Image forming apparatus

Details Image forming apparatus Image forming apparatus

2000-12-28

2004-07-06

Patel, Ashok (Department: 2879)

Electric lamp and discharge devices

With luminescent solid or liquid material

Vacuum-type tube

C313S496000

Reexamination Certificate

active

06759802

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates particularly to an image forming apparatus using an electron source.
2. Description of the Related Art
Hitherto, there are known two types of electron emitting devices, i.e., a thermionic cathode and a cold cathode. Of these two types, known examples of the cold cathode include a surface conductive type electron emitting device, a field emission type electron emitting device (referred to as “FE type” hereinafter), and a metal/insulator/metal type electron emitting device (referred to as “MIM type” hereinafter).
Some examples of the surface conductive type electron emitting devices are described in M. I. Elinson, Radio Eng. Electron Phys., 10, 1290(1965) and other papers mentioned below.
A surface conductive type electron emitting device utilizes a phenomenon that electron emission occurs when an electric current is supplied to a small-area thin film formed on a substrate so as to flow parallel to the film surface. Surface conductive type electron emitting devices known so far employ an SnO
2
thin film, as reported by M. I. Elinson et al., an Au thin film [see, e.g., G. Dittmer: “Thin Solid Films”, 9, 317(1972)], an In
2
O
3
/SnO
2
thin film [see, e.g., M. Hartwell and G. G. Fonstad: “IEEE Trans. ED conf.”, 519(1975)], a carbon thin film [see, e.g., Hisashi Araki et al.: Shinku (Vacuum), vol. 26, No. 1, 22(1983)], etc.
As a typical example of one of those surface conductive type electron emitting devices,
FIG. 12
shows a plan view of the device reported by M. Hartwell et al.
Referring to
FIG. 12
, numeral
3001
denotes a substrate and
3004
denotes a conductive thin film of a metal oxide formed by sputtering. As shown, the conductive thin film
3004
is formed into an H-shape as viewed from above. An electron emitting portion
3005
is formed by carrying out an energization process to be described later, called “energization forming”, on the conductive thin film
3004
. A spacing L shown in
FIG. 12
is set to 0.5-1 mm and a width W is set to 0.1 mm. Note that although the electron emitting portion
3005
is shown as having a rectangular shape at the center of the conductive thin film
3004
, the drawing has been illustrated for the sake of easier understanding and does not exactly express the exact position and shape of electron emitting portions actually physically produced.
Known FE type electron emitting devices are reported, for example, by W. 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 cathodes with molybdenum cones”, J. Appl. Phys., 47, 5248(1976).
As a typical example of a construction of a FE type electron emitting device,
FIG. 13
shows a sectional view of the device reported by C. A. Spindt et al.
Referring to
FIG. 13
, numeral
3010
denotes a substrate, and
3011
denotes an emitter wire made of a conductive material. Numeral
3012
denotes an emitter cone,
3013
denotes an insulating layer, and
3014
denotes a gate electrode. In the FE type device, field emission occurs from the top of the emitter cone
3012
by applying an appropriate voltage between the emitter cone
3012
and the gate electrode
3014
.
As another example of a FE type device construction, there also is known a planar structure wherein an emitter and a gate electrode are arranged on a substrate, and lay substantially parallel to a flat surface of the substrate, rather than as shown in FIG.
13
.
A known MIM type electron emitting device is reported, for example, by C. A. Mead, “operation of Tunnel-emission Devices”, J. Appl. Phys., 32, 646(1961).
A typical example of a construction of the MIM type electron emitting device is shown in a sectional view of FIG.
14
. Referring to
FIG. 14
, numeral
3020
denotes a substrate, and
3021
denotes a metal lower electrode. Numeral
3022
denotes a thin insulating layer having a thickness of about 10 nm, and
3023
denotes a metal upper electrode having a thickness of about 8-30 nm. In the MIM type device, electron emission occurs from the surface of the upper electrode
3023
by applying an appropriate voltage between the upper electrode
3023
and the lower electrode
3021
.
Any of the cold cathodes described above do not require a heater for heating the devices because the cold cathodes can produce an electron emission at a lower temperature than that needed in the thermionic cathode. Therefore, a cold cathode can be formed with a simpler structure and a finer pattern than a thermionic cathode. Also, when a large number of cathodes are arrayed on a substrate with a high density, a problem such as thermal fusion of the substrate is less likely to occur. Further, a cold cathode has a high response speed, whereas a thermionic cathode has a low response speed because it starts operation upon heating by the heater.
For those reasons, studies regarding applications of cold cathodes have been actively conducted.
As to applications of the electron emitting devices, image forming apparatuses such as an image display unit and an image recording apparatus, charged beam sources, etc., have been studied.
Applications of the electron emitting devices to image forming apparatuses are disclosed in, for example, U.S. Pat. Nos. 5,532,548, 5,770,918 and 5,903,108, WO Nos. 98/28774 and 99/03126, as well as Japanese Patent Laid-Open Nos. 01-241742, 04-094038, 04-098744, 04-163833 and 04-284340.
Of those image forming apparatuses employing the electron emitting devices, attention often is focused on a flat display which has a thin body contributing to saving space, and which also is lightweight and expected to be eventually substituted for a CRT type display.
FIG. 20
is a perspective view schematically showing a partially uncovered flat image forming apparatus (airtight container) that employs an electron source comprising a number of electron emitting devices arrayed in the form of a matrix. In
FIG. 20
, numeral
27
denotes an electron emitting device of any type described above, and numerals
23
and
24
denote wires connected to the electron emitting device
27
. Numeral
1
denotes a rear plate on which the electron emitting devices are arrayed,
20
denotes an image forming member made up of a phosphor, etc., and
19
denotes a metal film (metal back) to which a high voltage (Hv) is applied for irradiating electrons emitted from the electron emitting devices towards the image forming member. Numeral
11
denotes a face plate on one side of which the image forming member is arranged, and
4
denotes a support frame which, together with the face plate
11
and the rear plate
1
, constitutes an airtight container
100
. An inner space of the airtight container
100
is held in a vacuum state at a level of about 10
−4
Pa (Pascal).
SUMMARY OF THE INVENTION
The image forming apparatus described above has the following problems.
FIG. 15
is a partial schematic sectional view of a portion of the airtight container
100
(
FIG. 20
) constituting the above-described image forming apparatus.
Since the inner space of the airtight container
100
must be held in a vacuum state at a pressure level of about 1.3×10
−4
Pa as described above, some means for maintaining such a vacuum level is required. According to one conventional solution, an evaporable getter
8
filled with Ba is disposed together with a support
9
outside an image area, as shown in FIG.
15
. After sealing off the vacuum container, Ba is scattered upon high-frequency heating, etc., to form a getter film, thereby holding the desired vacuum level substantially constant.
In
FIG. 15
, numeral
1
denotes a rear plate including an area (electron source area)
2
in which a number of electron emitting devices (not shown) are arrayed. Numeral
4
denotes a support frame,
11
denotes a face plate, and
12
denotes an image forming member made up of a film including a phosphor, etc., and a metal film (e.g., Al) called a metal back.
On the other hand, to accelerate elect

Affiliated with

Also associated with

Rating

Image forming apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Image forming apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Image forming apparatus will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3192498