than that when MgO is used. For example, when (SrCa) O, which is a composite oxide of Ca and Sr, is used as the protective film material, the discharge voltage is about 30 V lower than when MgO is used, but the luminous efficiency is reduced. There was a problem.

  As described above, since there is a problem of reduction in luminous efficiency, a protective film material made of a material other than MgO has not been put into practical use.

  On the other hand, in order to improve the luminous efficiency in the case of using a conventional protective film made of MgO, a method of increasing the partial pressure of Xe added to the sealed gas sealed in the discharge space can be considered.

  FIG. 1 is a graph showing the relationship between the ratio (%) of the partial pressure of Xe to the total pressure of the sealed gas in the discharge space and the luminous efficiency when MgO is used as the protective film material. Referring to FIG. 1, it can be seen that the luminous efficiency is improved as the Xe partial pressure in the discharge space is increased. However, as will be described below, the discharge voltage increases as the Xe partial pressure increases, so there is a limit to improving the light emission efficiency by increasing the Xe partial pressure.

  FIG. 2 shows the relationship between the ratio (%) of the partial pressure of Xe to the total pressure of the gas enclosed in the discharge space and the discharge voltage (minimum discharge maintenance voltage, minimum discharge start voltage) when MgO is used as the protective film material. FIG.

  Referring to FIG. 2, it can be seen that both the minimum discharge sustain voltage and the minimum discharge start voltage increase as the Xe partial pressure in the discharge space increases. For example, the upper limit of the minimum discharge sustaining voltage is 150 V, and the upper limit of the minimum discharge starting voltage is about 250 V. From these, it can be seen that the Xe partial pressure needs to be less than 10%.

  Thus, it has been difficult to improve the luminous efficiency while suppressing the discharge voltage of the PDP.

  Therefore, the present invention has a general object to provide a new and useful PDP that solves the above problems.

  A specific problem of the present invention is to provide a PDP in which the discharge voltage is suppressed low and the light emission efficiency is good.

  The present invention solves the above problem by providing a first substrate on which a first electrode, a dielectric layer covering the first electrode, and a protective film covering the dielectric layer are formed, and a second electrode And the second substrate on which the phosphor layer is formed are opposed to each other across a discharge space in which a sealing gas containing Xe is sealed, and the protective film contains SrO at X atomic% (however, 5 ≦ X <100), and the ratio of the partial pressure of Xe to the total pressure of the sealed gas is Y% (where 10 ≦ Y ≦ 50).

  The plasma display panel has features that the discharge voltage is kept low and the luminous efficiency is good.

  Further, it is preferable that the protective film further contains at least one of MgO, CaO, and BaO because the stability and durability of the protective film are improved.

  Further, it is preferable that the total pressure of the sealed gas is ZkPa (where 26.6 ≦ Z ≦ 101.3), because damage to the protective film due to sputtering is suppressed, and the sealed gas can be easily sealed.

  According to the present invention, it is possible to provide a PDP with a low discharge voltage and good luminous efficiency.

  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. 3A and 3B 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. The display electrode 12 is covered with a dielectric layer 13 made of, for example, lead oxide glass, and the like. The dielectric layer 13 is covered with a protective film 14 containing SrO. The display electrode 12 is configured by arranging a pair of strip-like scan electrodes and sustain electrodes in parallel with each other.

  In the conventional PDP, MgO is generally used as a material constituting the protective film. However, in the PDP according to the present embodiment, the protective film 14 is formed using a material containing SrO. For this reason, it is possible to reduce the discharge voltage when a discharge occurs in the discharge space 20, and to suppress the driving voltage of the PDP. Details of the effect when such a film containing SrO is used as the protective film will be described later.

  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 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 electrodes 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. 4 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. Note that, depending on the material of the phosphor layer 19, it can also function as a dielectric layer. In this case, the dielectric layer 17 can be omitted.

  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 is generated in the discharge space 20, and depending on the number of sustain discharges in the discharge space 20, an image can be obtained. An image can be displayed by controlling display gradation.

  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 made of, for example, ITO or SnO ₂ 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. To do.

  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 electrode 12 is formed, dried, and then fired to form the dielectric layer 13 having a thickness of about 20 μm. .

  Next, the protective film 14 containing SrO, for example, a protective film 14 made of SrO and CrO (made of (SrCa) O) is coated by electron beam (EB) deposition so as to cover the dielectric layer 13. The film is formed under the following conditions.

As the vapor deposition target, a mixture of SrO (50 atomic%) and CaO (50 atomic%) was used, the pressure during vapor deposition was 6.0 × 10 ⁻² Pa or less, and the substrate temperature T was 150 ° C. < By setting T <350 ° C. and a deposition rate of 0.5-15 nm / sec, a thin film of Sr and Ca complex oxide (SrCa) O having a film pressure of 700 nm is formed.

  In this case, the method for forming the protective film 14 is not limited to EB vapor deposition, and it is also possible to form the film using, for example, a sputtering method, an ion plating method using a plasma gun, The protective film formed by these methods can provide the same effects as those formed by EB vapor deposition.

  In the above example, a mixture of 50 atomic% of SrO and 50 atomic% of CaO is used as a target, and the protective film formed also contains 50 atomic% of SrO and 50 atomic% of CaO. Yes. In this case, if the protective film 14 contains at least 5 atomic% of SrO, the effect of reducing the discharge voltage described later can be obtained.

  Moreover, the material which comprises the said protective film 14 with SrO is not limited to CaO, For example, it is also possible to use the material which compounded BaO, MgO, or these. By including at least one of these CaO, BaO, and MgO in the protective film, there is an effect of improving the stability and durability of the protective film. That is, the SrO content is preferably less than 100 atomic%.

  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 is formed to cover the data electrode 16.

  Further, the barrier rib 18 having a width of 60 μm and a height of 130 μm is formed on the dielectric layer 17, and the phosphor 19 is applied onto the surfaces of the barrier rib 18 and the dielectric layer 17.

  Next, the front plate 11 and the back plate 15 are bonded and sealed so that the display electrode 12 and the data electrode 16 are orthogonal to each other, and the discharge space 20 formed inside is evacuated. In this case, for example, since the surface of the protective film containing an alkaline earth metal easily reacts with water or the like, the sealing step is preferably performed in a vacuum (reduced pressure atmosphere) or in an inert gas.

  Next, the PDP 10 can be formed by enclosing the discharge space 20 with, for example, a gas mixture of Xe and at least one of He, Ne, Ar, and Kr. The preferable pressure, mixing ratio, etc. of the sealed gas will be described later.

  In the PDP 10 formed as described above, the discharge voltage in the discharge space 20 greatly depends on the ease with which secondary electrons are emitted from the protective film 14 (secondary electron gain γ). In this case, the secondary electron gain γ is emitted from the surface of the protective film 14 when ions or excited particles (atoms or molecules) of the gas sealed in the discharge space 20 enter the protective film 14. The larger the value, the lower the discharge voltage.

  The secondary electron gain γ is substantially determined by the band structure of the material constituting the protective film 14 and the potential energy of the incident particles, and MgO has a relatively large value compared to other materials, which is currently MgO. Is used as a protective film.

  In addition, in the current PDP that emits light using ultraviolet rays from excited Xe among the sealed gas, Xe has the largest number of particles incident on the protective film during discharge in the discharge space. Ion. Therefore, when the amount of secondary electrons emitted is large when Xe ions are incident on the protective film 14 (when the secondary electron gain γ is large), the discharge voltage is most efficiently lowered.

  However, even if MgO has a relatively large secondary electron gain γ, if there is no localized level in the band, secondary electrons are not emitted when Xe ions are incident, and the secondary electron gain is 0. End up. The reason is as follows.

  For example, the conditions for the secondary electrons to be emitted from the protective film by ions are as follows: Ei is the ionization energy of incident ions to the protective film, Eg is the band gap of the protective film material, and x is the electron affinity. It can be approximated by> 2 (Eg + x) (hereinafter, condition 1). When MgO is used for the protective film, the condition 1 is not satisfied and secondary electrons are not emitted. For this reason, a method has been proposed in which the MgO material has a localized level and emits secondary electrons from the localized level, but the value of the secondary electron gain is only about 0.01. The effect is considered to be limited (see Y. Motoyama et al, J. Appl. Phys., Vol. 95, No. 12, 15 June 2004).

As described above with reference to FIGS. 1 and 2, in the conventional protective film using MgO, increasing the partial pressure of the Xe gas in the sealed gas improves the light emission efficiency but increases the discharge voltage. As a result, the power loss CV ² that cannot be recovered due to the panel capacity (C) increases. For this reason, in the conventional PDP, the ratio of the partial pressure of Xe to the total pressure of the sealed gas needs to be less than 10%. That is, when a protective film made of MgO is used, there is a limit to increasing the Xe partial pressure to improve the light emission efficiency and lowering the discharge voltage.

  Therefore, the PDP according to the present embodiment has a structure capable of suppressing the discharge voltage by configuring the protective film 14 with a material containing SrO. In a protective film made of a material containing SrO, for example, (SrCa) O, secondary ions are easily emitted from the surface when ions of encapsulated gas or excited particles (atoms or molecules) are incident on the protective film. The electronic gain γ is large.

  For this reason, in the PDP 10 according to the present embodiment, the discharge voltage can be lowered as compared with the conventional PDP using MgO as a protective film material. In this case, it is preferable to further increase the Xe partial pressure in the sealed gas. That is, by using a material containing SrO as the protective film and further increasing the ratio of the Xe partial pressure in the sealed gas, it is possible to configure a PDP with good luminous efficiency while suppressing an increase in discharge voltage. It becomes.

  The effect of using a material containing SrO for the protective film and the effect of increasing the Xe partial pressure of the sealed gas in the discharge space were manufactured and confirmed through experiments. . The experimental PDP has the same structure as the PDP 10 described above, has a partition pitch of 220 μm, a partition height of 100 μm, and has a protective film made of (SrCa) O. In the discharge experiment, driving is performed with an AC rectangular wave (frequency: 10 kHz), and the result will be described below with reference to FIGS.

  FIG. 5 and FIG. 6 are diagrams showing the results of a discharge experiment performed using the experimental PDP. FIG. 5 shows the minimum discharge sustaining voltage and the minimum discharge starting voltage when the ratio (%) of the partial pressure of Xe to the total pressure of the sealed gas is varied. On the other hand, FIG. 6 shows the luminous efficiency when the ratio (%) of the partial pressure of Xe to the total pressure of the sealed gas is varied. In this case, for comparison, in each case, the results for the case of using a protective film made of MgO are also shown.

  Referring to FIG. 5, both the minimum discharge sustain voltage and the minimum discharge start voltage are lower when the protective film according to the present embodiment is used than when the conventional protective film made of MgO is used. I understand that. For this reason, it is possible to increase the ratio of the Xe partial pressure to the total pressure of the sealed gas (hereinafter referred to as the Xe partial pressure ratio) in comparison with the prior art.

  Further, from the results shown in FIG. 6, when the Xe partial pressure ratio is the same, the luminous efficiency is almost the same when the MgO protective film is used and when the (SrCa) O film according to the present embodiment is used. Has been confirmed.

  For example, when a conventional MgO protective film is used, the Xe partial pressure ratio needs to be less than 10%, but in this embodiment, it can be made 10% or more. In this case, the Xe partial pressure ratio is preferably 50% or less from the upper limit of the minimum discharge sustaining voltage and the upper limit of the minimum discharge starting voltage.

  That is, in the case of the present embodiment, the Xe partial pressure ratio is preferably 10% or more and 50% or less. In this case, the discharge voltage of the PDP is suppressed and the light emission efficiency is improved. Further, when the Xe partial pressure ratio is 20% or more and 50% or less, the luminous efficiency is further improved, which is more preferable.

  Further, when the total pressure of the sealed gas is 26.6 kPa or more, it is possible to suppress damage to the protective film by suppressing damage due to sputtering of the protective film. In addition, when the total pressure of the sealed gas is 101.3 kPa (atmospheric pressure) or less, it is easy to fill the sealed gas, which is preferable in manufacturing the PDP. That is, the total pressure of the sealed gas is preferably 26.6 kPa or more and 101.3 kPa or less.

  Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to the specific embodiments described above, and various modifications and changes can be made within the scope described in the claims.

It is a figure which shows the Xe partial pressure dependence of the luminous efficiency of the conventional PDP. It is a figure which shows the Xe partial pressure dependence of the discharge voltage of the conventional PDP. (A), (B) is sectional drawing which showed typically PDP by Example 1. FIG. It is the perspective view which showed typically PDP by Example 1. FIG. It is a figure which shows the discharge voltage reduction effect of PDP which concerns on Example 1. FIG. It is a figure which shows the luminous efficiency of PDP which concerns on Example 1. FIG.

Explanation of symbols

10 PDP
DESCRIPTION OF SYMBOLS 11 Front plate 12 Display electrode 13 Dielectric layer 14 Protective film 16 Data electrode 17 Dielectric layer 18 Partition 19 Phosphor 20 Discharge space

Claims (3)

A first substrate on which a first electrode, a dielectric layer covering the first electrode, and a protective film covering the dielectric layer are formed;
A plasma display panel, wherein the second electrode and the second substrate on which the phosphor layer is formed are opposed to each other across a discharge space in which a sealed gas containing Xe is sealed,
The protective film contains SrO in X atomic% (where 5 ≦ X <100), and the ratio of the partial pressure of Xe to the total pressure of the sealed gas is Y% (where 10 ≦ Y ≦ 50). Plasma display panel.   The plasma display panel according to claim 1, wherein the protective film further includes at least one of MgO, CaO, and BaO. 3. The plasma display panel according to claim 1, wherein the total pressure of the sealed gas is ZkPa (where 26.6 ≦ Z ≦ 101.3).

Images