Electric lamp and discharge devices – Discharge devices having a thermionic or emissive cathode
Reexamination Certificate
2001-04-27
2004-07-13
Zarneke, David (Department: 2827)
Electric lamp and discharge devices
Discharge devices having a thermionic or emissive cathode
C313S306000, C313S308000, C313S309000, C313S336000, C313S351000, C313S495000, C313S496000
Reexamination Certificate
active
06762542
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electron source and an image forming device using the electron source.
2. Description of the Related Art
Thin and planar image forming devices have been actively developed as display devices due to their efficient use of installation spaces. For example, a liquid crystal display device has been popularly used for a display member of portable type personal computers. However, the liquid crystal display device has the problems of dark image, difficulty of making the panel size large, and narrow angle of vision. Consequently, a spontaneous light emission type display has been noticed. The spontaneous light emission display using a plasma display and an electron emission element is more luminous and has a wider angle of vision as compared with the liquid crystal display.
The electron emission element is mainly divided into two categories of a thermionic emission element and cold emission element. The cold emission element include field emission type (abbreviated as a FE type hereinafter), metal/insulation layer/metal type (abbreviated as a MIM type hereinafter) and surface conduction type electron emission elements. Examples of the FE type elements include those disclosed in P. Dyke & W. W. Dolan “Field Emission”, Advance in Electron Physics, 8, 89 (1956) and C. A. Spindt, “Physical Properties of Thin-film Field Emission Cathode with Molybdenum Cones”, J. Appl. Phys., 47, 5248 (1976). Examples of the MIM type elements include those disclosed in A. Mead, “Operation of Tunnel-Emission Devices”, J. Aply. Phys., 32, 646 (1961).
Examples of the surface conduction type electron emission elements include those disclosed in M. I. Elinson, Radio Eng. Electron Phys., 10, 1290 (1965). The surface conduction type electron emission element takes advantage of a phenomenon by which electrons are emitted by flowing an electric current in parallel to the film surface formed as a small area thin film on a substrate. These surface conduction type electron emission elements include those using a SnO
2
thin film reported by Elinson et. al., using an Au thin film [G. Dittmer, “Thin Solid Films”, 9, 317 (1972)], using an In
2
O
3
/SnO
2
thin film [M. Hartwell and C. G. Fonstad, “IEEE Trans. ED Conf.”, 519, (1975)], and using a carbon thin film [Hisashi Araki, “Sinku (Vacuum)”, vol. 26, No. 1, p22 (1983)].
FIGS. 13A and 13B
show one example of the surface conduction type electron emission element.
FIG. 13A
is a plane view and
FIG. 13B
is a cross section. The reference numeral
6
denotes an insulation substrate, the reference numerals
2
and
3
denote element electrodes for attaining electrical connection, the reference numeral
4
denotes a conductive film, and the reference numeral
5
denotes an electron emission part.
FIG. 8
shows a schematic drawing of one example of the image forming device using an electron source formed by aligning the surface conduction type electron emission elements in a matrix.
The construction of the element shown in
FIGS. 13A and 13B
is a construction of a unit element, and a number of these unit elements
76
are aligned on the substrate (a rear plate)
81
corresponding to pixels, thereby forming an electron source in the image forming device shown in FIG.
8
. Wiring lines
72
in the X-direction and wiring lines
73
in the Y-direction are formed on the substrate
81
by being separated by an insulation layer (not shown) forming a matrix of the wiring lines in order to arbitrarily select each element. A glass plate is often used for the substrate
81
.
The reference numeral
88
denotes an external case and the reference numeral
86
denotes face plates in the image forming device shown in FIG.
8
. Bonding portions among the external case
88
, rear plate
81
and face plates
86
are bonded (sealed) with a binder such as a low melting point glass frit (not shown) to constitute an airtight vessel for evacuating the inside of the image forming device. The vessel is usually sealed by fusion of the frit glass. The heating temperature is typically about 400 to 500° C., and the heating time is typically 10 minutes to 1 hour, although it differs depending on the size of the external case
88
.
A blue sheet glass is preferably used as the material of the external case
88
because it can be easily and certainly fused with the frit and because it is relatively cheap. A high distortion point glass having a high distortion point prepared by substituting a part of Na with K may be preferably used since it is also readily fused with the frit. The blue sheet glass or the high distortion point glass may be also preferably used for the substrate
81
since these materials can be certainly fused with the external case
88
.
A fluorescent film
84
made of a fluorescent substance is formed on the lower face of the face plate
86
. A metal back
85
made of, for example, Al is formed on the rear plate side surface of the fluorescent film
84
. The fluorescent film is divided into three portions coated with three kinds of fluorescent substances (not shown) having primary colors of red (R), green (G) and blue (B), respectively. The colored fluorescence films forming the fluorescence film
84
are separated with black films (not shown).
The inside of the airtight vessel is evacuated at a pressure of as low as 10
−4
Pa or below. The distance between the rear plate
81
on which the electron emission elements are formed and the face plate
86
on which the fluorescent film
84
is formed is usually maintained at several hundreds micrometers to several hundreds millimeters.
The image forming device as hitherto described is addressed by applying a voltage to each electron emission element
76
through terminals Doxl to Doxm and Doyl to Doym at the outside of the vessel, and the wiring lines
72
and
73
to emit electrons from each element
76
. A high voltage is simultaneously applied to the metal back
85
through a terminal Hv at the outside of the vessel, thereby accelerating the emitted electrons from each element
76
and allowing the electrons to collide with each corresponding fluorescent substance. The fluorescent substance is excited and emits a light by collision of the electrons.
While the substrate of the electron source (rear plate) having the wiring matrix on it described above may be formed by various methods, all the element electrodes and wiring lines can be manufactured by a photolithographic method.
Printing methods such as a screen printing and offset printing may be diverted for manufacturing the substrate for the electron source. The printing methods are suitable for forming a pattern of a large area screen, and are preferable for facilitating to align a number of the electron emission elements on the substrate. For example, Japanese Patent Laid-Open Nos. 08-185818, 08-034110, 08-236017 and
09-283061
disclose a method for manufacturing the rear plate by the printing method, and a method for forming the wiring lines in the X-direction, interlayer insulation layer and wiring lines in the Y-direction by screen printing.
One example of the method for manufacturing the electron source substrate disclosed in the patent publications cited above is described with reference to
FIGS. 14A
to
14
E. At first, a pair of the element electrodes
2
and
3
are formed on the rear plate
81
as a matrix (FIG.
14
A). Then, n lines of the wiring lines
73
in the Y-direction are printed with a paste containing conductive material particles so that the electrodes
2
are commonly connected, and the printed wiring lines are fired (FIG.
14
B). Subsequently, the insulation layer
74
is printed with a paste containing insulating particles (glass particles) into a comb teeth shape followed by firing (FIG.
14
C). Then, a paste containing a conductive material is printed so that the wiring lines
72
in the X-direction is commonly connected
25
to the electrodes
3
on each insulation layer
74
, followed by firing (FIG.
14
D). A conductive film
4
Danjo Keishi
Enomoto Takashi
Nukanobu Kouki
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Tran Thanh Y.
Zarneke David
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