Radiant energy – Corona irradiation – Charging of objects
Reexamination Certificate
1999-04-27
2001-10-30
Berman, Jack (Department: 2878)
Radiant energy
Corona irradiation
Charging of objects
C361S229000, C361S230000
Reexamination Certificate
active
06310344
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a wire-type corona charger for electrophotographically manufacturing a screen of a CRT, and more particularly to a wire-type corona charger and a method using the charger for electrophotographically manufacturing a screen of a CRT, in which the photoconductive layer can be uniformly charged by a wire electrode.
BACKGROUND OF THE INVENTION
Referring to
FIG. 1
, a color CRT
10
generally comprises an evacuated glass envelope consisting of a panel
12
, a funnel
13
sealed to the panel
12
and a tubular neck
14
connected by the funnel
13
, and electron gun
11
centrally mounted within the neck
14
, and a shadow mask
16
removably mounted to a sidewall of the panel
12
. A three-color phosphor screen is formed on the inner surface of a display window or faceplate
18
of the panel
12
.
The electron gun
11
generates three electron beams
19
a,
or
19
b,
said beams being directed along convergent paths through the shadow mask
16
to the screen
20
by means of several lenses of the gun and a high positive voltage applied through an anode button
15
and being deflected by a deflection yoke
17
so as to scan over the screen
20
through apertures or slits
16
a
formed in the shadow mask
16
.
In the color CRT
10
, the phosphor screen
20
, which is formed on the rear surface of the faceplate
18
, comprises an array of three phosphor elements R, G and B of three different emission colors arranged in a cyclic order of a predetermined structure of multiple-stripe or multiple-dot shape and a matrix of light absorptive material surrounding the phosphor elements R, G and B, as shown in FIG.
2
.
A thin film of aluminum
22
or an electro-conductive layer, overlying the screen
20
in order to provide a means for applying the uniform potential applied through the anode button
15
to the screen
20
, increases the brightness of the phosphor screen and prevents ions in the phosphor screen from being lost and the potential of the phosphor screen from decreasing. And also, a film of resin
22
′such as lacquer (not shown) may be applied between the aluminum thin film
22
and the phosphor screen
20
, so as to enhance the flatness and reflectivity of the aluminum thin film
22
.
In a photolithographic wet process, which is well known as a prior art process for forming the phosphor screen, a slurry of a photosensitive binder and phosphor particles is coated on the inner surface of the faceplate. It does not meet the higher resolution demands and requires a lot of complicated processing steps and a lot of manufacturing equipments, thereby requiring high cost in manufacturing the phosphor screen. In addition, it discharges a large quantity of effluent such as waste water, phosphor elements, 6th chrome sensitizer, etc., with the use of a large quantity of clean water.
To solve or alleviate the above problems, the improved process of electrophotographically manufacturing the screen utilizing dry-powdered phosphor particles is developed.
U.S. Pat. No. 4,921,767, issued to Datta at al. on May 1, 1990, discloses one method of electrophotographically manufacturing the phosphor screen assembly using dry-powdered phosphor particles through a series of steps represented in
FIGS. 3A
to
3
E, as is briefly explained in the following.
After the panel
12
is washed, an electro-conductive layer
32
is coated on the faceplate
18
of the panel
12
and the photoconductive layer
34
is coated thereon, as shown in FIG.
3
A. Conventionally, the electro-conductive layer
32
is made from an inorganic conductive material such as tin oxide or indium oxide, or their mixture, and preferably, from a volatilizable organic conductive material such as a polyelectrolyte commercially known as polybrene (1,5,-dimethyl-1,5-diaza-undecamethylene polymethobromide, hexadimethrine bromide), available from Aldrich Chemical Wisc., or another quaternary ammonium salt.
The polybrene is applied to the inner surface of the faceplate
18
in an aqueous solution containing about 10 percent by weight of propanol and bout 10 percent by weight of a water-soluble adhesion-promoting polymer (poly vinyl alcohol, polyacrylic acid, polyamides and the like), and the coated solution is dried to form the conductive layer
32
having a thickness from about 1 to 2 microns and a surface resistivity of less than about 10
8
l (ohms per square unit).
The photoconductive layer
34
is formed by coating the conductive layer
32
with a photoconductive solution comprising a volatilizable organic polymeric material, a suitable photoconductive dye and a solvent. The polymeric material is an organic polymer such as polyvinyl carboazole, or an organic monomer such as n-ehtyl carbazole, n-vinyl carbazole or tetraphenylbutatriene dissolved in a polymeric binder such as polymethylpolypropylene carbonate. The photoconductive composition contains from about 0.1 to 0.4 percent by weight such dyes as crystal violet, chloridine blue, rhodamine EG and the like, which are sensitive to the visible rays, preferably rays having wavelength of from about 400 to 700 nm. The solvent for the photoconductive composition is an organic such as chlorobenzene or cyclopentanone and the like which will produce as little cross contamination as possible between the layers
32
and
34
. The photoconductive layer
32
is formed to have a thickness from about 2 to 6 microns.
FIG. 3B
schematically illustrates a charging step, wherein the photoconductive layer
34
overlying the electro-conductive layer
32
is positively charged in a dark environment by a conventional positive corona discharger
36
. As shown, the charger or charging electrode of the discharger
36
is positively applied with direct current while the negative electrode of the discharger
36
is connected to the electro-conductive layer
32
and grounded. The charging electrode of the discharger
36
travels across the layer
34
and charges it with a positive voltage in the range from −200 to +700 volt.
FIG. 3C
schematically shows an exposure step, wherein the charged photoconductive layer
34
is exposed through a shadow mask
16
by a xenon flash lamp
35
having a lens system
35
′ in the dark environment. In this step, the shadow mask
16
is installed on the panel
12
and the electro-conductive layer
32
is grounded. When the xenon flash lamp
35
is switched on to shed light on the charged photoconductive layer
34
through the lens system′ and the shadow mask
16
, portions of the photoconductive layer
34
corresponding to apertures or slits
16
a
of the shadow mask
16
are exposed to the light. Then, the positive charges of the exposed areas are discharged through the grounded conductive layer
32
and the charges of the unexposed areas remain in the photoconductive layer
34
, thus establishing a latent charge image in a predetermined array structure, as shown in FIG.
3
C. In order to exactly form light-absorptive matrices, it is preferred that the xenon flash lamp
35
travels along three positions while coinciding with three different incident angles of the three electron beams.
FIG. 3D
schematically shows a developing step which utilized a developing container
35
″ containing dry-powdered light-absorptive or phosphor particles and carrier beads for producing static electricity by coming into contact with the dry-powdered particles. Preferably, the carrier beads are so mixed as to charge the light-absorptive particles with negative electric charges and the phosphor powders with positive electric charges, when they come into contact with the dry-powdered particles.
In this step, the panel
12
, from which the shadow mask
16
is removed, is put on the developing container
35
′ containing the dry-powdered particles, so that the photoconductive layer
34
can come into contact with the dry-powdered particles. In this case, the negatively charged light-absorptive particles are attached to the positively charged unexposed areas of the photoconductive layer
34
by electric attraction, w
Ahn Kwang Duk
Kang Cheon Su
Kwon Sang Bong
Lee Hyo Sup
Oh Myung Hwan
Berman Jack
Nataro & Michalos P.C.
Orion Electric Co. Ltd.
LandOfFree
Wire type corona charger for electrophotographical... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Wire type corona charger for electrophotographical..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Wire type corona charger for electrophotographical... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2592079