JP3918879B2 - Secondary electron emission material for plasma display and plasma display panel - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a secondary electron emission material and a PDP in a plasma display panel (hereinafter referred to as PDP), and more particularly, to an improvement of a secondary electron emission material for forming a protective layer of a dielectric layer in the PDP and the use thereof. Related to the PDP.
There are two types of PDP: direct discharge type (DC type PDP) and indirect discharge type (AC type PDP), which adopts surface discharge type. PDPs are easy to enlarge, self-luminous type, good display quality, response speed There are features such as fast. In addition, since it can be reduced in thickness, it has been attracting attention as a wall-mounted display together with a liquid crystal display device (LCD). In the future, higher definition is desired.
[0002]
In both DC type and AC type PDPs, MgO is used as a protective layer for the dielectric layer. In order to achieve higher resolution, the current discharge start voltage (Vf) is lowered and the operation is stabilized. In order to maintain the characteristics, it is necessary to increase the width between the minimum discharge sustain voltage and the maximum discharge sustain voltage.
[0003]
[Prior art]
FIG. 8 is a cross-sectional view of a conventional surface discharge AC type PDP. As shown in FIG. 8, a discharge sustaining electrode pair is formed on the rear glass substrate 1. The discharge sustaining electrode pair includes two parallel strip-shaped display electrodes 2 and 3. The display electrodes 2 and 3 are covered with a dielectric layer 4, and a thin protective layer 5 made of MgO is formed on the dielectric layer 4. Here, the dielectric layer 4 is provided for accumulating electric charges generated by applying a voltage to the display electrodes, and the protective layer 5 is provided for preventing the dielectric layer 4 from being destroyed by collision of ions generated by discharge.
[0004]
On the other hand, a strip-shaped address electrode 7 and a phosphor layer 8 are formed on the front glass substrate 6.
The rear glass substrate 1 and the front glass substrate 6 are overlapped so that the protective layer 5 and the phosphor layer 8 face each other, and the display electrodes 2 and 3 and the address electrode 7 intersect each other. A gap 9 is formed between the protective layer 5 and the phosphor layer 8, and an inert gas that causes discharge is sealed in the gap 9.
[0005]
Next, the operation of the above PDP will be described. An AC voltage corresponding to the discharge sustain voltage is applied between the display electrodes 2 and 3 to accumulate charges in the dielectric layer 4. Next, when an AC voltage that reaches the discharge start voltage is applied to the address electrode 7, the inert gas is separated into electrons and ions by a high electric field generated in the gap and is turned into plasma. The phosphor layer 8 develops color upon receiving ultraviolet rays generated when electrons and ions recombine. Thereafter, the inert gas is discharged by only applying an AC voltage corresponding to the discharge sustain voltage between the display electrodes 2 and 3 by the electric charge accumulated in the dielectric layer 4, and the phosphor layer 8 is colored.
[0006]
[Problems to be solved by the invention]
However, if the distance between the display electrodes 2 and 3 is reduced due to the demand for high-definition AC-type PDP, the discharge start voltage increases or the dielectric layer 4 is electrostatically damaged. For this reason, the discharge start voltage must be lowered.
In addition, it is considered that the discharge maintenance minimum voltage increases as the discharge start voltage increases. Further, since the electric field generated between the display electrodes 2 and 3 becomes narrower and the electrostatic breakdown voltage of the dielectric layer 4 decreases, the upper limit of the discharge sustaining maximum voltage is limited. As described above, as the PDP is highly refined, the difference between the discharge sustaining minimum voltage and the discharge sustaining maximum voltage (discharge margin voltage) tends to decrease. In order to operate the PDP with a margin and to stabilize the operation, it is desirable to increase the discharge margin voltage.
[0007]
The present invention was created in view of the above-described problems of the conventional example, and provides a secondary electron emission material in a PDP capable of reducing a discharge start voltage and widening a discharge margin voltage. It is the purpose.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, a first invention relates to a secondary electron emission material for a plasma display, wherein a part of Mg constituting MgO is replaced with at least Fe, Cr and V (vanadium) elements. Secondary electron emission material, wherein the substitution amount is set so that the emission intensity from the Fe and Cr is strong and the emission from the V is weak,
A second invention relates to a plasma display panel, wherein two substrates are opposed to each other with a gap interposed therebetween, and an inert gas to be discharged is sealed in the gap. A protective layer made of the secondary electron emission material according to claim 1 is formed on the surface in contact with the active gas,
A third invention relates to the plasma display panel according to the second invention, wherein the two substrates are each formed by sequentially laminating a strip electrode, a dielectric layer and the protective layer on a glass substrate, and the protection The two substrates are stacked such that the layers face each other and the electrodes cross each other,
According to a fourth aspect of the present invention, there is provided the plasma display panel according to the third aspect, wherein one of the two substrates is a strip-shaped discharge sustaining electrode pair parallel to each other on the glass substrate, the dielectric layer, and the substrate. A protective layer is sequentially laminated, and the other substrate is a glass substrate in which a strip-like writing electrode and a phosphor layer are sequentially laminated, and the protective layer and the phosphor layer face each other, and The two substrates are overlapped so that the electrode pair and the writing electrode cross each other.
[0009]
[Action]
The discharge start voltage of the plasma display panel is greatly affected by the amount of secondary electrons emitted from the protective layer.
That is, ions generated by ionization of the inert gas collide with the protective layer and enter the inside. In response to this kinetic energy, secondary electrons are generated from the protective layer, further promoting ionization. Therefore, in order to reduce the discharge start voltage, it is necessary to increase the amount of secondary electrons emitted from the protective layer.
[0010]
Further, since it is considered that the discharge sustaining minimum voltage is lowered by increasing the secondary electron emission amount, it is considered better to increase the secondary electron emission amount in order to widen the discharge margin voltage.
The inventor of the present application uses MgO that is strong against ion bombardment, and can replace a part of the Mg with at least one of iron (Fe) and chromium (Cr) to increase the discharge margin voltage. And found by experiment. In particular, it has been found that the effect is increased if a small amount of vanadium (V) is substituted in addition to iron and chromium in comparison with the total amount of iron and chromium.
[0011]
Moreover, since it is thought that the amount of secondary electrons emitted from the protective layer is increased by the above substitution, it is possible to lower the discharge start voltage.
[0012]
【Example】
Next, embodiments of the present invention will be described with reference to the drawings.
(1) Secondary electron emission material according to the first embodiment of the present invention The results of experiments on the secondary electron emission material according to the first embodiment will be described below.
[0013]
(i) Preparation of sample A sample for investigation having the structure shown in FIG. 1 was prepared. As a sample for investigation, a plasma display panel is formed by sealing an inert gas in a gap 13 between two substrates 11 and 12 and has a monochrome type PDP configuration. Then, six types (# 1 to ##) in which iron (Fe), chromium (Cr), and vanadium (V) are used as elements for substituting Mg in MgO used as a protective layer, and their contents are changed in various ways 6) Created.
[0014]
Hereinafter, the structure of the investigation sample will be described. That is, one substrate 11 is formed by sequentially laminating a strip-shaped first display electrode 22a, a dielectric layer 23a, and a protective layer 24a on a glass substrate 21a, and the other substrate 12 is a strip-shaped second layer on the glass substrate 21b. The display electrode 22b, the dielectric layer 23b, and the protective layer 24b were laminated in order. Note that lead wires 25a and 25b are connected to the first display electrode 22a and the second display electrode 22b, respectively.
[0015]
The two substrates 11 and 12 are overlapped so that the protective layers 24a and 24b face each other and the first display electrode 22a and the second display electrode 22b intersect with each other. A gap 13 of 30 μm for enclosing the inert gas is formed.
As the first and second display electrodes 22a and 22b, a three-layer conductive film of Cr film / Cu film / Cr film formed by a sputtering method is used, and a film thickness of about a film thickness formed by a coating method or the like as a dielectric layer 23a. A 20 μm lead oxide (PbO) glass film was used.
[0016]
Further, as the protective layers 24a and 24b, MgO films having a thickness of about 0.5 μm in which magnesium (Mg) is substituted with transition metals such as iron (Fe), chromium (Cr) and vanadium (V) are used. For the MgO films 24a and 24b, MgO single crystals mixed with iron (Fe), chromium (Cr) and vanadium (V) with various contents are put in a crucible and melted, and this is electron beam vapor deposition (EB vapor deposition). It was formed by doing.
[0017]
(ii) Experimental method (a) Photoluminescence measurement method The element substituting for Mg in the protective layers 24a and 24b obtained by EB deposition using MgO single crystals is specified, and the amounts of Fe, Cr and V are determined. In order to detect this, photoluminescence measurement was performed.
[0018]
In the photoluminescence measurement, light generated when photoexcited electrons fall to the level of impurity ions is observed. Since the light has a wavelength characteristic of impurity ions and has an intensity proportional to the abundance, the type and amount of impurities can be specified.
Ar lasers with wavelengths of 488 nm and 514.5 nm were used as light sources, and the protective layers 24a and 24b were excited with powers of 50 mW and 36 mW, respectively. It should be noted that light with excitation wavelengths of 488 nm and 514.5 nm corresponds to 2.54 eV and 2.41 eV, respectively, and has only about 1/3 of the MgO band gap of 7.75 eV. It is impossible to excite electrons in the valence band to the conduction band. Nevertheless, luminescence is observed, as shown in FIG. 7, in which several localized levels such as oxygen defects exist in the band gap of MgO, from which electrons are excited in the conduction band. This is considered to be because of this.
[0019]
(B) Measuring method of minimum discharge maintenance voltage, maximum discharge maintenance voltage, and discharge margin voltage An AC power source having a frequency of 2 KHz is connected to the first and second display electrodes 22a, 22b, and the voltage is gradually increased. Was measured (discharge start voltage; Vf). Further, the voltage was lowered after the start of discharge, and the voltage at which the discharge disappeared (discharge sustaining minimum voltage; Vsmin) was measured. Further, the voltage was increased, and the voltage (discharge sustaining maximum voltage; Vsmax) when the discharge disappeared or the dielectric layers 23a and 23b were destroyed was measured.
[0020]
Further, a discharge margin voltage (Vsmax−Vsmin) was calculated from the maximum discharge sustain voltage and the minimum discharge sustain voltage.
(iii) Experimental results (a) Photoluminescence measurement results FIGS. 3 (a) and 3 (b) show the measurement results. FIG. 3A is a characteristic diagram showing the emission intensity with respect to the measurement wavelength, and FIG. 3B is an enlarged view around the measurement wavelength of 700 nm. In both cases, the vertical axis represents the emission intensity in arbitrary units, and the horizontal axis represents the measurement wavelength [nm] expressed in a linear scale. In FIG. 3A, the horizontal axis shown at the top of the figure indicates the photon energy [eV] corresponding to the measurement wavelength.
[0021]
As shown in FIGS. 3 (a) and 3 (b), several characteristic peaks were observed. Since the measurement wavelength indicating the peak position does not change depending on the excitation wavelength of 488 nm and 514.5 nm of the light source, it can be determined that it appears due to luminescence rather than the Raman effect. This is because the peak due to the Raman effect is due to the interaction between light and phonons, and therefore when the excitation wavelength changes, the peak position of Raman scattering also shifts by the amount of change in the excitation wavelength.
[0022]
Hereinafter, the type of impurity corresponding to the peak is specified. Since the luminescence observed in the range of the measurement wavelength of about 650 to 920 nm has been observed in the past, it was based on these data.
According to the literature [S. Datta, KEAeberli, IM Boswarva, and DBHolt, J. Microscopy 118 (1980) 367, the cathodoluminescence measurement results of MgO doped with 200 to 250 ppm of Fe are described. 688,706,723 , A clear peak at 747 nm is observed. Therefore, it can be considered that the peak at a position close to these in the figure indicates the presence of the Fe element.
[0023]
Furthermore, the luminescence measurement result from Cr ^{3 + in} MgO according to the literature [CCChao, J. Phys. Chem. Solids, 32 (1971) 2517 is considered to observe emission at 698, 712, 720, 725 nm. . Therefore, it is considered that the peak at a position close to these in the figure indicates the presence of the Cr element.
In addition, there is a report that the emission in the region of 659.5 to 680 nm is from Mn ^{4 +} [K. Dunphy, and WWDuley, J, Phys. Chem. Solids, 51 (1990) 1077, and luminescence at 660 nm. Seems to correspond to it. Therefore, it is considered that the peak at a position close to these in the figure indicates the presence of the Mn element.
[0024]
Furthermore, with respect to the emission observed at 880 to 920 nm, according to the literature [I. Femandez and J. Llopis, Phys. Stat. Sol. (A) 108 (1988) K163, in the figure, particularly strong emission at 870 nm is V The luminescence from ^{2 +} is considered.
(B) Measurement results of minimum discharge sustain voltage, maximum discharge sustain voltage and discharge margin voltage Light emission intensity [cps], minimum discharge sustain voltage (Vsmin), maximum discharge sustain voltage (Vsmax) [V] at measurement wavelengths 700, 720, and 870 nm ] Is shown in FIG. The values of Vsmin and Vsmax are measured values after aging the sample for 1 hour. From FIG. 4A, it can be seen that Vsmax is substantially proportional to the emission intensity at 720 nm.
[0025]
FIG. 4B shows the relationship between the discharge margin voltage (Vsmax−Vsmin) and each emission intensity. It can be seen that the discharge margin voltage is almost in inverse proportion to the emission intensity at 870 nm.
In order to clarify the correlation between these, the dependence of Vsmin, Vsmax, and Vsmax−Vsmin on each emission intensity is shown in FIGS. 5 (a), 5 (b), and 6, respectively. In each figure, the trend of data is shown by a solid line.
[0026]
Interesting results were obtained for the discharge margin voltage of FIG. That is, the emission intensity at the measurement wavelength of 700 nm is substantially constant with respect to the discharge margin voltage, whereas the emission intensity at the measurement wavelengths of 720 nm and 870 nm changes greatly.
When the discharge margin voltage increases with 11V as a boundary, the emission intensity at the measurement wavelength of 720 nm increases rapidly. This is because, as the amount of Mg substitution of at least one of Fe and Cr increases, a large number of impurity levels are formed in the band gap, and electrons with high energy are trapped there and the impurity levels are increased. It is considered that the transition to the ground state indicates that many secondary electrons are generated from the surface of MgO.
[0027]
On the other hand, when the discharge margin voltage increases with 11V as a boundary, the emission intensity at the measurement wavelength of 870 nm decreases.
From the above, it was found that the discharge margin voltage increases when the emission intensity from Fe and Cr in the MgO film used for the protective layer of the PDP is strong or the emission from V is weak. This is considered to be because Mg was substituted with at least one of Fe and Cr, or because the effect of V addition was added thereto.
[0028]
Although no data has been acquired for the discharge start voltage (Vf), since it is expected that many secondary electrons are generated from the surface of MgO, the discharge of the inert gas in contact with the protective layer is promoted. Therefore, it is considered that the discharge start voltage (Vf) also decreases.
(2) Plasma display panel according to the second embodiment of the present invention A color PDP according to the second embodiment will be described below with reference to FIGS. 2 (a) and 2 (b). The secondary electron emission material is used as the protective layer 38. 2A and 2B are a perspective view and a partial cross-sectional view showing the structure of a surface discharge type PDP capable of color display, respectively.
[0029]
In the figure, 31 is a front glass substrate, 32a and 32b are a pair of strip-shaped display electrode pairs formed on the surface of the front glass substrate 31 and extending in parallel in one direction, each of Cr film / Cu film / Cr film The three-layer conductive film. Reference numeral 33 denotes a lead oxide (PbO) glass layer (dielectric layer) having a thickness of about 20 μm formed so as to cover the display electrodes 32a and 32b.
[0030]
Reference numeral 34 denotes a protective layer made of the secondary electron emission material shown in the first embodiment.
The above constitutes one substrate 14.
35 is a rear glass substrate formed so as to face the front glass substrate 31, 36a and 36b are formed on the rear glass substrate 35, and are strip-like partition walls parallel to each other in one direction, and 37 is between the partition walls 36a and 36b. The address electrodes (write electrodes) 38 formed along the partition walls 36a and 36b in the recesses of FIG. 6 are phosphors that cover the address electrodes 37, and the address electrodes 37 and the phosphors 38 display, for example, red. In addition, although it does not attach | subject the code | symbol, the display of green, blue, red, ... is lined up in order next to the red display part. The phosphors of the respective colors are made of different materials. In the case of blue, for example, BaMgAl ₁₄ O ₂₃ : En ²⁺ is used, in the case of green, for example, BaAl ₁₂ O ₁₉ : Mn is used, and in the case of red, for example, Y _0.65 Gd _0.35 BO ₃ : En ³⁺ is used. . The address electrodes 37 and the phosphors 38 are partitioned by partition walls 36a and 36b.
[0031]
The above constitutes the other substrate 15.
In an actual PDP, a large number of partition walls, address electrodes, phosphors, and display electrodes are formed with the same configuration as described above. However, in the above description, only one set is described for simplicity. Absent.
The phosphor 38 of the rear glass substrate 35 and the display electrodes 32a and 32b of the front glass substrate 31 face each other with a gap 39 of several tens of μm, and the display electrodes 32a and 32b and the address electrodes 37 of the rear glass substrate 35 are The substrates 14 and 15 are overlapped so as to cross each other.
[0032]
FIG. 2B is a partial cross-sectional view showing a recess 39 between the partition wall 36a and the partition wall 36b. In the recess, a mixed gas of neon (Ne) and xenon (Xe) or helium (He) and Xe is mixed. An inert gas such as a mixed gas is sealed under reduced pressure.
When the PDP is operated, a discharge sustaining voltage (AC or DC) before the start of discharge is applied between the display electrodes 32a and 32b to accumulate charges in the dielectric layer 33. In this state, a voltage (AC or DC) is applied to the address electrode 37 so as to reach the discharge start voltage, thereby causing discharge. As a result, plasma is generated in the gap 39 of the recess, and the phosphor 38 emits light by the excitation light emitted from the plasma, and color display is performed.
[0033]
According to the color PDP according to the second embodiment, since the secondary electron emission material according to the first embodiment is used as the material of the protective layer 34, the amount of secondary electron emission is increased and sealed. Ionization of inert gas is promoted.
Thereby, since the discharge start voltage can be lowered, the interval between the discharge sustaining electrodes can be narrowed, and the color PDP can be highly refined.
[0034]
In addition, since the discharge margin voltage can be widened, the PDP can be stably operated.
In the second embodiment, the present invention is applied to the surface discharge type PDP. However, the present invention is not limited thereto, and secondary electron emission from a protective layer in contact with the inert gas is used. Thus, the present invention can be applied to a PDP configured to promote discharge of an inert gas.
[0035]
【The invention's effect】
As described above, according to the secondary electron emission material for plasma display according to the present invention, a part of Mg constituting MgO is substituted with at least one element of Fe, Cr, and V. For this reason, since the amount of secondary electron emission increases, the discharge is promoted, the discharge start voltage is lowered, and the discharge margin voltage is widened. In particular, the effect can be enhanced by making the amount of V smaller than the total amount of Fe and Cr.
[0036]
In addition, according to the plasma display panel of the present invention, the discharge start voltage can be lowered, so that the interval between the discharge sustaining electrodes can be narrowed and the plasma display panel can be enhanced in color. In addition, since the discharge margin voltage can be widened, the plasma display panel can be stably operated.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a PDP for investigating a secondary electron emission material according to a first embodiment of the present invention.
FIGS. 2A and 2B are a perspective view and a sectional view showing a surface discharge type PDP according to a second embodiment of the present invention. FIGS.
FIG. 3 is a characteristic diagram showing a photoluminescence investigation result of the secondary electron emission material according to the first example of the present invention.
FIG. 4 is a characteristic diagram showing a result of investigating a discharge sustaining minimum voltage, a discharge maintaining maximum voltage, and a discharge margin voltage of the secondary electron emission material according to the first embodiment of the present invention.
FIG. 5 is a characteristic diagram showing the results of investigating the dependency of the discharge sustaining minimum voltage and the discharge maintaining maximum voltage on the emission intensity of the secondary electron emission material according to the first embodiment of the present invention.
FIG. 6 is a characteristic diagram showing a result of investigating the discharge margin voltage dependence on the emission intensity of the secondary electron emission material according to the first example of the present invention.
FIG. 7 is a view showing a band structure of a secondary electron emission material according to the first embodiment of the present invention.
FIG. 8 is a cross-sectional view showing a PDP according to a conventional example.
[Explanation of symbols]
11, 12, 14, 15 substrate,
13,39 gap,
21a, 21b, 31, 35 glass substrate,
22a, 32a first display electrode,
22b, 32b second display electrodes,
23a, 23b, 33 dielectric layers,
24a, 24b, 34 protective layer,
25a, 25b Lead wiring,
36a, 36b partition wall,
37 Address electrode (write electrode),
38 Phosphor layer.

Claims (1)

Two substrates are opposed to each other with a gap, and an inert gas to be discharged is sealed in the gap. At least one of the substrates has a strip-shaped electrode, a dielectric layer covering the electrode, and a dielectric layer on the dielectric layer. In the plasma display panel formed by forming a protective layer made of MgO as a secondary electron emission material on the surface in contact with the inert gas,
A part of Mg constituting the MgO protective layer is replaced with Fe, Cr, V, respectively, and the emission intensity from the Fe and Cr is strong and the emission intensity from the V is weak. A plasma display panel, wherein the amount is smaller than the total amount of Fe and Cr.

Images