Active solid-state devices (e.g. – transistors – solid-state diode – Regenerative type switching device – With light activation
Reexamination Certificate
2000-07-26
2002-12-24
Chaudhuri, Olik (Department: 2813)
Active solid-state devices (e.g., transistors, solid-state diode
Regenerative type switching device
With light activation
C257S088000, C257S046000
Reexamination Certificate
active
06498356
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an LED chip and an LED array chip, and also relates to an LED array head for use as a recording light emitting element for forming a permanent visual image on a recording material by an electrophotographic recording system and an LED array chip disposed on the head. Moreover, the present invention relates to an image-forming apparatus provided with an LED array head.
2. Related Background Art
A conventional self-scan LED array (hereinafter referred to as “SLED”) is disclosed in Japanese Patent Application Laid-open Nos. 1-238962, 2-208067, 2-212170, 3-20457, 3-194978, 4-5872, 4-23367, 4-296579, and 5-84971, Japan Hard Copy '91 (A-17) “Proposal of Light Emitting Element Array for Optical Printer with integrated Drive Circuit” and the Society of Electronic Information Communication ('91. 3.5) “Self-scan Light Emitting Element (SLED) using PNPN Thyristor Structure”, and the like, and has been noted as a recording light emitting element. An LSI chipped self-scan LED array is hereinafter referred to simply as an LED array chip.
Here, an SLED array head constitution will be described. For the head, a schematic view is shown in FIG.
12
. Numeral
211
denotes an SLED semiconductor chip (LED array chip), and
212
denotes a base substrate with the SLED semiconductor chip mounted thereon, in which a printed wiring board of a glass epoxy material, a ceramic material, or the like is used. Numeral
213
denotes a connector for receiving a control signal, and a power source from the outside. Numeral
214
denotes a lighting control circuit (driver IC) for generating a lighting control signal of the SLED semiconductor chip.
Numeral
215
denotes a bonding for connecting output signals &phgr;
1
, &phgr;
2
, &phgr;S, &phgr;I from the driver IC and a negative electrode side power source input (GND in the present example) to the respective SLED semiconductor chips,
216
denotes a positive electrode side power source pattern (+5 V in the present example) drawn to the base substrate
212
, and
217
denotes a silver paste for establishing an electric conduction between the positive electrode side power source pattern
216
drawn to the base substrate
212
and a back surface electrode of the SLED semiconductor chip
211
and for bonding/fixing the chip.
Referring to
FIG. 13
, in order to radiate light
222
emitted from a light emitting portion
221
of the LED array chip
211
to a light-sensitive drum
224
without any loss, air and a condensing rod lens array
223
are usually present on a light path of the LED array chip
211
mounted on the substrate
212
. The surface of the LED array chip
211
is usually provided with a pattern wiring
231
by aluminum. When the aluminum wiring
231
is exposed to the surface, however, aluminum is corroded by humidity, impurities, and the like in the air, and resistance value increase and wire breaking defect are sometimes caused in a short period. Therefore, in a conventional art, a polyimide or another resin film
232
functioning as a light transmission protective film is formed on the chip surface, so that the aluminum wiring
231
is prevented from being exposed.
However, since it is difficult to form the resin film
232
in a uniform and thin film thickness on the chip surface, a quantity of light emitted from the LED light emitting portion
221
and passed through the resin film
232
, and light quantity unevenness among light emitting pixels are remarkably adversely affected. Moreover, for this purpose, particularly when a special semiconductor thin film forming process is added to form the resin film
232
, considerable equipment investment is necessary, and manufacture cost of the LED array chip largely increases.
Moreover, as shown in
FIG. 13
, when the surface protective resin film
232
with a thickness longer than a light emitting wavelength is added, multi-reflection remarkably occurs in the surface protective film, and therefore flare light mixed from portions other than the light emitting portion deteriorates LED array optical properties.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an LED array chip which can minimize LED optical property deterioration by addition of a surface protective film, and mainly side effects such as light quantity drop and light quantity dispersion increase among light emitting bits, an LED array head provided with the LED array chip, and an image-forming apparatus provided with the LED array chip.
According to the present invention, there is provided an LED array chip comprising a plurality of LED light emitting elements arrayed in a row, in which a surface insulating film formed by using the same material as a material of an inner-layer insulating film for forming a window to connect a wiring pattern in an internal electric circuit constitution and for establishing electric insulation between circuits and by using the same thin film forming process as a process of the inner-layer insulating film, and is formed on the entire surface of a final surface layer excluding a wire bonding pad and including a light emitting portion surface in a film thickness shorter than any light emitting wavelength of the plurality of LED light emitting elements.
Moreover, in the aforementioned LED array chip of the present invention, for the thickness of the surface insulating film, a center value is not more than 0.5 &mgr;m and not less than 0.1 &mgr;m.
Furthermore, in the aforementioned LED array chip of the present invention, the materials of the inner-layer insulating film and the surface insulating film are SiO
2
.
Additionally, in the aforementioned LED array chip of the present invention, the thickness of the inner-layer insulating film is not less than once and not more than twice the thickness of the surface insulating film.
Moreover, in the aforementioned LED array chip of the present invention, a pattern wiring is disposed between the inner-layer insulating film and the surface insulating film.
According to the present invention, there is provided an LED array head comprising the aforementioned LED array chip.
According to the present invention, there is provided an image-forming apparatus comprising the aforementioned LED array head.
According to the present invention, there is further provided an LED chip comprising a substrate, a light emitting portion comprising an LED, and a driving portion for driving light emission of the light emitting portion, in which the light emitting portion and the driving portion are disposed on the same surface of the substrate, a surface protective layer for covering the light emitting portion also covers the driving portion, and a thickness of the surface protective layer is shorter than a wavelength of light emitted by the light emitting portion.
REFERENCES:
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patent: 5038186 (1991-08-01), Nishioka et al.
patent: 5045895 (1991-09-01), Yoshida et al.
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patent: 5684523 (1997-11-01), Satoh et al.
patent: 5814841 (1998-09-01), Kusuda et al.
patent: 5866439 (1999-02-01), Nobori et al.
patent: 5952680 (1999-09-01), Strite
patent: 6297842 (2001-10-01), Koizumi et al.
patent: 1-238962 (1989-09-01), None
patent: 2-208067 (1990-08-01), None
patent: 2-212170 (1990-08-01), None
patent: 3-20457 (1991-01-01), None
patent: 3-194978 (1991-08-01), None
patent: 4-5872 (1992-01-01), None
patent: 4-23367 (1992-01-01), None
patent: 4-296579 (1992-10-01), None
patent: 5-84971 (1993-04-01), None
“Proposal of Light Emitting Element Array for Optical Printer With Integrated Drive Circuit,”Japan Hard Copy, 1991 (A-17).
“Self-scan Light Emitting Element (SLED) Using PNPN Thyristor Structure,” Society of Electronic Information Communication ('90.3.5).
Ishikawa Junji
Mine Ryuta
Sekiya Toshiyuki
Shiraishi Mitsuo
Canon Kabushiki Kaisha
Chaudhuri Olik
Fitzpatrick ,Cella, Harper & Scinto
Schillinger Laura M
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