JP3081112B2 - Method for forming protective film of gas discharge panel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a protective film in an AC gas discharge panel.

[0002]

2. Description of the Related Art An AC-type gas discharge panel (hereinafter referred to as AC-P)
Sometimes referred to as DP or simply panel. ) Is a dielectric layer for accumulating charges (also referred to as wall charges) on a pair of display electrodes, and a protective film on the dielectric layer for preventing damage to the dielectric layer when discharging. Are provided.
In general, MgO is used as a material for the protective film. MgO has excellent characteristics such as a high secondary electron emission ratio and resistance to ion bombardment.

At present, a protective film using MgO (hereinafter referred to as Mg
O protective film or MgO film) is generally formed by a vacuum deposition method. Since MgO is present evenly in the protective film formed by using this method, the original characteristics of MgO can be utilized. However, in order to facilitate the enlargement of the panel and the simplification of the panel manufacturing process, for example, the literature (Television Society Report,
IDY94-14, pp. As disclosed in 1-6), formation of an MgO protective film using a screen printing method has been studied.

[0004]

However, when a protective film is formed by screen printing using a paste containing MgO, there are the following problems.

Since this protective film is not transparent, it cannot be formed on the front panel substrate, and must be formed on the rear panel substrate. Then, a transmissive panel in which a phosphor layer is formed on the front panel substrate is obtained. However, a transmissive panel has lower luminous efficiency than a CRT or the like. Therefore, it is necessary to consider means for increasing the luminous efficiency.

As one means for solving this problem, it is conceivable to increase the thickness of the protective film. When the thickness of the protective film is increased, the luminous efficiency can be increased, and the generation of pinholes in the protective film can be prevented. Pinholes also cause cracks in the protective film, so eliminating them leads to a longer panel life. However, when the protective film is thickened, the discharge voltage at the time of driving the panel increases. Although MgO originally has a function of suppressing the discharge voltage at the time of driving the panel, when screen printing is used, the uniformity is inferior to that of a vapor-deposited film which is a continuous thin film. Since the bias is generated and there is a non-existent region, it is impossible to sufficiently utilize the original characteristics of MgO as described above.

[0007] Therefore, there has been a demand for a method of forming a protective film that can suppress the discharge voltage at the time of driving the panel and increase the luminous efficiency at the same time even when the screen printing method is used.

[0008]

SUMMARY OF THE INVENTION For this reason, the present invention relates to A
According to the method for forming a protective film of C-PDP, the following process features are provided.

(A) MgO powder and this MgO
A paste containing a liquid binder that becomes a solid that binds the particles of the O powder is printed on the rear substrate by a screen printing method to form a paste layer, and then the paste layer is dried and fired.

(B) By repeating the step (a), the fired paste layers are laminated to form a laminated protective film.

In practicing the present invention, the above-mentioned liquid binder is mixed with MgO powder by sintering.
As the liquid binder that becomes gO, it is preferable to use a stabilized magnesium diethoxide solution.

In carrying out the present invention, when the content of the MgO powder in the above-mentioned paste is 25 wt%,
It is preferable that the screen used at the time of printing has a screen size of 400 mesh, a wire diameter of 18 μm and a gauze thickness of 36 μm.

Further, MgO in the above-mentioned paste is used.
When the content of the powder is 10 wt% or 15 wt%, the MgO powder to be used is mixed with a powder having a particle diameter of 100 nm and a powder having a particle diameter of 50 nm at a weight ratio of 3: 1. Good things to do.

[0014]

According to the method of forming an AC-PDP protective film of the present invention described above, first, MgO powder and M
A paste containing a liquid binder that becomes a solid that binds the particles of the gO powder is printed by a screen printing method, dried, and then fired. Next, this step is repeated to laminate the protective film. In this manner, by always firing and stacking every time printing is performed, the fired paste layer obtained for each firing, that is, the protective film of each layer,
MgO from the MgO powder and a solid that binds the MgO (this solid is also a component of the protective film.
Here, this solid is also referred to as a component caused by the binder. ). In this protective film, the component caused by the binder is present in the upper surface region in the MgO layer from the MgO powder, and is substantially fixed. Therefore, when printing-drying-firing is repeated and a plurality of fired body layers are sequentially laminated to form one protective film as a whole,
The protective film is a protective film in which a large amount of components due to the binder are periodically present along the thickness direction from the dielectric layer side on which the protective film is provided to the upper surface of the protective film.

When a liquid binder containing a component that becomes MgO by firing is used as the binder, the component caused by the binder, that is, MgO, is more concentrated and unevenly distributed in the upper surface region of the MgO layer due to the MgO powder for each of the laminated layers. The resulting protective film is obtained.

When the entire laminated protective film thus obtained is viewed, the component (eg, MgO) caused by the binder is not unevenly distributed in the surface region of the laminated protective film opposite to the dielectric layer. The component due to the binder is M
It means that the MgO powder is dispersed in each MgO layer.

Therefore, components caused by the binder are scattered in the entire laminated protective film, and a region where this component hardly exists does not exist. Therefore, the inherent characteristics of the protective film are generated. When an AC-PDP is manufactured and driven by using the protective film, the protective film has excellent characteristics of low voltage, low current, and high efficiency.

The liquid binder used at this time is
If a liquid binder containing a component (Mg and O) that becomes MgO upon firing is used, the particles and the binder become the same, so that the protective film can be made dense.

When this protective film is formed under any one of the following conditions, the thickness of one layer becomes thinner, so that the width of uneven distribution of MgO becomes narrower and the protective film becomes denser. Can be.

Mg in paste used for printing
The content of the O powder is 25 wt%, and the screen used at this time is 400 mesh, the wire diameter is 18 μm, and the gauze thickness is 36 μm.

Mg in paste used for printing
The content of the O powder is set to 10 wt% or 15 wt%, and the MgO powder has a particle diameter of 100 nm,
Are mixed at a weight ratio of 3: 1.

By making the MgO protective film dense in this way, the original characteristics of MgO can be utilized.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. It should be noted that the drawings are only schematically shown to the extent that the invention can be understood. In the following description, specific materials and conditions are used, but these are only one of preferred examples, and therefore, the present invention is not limited thereto.

FIG. 1 is a perspective view of an essential part for explaining a basic structure of a surface discharge type AC-PDP used in an embodiment of the present invention.

On the back substrate 11 of the panel 10, display electrodes 13 are arranged in parallel in pairs. A dielectric layer 15 for charge storage is provided so as to cover the display electrode, and a protective film 17 is provided on the entire surface of the dielectric layer 15. The rear substrate 11 and a front substrate 21 having a wall (not shown) and a green phosphor layer 19 are overlapped so as to face each other via a discharge space 23. In the discharge space 23, a discharge gas (for example, He is 95 Vol
% And a mixed gas of 5 vol% Xe) are sealed at 500 Torr. In this example, black glass is used as the wall, ZnSiO ₄ : Mn (zinc silicate manganese, P1-G1 (trade name), manufactured by Kasei Optonics Co., Ltd.) as the green phosphor, and gold (A-3725 (trade name)) as the electrode material. , Engelhard), transparent glass as dielectric (G3-0)
496 (trade name), manufactured by Okuno Pharmaceutical Co., Ltd.).

The panel 10 was driven at 20 kHz, and an experiment was performed to compare the discharge characteristics and the like under each condition. Hereinafter, a first embodiment of the present invention will be described.

<First Embodiment> First, a method for forming a protective film of a gas discharge panel according to the present invention will be described.

The paste used as the material for the protective film is composed of 25 wt% of MgO powder, 25 wt% of magnesium diethoxide solution as a liquid binder (10 wt% in terms of MgO based on MgO powder), and 6 wt% of ethyl cellulose resin.
%, Solvent at 44%. This magnesium diethoxide solution is in a so-called stabilized state in which hydrolysis is suppressed, and the solution contains about 10 wt% of organic Mg in terms of MgO. As described above, the powder and the binder are made of the same quality, and the protective film is densified. The solvent is a mixture of butyl carbitol, terpineol and texanol. The viscosity of the paste is 30 Pa · s / 25 ° C.
(300 poise at 25 ° C.).

The above-mentioned paste is printed on a dielectric layer provided on a back substrate constituting a panel by using a 400-mesh, linear 18 μm, 36 μm thick screen to form a paste layer. Thereafter, the paste layer is dried for 150
The first protective film is formed by baking at 580 ° C. for 10 minutes each at ℃. In this embodiment, the printing-
The drying-firing process was repeated three times to form a first, second, and third protective films, that is, a three-layer MgO protective film. The thickness of the protective film thus formed is approximately 2 μm per layer.

In the step of baking after drying the paste layer, the solvent in the paste is evaporated by drying, and the magnesium diethoxide solution is collected near the surface of the protective film. Further, the calcination burns the ethylcellulose resin and the magnesium diethoxide solution. As a result, the magnesium diethoxide solution is decomposed, and the organic Mg as a component in the solution is combined with the component O to form MgO, and the MgO as a component due to the binder is converted into powder Mg near the surface.
As a result, a protective film as a sintered body of MgO of both MgO from the MgO powder and MgO from the binder is obtained. As described above, since MgO caused by the binder is localized near the surface of the protective film,
The amount of MgO observed in the thickness direction of the protective film obtained after firing increased near the surface of the MgO, and was increased over the entire thickness.
Is uneven in the distribution.

FIG. 2 is a scanning electron microscope (SEM) showing a region where MgO is present in the three-layer protective film and fixed after firing and caused by the binder.
FIG. 4 is a cross-sectional view schematically showing the result of observation in FIG. In order to compare with the case of this embodiment in which the first layer 17a, the second layer 17b, and the third layer 17c are baked every time the printing is performed ((A) in FIG. 2), the layers are stacked three times and finally A conventional case in which baking is performed only once (FIG. 2B) is also shown. In this case, the protective film is indicated by 18, the first layer is 18a, the second layer is 18b,
The layers are indicated by 18c. Note that hatching representing a cross section is omitted except for a part. In these schematic diagrams, the region where MgO exists due to the binder is clearly shown as one region 30 or 32. However, actually, the region does not exist as such a clear region.
Since the amount of MgO present changes sequentially, the boundary of this existing region is blurred.

FIG. 3 is a diagram schematically showing the measurement results of the distribution of MgO in the thickness direction caused by the fixed binder in the three-layered protective film which is similarly fired for each printing. As in FIG. 2, the case of this embodiment (FIG. 3A) and the conventional case of laminating three times and then firing only once (FIG. 3B). It is shown in comparison. Each horizontal axis indicates the thickness up to the surface of the third protective film, with the surface of the dielectric layer 15 of the panel 11 as 0. The vertical axis indicates the amount of MgO present due to the binder. In FIG. 2A, the curves of MgO caused by the binder are represented by I and I, respectively.
These are indicated by I and III, and are indicated by IV in FIG.

As shown in FIG. 2A, in this embodiment, the protective layer is laminated three times and a baking step is always performed for each printing. It can be seen that it is present in all three layers of the eye 17b and the third layer 17c. That is, the distribution curves I, II and III
As is clear from FIG.
It will be distributed in layers. In contrast, FIG.
As can be seen from the distribution curve IV of (B), when the layers were laminated three times and finally baked together, the fixed MgO layer 32 was laminated especially in the third time, that is, 3
It is concentrated near the surface of the protective film 18c of the layer, hardly exists in the lower layer 18a,
It can be seen that it is slightly present in the layer b.

Further, from FIG. 3A, in this embodiment,
The region with a large amount of fixed MgO is the first layer 17a, the second layer 1
7b, the third layer 17c is dispersed, and it can be seen that the amount of MgO increases in the direction of increasing the thickness of each layer. That is, the amount of MgO in each of the layers 17a, 17b and 17c increases from the dielectric layer surface side toward the surface of each layer. However, as shown in FIG. 2B, when the layers are stacked three times and finally fired together, the fixed MgO, that is, MgO caused by the binder is concentrated in the third layer 18c. It can be seen that the MgO is considerably reduced in the second layer 18b, and that the MgO hardly exists in the first layer 18a.

As described above, in the present embodiment, the powder and the component due to the binder remaining after firing are made of the same MgO, and the firing step is performed for each printing, and the layers are laminated. Since the protective film 17 in which MgO caused by the binder is dispersed can be obtained, current suppression and long life, which are inherent characteristics of MgO, can be achieved, and the voltage at the time of driving the panel can be suppressed, and at the same time, Luminous efficiency can also be improved. Further, since the MgO powder and the binder were of the same quality, the obtained protective film 17 was uniform. Further, when printing is performed using a thin screen having a gauze thickness of 36 μm, the protective film 17 also has one layer (17a, 17a).
b, 17c), the thickness is reduced to approximately 2 μm.
Is unevenly distributed in the thickness direction, and the protective film 1 is further reduced.
7 could be refined. If the protective film 17 is simply thin, a defect may occur. However, the defect can be prevented by stacking.

Table 1 shows the discharge characteristics of the panel of this embodiment. Table 2 shows that the conventional panel which was printed three times using a screen (250 mesh, wire diameter 30 μm, gauze thickness 60 μm) which is generally used when printing the protective film of the panel, and finally baked. 3 shows the discharge characteristics. For each of these panels,
Each time one layer is stacked, the panel sustaining voltage Vs
, The luminous efficiency η of the panel, the discharge current I flowing per unit cell (space where the discharge occurs) of the panel, and the luminance L were measured. In Tables 1 and 2, 1, 2, 3 in the left column
Indicates that the protective film has one layer, two layers, and three layers, and the film thickness indicates the total thickness of the protective film.

[0037]

[Table 1]

[0038]

[Table 2]

As is clear from Tables 1 and 2, in the present embodiment shown in Table 1, the discharge current was suppressed even though the thickness of the MgO protective film was smaller than that of the embodiment shown in Table 2. And
Luminous efficiency is improved. In particular, as compared with the case where three layers were stacked, the discharge current was suppressed by 5.57 μA per cell, the discharge sustaining voltage could be reduced by 89 V, and the luminous efficiency could be improved by about three times.

<Second Embodiment> Next, a second embodiment of the present invention will be described. In this embodiment, the paste which is the material of the protective film is made of 10 wt% of MgO powder and 10 wt% of magnesium diethoxide solution as a liquid binder.
(10 wt% in terms of MgO based on MgO powder),
Ethyl cellulose resin 20wt%, solvent 60wt%
Make as The MgO powder used at this time has a particle size of 1
00 nm and 50 nm have a weight ratio of 3:
It was assumed that they were mixed at a ratio of 1. The solution is a mixture of butyl carbitol, terpineol and texanol as in the first embodiment. The paste has a viscosity of 25.
Pa · s / 25 ° C. (250 poise at 25 ° C.).

The above paste is printed on a dielectric layer 15 provided on a back substrate constituting the panel 11 by using a screen of 250 mesh, a wire diameter of 30 μm, and a gauze thickness of 60 μm to form a paste layer. Thereafter, the paste layer is dried at 150 ° C. and baked at 580 ° C. for 10 minutes each. The above is repeated three times to form the MgO protective film on the first and second layers.
And a three-layer structure of a third protective film. The thickness of the laminated protective film thus formed is the same as in the first embodiment.
It is approximately 2 μm per layer.

FIGS. 4 and 5 are graphs for explaining the effect of mixing MgO powders having different particle diameters. FIG.
Then, the horizontal axis shows 50% of the total MgO powder in the paste.
The ratio of the MgO powder having a particle size of nm is plotted on the vertical axis, and the luminous efficiency of the panel is plotted to show the relationship between the two. According to this, it can be seen that the luminous efficiency increases to 0.982 lm / w when 50% of the particles having a diameter of 50 nm are added, but starts to decrease when the particles are further added. In FIG. 5, the horizontal axis represents the ratio of the MgO powder having a particle size of 50 nm to the total MgO powder in the paste, and the vertical axis represents the discharge starting voltage Vf and the discharge sustaining voltage Vs at the time of driving the panel. Represents a relationship. According to this, particles having a diameter of 50 nm
When 5% is applied, Vf is 254 V and Vs is 307 V, both of which are suppressed to the lowest. In addition, about mixing MgO powders having different particle diameters as described above,
The following effects are also conceivable. In order to make the protective film dense, it is advantageous to use MgO having a large particle size.
Pinholes are likely to occur. In order to prevent pinholes, it is necessary to reduce the gap between the particles and increase the number of particles per unit thickness, and the particle size must be reduced. Mixing MgO with different particle sizes is effective in simultaneously satisfying the two requirements.

As described above, the powder having a small particle size is mixed to reduce the ratio of the MgO powder, that is, the solid content in the paste, or to lower the viscosity of the paste to make the protective film thinner. , Laminate.

Table 3 shows the discharge characteristics of the panel of this example. In order to show the effects of thinning, lamination printing, and firing for each printing, the results are shown in comparison. Paste A is obtained by printing the paste used in the first embodiment only once on the same screen as that used in the present embodiment. Paste B is obtained by reducing the MgO powder in the paste, that is, the solid content by 1
5 wt%, printed twice on the same screen to form a two-layered protective film, and compared the result of firing after printing twice with the result of firing for each printing. . Note that the paste B is M
gO powder is obtained by mixing a powder having a particle diameter of 100 nm and a powder having a particle diameter of 50 nm at a ratio of 3: 1.
(10 wt% in terms of MgO), resin is 10 wt%, and solvent is 60 wt%. Paste C was used in this example, and was printed three times to form a three-layer protective film. As in the case of the paste B, a comparison is made between the last baking and the baking each printing. The film thickness is the total film thickness of the protective film, and shows that the discharge characteristics of panels having different numbers of printings and firings were compared when the total film thickness was approximately the same. For the panels printed using these pastes A to C, the discharge starting voltage Vf, the luminous efficiency η, the discharge current I per cell, and the luminance L were examined.

[0045]

[Table 3]

As is clear from Table 3, the panel in which the protective film is formed in two layers by using the paste B has a slightly thicker film thickness than the other panels. The panel was near 255V. For this reason, the panel of paste B is 260V, and the other panels are 2V.
Measured at 55V. Compared to Paste A, Paste 2 and Paste 3 have higher luminous efficiency and current suppressing effects. In addition, even when the same paste was used, firing each printing showed a higher effect. In the panel in which the protective film is formed into two layers by using the paste B, the panel fired for each printing has a lower discharge start voltage Vf of 7 V and a luminance of 13 cd.
/ M ² , and the luminous efficiency is increased by 0.1 lm / W. Even in a panel in which the protective film is formed into three layers using the paste C, firing each time printing reduces the Vf to 22 V, the luminance is 5 cd / m ² , and the luminous efficiency is 0.01 lm / W.
Is getting higher. In particular, in the panel in which the protective film is formed into three layers using the paste C of the present embodiment, the discharge starting voltage Vf is almost the same as that of the panel in which the protective film is formed using the paste A.
The luminance is 97 cd / m ² higher, and the luminous efficiency shows a value nearly 50% higher.

As described above, even when the protective film is thinned by laminating the solid content in the paste and laminated,
The original characteristics of the MgO protective film can be utilized.

It is clear that the invention is not limited only to the embodiments described above. For example, although the surface discharge type AC-PDP is used in the above-described embodiment, a counter electrode type AC-PDP may be used. If the liquid binder becomes MgO after firing, for example, a solution of magnesium dimethoxide, magnesium propoxide, magnesium butoxide or the like may be used. Further, the thickness of the protective film and the number of laminations are not limited to those of the embodiment.

[0049]

As is apparent from the above description, according to the method for forming a protective film of an AC-PDP of the present invention, a liquid binder containing MgO powder as a paste and a component which becomes a solid to bind MgO by firing. Using a paste consisting of the following, a paste layer is printed by printing this, and then dried, and thereafter, the step of firing the paste layer is repeated to form a protective film of a type in which several fired body layers are laminated. Since it is formed, components caused by the binder can be easily dispersed in the completed protective film without being unevenly distributed on one surface side. As described above, when the AC-PDP is manufactured using the protective film in which the component caused by the binder is dispersed and driven, the discharge current at the time of driving the panel can be suppressed, and the life of the panel can be extended. This makes it possible to simultaneously reduce the discharge voltage when driving the panel and improve the luminous efficiency of the panel. Also, the MgO powder particles and the binder contained in the paste, which is the material for the protective film, are made of the same quality, and each time the paste is printed, a baking step is always carried out and laminated to form a protective film. In this case, MgO
The thickness of the entire protective film can be reduced, the MgO protective film can be formed densely, and MgO, which is a component caused by the binder, can be dispersed in the MgO protective film. Further, printing of the paste is performed under the following conditions.

Mg in paste used for printing
The content of the O powder is 25 wt%, and the screen used at this time is 400 mesh, the wire diameter is 18 μm, and the gauze thickness is 36 μm.

Mg in paste used for printing
The content of the O powder is set to 10 wt% or 15 wt%, and the MgO powder has a particle diameter of 100 nm and a particle diameter of 50 nm.
Are mixed at a weight ratio of 3: 1.

As described above, even when the MgO powder particles and the binder are made homogeneous and the above-mentioned or any of the above conditions is added to form the protective film of the present invention, the M
The entire thickness of the gO protective film can be reduced, the MgO protective film can be formed more densely, and also in this case, MgO caused by the binder can be dispersed in the MgO protective film.

Therefore, in any case, the cycle of forming a paste layer of a starting material by using a screen printing method, drying the paste layer, and then firing the paste layer is repeated, so that the protective film is dense and thin. In addition, a protective film in which a component (for example, MgO) caused by the binder is dispersed can be easily formed.

Further, even if the protective film is formed by using the screen printing method, the MgO protective film can be made dense, so that it is possible to suppress the discharge current at the time of driving the panel and extend the life, which are the inherent characteristics of MgO. Can be achieved. This makes it possible to simultaneously reduce the discharge voltage when driving the panel and improve the luminous efficiency of the panel.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a surface discharge type AC-PDP according to first and second embodiments of the present invention.

FIG. 2 shows a protective film having a three-layer structure formed by laminating three times.
It is sectional drawing which represented typically the area | region of MgO fixed after baking.

FIG. 3 shows a protective film having a three-layer structure formed by stacking three times.
It is the figure which represented distribution of the depth direction of MgO fixed after baking typically.

FIG. 4: 50 nm occupying in total MgO powder in paste
FIG. 4 is a curve diagram illustrating a relationship between a ratio of particles having a diameter and luminous efficiency of a panel.

FIG. 5: 50 nm in total MgO powder in paste
FIG. 4 is a curve diagram illustrating a relationship between a ratio of particles having a diameter and a discharge voltage when the panel is driven.

[Explanation of symbols]

 10: AC-PDP (or panel) 11: Back substrate 13: Display electrode 15: Dielectric layer 17, 18: Protective film 19: Phosphor layer 21: Front substrate 23: Discharge space 30, 32: Fixed MgO layer

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takao Kanehara 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. (72) Inventor ▲ Taka ▼ Shigeru 1-7 Toranomon, Minato-ku, Tokyo No. 12 Oki Electric Industry Co., Ltd. (72) Inventor Aya Yamanaka 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. (56) References JP-A-4-10330 (JP, A JP-A-6-316671 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 9/02 H01J 11/00-11/02

Claims (2)

(57) [Claims] 1. A method for forming a protective film provided on one of two substrates constituting an AC type gas discharge panel with a dielectric layer for charge storage interposed therebetween, comprising: (a) MgO powder; A paste containing a liquid binder that becomes a solid that binds the particles of the MgO powder is printed on the dielectric layer by a screen printing method to form a paste layer, and then the paste layer is dried and then fired. b) The step (a) is repeated to laminate the protective film, and the content of the MgO powder in the paste is reduced to 25.
A method for forming a protective film for a gas discharge panel, wherein a screen used for the printing is 400 mesh, a wire diameter is 18 μm, and a gauze thickness is 36 μm when the content is set to wt%. 2. A method for forming a protective film provided on one of two substrates constituting an AC type gas discharge panel with a dielectric layer for charge storage interposed therebetween, comprising: (a) MgO powder; A paste containing a liquid binder that becomes a solid that binds the particles of the MgO powder is printed on the dielectric layer by a screen printing method to form a paste layer, and then the paste layer is dried and then fired. b) The step (a) is repeated to laminate the protective film, and the content of the MgO powder in the paste is set to 10
When the content of the MgO powder is 100 wt% or 50 nm, the content of the MgO powder is 50 wt% or 15 wt%.
A method for forming a protective film for a gas discharge panel, characterized in that they are mixed at a weight ratio of 3: 1.