Electric lamp or space discharge component or device manufacturi – Process – With assembly or disassembly
Reexamination Certificate
2001-10-10
2004-10-26
Williams, Joseph (Department: 2879)
Electric lamp or space discharge component or device manufacturi
Process
With assembly or disassembly
C428S480000, C427S121000
Reexamination Certificate
active
06808435
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a paint for forming an insulating film used in a plasma display panel, a plasma address liquid crystal display, or an image forming apparatus using electron-emitting elements, and to a plasma display panel in which an address electrode protective film and partition walls provided on its back plate and a dielectric layer provided on its front plate are formed using this paint. It is to be noted that the term “paint” used in this application means a liquid composition using a volatile carrier and coating a components in which the coating components are left behind on a surface after the evaporation of the carrier.
2. Description of the Related Art
As an image forming apparatus that can be substituted for a heavy and large conventional cathode-ray tube, there has been increasing demand for a thin and light flat-type display or, as it is called, a flat panel display (FPD). A typical FPD is a liquid crystal display (LCD). However, LCDs have problems such that images obtained are dark, a viewing angle is narrow, and it is difficult to increase an area thereof. Therefore, in recent years, a plasma display panel (PDP) and an image forming apparatus using electron-emitting elements are attracting great attention and the demand for them has been growing because they can be increased in definition and in size further than LCD.
FIG. 1
shows one example of a structural view (cross-sectional view) of PDP. Hereinafter, the principle of display by PDP will be explained with reference to FIG.
1
.
Between each pair of display electrodes
3
provided on a front glass substrate
1
, plasmas are discharged to generate ultraviolet rays. The ultraviolet rays excite phosphors
6
, which are separated from each other by partition walls
9
provided on a back glass substrate
2
, to make the phosphors emit visible lights. The visible lights emitted from the respective phosphors
6
pass through an MgO film
10
, a front dielectric layer
7
, and the front glass substrate
1
to be displayed as an image. At this time, by applying signals to selected address electrodes
5
to specify the discharge cells to be displayed, a desired image can be obtained.
To generate and maintain plasmas, the electrodes need to be insulated from each other. The front dielectric layer
7
is provided to obtain an insulating effect. The front dielectric layer
7
is obtained as follows: a paint obtained by dispersing a resin and inorganic fine particles, which are glass powder mainly containing Si or the like, in an organic solvent is coated onto the front glass substrate, and the paint is dried and fired, thereby giving the dielectric layer
7
. The organic solvent is vaporized during the drying process. During the firing process, the resin is vaporized and the glass powder melt to be joined to each other. The paint turns into a glass film when cooled after the firing, thus forming the front dielectric layer
7
.
On the back glass substrate
2
, the back dielectric layer
8
is provided for the purpose of protecting the address electrodes
5
. The back dielectric layer
8
is formed in the same manner as that for the front dielectric layer
7
.
Typically, an insulating film formed using glass is used as the front dielectric layer
7
and the back dielectric layer
8
. For example, JP 2000-16835 A proposes using an insulation paste containing 70 to 95 wt. % of glass powder having an average particle diameter of 0.3 to 1.5 &mgr;m and a maximum particle diameter of not more than 10 &mgr;m and 5 to 30 wt. % of an organic component as a paste for forming thin insulating films as protective films provided on a front glass substrate and a back glass substrate and thick insulating films covering the electrodes on both the glass substrates.
As the phosphors
6
, phosphors that emit lights of R (red), G (green), and B (blue), respectively, are used, and the partition walls
9
are provided to prevent these three colors from being mixed with each other. Like the front dielectric layer
7
and the back dielectric layer
8
, the partition walls
9
are obtained also by coating a paint obtained by dispersing a resin and inorganic fine particles, which are glass powder mainly containing Si or the like, in an organic solvent, drying the paint, and then exposing/developing the paint in a desired pattern (photolithography) or etching the paint in a desired pattern by having fine particles of Zr or the like collide with the paint (sandblasting).
Known electron-emitting elements can be broadly classified into two types: hot cathode electron-emitting elements and cold cathode electron-emitting elements. In recent years, an image forming apparatus using cold cathode electron-emitting elements has been attracting attention because it does not consume powder during the standby period and can attain a high current density. The cold cathode electron-emitting elements can be classified into those of field emission type (FE type), metal/insulator/metal type (MIM type), and the like. In an image forming apparatus using cold cathode electron-emitting elements, phosphors emit lights upon being irradiated with electron beams emitted from the electron-emitting elements, thereby displaying an image.
Like the plasma display panel, the image forming apparatus using cold cathode electron-emitting elements also employs a glass insulating film. For example, a back glass substrate of the image forming apparatus includes a plurality of electron-emitting elements and wirings arranged in matrix for connecting these elements. These wirings are arranged in the X direction and Y direction to intersect with each other at the portions of the electrodes of the electron-emitting elements. To insulate the wirings and the electrodes at these intersections, a belt-shaped insulating film is needed. Such an interlayer insulating film is formed using, for example, glass containing lead oxides as a main component so that the thickness of the film becomes 10 to 100 &mgr;m, preferably 20 to 50 &mgr;m.
For example, JP 9(1997)-283060 A discloses that lower wirings are formed under an insulating film, a belt-shaped insulating film is then provided so as to intersect with the lower wirings at a right angle, and upper wirings are provided on the belt-shaped insulating film.
Therefore, like the plasma display panel, the image forming apparatus using cold cathode electron-emitting elements needs an insulating film, and the insulating film needs to have electrical insulating properties and exhibit a shielding effect as a protective film. Typically, such an insulating film is formed by a method such as vacuum evaporation, spattering, coating, or the like.
However, the methods utilizing a vacuum such as vacuum evaporation and spattering require costly production facilities. Especially in the case of manufacturing FPD, which seeks an increased area as described above, the manufacturing costs become even higher. Therefore, in FPD, reasonable coating methods such as screen printing and die coating commonly are used as a method of forming an insulating film.
However, when an insulating film is formed by the coating method, voids and/or pin-holes are generated in the resultant insulating film unless characteristics of the paint used for forming the film has been optimized. Thus, according to the coating method, it is difficult to obtain an insulating film producing a desired insulating effect. The voids and/or pin-holes are considered to be generated as a result of incorporation of foreign materials and/or air bubbles. Other than this, the insufficient wettability of the solvent contained in the paint is considered to be the major cause of the generation of the voids and/or pin-holes.
If the solvent has a poor wettability to the surface to be coated with the paint, crawling occurs, which accompanies the generation of cavities. Crawling is the phenomenon in which the paint is not spread evenly on the surface so that uncoated portions result. Therefore, the resultant insulating film is form ed unevenly and a de
Hayashi Tomohiro
Mifune Tatsuo
Matsushita Electric - Industrial Co., Ltd.
Merchant & Gould P.C.
Williams Joseph
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