BACKGROUND OF THE INVENTION
[0001] This invention relates to an electron-beam generating apparatus comprising a support
member (spacer) and an image forming apparatus such as a display device, to which
the electron-beam generating apparatus is applied to and, more particularly to an
electron-beam generating apparatus comprising a large number of electron-emitting
devices and an image forming apparatus using the electron-beam generating apparatus.
[Description of Related Art]
[0002] Generally, an image forming apparatus has an outer casing maintaining vacuum status,
an electron source for emitting electrons and its driver, an image forming portion
having a fluorescent member which emits light by collision of electrons or the like,
an acceleration electrode for accelerating the electrons toward the image forming
portion and its high-voltage power source. In an image forming apparatus having a
flat outer casing such as a thin-type image display device, a support member (spacer)
is employed to obtain atmospheric-pressure-proof structure.
[0003] Conventionally, a cold cathode electron-emitting device is known as the electron-emitting
device used in an electron source of an image forming apparatus. The cold cathode
electron emitting device includes a field emission (hereinafter abbreviated to "FE")
type device, a metal/insulating-layer/metal type (hereinafter abbreviated to "MIM")
device, or a surface-conduction emission type device.
[0004] Known examples of the FE type electron-emitting devices are described by W.P. Dyke
and W.W. Dolan, "Field Emission", Advance in Electron Physics, 8, 89 (1956) and by
C.A. Spindt, "Physical properties of thin-film field emission cathodes with molybdenum
cones", J. Appl. Phys., 47,5248 (1976).
[0005] A known example of the MIM type electron-emitting devices is described by C.A. Mead,
"Operation of Tunnel-Emission Devices", J. Appl. Phys., 32,646 (1961).
[0006] A known example of the surface-conduction emission type electron-emitting devices
is described by, e.g., M.I. Elinson, "Radio Eng. Electron Phys., 10, 1290 (1965).
[0007] The surface-conduction emission type electron-emitting device utilizes a phenomenon
where electron-emission is produced in a small-area thin film formed on a substrate,
by passing a current parallel to the film surface. As the surface-conduction emission
type electron-emitting devices, electron-emitting devices using an SnO2 thin film
according to Elinson mentioned above, an Au thin film according to G. Dittmer ("Thin
solid Films", 9,317 (1972)), an In2O3/ SnO2 thin film according to M. Hartwell and
C.G. Fonstad ("IEEE Trans. ED Conf.", 519 (1975)), a carbon thin film according to
Hisashi Araki et al. ( "Vacuum", vol. 26, No. 1, p. 22 (1983))are reported.
[0008] Fig. 20 shows the structure of the above-mentioned device by M. Hartwell and Fonstad
as a typical example of these surface-conduction emission type electron-emitting devices.
In Fig. 20, numeral 3001 denotes a substrate; and 3002, a conductive thin film comprising
a metal oxide thin film formed by sputtering on an H-shaped pattern. An electron-emitting
portion 3003 is formed by electrification process referred to as "forming" to be described
later.
[0009] Conventionally, in these surface-conduction emission type electron-emitting devices,
it is general to form the electron-emitting portion by electrification process "forming"
on the conductive thin film prior to electron emission. That is, the forming processing
is forming the electron-emitting portion with electrically high-resistance by application
of a predetermined voltage to the both ends of the conductive thin film to partially
destroy or deform the thin film. Note that in Fig. 20, as the electron-emitting portion
3003, the_destroyed or deformed part of the conductive thin film 3002 has a fissure,
and electron emission is made around the fissure. Hereinafter, the conductive thin
film 3002 including the electrification forming-processed electron-emitting portion
3003 will be referred to as a thin film 3004 including the electron-emitting portion.
The electrification forming-processed electron beam emits electrons from the electron-emitting
portion 3003 by applying a predetermined voltage to the thin film 3004 and passing
a current through the electron-emitting devices.
[0010] As an example of the electron source having the surface-conduction emission type
electron-emitting devices, Japanese Patent Application Laid-Open No. 64-31332 discloses
an electron source having numerous surface-conduction emission type electron-emitting
devices, arranged in parallel lines, where both ends of each device are wire-connected.
[0011] The combination of the electron source having a plurality of electron beam with a
fluorescent member as an image forming member which emits light (visible light) by
emitted electrons from the electron source provides various image forming apparatuses.
Especially, image display devices (e.g., U.S. Patent 5,066,883 by the present applicant)
can be easily applied to large-display screen devices, and can provide excellent display
quality as voluntary light-emitting devices. Accordingly, these image forming apparatuses
are expected to take the place of CRT display devices.
[0012] For example, in an image forming apparatus as disclosed in Japanese Patent Application
Laid-Open NO. 2-257551 by the present applicant, selection of the electron beam is
made by application of appropriate drive signals to wiring electrodes (row-direction
wiring) connecting parallel arrays of surface-conduction emission type electron-emitting
devices, and to wiring electrodes (column-direction wiring) connecting control electrodes
arranged between the electron source and the fluorescent member in directions orthogonal
to the above wiring directions.
[0013] As described above, in the recently proposed image forming apparatuses (flat type
CRT's), cold cathode electron-emitting devices have been used for an electron source
and support members (spacers) are incorporated for atmospheric-pressure-proof structure,
so as to reduce the weight and depth of the apparatus.
[0014] However, in such flat type CRT's, disturbance of display image occurs around the
support members. The considerable main cause is electric charge-up of the support
members which may influence the trajectories of electrons. To prevent the electric
charge-up, it has been arranged such that the support members which have conductivity
has been considered.
[0015] However, the disturbance of display image cannot be fully corrected by merely providing
the conductivity to the support members, and the shift of light-emission position,
luminance degradation, change of color still occur around the support members.
SUMMARY OF THE INVENTION
[0016] The present invention has been made in consideration of the above problems, and has
its object to form an image of uniform display status, and especially to provide an
image forming apparatus which prevents shift of light-emission position, luminance
degradation, change of color, which occur around support members.
[0017] According to the present invention, the foregoing object is attained by providing
an electron-beam generating apparatus, comprising a plurality of electron-emitting
devices, a plurality of row-direction wiring electrodes of conductive material, for
applying a predetermined voltage to the electron-emitting devices, an accelerating
electrode opposite to the electron-emitting devices, and a semiconductive support
member provided between part of the row-direction wiring electrodes and the accelerating
electrode, wherein the semiconductive support member is provided on the row-direction
wiring electrode via a conductive connection member, and wherein a height of the upper
surface of the conductive connection member on the row-direction wiring electrode
and a height of the upper surface of conductive material of the row-direction wiring
electrode where the semiconductive support member is not provided are substantially
the same.
[0018] Further, in the electron-beam generating apparatus, wherein the row-direction wiring
electrode where the semiconductive support member is provided has a concave portion,
and wherein the conductive connection member is arranged in the concave portion, further
wherein the height of the upper surface of the conductive connection member on the
row-direction wiring electrode and the height of the row-direction wiring electrode
where the semiconductive support member is not provided are substantially the same.
[0019] Further, in the electron-beam generating apparatus, wherein the row-direction wiring
electrode where the semiconductive support member is not provided has a conductive
member, and wherein a height of the upper surface of the conductive member and the
height of the upper surface of the conductive connection member are substantially
the same.
[0020] Further, in the electron-beam generating apparatus, wherein a thickness of the row-direction
wiring electrode where the semiconductive support member is provided and a thickness
of the row-direction wiring electrode where the semiconductive support member is not
provided are different, and wherein a height of the upper surface of the conductive
connection member on the row-direction wiring electrode and a height of the row-direction
wiring electrode where the semiconductive support member is not provided are substantially
the same.
[0021] Further, the foregoing object is attained by providing an electron-beam generating
apparatus, comprising a plurality of electron-emitting devices, a plurality of row-direction
wiring electrodes of conductive material, for applying a predetermined voltage to
the electron-emitting devices, an accelerating electrode opposite to the electron-emitting
devices, and a semiconductive support members provided between part of the row-direction
wiring electrodes and the accelerating electrode, wherein the semiconductive support
member is provided on the row-direction wiring electrode via a conductive connection
member, and wherein if predetermined electric potentials of the same level are applied
to the row-direction wiring electrode where the semiconductive support member is provided
and the row-direction wiring electrode where the semiconductive support member is
not provided, a thickness of conductive connection member is controlled such that
electric-potential distribution on a surface of the semiconductive support member
and that in space between the row-direction wiring electrode where the semiconductive
support member is not provided and the accelerating electrode become the same.
[0022] In accordance with the present invention as described above, in a case where the
support member(s) (spacer(s)) is an insulating member, the support member has a semiconductive
film on its surface. This is made to prevent the above-described electric charge-up.
The apparatus has a function to neutralize electric charge by passing a weak current
in the semiconductive film. Note that the support member(s) (spacer(s)) may be a semiconductive
member. In this case, the current that flows the surface area of the support member
contributes to the prevention of electric discharge. For this reason, in a case where
the support member(s) (spacer) is a semiconductive member, there is no need to have
a semiconductive film on its surface.
[0023] In maintaining the support member (spacer), a conductive connection member is inserted
between the spacer and the wiring electrodes for electrical connection between the
semiconductive film of the insulating member surface or the semiconductive support
member and wiring electrodes. This is made to prevent the electric charge-up by passing
a weak current on the surface of the spacer. However, if the conductive connection
member between the wiring electrodes and the spacer are thick, a slope of electric
potential is generated around these members. This causes shifting of the trajectories
of electrons emitted from the electron-emitting devices.
[0024] In consideration of the above problem, the construction as described above is proposed.
[0025] According to the present invention, the electron-beam generating apparatus is not
only applicable to an image forming apparatus preferable as a display device but to
other devices. For example, in an optical printer that comprises an electrostatic
drum, light-emitting diode and the like, the electron-beam generating apparatus is
used as a light-emitting source substituting for the light-emitting diode. In this
case, the substitute light-emitting source may be two-dimensional light-emitting source
as well as a line-type light-emitting source.
[0026] Further, according to the present invention, the present invention is applicable
to other devices than the image forming apparatus and the electron-beam generating
apparatus. For example, the present invention can be applied to an apparatus utilizing
electrons emitted from an electron source, such as an electron microscope.
[0027] Other features and advantages of the present invention will be apparent from the
following description taken in conjunction with the accompanying drawings, in which
like reference characters designate the same name or similar parts throughout the
figures thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The accompanying drawings, which are incorporated in and constitute a part of the
specification, illustrate embodiments of the invention and, together with the description,
serve to explain the principles of the invention.
Fig. 1 is a partially cut-away perspective view showing the structure of an image
forming apparatus according to an embodiment of the present invention;
Fig. 2 is a cross-sectional view showing the structure of a spacer provided in the
image forming apparatus of the embodiment;
Fig. 3 is a plan view showing a significant part of an electron source 1 of the image
forming apparatus in Fig. 1;
Fig. 4 is a cross-sectional view cut out along a line B-B' in Fig. 3, showing the
structure of the electron source 1;
Figs. 5A to 5H are cross-sectional views respectively showing an electron-source manufacturing
process of the present invention;
Fig. 6 is a plan view showing the electron source in pre-manufacture status;
Fig. 7 is a line graph showing an example of waveform of voltage used in an electrification
forming-process for forming electron-emitting devices in the embodiment;
Fig. 8 is a block diagram showing the construction, estimation and operation of the
electron source with one electron-emitting device;
Fig. 9 is a line graph showing the relation between an emission current Ie and a device
current If of the electron-emitting device, measured by a measurement estimation device;
Figs. 10A and 10B are plan view showing examples of the structure of a fluorescent
film 7 in the embodiment;
Fig. 11 is a cross-sectional view showing electron emission and scattered particles
in the image forming apparatus of the embodiment, viewed from a column direction;
Fig. 12 is a cross-sectional view showing the occurrence of the electron emission
and the scattered particles in the image forming apparatus of the embodiment, viewed
from a low direction;
Figs. 13 and 14 are perspective views respectively showing the arrangement of support
members (spacers) of the embodiment;
Fig. 15 is a block diagram showing the construction of a driver of the image forming
apparatus of the embodiment;
Fig. 16 is an example of a matrix wiring arrangement of the electron-emitting devices
of the image forming apparatus of the embodiment;
Fig. 17 is a sample image for image formation according to the embodiment;
Fig. 18 is an explanatory view showing a driving method for the sample image in Fig.
17;
Fig. 19 is a block diagram showing the construction of a multifunction display device,
according to the embodiment having a display panel using the surface-conduction emission
type electron-emitting devices as an electron-beam source,;
Fig. 20 is a plan view showing the structure of the electron-emitting device by M.
Hartwell and C.G. Fonstad as a typical surface-conduction emission type electron-emitting
device;
Fig. 21 is a cross-sectional view for explaining the forming processing according
to the first embodiment;
Fig. 22 is a cross-sectional view for explaining electrification activation process
according to the first embodiment;
Fig. 23A is a line graph showing an example of a signal applied in the electrification
activation process;
Fig. 23B is a histogram showing the relation between electrification activation process
amount (time) and the emission current Ie;
Figs. 24A to 24D are explanatory views showing a cause of shifting of electron-beam
trajectories from the electron-emitting devices and improved electron-beam trajectories;
Fig. 25 is a plan view showing the structure of the electron-emitting device according
to a third embodiment;
Fig. 26 is a perspective view showing the structure of a conductive connection member
of the image forming apparatus in Fig. 2;
Fig. 27 is a plan view showing a convave portion 57 according to the fifth embodiment;
Fig. 28 is a cross-sectional view showing the structure of the conductive connection
member of the image forming apparatus according to a sixth embodiment;
Fig. 29 is a plan view showing the structure of the electron-emitting device of the
sixth embodiment;
Figs. 30A and 30B are perspective views respectively showing a manufacturing process
according to the fourth embodiment; and
Fig. 31 is a perspective view showing the conductive connection member according to
another example of the fourth embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] Preferred embodiments of the present invention will now be described in detail, after
explanation of general concept of the present invention in accordance with Figs. 1,
11, 12, 13 and 24.
[0030] In Fig. 1, reference numeral 1 denotes an electron source; 2, a rear plate; 3, a
face plate; 4, a support frame; 5, a spacer; 6, a glass substrate; 7, a fluorescent
film; 8, a metal back; 10, an outer casing; 12, row-direction wiring electrodes; 13,
column-direction wiring electrodes; 15, electron-emitting devices; 58, conductive
connection member; and 70, conductive members.
(a) Trajectories of Emitted Electrons
[0031] In Fig. 1, when a predetermined voltage Vf is applied to the plurality of electron-emitting
devices 15 via external terminals Dox1 to Doxm, Doy1 to Doyn of the outer casing 10,
the devices emit electrons from an electron-emitting portion 23 (Fig. 11). At the
same time, a predetermined high voltage of several kV is applied to the metal back
8 (or to unshown transparent electrode) via a high-voltage terminal Hv, to accelerate
the electrons emitted by the electron-emitting portion 23, and to collide with the
electrons to the inner surface of the face plate 3. This excites a fluorescent member
of the fluorescent film 7, which emits light, thus an image can be displayed.
[0032] Figs. 11 and 12 show the electron emission as described above and occurrence of scattered
particles to be described later. Fig. 11 is viewed from a direction Y, and Fig. 12,
from a direction X in Fig. 1. In Fig. 11, the electrons, emitted from the electron-emitting
portion 23 by application of the voltage Vf, traverse a parabola trajectory 25t shifted
toward a device electrode 17 on a high-voltage side, away from a normal line (presented
by a broken line) from the electron-emitting portion 23 to the surface of the face
plate 3. For the movement, the central light-emitting position of the fluorescent
film 7 is shifted from the normal line. It is considered asymmetric electric potential
distribution within a plane parallel to an electron source 1 with respect to the normal
line is the main factor of this emission characteristic.
(b) Shift of Electron Trajectories
[0033] As described above, in a study of the image forming apparatus using an electron source
having a plurality of matrix-arranged surface-conduction emission type electron-emitting
devices, the present inventors have found that the light-emitting position of the
fluorescent film and the form of the light emission may be shifted from the designed
values. Especially when a colour image forming device is used, luminance degradation
and colour shift in addition to the shift of light-emitting position have been observed.
Further, it is confirmed that the shift of light-emitting position occurs near a support
member (spacer) provided between the electron source and the image forming member
or peripheral portion(s) of the image forming member.
[0034] In the present invention, the above problem that occurs near the support member (spacer)
is solved.
[0035] The trajectories of the electrons near a spacer 5 are considered as follows.
[0036] In addition to light-emission by the fluorescent film 7 due to collision of the electrons
emitted from the electron source 1 with the inner surface of the face plate 3, scattered
particles (ions, secondary electrons, neutral particles etc.) are generated with a
certain probability, due to the collision of the electrons with the fluorescent film
7, and with lower probability, collision of the electrons with residual gas in vacuum
atmosphere. In the example of Fig. 12, the scattered particles traverse the trajectories
26t in the outer casing 10.
[0037] The present inventors have found that the light-emitting positions (electron-collision
position) on the fluorescent film 7 near the spacer 5 and the form of light-emission
are shifted from designed values. Especially in a case where a colour image forming
device is employed, luminance degradation and colour shift as well as the shift of
the light-emitting positions have been observed.
[0038] It is considered that the main cause of this phenomenon is collision of a part of
the above-described scattered particles against an exposed part of an insulating member
5a of the spacer 5, resulting in electric charge-up of the exposed part. The electric
field around the electrically-charged exposed part changes, which causes shift of
electron trajectories, then shifts the light-emitting position of the fluorescent
member and changes the light-emission form.
[0039] Further, it is found, from the shift of light-emitting position of the fluorescent
member and the change of light-emission form, that the above exposed part carries
mainly positive electric charge. It is considered that attachment of positive ions
among the scattered particles to the exposed part or positive electric charge by emission
of the secondary electrons generated upon collision of the scattered particles with
the exposed part are possible causes of the positive electric charge-up.
(C) Prevention of Shift of Electron Trajectories
[0040] To prevent the above-described positive electric charge, the present inventors applied
a semiconductive film onto the surface of the spacer 5, thus neutralized the positive
electric charge. At this time, to form an electric path between the semiconductive
film, the electron source and the face plate, a conductive connection member 58 and
59 were provided.
[0041] However, the image forming apparatus has wiring electrodes connected to the support
member (spacer) via the conductive connection member 58 and wiring electrodes not
connected to the support member (spacer), the regularity of electric field is distorted
due to the conductive connection member 58. To keep the regularity of electric field
in the image forming apparatus of this invention having the wiring electrodes connected
to the support member via the conductive connection member and also having the wiring
electrodes without the support member, the shift of electron-beams near the spacer
can be prevented, by setting the height of the upper surface of the conductive connection
member connected to the support member and that of the upper conductive surface of
the wiring electrodes where the support member is not provided to the same height.
[0042] The effect of this arrangement will be described with reference to Figs. 24A to 24D
showing electric-potential distribution represented by equipotential lines, as results
of electric-field simulation.
[0043] In Figs. 24A to 24D, numeral 25 denotes emitted electrons; 60, equipotential lines;
and 23, electron-emitting portion of electron emitting device.
[0044] Fig. 24A shows a case where the spacer 5 is not provided. When the accelerating voltage
is applied to the metal back 8, the equipotential line 60 has balanced shape respectively
at both side of the electron-emitting portions. When electrons are emitted from the
electron-emitting devices, the electrons move in a direction toward the acceleration
electrode (toward fluorescent film) in accordance with the electric field, however,
the electron trajectories are not bent toward one row-direction wiring as described
later.
[0045] Fig. 24B shows a case where the present invention is not applied, and the conductive
connection member 58 is formed on the row-direction wiring electrode 12, to hold the
spacer 5, electrical contact with the spacer 5. However, around the spacer 5 having
the conductive connection member 58, the potential of the conductive connection member
58 is substantially equal to that of the row-direction wiring electrode 12. The equipotential
lines are distorted as shown in Fig. 24B, and the balance between the right and left
portion of the electron-emitting portion 23 is lost. This distorts the equipotential
lines, as shown in Fig. 24B, and thus shifts the electron-beam.
[0046] Fig. 24C and 24D show cases where the present invention is applied. In Fig. 24C,
the height of one wiring electrodes 12 is equal to that of the conductive connection
member 58 mounted on another wiring electrode 12. In Fig. 24D, the conductive connection
member 58 is mounted on one wiring electrode, and the conductive member 70 is mounted
on the other wiring electrode, so that the heights of these neighboring conductive
portions are the same. As it is understood from Figs. 24C to 24D, setting the height
of a wiring electrode on which a conductive connection member is provided and that
of a wiring electrode on which no conductive connection member is provided to the
same height forms symmetrical electric-potential distribution in the right and left
portions of the electron-emitting portion 23, thus moves the emitted electrons 25
in a desired direction (toward the fluorescent film 7). That is, in Fig. 24D, the
conductive member 70 is formed on the row-direction wiring electrode 12 where the
spacer is not arranged so that the height of the conductive member 70 is equal to
that of the conductive connection member 58 provided on the other wiring electrode
12 and the electric-field distribution around the electron-emitting portion 23 becomes
symmetrical. This construction of the present invention prevents the shift of the
electron-beam trajectories around the spacer 5 due to a slope of the electric-field
around the electron-emitting portion 23.
[0047] In this manner, the shift of electron-beam trajectories around the spacer can be
prevented by effectively utilizing conductive material.
[0048] To neutralize electric charge by passing a weak current through a semiconductive
member, it is necessary to make electrical connection of the semiconductive portion
of the spacer with the electrodes of a device base plate (or wiring portion). Further,
in thin-type image forming apparatuses, it is necessary to firmly hold the support
members (spacers) used to maintain atmospheric-pressure-proof structure, as constituting
members.
[0049] Next, materials of conductive connection member to firmly hold the support member
(spacer) and make electrical connection with the spacer will be described.
[0050] For the purpose of firmly holding the support members (spacers), bonding material
is used, and for the electrical connection, conductive filler is used. In the present
invention, the bonding material where the conductive filler is scattered is used as
conductive connection member. Hereinbelow, the bonding material and the conductive
filler will be described.
[0051] Using low-fusing-point glass (frit glass), as the bonding material, heat-melt bonding
is made at about 400 to 500 °C. The frit glass includes crystalline and non-crystalline
type structures and further includes various types having different components. An
appropriate type of frit glass may be selected in accordance with a heat-melt temperature
and/or thermal-expansion coefficient of material. As frit glass unit material is a
powdery material, for application of the bonding material, the frit glass powder is
mixed with an organic solvent, or an organic solvent as a mixture of clay with a binder
such as nitrocellulose or acrylic material, into a paste of frit-glass mixture. In
consideration of working condition for the bonding operation, the frit-glass paste
at a room temperature and with viscosity is used.
[0052] As another material of the conductive connection member, a conductive filler is obtained
by forming a metal film by plating a ball of soda-lime glass or silica with a 5 to
50 µm diameter.
[0053] Then, the conductive connection member is formed by applying frit-glass paste, obtained
by mixing the above-mentioned frit-glass paste with the conductive filler, to an attachment
portion by a screen printing method or by using a dispenser and then sintering the
applied paste.
[0054] One example of manufacturing the conductive connection member using non-crystalline
frit glass (LS-3081 by Nippon Electric Glass Co. Ltd.) and gold-plated soda-lime glass
as the conductive filler will be described.
[0055] In this example, soda-lime glass balls having an average 30 µm diameter are employed
as the conductive filler. The conductive layer of the filler is formed by sequentially
piling a 0.1 µm Ni film as a base, then a 0.05 µm Au film over the base Ni film, in
accordance with an electroless plating method. Then, frit-glass paste is obtained
by mixing the conductive filler with the flit-glass powder, and further mixed with
a binder as described below.
(1) Process of Manufacturing of Conductive Frit-Glass Paste, and Application and Drying
of Paste
[0056] The conductive filler is mixed by 30 wt% with respect to the frit-glass powder, then
mixed with a binder where acrylic resin is melted in solvent into paste (conductive
frit-glass paste). After the paste is applied to the attachment portion, it is dried
at 120°C for 10 to 20 minutes.
[0057] In a conventional frit-glass paste application method, a dispenser robot as a combination
of a dispenser which discharges frit-glass paste from a needle, with a robot capable
of three-dimensional movement with high-speed and high-precision between a paste-discharge
portion to an applied member is employed. An dispenser robot can be used for application
of the frit-glass paste of the present embodiment. The dispenser robot is widely used
for industrial purposes, as an application device for various paste materials such
as soldering paste.
(2) Temporary Sintering Process
[0058] To remove the binder in the conductive frit glass paste, temporary sintering process
is performed such that the maximum sintering temperature is 320°C to 380°C at which
the binder decomposes. By this process, the conductive frit-glass paste has sintered
at its surface.
(3) Sintering Process
[0059] The conductive frit-glass paste is heated such that the maximum temperature becomes
410°C corresponding to a melting temperature. By this process, the conductive frit-glass
paste is melt-broken down and solidified by cooling, thus fixing is completed. The
heat-application requires two heating steps.
[0060] Note that in the present construction, it is preferable that the following relation
can be held:
[0061] Preferably, the spacer's resistance value is held to be 10
4 [Ω/□] or greater (spacer-surface resistance). On the other hand, the respective resistance
values of the conductive connection member and the wiring electrodes are preferably
2 orders less of magnitude, or more preferably 4 orders less of magnitude than the
spacer resistance value. Further, the difference between the resistances of the conductive
connection member and the wiring electrodes can be ignored when the respective differences
of the resistance values between the wiring electrodes with respect to the spacer
reside within the above-mentioned range. A large difference between the conductive
connection member's resistance value and the wiring electrodes' resistance values
may cause disturbance of the electric field, however, a large difference between the
spacer resistance value and the resistance values of other portions effects the electron
trajectories around the wiring electrodes and the conductive connection member, at
an ignorable level. However, to reduce the effect, the resistance difference should
preferably be less than two orders of magnitude.
[General Embodiment]
[0062] Next, the image forming apparatus to which the general embodiment is applied will
be described. The image forming apparatus basically comprises, within a thin-type
vacuum container, a multi electron source having a plurality of cold cathode electron-emitting
devices arranged on a base plate, and an image forming member, opposite to the electron
source, which forms images by irradiation from the electron source.
[0063] The cold cathode electron-emitting devices can be formed by precisely aligning the
devices on a base plate using, e.g., a photolithography etching technique. Therefore,
a large number of electron-emitting devices can be arranged at minute intervals. In
addition, in comparison with the thermal cathode electron-emitting devices, employed
in conventional CRT's or the like, the cathode itself and its peripheral portion can
be driven at a comparatively low temperature, which enables it easily to realize a
multi electron source of further minute device pitch.
[0064] The most preferable cold cathode electron-emitting device is the aforementioned surface-conduction
emission type electron-emitting device. That is, in the MIM type electron-emitting
device, its insulating layer and that of the upper electrode must respectively have
a comparatively-precise predetermined thickness. Also, in the FE type electron-emitting
device, precise formation of the distal end of its electron-emitting portion is required.
For these reasons, these two types of devices raise manufacturing costs or cause difficulties
in forming a large-screened image forming apparatus due to limitations of manufacturing
processes.
[0065] In contrast, the surface-conduction emission type electron-emitting device has a
simple structure and can be easily manufactured, thus enables formation of a large-screened
image forming apparatus. Recent situation where large-screened and low-price display
devices are needed, surface-conduction emission type electron-emitting devices are
the most preferable cold cathode electron-emitting devices.
[0066] The present inventors have found that among the surface-conduction emission type
electron-emitting devices, a device where the electron-emitting portion or its peripheral
portion is formed using fine-particle film is preferable from the point of electron-emission
characteristic or the point of large-screened image forming apparatus.
[0067] Accordingly, in the following the first embodiment of the present invention, an image
display device using a multi electron source having the surface-conduction emission
type electron-emitting devices formed using a fine-particle film, is used as a preferable
example of the image forming apparatus of the present invention.
[0068] Note that in the following embodiments, the regularly arranged wiring electrodes
partially connected to the support members are referred to as the "row-direction wiring
electrodes" However, this name is made for the purpose of convenience of explanation,
and it may also be replaced with the column-direction wiring electrodes, without causing
any problem from the point of the present invention.
〈First Embodiment〉
[0069] Fig. 1 is a partially-cutaway perspective view showing the structure of the image
forming apparatus, and Fig. 2, a cross-sectional view of a significant part of the
image forming apparatus in Fig. 1 cut along the line A-A'.
[0070] In Figs. 1 and 2, the electron source 1 where the plurality of surface-conduction
emission type electron-emitting devices 15 are arranged in a matrix, is fixed on the
rear plate 2. The face plate 3, as an image forming member, where the fluorescent
film 7 and the metal back 8 as an acceleration electrode are provided on the inner
surface of the glass substrate 6, is provided to be opposite to the electron 1 via
the support frame 4 comprising insulating material. The predetermined high voltage
is applied between the electron 1 and the metal back 8 from a power source (not shown).
The rear plate 2, the support frame 4 and the face plate 3 are fixed with each other
with the fric-glass or the like, and these members construct the outer casing 10.
[0071] As the outer casing 10 maintains pressure inside about 10
-4Pa (10
-6 Torr) vacuum condition, the spacers 5 are provided in the outer casing 10 for the
purpose of preventing breakage of the outer casing 10 due to atmospheric pressure
or unexpected shock. The spacer 5 comprises the insulating substrate member 5a and
the semiconductive film 5b formed on the insulating substrate member 5a. The spacers
5 of an necessary number are arranged on the inner surface of the outer casing 10
and the front surface of the electron source 1, in parallel in the direction X at
necessary intervals, and fixed with the conductive connection member. The semiconductive
film 5b is electrically connected to the inner surface of the face plate 3 and the
front surface of the electron source 1 (row-direction wiring electrodes 12).
[0072] Next, the respective components of the above construction will be described in detail.
(1) Electron Source 1
[0073] Fig. 3 is a plan view of a significant part of the electron source 1 of the image
forming apparatus in Fig. 1, and Fig. 4, a cross-sectional view of the electron source
1 shown in Fig. 3, cut away along the line B-B'.
[0074] In Figs. 3 and 4, m row-direction wiring electrodes 12 and n column-direction wiring
electrodes 13 are arranged in a matrix on the insulating substrate 11 comprising a
glass substrate or the like, electrically insulated from each other. Each of the electron-emitting
devices 15 is electrically connected between a row-direction wiring electrode 12 and
a column-direction wiring electrode 13. Each electron-emitting device 15 comprises
a pair of device electrodes 16 and 17, and a conductive thin film 18 connecting the
electrodes 16 and 17. The device electrode 16 is electrically connected to the row-direction
wiring electrode 12, and the device electrode 17, to the column-direction wiring electrode
13. The line- and column-direction wiring electrodes 12 and 13 are pulled out of the
outer casing 10 as the external terminals Dox1 to Doxm otherwise Doy1 to Doyn shown
in Fig. 1.
[0075] As the insulating substrate 11, glass substrates of, e.g., quartz glass, soda-lime
glass, soda-lime glass where a SiO
2 layer is formed by a sputtering or the like, and a ceramic substrates of alumina
or the like can be employed. The size and thickness of the insulating substrate 11
are determined in accordance with the number and the shape of the electron-emitting
device 15 provided on the insulating substrate 11, conditions for maintaining vacuum
atmospheric status in a case where the electron source 1 itself constitutes a part
of the outer casing 10 and the like.
[0076] The line- and column-direction wiring electrodes 12 and 13 respectively comprise
a conductive metal member formed into a predetermined pattern on the insulating substrate
11, by vacuum evaporation, printing, sputtering and the like. The material, the film
thickness and wiring-electrode width of these electrodes are determined so as to supply
a voltage as uniform as possible to the electron-emitting devices 15.
[0077] The insulating film 14 comprises SiO
2 material or the like, formed by vacuum evaporation, printing, sputtering and the
like. The insulating film 14 is formed in a predetermined form. The thickness, material
and manufacturing method of the insulating film 14 are appropriately determined, especially
to keep insulation at the intersections of the row-direction wiring electrodes 12
and the column-direction wiring electrodes 13.
[0078] The device electrodes 16 and 17 of each electron-emitting device 15 respectively
comprise a conductive metal material and respectively formed into a desired pattern
by vacuum evaporation, printing, sputtering and the like.
[0079] A part or all the constituting elements of the conductive metal material of the device
electrodes 16 and 17 may be the same; otherwise, all the elements may be different.
These elements are appropriately selected from metals such as Ni, Cr, Au, Mo, W, Pt,
Ti, Al, Cu and Pd, alloys, printing conductors comprising metals or metal oxide such
as Pd, Ag, Au, RuO
2 and Pd-Ag with glass and the like, or transparent conductors such as In
2O
2-SnO
2 and semiconductive materials such as polysilicon and the like.
[0080] The material of the conductive thin film 18 may be a fine-particle film of metals
such as Pd, Ru, Ag, Au, Ti, In, Cu, Cr, Fe, Zn, Sn, Ta, W and Pd, oxides such as PdO,
SnO
2, In
2O
3, PbO and Sb
2O
3, borides such as HfB
2, HfC, LaB
6, CeB
6, YB
4 and GdB
4, carbides such as TiC, ZrC, HfC, TaC, SiC and WC, nitrides such as TiN, ZrH and HfN,
semiconductors such as Si and Ge.
[0081] The row-direction wiring electrodes 12 are electrically connected to scan-signal
generating means (not shown) for applying a scan signal for arbitrary scanning of
the lines of the electron-emitting devices 15 arrayed along the direction X. On the
other hand, the column-direction wiring electrodes 13 are electrically connected to
modulation-signal generating means (not shown) for applying a modulation signal for
arbitrary modulation of the columns of the electron-emitting devices 15 arrayed along
the direction Y. At each electron-emitting device 15, a drive voltage to be applied
to the device is supplied as a difference voltage between the scan signal and the
modulation signal applied to the electron-emitting device.
[0082] Next, an example of manufacturing method of electron source 1 will be described with
reference to Figs. 5A to 5H. Note that the following steps (a) to (h) correspond to
Figs. 5A to 5H.
Step a: A Cr film with a thickness of 5nm (50 Å) and Au film with a thickness of 500nm
(5000 Å) are sequentially accumulated by vacuum evaporation, on an insulating substrate
11, formed by piling a silicone oxide film with a thickness of 0.5 µm by sputtering,
on a cleaned soda-lime glass material; Photoresist is spin-coated by a spinner, and
baking the applied layered film; the photomask image is exposed and developed to form
a resist pattern of the column-direction wiring electrodes 13; and the layered Au/Cr
film is wet-etched to form the predetermined patterned column-direction wiring electrodes
13.
Step b: Next, the insulating film 14 comprising a silicone oxide film with a thickness
of 1.0 µm is accumulated by RF sputtering.
Step c: To form a contact holes 14a in the silicon oxide film formed at step b, a
photoresist pattern is formed. The insulating film 14 is etched using the photoresist
pattern as the etching mask, thus the contact holes 14a are formed. The etching is
made in accordance with an RIE (Reactive Ion Etching) method using CF4 and H2 gas.
Step d: Thereafter, a pattern to be a gap between the device electrodes is formed
with the photoresist (RD-2000N-41 by Hitachi Chemical Co. Ltd.), and a Ti film with
a thickness of 5nm (50 Å) and a Ni film with a thickness of 100nm (1000 Å) are sequentially
accumulated by vacuum evaporation.
The photoresist pattern is dissolved with an organic solvent, and the layered Ni/Ti
film is lifted off, then the device electrodes 16 and 17, having a width of 300 µm
(device-electrode width W1) are formed at 3 µm intervals (device-electrode interval
L1 (see Fig. 3)).
Step e: Ag electrodes as the row-direction wiring electrodes 12 are formed by screen-printing,
on the device electrodes 16 and 17. The formed wiring-electrodes have a thickness
of 20 µm, and wiring-electrode width is 300 µm.
Step f: A pattern of Cr film 21 with a thickness of 100nm (1000 Å) is accumulated
by vacuum evaporation, using a mask having openings 20a each covers each pair of device
electrodes 16 and 17, positioned at the intervals L1 as shown in Fig. 6. An organic
solvent (ccp4230 by Okuno Pharmaceutical Co. Ltd.) is spin-coated onto the pattern,
then sintering process is made at 300 °C for 10 minutes.
The conductive thin film 18 of a fine-particles including Pd as main element, formed
in the above manner has a thickness of about 10nm (100 Å) and a sheet resistance value
of 5 X 104 [Ω/□]. The fine-particle film is a film where a plurality of fine particles are gathered.
The minute structure is not only a state where the particles are scattered but also
a state where the particles are adjacent to each other, or they are overlapped with
each other (island-formed state included).
Note that the organic solvent (organic Pd solvent in this embodiment) is a solvent
of an organic compound mainly including metal(s) such as Pd, Ru, Ag, Au, Ti, In, Cu,
Cr, Fe, Zn, Sn, Ta and W. In this example, the conductive thin film 18 is manufactured
by application of an organic solvent, however, this does not limit the method for
manufacturing the conductive thin film 18. The conductive thin film 18 may be formed
by vacuum evaporation, sputtering, chemical vapor deposition, scattered applying,
dipping, spinner method or the like.
Step g: The Cr film 21 is removed by an acid etchant and the conductive thin film
18 of a desired pattern is formed.
Step h: A pattern for applying resist material to portions other than the contact
holes 14a is applied, and a Ti film with a thickness of 5nm (50 Å) and an Au film
with a thickness of 500nm (5000 Å) are sequentially accumulated by vacuum evaporation,
on the pattern. Unnecessary portions are removed by lift-off operation. Thus, the
contact holes 14a are filled.
[0083] Though the above steps, the row-direction wiring electrodes 12, the column-direction
wiring electrodes 13 and the conductive thin film 18 are formed two-dimensional manner,
at equal intervals, on the insulating substrate 11.
[0084] Then, the air within the outer casing 10 (Fig. 1) including the electron source 1
is exhausted by a vacuum pump through an exhaust pipe (not shown). After the atmospheric
condition there reaches a sufficient vacuum level, a predetermined voltage is applied
between the device electrodes 16 and 17 through the external terminals Dox1 to Doxm,
or Doy1 to Doyn. Thus the electron-emitting portion 23 is formed by electrification
(forming) process on the conductive thin film 18.
[0085] Next, the forming processing will be described with reference to Figs. 21 and 7.
In these figures, numerals 1102 and 1103 denote device electrodes; 1104, a conductive
thin film; 1105, an electron-emitting portion; 1110, a forming power source; and 1111,
a galvanometer.
[0086] As shown in Fig. 21, an appropriate voltage from the forming power source 1110 is
applied between the device electrodes 1102 and 1103, thus the forming processing is
made, and the electron-emitting portion 1105 is formed.
[0087] The forming processing is electrification of the conductive thin film 1110 of a fine-particle
film, so as to partially destroy or deform the film, otherwise change the film in
quality, for obtaining a structure preferable to perform electron emission. In such
structure (i.e., the electron-emitting portion 1105), the thin film has an appropriate
fissure. Note that after the electron-emitting portion 1105 has been formed, electric
resistance measured between the device electrodes 1102 and 1103 is increased greatly.
[0088] Fig. 7 shows an example of voltage waveform from the forming power source 1110 for
detailed explanation of the forming processing. To perform forming processing on a
conductive thin film of a fine-particle film, pulse waveform is preferable for the
voltage to be applied. In the present embodiment, a triangular pulse having a pulsewidth
T1 is continuously applied at pulse intervals T2, as shown in Fig. 7. Upon application,
a wave peak value Vpf of the triangular-wave pulse is sequentially increased.
[0089] In this example, in 10
-3 Pa (10
-5 Torr) vacuum atmosphere, the pulsewidth T1 is set to 1 msec; and the pulse interval
T2, to 10 msec. The wave peak value Vpf is increased by 0.1 V, at each pulse. Each
time the triangular-wave has been applied for five pulses, the monitor pulse Pm is
inserted. To avoid ill-effecting during the forming processing, a voltage Vpm of the
monitor pulse is set to 0.1 V. When the electric resistance between the device electrodes
1102 and 1103 becomes 1 × 10
6 Ω, i.e., the current measured by the galvanometer 1111 upon application of monitor
pulse becomes 1 × 10
-7 Ω or less, the electrification of the forming processing is terminated.
[0090] Note that the above processing method is preferable to the SEC type electron-emitting
device of the present embodiment. In case of changing the design of the SEC type electron-emitting
device concerning, e.g., the material or thickness of the fine-grained film, or the
device electrode interval L, the conditions for electrification are preferably changed
in accordance with the change of device design.
[0091] Next, electrification activation process will be described with reference to Figs.
22, 23A and 23B. In Fig. 22, numeral 1112 denotes an electrification activation power
source; 1113, an accumulated material; 1114, an anode; 1115, a direct-current high-voltage
power source; and 1116, a galvanometer.
[0092] The electrification activation processing here is electrification of the electron-emitting
portion 1105, formed by the forming processing, on appropriate condition(s), for accumulating
carbon or carbon compound around the electron-emitting portion 1105 (In Fig. 22, the
accumulated material of carbon or carbon compound is shown as material 1113). Comparing
the electron-emitting portion 1105 with that before the electrification activation
processing, the emission current at the same applied voltage has become, typically
100 times or greater.
[0093] The electrification activation is made by periodically applying a voltage pulse in
10
-2 or 10
-3 Pa (10
-4 or 10
-5 Torr)vacuum atmosphere, to accumulate carbon or carbon compound mainly derived from
organic compound(s) existing in the vacuum atmosphere. The accumulated material 1113
is any of graphite monocrystalline, graphite polycrystalline, amorphous carbon or
mixture thereof. The thickness of the accumulated material 1113 is 50nm (500 Å) or
less, more preferably, 30nm (300 Å) or less.
[0094] The electrification activation processing will be described in more detail with reference
to Fig. 23A showing an example of waveform of appropriate voltage applied from the
electrification activation power source 1112. In this example, a rectangular-wave
voltage Vac is set to 14 V; a pulsewidth T3, to 1 msec; and a pulse interval T4, to
10 msec. Note that the above electrification conditions are preferable for the surface-conduction
emission type electron-emitting device of the embodiment. In a case where the design
of the surface-conduction emission type electron-emitting device is changed, the electrification
conditions are preferably changed in accordance with the change of device design.
[0095] In Fig. 22, the anode 1114 is connected to the direct-current high-voltage power
source 1115 and the galvanometer 1116, for monitoring emission current Ie emitted
from the surface-conduction emission type electron-emitting device (in a case where
a substrate 1101 is incorporated into the outer casing of the display panel before
the electrification activation processing, the fluorescent surface of the display
panel is used as the anode electrode 1114).
[0096] While applying voltage from the electrification activation power source 1112, the
galvanometer 1116 measures the emission current Ie, thus monitors the progress of
electrification activation processing, to control the operation of the electrification
activation power source 1112. Fig. 23B shows an example of the emission current Ie
measured by the galvanometer 1116. In this example, as application of pulse voltage
from the electrification activation power source 1112 is started, the emission current
Ie increases with elapse of time, gradually comes into saturation, and almost never
increases then. At the substantial saturation point, the voltage application from
the electrification activation power source 1112 is stopped, then the electrification
activation processing is terminated.
[0097] Note that the above electrification conditions are preferable to the surface-conduction
emission type electron-emitting device of the embodiment. In case of changing the
design of the surface-conduction emission type electron-emitting device, the conditions
are preferably changed in accordance with the change of device design.
[0098] As described above, the flat surface-conduction emission type electron-emitting device
is manufactured.
[0099] Next, evaluation of electron-emitting characteristic of the electron-emitting device
of the present invention, having the above construction manufactured as above, will
be described with reference to Fig. 8 showing the schematic construction of an evaluation
device.
[0100] Fig. 8 shows an electron source having one electron-emitting device. In Fig. 8, numeral
11 denotes an insulating substrate; 15, an electron-emitting device formed on the
insulating substrate 11; 16 and 17, device electrodes; 18, a thin film including an
electron-emitting portion; and 23, the electron-emitting portion. Numeral 31 denotes
a power source for applying a device voltage Vf between the device electrodes 16 and
17; 30, a galvanometer for measuring a device current If that flows through the thin
film 18 between the device electrodes 16 and 17; 34, an anode for capturing an emission
current Ie emitted from the electron-emitting portion 23; 33, a high-voltage power
source for applying a voltage Va to the anode 34; and 32, a galvanometer for measuring
the emission current Ie from the electron-emitting portion 23. For measurement of
the device current If and the emission current Ie, the device electrodes 16 and 17
are connected to the power source 31 and the galvanometer 30, and the anode 34 connected
to the power source 33 and the galvanometer 32 is provided above the electron-emitting
device 15. The electron-emitting device 15 and the anode 34 are arranged within the
vacuum device which comprises necessary tools such as an exhaust pump, a vacuum system
(both not shown) and the like and which can perform the measurements at a desired
vacuum condition.
[0101] Note that the voltage Va applied to the anode 34 is set to 1 to 10 kV; and a distance
H between the anode 34 and the electron-emitting device 15, 3 to 8 mm.
[0102] Next, the electron-emitting characteristic, observed by the present inventors, will
be described below.
[0103] Fig. 9 shows a typical example of the relation among the emission current Ie, the
device current If and the device voltage Vf, measured by the evaluation device in
Fig. 8. Since the values of the emission current Ie and the device current If are
extremely different, Fig. 9 represents the values at arbitrary units. As it is apparent
from Fig. 9, the electron-emitting device has the following three characteristics
with respect to the emission current Ie.
[0104] First, at the present electron-emitting device, if the device voltage Vf at a predetermined
level, i.e., a threshold voltage Vth (see Fig. 9) or higher is applied, the emission
current Ie value increases drastically. On the other hand, if the device voltage Vf
at a lower level than the threshold voltage, the emission current Ie value is almost
zero. That is, the present electron-emitting device has a non-linear electron-emitting
characteristic with the clear threshold voltage Vth with respect to the emission current
Ie. Regarding the device current If, the electron-emitting device has so-called MI
characteristic where the device current If increases monotonously with respect to
the device voltage Vf.
[0105] Secondly, since the emission current Ie depends on the device voltage Vf, the emission
current Ie can be controlled by controlling the device voltage Vf.
[0106] Thirdly, the emission charge captured by the anode 34 depends on time for applying
the device voltage Vf. That is, the amount of the electric charge captured by the
anode 34 can be controlled with the time for applying the device voltage Vf.
(2) Fluorescent Film 7
[0107] For monochromatic image formation, the fluorescent film 7 (Fig. 1) only comprises
a fluorescent member, however, for colour image formation, it comprises a black conductive
material 7b, referred to as "black stripe" or "black matrix", and a fluorescent material
7a as shown in Fig. 10a. The purpose of providing the black stripe or black matrix
is to render colour mixture of respective three-primary colours inconspicuous by blackening
the boundaries between the respective colour fluorescent substances 7a, and to reduce
degradation of contrast due to external light reflection at the fluorescent film 7.
The material of the black conductive member 7b may be any conductive material that
has a low light-transmittance and a low reflectance, as well as normally used graphite.
The application of the fluorescent material 7a to the glass substrate 6 is made by
precipitation or printing, regardless of monochrome or colour image formation.
[0108] Further, the colouring of the fluorescent material 7a in three primary-colours is
not limited to the stripe arrangement as shown in Fig. 10A, but delta arrangement
as shown in Fig. 10B or other arrangement can be employed.
[0109] Note that when a monochrome display panel is manufactured, a monochromatic fluorescent
material may be used.
(3) Metal Back 8
[0110] The purpose of providing the metal back 8 (Fig. 1) is to improve luminance by mirror-reflecting
light toward the inner surface side, in the light emitted from the fluorescent material
7a, to the face plate 3 side, and to act as acceleration electrode for application
of electron-beam accelerating voltage, and to protect the fluorescent material 7a
from damaging due to collisions of negative ions generated in the outer casing 10.
The metal back 8 is formed as follows. After the fluorescent film 7 has been formed,
smoothing (generally referred to as "filming") is performed on the inner surface of
the fluorescent film 7, then Al is accumulated on the smoothed surface by vacuum evaporation
or the like. To improve conductivity of the fluorescent film 7, the face plate 3 may
have a transparent electrode (not shown) such as ITO, between the fluorescent film
7 and the glass substrate 6.
(4) Outer Casing 10
[0111] The outer casing 10 (Fig. 1) is sealed after about 10
-4 Pa (10
-6 Torr) vacuum condition is obtained. Preferably, the rear plate 2, the face plate
3 and the support frame 4 constructing the outer casing 10 can maintain the vacuum
atmosphere and have insulation resistance against the high voltage applied between
the electron source 1 and the metal back 8. The materials of these members may be
glass materials such as quartz glass, soda-lime glass, ceramic materials such as alumina.
Regarding the respective members constituting the outer casing 10, it is preferable
to combine materials having thermal-expansion coefficients close to each other.
[0112] In a case where the outer casing 10 is constructed in a colour image forming apparatus,
the respective colour fluorescent materials 7a must be arranged corresponding to the
respective electron-emitting devices. For this reason, the position of the face plate
3 having the fluorescent materials 7a and that of the rear plate 2 where the electron
source 1 is fixed must be aligned with high precision.
[0113] To maintain vacuum condition after sealing the outer casing 10, gettering processing
may be performed. This is done by heating a getter (not shown) at a predetermined
position in the outer casing 10, by high-frequency heating or the like, to form a
film by evaporation, immediately after or before sealing. The getter normally has
Ba as its main element, and it maintains about 10
-4 and 10
-5Pa (10
-6 or 10
-7 Torr) vacuum condition by the above absorption of the film formed by evaporation.
(5) Spacer 5
[0114] As described above, the spacer 5 must have mechanical strength against the atmospheric
pressure, insulation resistance against the high voltage applied between the electron
source 1 and the metal back 8, and surface conductivity to prevent electric charge
on the spacer itself.
[0115] Accordingly, in the present embodiment, the spacer 5 comprises an insulating member,
having sufficient mechanical strength, coated with a semiconductive film.
[0116] Fig. 2 shows the structure of the spacer 5 of the present embodiment.
[0117] As the insulating substrate member 5a of the spacer 5, glass materials such as quartz
glass, soda-lime glass, and ceramic materials such as alumina may be employed. Preferably,
the material of the insulating substrate member 5a has a thermal-expansion coefficient
close to that of the outer casing 10 and the insulating substrate 11 of the electron
source 1.
[0118] In the present embodiment, the material of the spacer 5 is soda-lime glass plate
on which the semiconductive film 5b of tin oxide is formed. The height of the spacer
5 is 5 mm; the thickness, 200 µm; and the length, 20 mm.
(Semiconductive Film)
[0119] Preferably, the semiconductive film 5b has a surface resistance ranging from 10
5 to 10
12 [Ω/□], for maintaining prevention of electric charge-up and saving electric consumption
due to leakage current. The material of the semiconductive film 5b may be a metal
film containing an island-shaped adjacent or overlapped particles, made of; noble
metals such as Pt, Au, Ag, Rh and Ir, or metals such as Al, Sb, Sn, Pb, Ga, Zn, In,
Cd, Cu, Ni, Co, Rh, Fe, Mn, Cr, V, Ti, Zr, nb, Mo and W, and alloys comprising a plurality
of metals, otherwise, conductive oxides such as SnO
2 and ZnO.
[0120] The semiconductive film 5b is formed by selecting appropriate one of a film-forming
method such as vacuum evaporation, sputtering, chemical gaseous-phase accumulation,
or an application method such as dipping of an organic solvent or scattered-particle
solvent, or applying and sintering such solvent, or an electroless plating method
to form a metal film on the surface of an insulating member by utilizing chemical
reaction of a metal compound.
[0121] The semiconductive film 5b is formed in a part, which is at least exposed in the
vacuum atmosphere within the outer casing 10, of the surface of the insulating substrate
member 5a. The semiconductive film 5b is electrically connected to, e.g., the black
conductive material 7b or the metal back 8 on the face plate 3 side, and to the row-direction
wiring electrodes 12 on the electron source 1 side.
[0122] Regarding the spacer 5, the structure, setting position, setting method and electrical
connection on the face plate 3 side and the electron 1 side are not limited to the
above example. The semiconductive film 5b may be of any material, as far as it can
maintain the vacuum atmosphere against the atmospheric pressure and has insulation
resistance against high voltage applied between the electron source 1 and the metal
back 8, further it has surface conductivity at a level to prevent electric charge-up
on the surface of the spacer 5.
[0123] In this embodiment, as the semiconductive film 5b, a tin oxide film of a thickness
of about 100nm (1000 Å) is formed by ion plating. The surface resistance in this case
is 10
4 to 10
12 [Ω/□].
(Conductive Member)
[0124] Next, the conductive connection member 58 to firmly connect the support member (spacer)
and to attain electrical connection with the spacer, and the conductive member 70
of the present invention will be described with reference to Fig. 13.
[0125] Regarding the electron-emitting devices, electrically connected to the wiring electrodes,
only the electron-emitting portion 23 is shown to avoid complexity of illustration.
[0126] In this embodiment, the spacers 5 are provided on some of the row-direction wiring
electrodes 12 via the conductive connection members 58, and the conductive members
70 are provided on the other row-direction wiring electrodes 12, such that the height
of the upper surface of the conductive connection member 58 (h
1 in Fig. 13) and that of the conductive member 70 (h
2 in Fig. 13) are the same.
[0127] By this arrangement, the electric-potential distribution on the spacer surface and
that in the space above the row-direction wiring electrode without the spacer 5 are
equal to each other. That is, if the spacer 5 is provided on one row-direction wiring
electrode 12 with the conductive connection member 58, electro-optical characteristic
similar to that of the other row-direction wiring electrodes can be realized.
[0128] Since any electron beams emitted by any electron-emitting portions 23 transverse
similar trajectories, the conventional problems such as shift of light-emission point,
luminance degradation and change of color do not occur.
[0129] Note that to optimize the above feature, the conductive connection members 58 and
the conductive members 70 should preferably have the same width (
) in addition to the condition
, then the settings of the present embodiment are made in accordance with the above
conditions. (w
1: width of conductive connection member 58, w
2: width of conductive member 70).
[0130] Next, the manufacturing of the image forming apparatus according to the first embodiment
will be described.
[0131] In the present embodiment, the conductive connection member 58, which holds the spacer
5 and makes electrical connection with the spacer 5, is formed by dispersing Au-plated
soda-lime glass balls, as filler, in the frit-glass paste, and applying and sintering
the paste. In this example, the soda lime balls have an average diameter of 8 µm.
As the conductive layer of the filler surface, a Ni film with a thickness of 0.1 µm,
as a base, and an Au film with a thickness of 0.04 µm, on the base, are sequentially
formed by electroless plating. The paste to be applied is formed by mixing the conductive
filler at 30 wt% with respect to the frit-glass paste, and further adding a binder
to the mixture.
[0132] The conductive frit-glass paste is applied to the row-direction wiring electrode
12 of the electron source 1, by a dispenser, such that the applied width is the same
as the width of the electrode. After application, the spacer 5 is aligned with conductive
connection member 58, then connected portion is sintered in the atmosphere at 400
°C to 500 °C for 10 minutes or longer. On the face plate 3 side, the conductive frit-glass
paste is applied to the end of the spacer 5, also by a dispenser. The conductive flit-glass
paste is provided in correspondence with the black conductive material 7b (with 300
µm line width), then sintered in the atmosphere at 400 °C to 500 °C for 10 minutes
or longer. This holds the connection between the electron source 1 and the black conductive
material 7b and the spacer 5. The width of the conductive connection member 58 is
300 µm, the same as that of the row-direction wiring electrode 12, and the thickness
of the conductive connection member 58 is 400 µm. The conductive member 70 comprises
the same material as that of the conductive connection member 58.
(6) Driving Method
[0133] A driving method for driving the above-described image forming apparatus will be
described with reference to Figs. 15 to 18.
[0134] Fig. 15 is a block diagram showing the construction of a driver for television display
based on a TV signal in conformance with the NTSC standards. In Fig. 15, a display
panel 1701 is an image forming apparatus manufactured and operating as above. A scanning
circuit 1702 operates display lines, and a controller 1703 generates a signal to be
inputted into the scanning circuit and the like. A shift register 1704 shifts data
for one line, and a line memory 1705 inputs the one-line data from the shift register
1704 into a modulating-signal generator 1707. A synchronizing-signal separator 1706
separates a synchronizing signal from the NTSC signal.
[0135] Next, the function of the respective components in Fig. 15 will be described in detail.
[0136] The display panel 1701 is connected to external electric signals via terminals Dox1
to Doxm and terminals Doy1 to Doyn, and via a high-voltage terminal Hv. The terminal
Dox1 to Doxm receives a scanning signal for sequentially driving an m × n matrix-arranged
electron-emitting devices of an electron source provided in the display panel 1701,
by one line (n devices).
[0137] On the other hand, the terminal Doy1 to Doyn receives a modulating signal for controlling
electron beams outputted from the respective electron-emitting devices of a selected
one line. The high-voltage terminal Hv receives a high voltage of, e.g., 5kV, which
is the accelerating voltage that provides the electrons with sufficient energy to
excite the fluorescent member, from a direct-current voltage source Va.
[0138] Next, the scanning circuit 1702 will be described below.
[0139] The scanning circuit 1702 has m switching devices S1 to Sm electrically connected
to the terminals Dox1 to Doxm of the display panel 1701. Each switching device selects
the output voltage of a direct-current voltage source Vx or ground level 0V. The switching
devices S1 to Sm respectively operate in accordance with a control signal Tscan outputted
from the controller 1703. These devices are easily constructed by combining switching
devices such as FET devices.
[0140] In the present embodiment, the direct-current voltage source Vx outputs constant
voltage of 7V so that the driving voltage applied to the non-selected electron-emitting
devices in Fig. 9 is lower than the electron-emitting threshold value Vth.
[0141] The controller 1703 controls the operations of the respective components so that
appropriate display is made based on image signals inputted from an external device,
by issuing various control signals Tscan, Tsft and Tmry to the respective components,
based on the synchronizing signal Tsync from the synchronizing-signal separator 1706.
[0142] The synchronizing-signal separator 1706 is easily constructed by using a synchronizing-signal
component (filter) circuit for filtering the NTSC signal inputted from an external
device. As it is well known, the synchronizing signal separated by the synchronizing-signal
separator 1706 includes a vertical synchronizing signal, however, the synchronizing
signal is represented as the signal Tsync, for the sake of convenience of explanation.
on the other hand, a luminance signal component separated from the TV signal and inputted
into the shift register 1704 is represented as DATA signal.
[0143] The shift register 1704 performs serial/parallel conversion on the DATA signal which
is sequentially and serially inputted, by one line of an image. The shift register
1704 operates based on the control signal Tsft from the controller 1703. In other
words, the control signal Tsft works as a shift clock for the shift register 1704.
[0144] The serial/parallel converted data for one image line is outputted from the shift
register 1704, as n signals Id1 to Idn, into the line memory 1705.
[0145] The line memory 1705 is a storage device for storing data for one image line for
a necessary period. The signals Id1 to Idn are inputted into the line memory 1705,
in accordance with the control signal Tmry from the controller 1703. The stored contents
are outputted as signals I'd1 to I'dn into the modulating-signal generator 1707.
[0146] The modulating-signal generator 1707 is a signal source for appropriately modulating
the drive signals to the respective electron-emitting devices, in accordance with
the image data I'd1 to I'dn. The output signals from the modulating-signal generator
1707 are applied through the terminals Doy1 to Doyn to the electron-emitting devices
in the display panel 1701.
[0147] As described in Fig. 9, the electron-emitting device has the following characteristics
with respect to the emission current Ie. That is, as it is from the graph showing
the emission current Ie, there is a clear threshold voltage Vth (8V for the device
of the present embodiment) in electron emission, and only when the value of applied
voltage is equal to the threshold Vth or higher, electron emission occurs.
[0148] Further, with respect to the voltage value of the threshold Vth or higher, the emission
current Ie varies in accordance with the change of voltage as shown in the graph.
Note that changing the structure of the electron-emitting device and manufacturing
method may change the value of the threshold voltage Vth and the manner of change
of the emission current.
[0149] In any way, it is apparent that in a case where voltage in the form of pulse-output
is applied to the electron-emitting device, if the voltage is lower than the threshold
voltage (8V), electron-emission does not occur, but electron-beams are outputted if
the voltage is equal to the threshold voltage (8V) or higher.
[0150] The functions of the respective components in Fig. 15 are as described above. Next,
the operation of the display panel 1701 will be described in detail with reference
to Figs. 16 to 18, prior to description of the entire operation.
[0151] For the convenience of illustration, the number of pixels of the display panel is
36 (6 × 6 (m = n = 6)), however, the number of pixels in practical use of the display
panel 1701 may be greater.
[0152] Fig. 16 shows an electron source having a 6 × 6 matrix-wired electron-emitting devices.
In this example, the respective devices are identified by (X,Y) coordinates such as
D(1,1), D(1,2) and D(6,6).
[0153] Upon displaying an image by driving the electron source, the display image is formed
by line-sequential manner, i.e., the image is displayed by one line parallel to the
axis X in Fig. 16 at a time. To drive the six electron-emitting devices corresponding
to one line of the image, output of 0(V) is applied to one of terminals Dx1 to Dx6
of the line of the electron-emitting devices corresponding to the display image line,
while outputs of 7(V) are applied to the other terminals. In synchronization with
this operation, modulating signals are applied to the respective terminals Dy1 to
Dy6 in accordance with an image pattern of the display image line.
[0154] Next, an example where an image pattern as shown in Fig. 17 is displayed will be
described.
[0155] Fig. 18 shows voltage application to the electron-emitting devices when image display
based on the third line of the image pattern in Fig. 17 is displayed. Fig. 18 also
shows application voltage values during light emission corresponding to the third
line. The electron-emitting devices D(2,3), D(3,3) and D(4,3) receive voltage of 14V
higher than the threshold voltage value 8V (represented as solid-black devices in
Fig. 18), and outputs electron beams. On the other hand, the other electron-emitting
devices than the above devices D(2,3), D(3,3) and D(4,3) receive voltage of 7V (represented
as hatched devices) or 0V (represented blank devices). As the application voltage
values are lower than the threshold value 8V, these electron-emitting devices do not
output electron beams.
[0156] The other lines of the electron-emitting devices are driven in accordance with the
image pattern in Fig. 17 in the same manner. Thus, sequentially driving the lines
of the election-emitting devices sequentially from the first line attains display
of one image, and repeating this line-sequentially display operation at 60 images
per second enables image display without flicker.
[0157] Note that regarding half-tone image display, although detailed explanation is omitted
here, a half-tone image can be displayed by, e.g., varying pulse-width of voltages
to be applied to the electron-emitting devices.
[0158] Fig. 19 shows an example of a multifunction image display device which can display
image information supplied from various image-information sources such as TV broadcasting,
on a display panel using the electron source having the above-described surface-conduction
emission type electron-emitting devices.
[0159] In Fig. 19, numeral 500 denotes a display panel; 501, a driver for the display panel
500; 502, a display controller; 503, a multiplexor; 504, a decoder; 505, an input-output
interface circuit; 506, a CPU; 507, an image generator; 508 to 510, image-memory interface
circuits; 511, image-input interface circuit; 512 and 513, TV signal receivers; and
514, an input unit.
[0160] Note that in case of reception of image signals including both video information
and audio information such as TV signals, the display apparatus reproduces sound while
displaying video images. In this example, the explanation of circuits and speaker(s)
for the reception, separation, reproduction, processing, storing etc. of audio information
will be omitted.
[0161] Hereinbelow, the functions of the respective components will be described along with
the flow of image signal.
[0162] The TV signal receiver 513 receives TV image signals transmitted via a wireless transmission
system such as electric wave transmission or space optical transmission. The standards
of TV signal to be received are not limited to the NTSC standards. The TV signals
are transmitted in accordance with, e.g., NTSC standards, PAL standards, or SECAM
standards. Further, a TV signal having scanning lines more than those in the above
television standards (e.g., so-called high-quality TV such as MUSE standards) is a
preferable signal source for utilizing the advantageous feature of the display panel
applicable to a large display screen and numerous pixels. The TV signal received by
the TV signal receiver 513 is outputted to the decoder 504.
[0163] The TV signal receiver 512 receives the TV signal transmitted via a cable transmission
system such as a coaxial cable system or a optical fiber system. Similar to the TV
signal receiver 513, the standards of the TV signal to be received are not limited
to the NTSC standards. Also, the TV signal received by the TV signal receiver 512
is outputted to the decoder 504.
[0164] Further, the image input I/F circuit 511 receives image signals supplied from image
input devices such as a TV camera or an image reading scanner. Also, the read image
signal is outputted to the decoder 504.
[0165] The image memory I/F circuit 510 inputs image signals stored in a video tape recorder
(VTR). Also, the input image signals are outputted to the decoder 504.
[0166] The image memory I/F circuit 509 inputs image signals stored in a video disk. Also,
the input image signals are outputted to the decoder 504.
[0167] The image memory I/F circuit 508 inputs image signals from a device holding still-picture
image data (e.g., so-called still-picture disk). Also, the input still-picture image
data are outputted to the decoder 504.
[0168] The input-output I/F circuit 505 connects the display apparatus to an external computer,
a computer network or an output device such as a printer. The input-output I/F circuit
505 operates for input/output of image data, character information and figure information,
and for input/output of control signals and numerical data between the CPU 506 and
an external device.
[0169] The image generator 507 generates display image data based on image data, character
information and figure information inputted from an external device via the input-output
I/F circuit 505 or image data, character information or figure information outputted
from the CPU 506. The image generator 507 has circuits necessary for image generation
such as a rewritable memory for storing image data, character information and figure
information, a ROM in which image patterns corresponding to character codes are stored
and a processor for image processing.
[0170] The display image data generated by the image generator 507 is outputted to the decoder
504, however, it may be outputted to the external computer network or the printer
via the input-output I/F circuit 505.
[0171] The CPU 506 controls the operation of the display apparatus and operations concerning
generation, selection and editing of display images.
[0172] For example, the CPU 506 outputs control signals to the multiplexor 503 to appropriately
select or combining image signals for display on the display panel. At this time,
it generates control signals to the display panel controller 502 to appropriately
control a display frequency, a scanning method (e.g., interlaced scanning or non-interlaced
scanning) and the number of scanning lines in one screen.
[0173] Further, the CPU 506 directly outputs image data, character information and figure
information to the image generator 507, or it accesses the external computer or memory
via the input-output I/F circuit 505, to input image data, character information and
figure information.
[0174] Note that the CPU 506 may operate for other purposes; e.g., like a personal computer
or a word processor, it may directly generate and process information.
[0175] Otherwise, the CPU 506 may be connected to the external computer network via the
input-output I/F circuit 505, to cooperate with an external device in, e.g., numerical
calculation.
[0176] The input unit 514 is used for a user to input instructions, programs and data into
the CPU 506. The input unit 514 can comprise various input devices such as a joy stick,
a bar-code reader or a speech recognition device as well as a keyboard and a mouse.
[0177] The decoder 504 converts various image signals, inputted from the image generator
507, the TV signal receiver 513 and the like, into three-primary-color signals, or
luminance signals and I and Q signals. As indicated with a dotted line in Fig. 26,
the decoder 504 preferably comprises an image memory, since reverse-conversion of
TV signals based on standards of numerous scanning lines, such as MUSE standards,
requires an image memory. Further, the image memory enables the decoder 504 to easily
perform image processing such as thinning, interpolation, enlargement, reduction and
synthesizing, and editing, in cooperation with the image generator 507 and the CPU
506.
[0178] The multiplexor 503 appropriately selects a display image used on a control signal
inputted from the CPU 506. That is, the multiplexor 503 selects a desired image signal
from reverse-converted image signals inputted from the decoder 504, and outputs the
selected image signal to the driver 501. In this case, the multiplexor 503 can realize
so-called multiwindow television, where the screen is divided into plural areas and
plural images are displayed at the respective image areas, by selectively switching
image signals within display period for one image frame.
[0179] The display panel controller 502 controls the driver 501 based on control signals
inputted from the CPU 506.
[0180] Concerning the basic operations of the display panel, the display panel controller
502 outputs a signal to control the operation sequence of the power (not shown) for
driving the display panel to the driver 501.
[0181] Further, concerning the driving of the display panel, the display panel controller
502 outputs signals to control a display frequency and a scanning method (e.g., interlaced
scanning or non-interlaced scanning) to the driver 501.
[0182] In some cases, the display panel controller 501 outputs control signals concerning
image-quality adjustment such as luminance, contrast, tonality and sharpness to the
driver 501.
[0183] The driver 501 generates drive signals applied to the display panel 500. The driver
501 operates based on image signals inputted from the multiplexor 503 and control
signals inputted from the display panel controller 502.
[0184] The functions of the respective components are as described above. The construction
shown in Fig. 26 can display image information inputted from various image information
sources on the display panel 500.
[0185] That is, various image signals such as TV signals are reverse-converted by the decoder
504, and appropriately selected by the multiplexor 503, then inputted into the driver
501. On the other hand, the display panel controller 502 generates control signals
to control the operation of the driver 501 in accordance with the display image signals.
The driver 501 applies drive signals to the display panel 500 based on the image signals
and the control signals.
[0186] Thus, images are displayed on the display panel 500. The series of these operations
are made under control of the CPU 506.
[0187] As the present display apparatus uses the image memory included in the decoder 504,
the image generator 507 and the CPU 506, it can not only display images selected from
plural image informations, but also perform image processing such as enlargement,
reduction, rotation, movement, edge emphasis, thinning, interpolation, color conversion,
resolution conversion, and image editing such as synthesizing, deletion, combining,
replacement, insertion, on display image information. Although not especially described
in the above embodiments, similar to the image processing and image editing, circuits
for processing and editing audio information may be provided.
[0188] The present display apparatus can realize functions of various devices, e.g., a TV
broadcasting display device, a teleconference terminal device, an image editing device
for still-pictures and moving pictures, an office-work terminal device such as a computer
terminal or a word processor, a game machine etc. Accordingly, the present display
apparatus has a wide application range for industrial and private use.
[0189] Note that Fig. 26 merely shows one example of the construction of the display apparatus
using the display panel having an electron beam source comprising the surface-conduction
emission type electron-emitting devices of the present invention, but this does not
pose any limitation on the present invention. For example, in Fig. 26, circuits unnecessary
for some use may be omitted. Contrary, components may be added for some purpose. For
example, if the present display apparatus is used as a visual telephone, preferably,
a TV camera, a microphone, an illumination device, a transceiver including a modem
may be added.
[0190] In the present display apparatus, as the display panel having the electron beam comprising
the surface-conduction emission type electron-emitting devices can be thin, the depth
of the overall display apparatus can be reduced. In addition, as the display panel
can be easily enlarged, further it has high luminance and wide view angle, the present
display apparatus can display vivid images with realism and impressiveness.
[0191] Note that the construction as described in Fig. 19 can be applied to the following
second to eighth embodiments.
〈Second Embodiment〉
[0192] Fig. 14 is a perspective view showing the arrangement of spacers according to the
second embodiment, in which the form of the conductive member on the row-direction
wiring electrodes 12 on the insulating substrate 11 is different from that of the
first embodiment. In this embodiment, the row-direction wiring electrodes 12 have
a width of 400 µm and a thickness of 40 µm.
[0193] The second embodiment also realizes colour-image display without disturbance of electron
trajectories and with excellent colour reproducibility.
[0194] In the present embodiment, upon forming the conductive connection member 58, regarding
the row-direction wiring electrode 12 where the spacer 5 is provided, the conductive
connection member 58 is formed between the spacer 5 and the electrode 12; and regarding
the row-direction wiring electrode 12 where the spacer 5 is not provided, the conductive
member 70 having the same shape of the conductive connection member 58 is formed on
the electrode 12.
[0195] This reduces the amount of conductive connection material to be applied between the
row-direction wiring electrode 12 and the spacer 5, thus enables mass production.
〈Third Embodiment〉
[0196] The present invention can be applied to any of cold cathode electron-emitting devices
other than surface-conduction emission type electron-emitting devices. For example,
an electron-emitting device having a pair of electrodes opposing to each other, as
disclosed in Japanese Patent Application Laid-Open No. 63-274047 by the present applicant,
is known.
[0197] Fig. 25 is a plan view showing the structure of the electron-emitting device in an
FE type electron source. In Fig. 25, numeral 3101 denotes an electron-emitting portion;
3102 and 3103, device electrodes; 3104 and 3105, row-direction wiring electrodes;
3106, column-direction wiring electrodes; 3107, a conductive member; 3108, a conductive
connection member; and 3109, a spacer. The conductive spacer 3109 is provided on the
row-direction wiring electrode 3104 with the conductive connection member 3108. The
conductive member 3107 is provided to avoid asymmetry between an electric potential
in a direction (column direction) vertical to a voltage-application direction and
an electric potential including the electron-emitting portion 3101, vertical to the
substrate and parallel to the row-direction wiring electrode 3104, due to the conductive
connection member 3108.
[0198] Note that the width (w
1) of the conductive connection member 3108 and the width (w
2) of the conductive member 3107 are the same. Similar to the previous embodiments,
the heights of these members are set to
(not shown in Fig. 25). In Fig. 25, numeral P
1 denotes a direction in which the current flows; and P
2, a direction in which the spacer 3109 extends. The directions P
1 and P
2 are parallel to each other.
[0199] Further, the present invention can be applied to an electron source having any of
other arrangements of electron-emitting devices than the simple matrix arrangement.
For example, in an image forming apparatus as disclosed in Japanese Patent Application
Laid-Open No. 2-257551 by the present applicant, control electrodes may be employed
for selecting surface-conduction emission type electron-emitting devices.
[0200] Further, the above-described image forming apparatus is not limited to a display
device, but it can be used in an optical printer, usually comprising an electrostatic
drum, an LED and the like, as a line light-emitting source substituting for the LED.
In this case, by selecting the m row-direction wiring electrodes and n column-direction
wiring electrodes appropriately, the apparatus can be used as a two-dimensional light-emitting
source as well as the line light-emitting source.
[0201] Furthermore, the present image forming apparatus can be applied to a device such
as an electron microscope where an object that receives electron beams emitted from
an electron source is foreign material. Accordingly, the present invention can be
applied to an electron-beam generating apparatus which does not include an electron-receiving
member.
[0202] In the image display apparatus according to the above embodiment, the spacer (3109)
having a semiconductive film on its surface is provided on one of wiring electrodes
(3105), and to make electrical connection between the semiconductive film and the
wiring electrode and to hold the spacer, conductive connection member (3108) is provided
on the wiring electrode between the spacer and the wiring electrode. In another one
of the row-direction wiring electrodes (3104) where the spacer is not provided, to
obtain the same height as that of the row-direction wiring electrode (3105) with the
spacer, the conductive member (3107) having the same shape of the conductive connection
member (3108) is provided. This prevents the shift of electron-beam irradiated position
of a fluorescent member, to an adjacent image position, and prevents luminance degradation,
thus enables display of vivid images.
[0203] Further, in an electron generating apparatus having a plane multi-device electron
source, similar advantages can be obtained.
〈Fourth Embodiment〉
[0204] Next, a fourth embodiment of the present invention will be described with reference
to Fig. 26. In the manufacturing process according to this embodiment, the above-described
printing step is divided into several steps to form a concave portion on the wiring
electrodes for formation of conductive connection members.
Step e: Ag electrodes as the row-direction wiring electrodes 12 are formed by screen-printing,
on the device electrodes 16 and 17. The screen-printing is performed twice, i.e.,
printing operations (a) and (b), using different screen masks at respective printing
operations. The formed wiring-electrodes 12 have a concave portion 57 for application
of the conductive connection member 58 having a thickness of 20 µm.
[0205] The step e having the two printing operations will be described in detail with reference
to Fig. 30. In Fig. 30, reference numeral 100 denotes electron-emitting portions;
11, the insulating substrate; 121 to 122, row-direction wiring electrodes; and 57,
a concave portion for forming the conductive connection member 58.
Printing operation (a): On the insulating substrate 11, silver paste is applied to
the row-direction wiring electrodes 121. In Fig. 30A, the concave portion is provided
on the left electrode 121, but it is not provided on the right electrode 121. First,
the silver paste is applied to the left row-direction wiring electrode 121 such that
the concave portion 57 for the conductive connection member 58 is formed. In this
state, the portion where the silver paste has been applied is sintered at 150 °C for
30 minutes. Next, the silver paste is also applied to the right row-direction wiring
electrode 121 where the spacer is not held.
Printing operation (b): The silver-paste applied portions 122 are sintered at 580
°C for 15 minutes.
[0206] In this embodiment, the width of the row-direction wiring electrodes is 300 µm; the
thickness of the row-direction wiring electrodes, 20 µm; and the thickness of the
portions 122, 20 µm, such that the height (h
1) of the row-direction wiring electrode 121 where the spacer is provided and the height
(h
2) of the row-direction wiring electrode 121 where the spacer is not provided are the
same.
[0207] Next, the connection of the row-direction wiring electrode 12, having the concave
portion 57, as the feature of this embodiment, to the spacer 5 will be described in
detail with reference to Fig. 26.
[0208] In Fig. 26, the spacer 5 is provided at the concave portion 57 made at a part of
the row-direction wiring electrode 12 via the conductive connection member 58. The
measurements are set such that the height of the upper surface of the conductive connection
member 58 (h
1 in Fig. 26) and that of the upper surface of the row-direction wiring electrode 12
without the spacer 5 (h
2 in Fig. 26) are the same. This renders the electric-potential distribution on the
spacer surface and that in the space above the row-direction wiring electrode 12 without
the spacer 5 equal to each other. That is, even if the spacer 5 is provided via the
conductive connection member 58 on a row-direction wiring electrode 12, the electro-optical
characteristic at the row-direction wiring electrode can be the same as that at the
row-direction wiring electrode 12 without the spacer 5. Accordingly, since electron
beams emitted by any of the electron-emitting portions 23 traverse similar trajectories,
the conventional problems such as the shift of light-emitting points, the luminance
degradation and the change of color around the spacer can be prevented. In this embodiment,
to optimize this feature, the condition of the widths of the row-direction wiring
electrodes,
(w
1: width of the conductive connection member 58, w
3: width of row-direction wiring electrode 12), is added to the condition
.
[0209] Next, the manufacturing will be described in detail.
[0210] In the present embodiment, the conductive connection member 58, which holds the spacer
5 and makes electrical connection with the spacer 5, is formed by dispersing Au-plated
soda-lime glass balls, as filler, in the frit-glass paste, and applying and sintering
the paste. In this example, the soda lime balls have an average diameter of 8 µm.
As the conductive layer of the filler surface, a Ni film with a thickness of 0.1 µm,
as a base, and an Au film with a thickness of 0.04 µm, on the base, are sequentially
formed by electroless plating. The paste to be applied is formed by mixing the conductive
filler at 30 wt% with respect to the frit-glass paste, and further adding a binder
to the mixture.
[0211] Next, the conductive frit-glass paste is applied by a dispenser, to the concave portion
57 of the row-direction wiring electrode 12 on the electron source 1 side, while to
the end of the spacer 5 on the face plate 3 side. Then, the spacer 5 is aligned with
the concave portion 57 on the electron source 1 side, while with the black conductive
material 7b (with a width of 300 µm) on the face plate 3 side, and connected portions
are sintered in the atmosphere at 400 °C to 500 °C for 10 minutes or longer. This
fix-connects the electron 1, the black conductive material 7b and the spacer 5b, and
obtains electrical connection of the members. In this embodiment, on the electron
source 1 side, the difference between the upper surface of the conductive connection
member 58 and that of the row-direction wiring electrode 12 where the spacer 5 is
not provided is within 5 µm.
[0212] In the present embodiment, the material of the conductive connection members 58 and
that of the row-direction wiring electrodes 12 are selected such that the conductivity
of the conductive connection members 58 and that of the row-direction wiring electrodes
12 are substantially equal to each other. This equalizes the electric characteristics
of the row-direction wiring electrode 12 having the concave portion 57 and the row-direction
wiring electrode 12 without the concave portion 57.
[0213] At the same time, the conductivity of the semiconductive film on the spacer surface
is set such that the electric resistance in the heighthwise direction of the spacer
5 (resistance between the row-direction wiring electrode and the accelerating electrode)
is 10,000 times larger than that of the row-direction wiring electrode or the conductive
connection member 58. This setting of the resistance on the spacer 5 surface can reduce
voltage degradation which occurs at the conductive connection members 58 and the row-direction
wiring electrodes 12 due to current from the spacers 5. In other words, the accelerating
voltage can be completely applied between the accelerating electrode and the conductive
connection members (i.e., the both ends of the spacers 5).
[0214] These two operations equalize the electric-potential distribution on the spacer surface
and that in the space above the row-direction wiring electrode without the spacer.
That is, even if the spacer 5 is provided via the conductive connection member 58
on the row-direction wiring electrode 12, the electro-optical characteristic at the
row-direction wiring electrode can be the same as that at the row-direction wiring
electrode without the spacer 5. Accordingly, since electron beams emitted by any of
the electron-emitting portions 23 traverse similar trajectories, the conventional
problems such as the shift of light-emitting points, the luminance degradation and
the change of color around the spacer can be prevented.
[0215] Note that in the present embodiment, the spacer 5, the electron source 1 and the
face plate 3 are connected simultaneously, however, the connection may be made separately.
Further, to avoid deformation of the paste as the material of the conductive connection
member 58 by a considerably-great amount upon formation of the connection member 58,
temporary sintering may be performed before connecting the conductive connection member
58 with the spacer 5, at a temperature lower than a temperature of sintering after
the connection.
[0216] At this time, a two-dimensional array of light spots at equal intervals is formed,
including emitted-light spots of electrons from the electron-emitting devices 15 near
the spacers 5, which attains vivid colour image display with excellent colour reproducibility.
This indicates that the spacers 5 do not cause the disturbance of electric field that
may influence the electron trajectories.
[0217] In the present embodiment, the concave portions are formed at the row-direction wiring
electrodes, however, in accordance of necessity, the concave portions may also be
formed at the other electrodes provided on the electron source, e.g., a wiring pulled-out
portion if such portion is provided around the electron source, a support frame connection
electrode if a semiconductive film is provided at the support frame 4 for electrical
connection, and control electrodes if provided for control-voltage application. The
concave portions can be formed at any of these electrodes for forming the holding
members without disturbing the electron trajectories around the concave portions.
[0218] Fig. 31 shows another example of the present embodiment, where the concave portion
is formed with respect to the entire wiring electrode. In Fig. 31, numeral 12 denotes
the row-direction wiring electrode; 58, the conductive connection member; 5, spacer;
and 15, electron-emitting devices.
[0219] In this example, on the assumption that the height of the conductive connection member
58 is h
1 and that of the row-direction wiring electrode 12 without the spacer is h
2, the condition of the heights is set to
. Further, on the assumption that the width of the conductive connection member 58
is w
1 and that of the row-direction wiring electrode 12 without the spacer is w
2, the condition of the widths is set to
. Finally, on the assumption that the direction in which current flows at the electron-emitting
device is P1 and the direction in which the spacer 5 extends (i.e., the lengthwise
direction of the row-direction wiring electrode 12) is P2, the directions are set
to be parallel to each other.
[0220] In this example, the printing step for formation of conductive connection members
58 is divided into three printing operations. The height of the row-direction wiring
electrode where the spacer 5 is not provided is 30 µm; and that of the row-direction
wiring electrode where the spacer 5 is provided, 10 µm. The image forming apparatus
is manufactured in accordance with the steps a to h except the Step e, and as a result,
advantages the same as those in the former example can be obtained.
〈Fifth Embodiment〉
[0221] Next, a modification to the part of the fourth embodiment will be described as a
fifth embodiment.
[0222] Fig. 27 is a partial plan view showing the row-direction wiring electrode 12 where
the spacer is provided. The feature of this embodiment is that the width (W
4) of the concave portion 57 is narrower than the width W
1 of the row-direction wiring electrode 12. In Fig. 27, numeral 12 denotes the row-direction
wiring electrode; 57, the concave portion; and numeral 140 denotes an insulating substrate
on which the row-direction wiring electrodes 12 are formed. In the fifth embodiment,
the width of the row-direction wiring electrode 12 is 400 µm; the width of the concave
portion 57, 300 µm; the thickness of the row-direction wiring electrode 12, 60 µm;
and that of the row-direction wiring electrode 12 at the concave portion 57, 10 µm.
[0223] Also in this embodiment, vivid color image display with excellent colour reproducibility
can be obtained.
[0224] In the fifth embodiment, as the side wall of the row-direction wiring electrode 12
surrounds the concave portion 57, upon forming the conductive connection member 58,
the extrusion of the conductive connection member 58 can be prevented. In addition,
as the spacer 5 is plugged into the row-direction wiring electrode 12, the mechanical
strength at the connection portion is increased. This can provide atmospheric-pressure-proof
structure with a small number of spacers.
〈Sixth Embodiment〉
[0225] Fig. 28 shows the sixth embodiment of the present invention. In Fig. 28, numeral
150 denotes an insulating substrate; 151, a concave portion; 12, the row-direction
wiring electrode; 58, the conductive connection member; 5, the spacer.
[0226] The sixth embodiment differs from the fourth and fifth embodiments in that the concave
portion 151 is formed on the insulating substrate 150.
[0227] The concave portion 151 is formed by removing a portion of the insulating substrate
150 using a dicing saw. In this embodiment, the width of the concave portion 151 is
80 µm, and the depth is also 80 µm. Next, a pattern of the row-direction wiring electrodes
is formed with silver paste by screen-printing. Further, the patterned silver paste
is sintered at 58.0 °C for 15 minutes, thus the row-direction wiring electrodes 12
are formed on the insulating substrate 150. Next, the conductive connection members
58 and the spacers 5 in a similar manner to that of the fourth embodiment.
[0228] Also in the sixth embodiment, upon driving the image forming apparatus, a two-dimensional
emission-light spot array at equal intervals is formed, which attains vivid color
image display with excellent colour reproducibility. Further, any disturbance of electric
field that may influence the electron trajectories is not found.
[0229] Note that in the present embodiment, the row-direction wiring electrode where the
concave portion 151 is not provided is formed on the insulating substrate 150, however,
the insulating substrate 150 may have a groove for providing the entire row-direction
wiring electrode. Further, the conductive connection member 58 may be formed by, first
forming the concave portion 151 in the conductive substrate 150 with an even depth,
then forming the row-direction wiring electrode 12 there, removing a part of the row-direction
wiring electrode 12.
〈Seventh Embodiment〉
[0230] This embodiment shows an example using flat FE type electron-emitting devices in
the fourth embodiment.
[0231] Fig. 29 is a plan view showing a flat FE type electron-emitting source. In Fig. 29,
numeral 3101 denotes an electron-emitting portion; 3102 and 3103, a pair of device
electrodes for supplying a predetermined electric potential to the electron-emitting
portion 3101; 3014 and 3015, row-direction wiring electrodes; 3106, a column-direction
wiring electrode; and 3109, a spacer.
[0232] In this construction, the electron-emitting portion 3101 emits electrons from its
sharp distal end when a predetermined voltage is applied between the device electrodes
3102 and 3103. The emitted electrons are attracted to an accelerating voltage (not
shown), provided opposing to the electron source, and collide against the fluorescent
member (not shown), thus excite the fluorescent member to emit light. In this embodiment,
column-direction wiring electrodes 3106 are formed by forming a groove in the substrate
(both not shown), applying silver paste to the groove using a fradecoater, and sintering
the silver paste. Next, an insulating layer (not shown) is formed on the entire substrate,
then the device electrodes 3102 and 3103 and the electron-emitting portion 3101, and
a concave portion (not shown) is formed at the row-direction wiring electrodes 3104,
3105 by screen-printing similar to that used in the fourth embodiment. Thereafter,
the image forming apparatus is manufactured in accordance with manufacturing process
similar to that of the fourth embodiment. In the seventh embodiment, the printing
step is also divided into three printing operations such that the thickness of the
column-direction wiring electrodes is 50 µm; that of the row-direction wiring electrodes,
60 µm including the depth of the concave portion, 20 µm. Similar to the fourth embodiment,
when the image forming apparatus is driven, a two-dimensional array of emitted-light
spots at equal intervals is formed. Thus, this embodiment also provides an image forming
apparatus that emits light at high efficiency without shift of electron beams to an
adjacent pixel position.
[0233] The present invention is also applicable to other types of cold cathode electron-emitting
device.
[0234] For example, the present applicant has disclosed in Japanese Patent Application Laid-Open
No. 63-274047, electron-emitting devices, each having a pair of electrodes opposing
to each other, are arranged on a substrate.
[0235] Further, the present invention is also applicable to any image forming apparatuses
which use electron sources other than the electron source with a simple-matrix arrangement
of electron-emitting devices. For example, in an image forming apparatus which selects
surface-conduction emission type electron-emitting devices by using control electrodes,
as disclosed in Japanese Patent Application Laid-Open No. 2-257551 by the present
applicant, the above-described support members may be employed.
[0236] Further, the above-described image forming apparatus is not limited to a display
device, but it can be used in an optical printer, usually comprising an electrostatic
drum, an LED and the like, as a line light-emitting source substituting for the LED.
In this case, by selecting the m row-direction wiring electrodes and n column-direction
wiring electrodes appropriately, the apparatus can be used as a two-dimensional light-emitting
source as well as the line light-emitting source.
[0237] Furthermore, the present image forming apparatus can be applied to a device such
as an electron microscope where an object that receives electron beams emitted from
an electron source is foreign material. Accordingly, the present invention can be
applied to an electron-beam generating apparatus which does not include an electron-receiving
member.
[0238] As described above, in the electron-beam generating apparatus and image forming apparatus
of the present invention, support members (spacers) each having a semiconductive film
on its surface are provided on some row-direction wiring electrodes, and conductive
connection members are arranged for holding the support members and for electrical
connection between the semiconductive film of the support members and the wiring electrodes.
The existence of the support members does not cause disturbance of the trajectories
of electrons emitted from electron-emitting devices of the electron source, since
the conductive connection members are arranged such that the height of the row-direction
wiring electrodes on which the support members are provided is the same as that of
the row-direction wiring electrodes on which no support member is provided. This prevents
shift of electron-collision position on a fluorescent member from a position to emit
light, to an adjacent pixel position, and prevents luminance degradation, and thus
enables vivid image display.
[0239] The present invention can be applied to a system constituted by a plurality of devices
or to an apparatus comprising a single device.
[0240] A summary of the disclosure herein is given in the following paragraphs:
1. An electron-beam generating apparatus characterized by comprising:
a plurality of electron-emitting devices (15);
a plurality of row-direction wiring electrodes (12) of conductive material, for applying
a predetermined voltage to said electron-emitting devices;
an accelerating electrode (8) opposite to the electron-emitting devices; and
a semiconductive support member (5) provided between part of said row-direction wiring
electrodes and said accelerating electrode,
wherein said semiconductive support member is provided on said the row-direction wiring
electrode via a conductive connection member, and
wherein a height (h2) of the upper surface of said conductive connection member on
said row-direction wiring electrode and a height (h1) of the upper surface of conductive
material of said row-direction wiring electrode where said semiconductive support
member is not provided are substantially the same.
2. The electron-beam generating apparatus according to paragraph 1, wherein said row-direction
wiring electrode where said semiconductive support member is provided has a concave
portion, and wherein said conductive connection member is arranged in the concave
portion, further wherein the height of the upper surface of said conductive connection
member on said row-direction wiring electrode and the height of said row-direction
wiring electrode where said semiconductive support member is not provided are substantially
the same.
3. The electron-beam generating apparatus according to paragraph 1, wherein said row-direction
wiring electrode where said semiconductive support member is not provided has a conductive
member, and wherein a height of the upper surface of said conductive member and the
height of the upper surface of said conductive connection member are substantially
the same.
4. The electron-beam generating apparatus according to paragraph 1, wherein a thickness
of said row-direction wiring electrode where said semiconductive support member is
provided and a thickness of said row-direction wiring electrode where said semiconductive
support member is not provided are different, and wherein a height of the upper surface
of said conductive connection member on said row-direction wiring electrode and a
height of said row-direction wiring electrode where said semiconductive support member
is not provided are substantially the same.
5. The electron-beam generating apparatus according to paragraph 2, wherein said electron-emitting
devices are provided on a substrate which has concave portions, and wherein said row-direction
wiring electrodes are provided at said concave portions.
6. The electron-beam generating apparatus according to any of paragraphs 1 to 5, wherein
said row-direction wiring electrodes receive a scanning signal for scanning said electron-emitting
devices.
7. The electron-beam generating apparatus according to any of paragraphs 1 to 6, wherein
a surface resistance of said semiconductive support members is 104 [Ω/□] or greater.
8. The electron-beam generating apparatus according to any of paragraphs 1 to 7, wherein
said electron-emitting devices has a positive electrode, an electron-emitting portion
and a negative electrode, all provided in parallel to each other, on a substrate.
9. The electron-beam generating apparatus according to paragraph 8, wherein said semiconductive
support members comprise a plate member, and a lengthwise direction of the plate member
and a direction of current which flows between the positive and negative electrodes
of said electron-emitting devices are parallel to each other.
10. The electron-beam generating apparatus according to any of paragraphs 1 to 9,
wherein said semiconductive support members comprise insulating material covered with
semiconductive material.
11. The electron-beam generating apparatus according to any of paragraphs 1 to 10,
wherein said electron-emitting devices are connected with the plurality of row-direction
wiring electrodes and a plurality of column-direction wiring electrodes, both of which
are electrically insulated, on a substrate.
12. The electron-beam generating apparatus according to any of paragraphs 1 to 11,
wherein said electron-emitting devices are surface-conduction emission type electron-emitting
devices.
13. The electron-beam generating apparatus according to any of claims 1 to 11, wherein
said electron-emitting devices are lateral field-emission type electron-emitting devices.
14. The electron-beam generating apparatus according to any of paragraphs 1 to 13,
further comprising an image forming member opposite to said electron-emitting devices.
15. An electron-beam generating apparatus characterized by comprising:
a plurality of electron-emitting devices (15);
a plurality of row-direction wiring electrodes (12) of conductive material, for applying
a predetermined voltage to said electron-emitting devices; an accelerating electrode
(8) opposite to the
electron-emitting devices; and
a semiconductive support members (5) provided between part of said row-direction wiring
electrodes and said accelerating electrode,
wherein said semiconductive support member is provided on said the row-direction wiring
electrode via a conductive connection member, and
wherein if predetermined electric potentials of the same level are applied to said
row-direction wiring electrode where said semiconductive support member is provided
and said row-direction wiring electrode where said semiconductive support member is
not provided, a thickness of conductive connection member is controlled such that
electric-potential distribution on a surface of said semiconductive support member
and that in space between said row-direction wiring electrode where said semiconductive
support member is not provided and said accelerating electrode become the same.
16. The electron-beam generating apparatus according to paragraph 15, wherein said
row-direction wiring electrodes receive a scanning signal for scanning said electron-emitting
devices.
17. The electron-beam generating apparatus according to paragraph 15 to 16, wherein
a surface resistance of said semiconductive support member 104 [Ω/□] or greater.
18. The electron-beam generating apparatus according to any of paragraphs 15 to 17,
wherein said electron-emitting devices has a positive electrode, an electron-emitting
portion and a negative electrode, all provided in parallel to each other, on a substrate.
19. The electron-beam generating apparatus according to any of paragraphs 15 to 18,
wherein said semiconductive support members comprise a plate member, and a lengthwise
direction of the plate member and a direction of current which flows between the positive
and negative electrodes of said electron-emitting devices are parallel to each other.
20. The electron-beam generating apparatus according to any of paragraphs 15 to 19,
wherein said semiconductive support members comprise insulating material covered with
semiconductive material.
21. The electron-beam generating apparatus according to any of paragraphs 15 to 20,
wherein said electron-emitting devices are connected with the plurality of row-direction
wiring electrodes and a plurality of column-direction wiring electrodes, both of which
are electrically insulated, on a substrate.
22. The electron-beam generating apparatus according to any of paragraphs 15 to 21,
wherein said electron-emitting devices are surface-conduction emission type electron-emitting
devices.
23. The electron-beam generating apparatus according to any of paragraphs 15 to 21,
wherein said electron-emitting devices are lateral field-emission type electron-emitting
devices.
24. The electron-beam generating apparatus according to any of paragraphs 15 to 23,
further comprising an image forming member opposite to said electron-emitting devices.
25. An image forming apparatus comprising:
an electron-beam generating apparatus (1) according to any preceding paragraph; and
a fluorescent member (7) arranged to receive electrons generated and accelerated by
said electron-beam generating apparatus (1) and to emit light in response thereto.
26. The image forming apparatus of paragraph 25 including driver circuit means to
apply drive and acceleration voltages to said wiring electrodes (12) and acceleration
electrode (8) respectively.
[0241] The present invention is defined by the following claims.