Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Physical dimension specified
Reexamination Certificate
1999-12-10
2004-11-23
Jackson, Monique R. (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Physical dimension specified
C428S336000, C428S696000
Reexamination Certificate
active
06821616
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a protecting film for FPD (Flat Panel Display) such as PDP (Plasma Display Panel), PALC (Plasma Addressed Liquid Crystal Display), and the like, a method of producing the same, and FPD using the same.
2. Description of the Related Art
As a method of forming a protecting film at low cost with excellent productivity as compared with a method of forming a FPD protecting film using a vacuum process such as an electron beam deposition process, a sputtering process, an ion plating process, or the like, various methods have been proposed. These proposed methods use a wet process such as a screen printing process, a spin coating process, a spray coating process, or the like using paste or a coating solution containing a MgO powder, a Mg(OH)
2
powder, a mixture of MgO powder and Mg(OH)
2
powder, or a rare earth oxide powder (for example, Japanese Unexamined Patent Publication Nos. 3-67437, 7-220640, 7-147136, 7-335134, 8-111177, 8-111178, 8-212917, 6-325696, 8-167381, 8-264125, 9-12940, 9-12976, 8-96718, etc.).
As this type of protecting film, a secondary electron emitting material for a plasma display panel is disclosed, which comprises a pair of discharge maintaining electrodes, a dielectric layer and a protecting layer, which are laminated on a back glass substrate, a fluorescent layer formed on the rear side of a front glass substrate, and an inert gas sealed between both substrates and emitting ultraviolet rays by discharge, the protecting layer being composed of a secondary electron emitting material such as fluorinated MgO (Japanese Unexamined Patent Publication No. 7-201280). In this secondary electron emitting material, oxygen of MgO which constitutes the protecting layer is partially replaced by fluorine. Namely, the oxygen atoms of a lattice which forms a MgO ion crystal are partially replaced by fluorine atoms to form fluorinated MgO represented by the formula MgO
1-X-Y
F
Y
(wherein 0<X<1 and 0<y<1).
This secondary electron emitting material for a plasma display panel uses fluorinated MgO represented by MgO
1-X-Y
F
Y
as the protecting layer, and thus forms localized levels by valence control, thereby decreasing the break-down voltage. As a result, it is possible to form a high-definition panel, and obtain a protecting film stable with the passage of time.
On the other hand, as a PDP protecting film which is directly exposed to a discharge space and is thus a key material playing the most important role in discharge characteristics, a MgO film having the high secondary electron emitting ability, and excellent sputtering performance, light transmission, and insulating property is conventionally used.
However, the MgO film is easily degenerated due to reaction with CO
2
and H
2
O when exposed to air during the process. Therefore, it is known that in order to obtain the original characteristics of MgO, degassing evacuation must be carried out under vacuum and heating for a long time after panel sealing (for example, Latest Plasma Display Manufacturing Technology, edited by Sato, Press Journal, p. 118-123 and p. 291-295 (1997)). This is because impurity gases of H
2
O, H
2
, O
2
, CO, CO
2
, N
2
, and the like adversely affect discharge characteristics of PDP and a constituent material of a panel, and particularly, contamination with CO
2
deteriorates panel characteristics to an unrecoverable level.
Therefore, in order to prevent degeneration of MgO, it has been proposed to coat the surface of MgO with another material having low moisture permeability (Japanese Unexamined Patent Publication No. 10-149767, and W, T, Lee et al; “LaF
3
coated MgO protecting layer in AC-Plasma Display Panels”, IDW'98, P. 72-75).
The above Japanese Unexamined Patent Publication No. 10-149767 discloses a method of manufacturing PDP comprising forming a protecting film, forming a temporary protecting film with low moisture permeability on the protecting film, and then removing the temporary protecting film. In this method, the surface of the protecting film is protected by the temporary protecting film during manufacture of PDP, preventing the formation of a degenerated layer on the surface of the protecting film. As a result, a protecting film having good discharge characteristics can be obtained, and pyrolysis of the degenerated layer of the protecting film is made unnecessary.
The above document of W. T. Lee et al proposes that LaF
3
coating having low moisture permeability on a MgO protecting film can suppress degeneration of the MgO protecting film, and realize a higher degree of secondary-electron emitting property and a lower degree of discharge property.
However, in the conventional method of forming a protecting film disclosed in each of the above publications, a MgO powder, a Mg(OH)
2
powder, a MgO powder obtained by burning a mixture of MgO powder and Mg(OH)
2
powder, or a rare earth oxide powder comprises fine particles and thus has a large surface area, thereby causing the probability that the surfaces relatively readily react with carbon dioxide and moisture in air to form a carbonate and hydroxide. There is thus a problem in that carbon dioxide and moisture are released to the discharge space during discharge of PDP to deteriorate discharge characteristics.
In addition, the secondary-electron emitting material for a plasma display panel disclosed in Japanese Unexamined Patent Publication No. 7-201280 comprises a protecting layer composed of fluorinated MgO represented by MgO
1-X-Y
F
Y
, and thus has a problem in that since a difference between the thermal expansion coefficients of the protecting layer and a substrate (dielectric layer) is relatively large, the protecting layer and the substrate (dielectric layer) have low adhesion and matching therebetween, and poor electric insulation as compared with the use of a MgO film as a protecting layer.
Furthermore, the PDP manufacturing method disclosed in Japanese Unexamined Patent Publication No. 10-149767 and the document of W. T. Lee et al is difficult to match the temporary protecting film and the protecting film in formation of the temporary protecting film, and thus causes cracks in the temporary protecting film or peeling of the temporary protecting film, thereby causing the insufficient effect of preventing degeneration of the protecting film by the temporary protecting film. A possible method of improving this is to coat a thick temporary protecting film on a protecting film. However, this method has the problem of producing large amounts of impurities (decomposition products of the temporary protecting film) in removal of the temporary protecting film.
Furthermore, the document of W. T. Lee et al discloses that LaF
3
is coated to 5 to 90 nm on MgO. However, such a two-layer structure has a problem in that the break-down voltage is rapidly changed when the LaF
3
upper layer film is removed by sputtering, thereby failing to obtain a sufficient life time.
SUMMARY OF THE INVENTION
Accordingly, a first object of the present invention is to provide a FPD protecting film and a method of producing the same which is capable of preventing deterioration in adhesion and matching with a substrate (dielectric layer), and preventing deterioration in electric insulation.
A second object of the present invention is to provide a FPD protecting film and a method of producing the same which is capable of inhibiting or suppressing reaction of MgO or the like in a film body, a film or the protecting film with CO
2
gas and H
2
O gas in air to prevent or suppress degeneration of MgO to MgCO
3
, Mg(OH)
2
, etc. harmful to FPD, i.e., capable of improving the environment resistance of the film body, the film or the protecting film.
A third object of the present invention is to provide a FPD protecting film and a method of producing the same which is capable of preventing or suppressing the formation of a carbonate (MgCO
3
or the like), a hydroxide (Mg(OH)
2
), etc. of MgO before the formation of a fluoride layer on the surface of a film body
Kuromitsu Yoshirou
Sakurai Hideaki
Yamashita Yukiya
Jackson Monique R.
Mitsubishi Materials Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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