Electric lamp and discharge devices – Cathode ray tube – Envelope
Reexamination Certificate
2001-04-04
2004-03-09
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Envelope
C313S461000, C313S466000, C313S473000, C313S47700R
Reexamination Certificate
active
06703778
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a display device such as a light emitting element having a light emitting window, a plasma display panel (PDP), and a cathode-ray tube (CRT) display device.
In recent years, highly integrated semiconductor devices operable at a high speed are remarkably wide spread and more and more increasingly used. As active devices using the semiconductor devices, there are known a random access memory (RAM), a read-only memory (ROM), a microprocessor (MPU), a central processing unit (CPU), and an image processor arithmetic logic unit (IPALU), and so on. The above-mentioned active devices are improved every minute so that an operation speed and/or a signal processing speed is rapidly increased. Under the circumstances, an electric propagated at a high speed is accompanied with drastic changes in electric voltage or electric current. Such changes constitute a main factor in generation of a high-frequency noise.
On the other hand, the reduction in weight, thickness, and size of electronic components or electronic apparatuses is endlessly making a rapid progress. This results in a remarkable increase in degree of integration of the semiconductor devices and in density of mounting the electronic components to a printed wiring board. In this event, electronic devices and signal lines densely integrated or mounted are very close to one another. Such high-density arrangement, in combination with the increase in signal processing speed mentioned above, will cause the high-frequency noise to be readily induced.
Such a high-frequency noise may be, for example, emitted from a light emitting element such as a laser diode for use in an optical pickup for an optical disk drive. This is because the laser diode may be operable at a high speed and the laser diode, in this case, emits or radiates not only light (infrared rays) but also the high-frequency noise.
However, in prior art, any measure is not taken for the high-frequency noise radiated from the above-mentioned light emission element.
On the other hand, as one of display devices, a plasma display panel (hereinafter which will be also referred to as “PDP”) is known. In the manner which will later be described in conjunction with
FIG. 12
, a conventional plasma display panel comprises first and second glass substrates which are opposed to each other with a gap left therebetween. The first glass substrate is disposed at the front while the second glass substrate is disposed at the rear. Accordingly, the first glass substrate is called a front glass substrate while the second glass substrate is called a rear glass substrate. The front glass substrate and the rear glass substrate have first and second principal surfaces, respectively, at opposite sides. A plurality of front electrodes extend in a predetermined direction parallel to one another and are formed on the first principal surface of the front glass substrate. Each front electrode is formed as a transparent electrode which is made of a transparent material such as SnO
2
, ITO, or the like. The plurality of front electrodes are covered with a first dielectric layer. A plurality of rear electrodes extend in a direction perpendicular to the predetermined direction parallel to one another and formed on the second principal surface of the rear glass substrate. Each rear electrode is made, for example, of Ag. The plurality of rear electrodes are covered with a second dielectric layer. A plurality of barrier ribs are disposed between the first and the second dielectric layers.
Such a plasma display panel is called an opposite discharge-type plasma display panel. The plasma display panel generates discharge rays between the front electrodes and the rear electrodes that are observed through the front electrodes acting as the transparent electrodes. Accordingly, the plasma display panel generates or radiates electromagnetic waves from all over the panel surface of the plasma display panel in accordance with the principle of its discharge. Those generated electromagnetic waves serve as interference electromagnetic waves in other parts or other apparatuses. As a measure for suppressing the interference electromagnetic waves, in the manner which will later be described in conjunction with
FIG. 13
, the front glass substrate is divided into two sub-substrates in a thickness direction and a conductive mesh is disposed between the two sub-substrates.
However, the measure for suppressing the interference electromagnetic waves with regard to the conventional plasma display panel becomes an issue as follows. At first, the conventional plasma display panel is disadvantageous in that the number of parts is increased and work hours required to assemble are also increased because the front substrate is divided into the two sub-substrates in the conventional plasma display panel. Secondly, the conductive mesh disposed within the front substrate results in degrading an optical characteristic of the PDP. Thirdly, as regards absorption of electromagnetic waves in the conductive mesh, the conductive mesh has a restricted frequency band up to a frequency band of the order of megahertz (MHz) that is capable of absorbing the electromagnetic waves. That is, the conventional plasma display panel is disadvantageous in that the conductive mesh cannot cope with absorption of the electromagnetic waves up to a frequency band of the order of gigahertz (GHz) which becomes an issue in resent years.
As another one of the display devices, a cathode-ray tube (hereinafter which will be also referred to as “CRT”) display device is known. In the manner known in the art, the cathode-ray tube display device is used, for example, as a television (TV) picture tube of a television set, a monitor for a personal computer, or the like. Originally, a cathode-ray tube (CRT) is known as Braun tube or as an electron-ray tube. In the manner which will later be described in conjunction with
FIG. 22
, a conventional CRT display device comprises a cathode-ray tube or a glass vessel having an evacuated space inside and a deflecting yoke. The cathode-ray tube comprises a display panel having an inner surface, fluorescent substances having a predetermined pattern formed on the inner surface of the display panel, a shadow mask opposite to the display panel with the fluorescent substances disposed therebetween, and an electron gun. The electron gun radiates an electron beam which passes through one of hollow holes of the shadow mask and hits on a position of the fluorescent substances to make the position of the fluorescent substances emit.
The conventional CRT display device generates or radiates interference electromagnetic waves when the electron beam hits on the position of the fluorescent substances to make the position of the fluorescent substances emit. As a measure for suppressing the interference electromagnetic waves in the conventional CRT display device, in the manner which will later be described in conjunction with
FIG. 23
, a conductive mesh is embedded in the display panel in the cathode-ray tube.
However, the above-mentioned conventional CRT display device provided with the conductive mesh is disadvantageous in that image quality of the CRT display device is degraded because the conductive mesh interrupts emission in the fluorescent substances and the conductive mesh has a low absorption efficiency of the interference electromagnetic waves if the conductive mesh has a low arrangement density in order to improve the image quality. The above-mentioned conventional CRT display device provided with the conductive mesh is also disadvantageous in that a production cost thereof becomes high to embed the conductive mesh in the display panel. Furthermore, the conductive mesh has a frequency band enable to absorb the electromagnetic waves that is restricted up to a frequency band of the order of MHz. That is, the conventional CRT display device provided with the conductive mesh is disadvantageous in that the conductive mesh cannot cope with absorption of the electromagnetic waves up to a frequency
Kamei Koji
Nemoto Michio
Ono Hiroshi
Watanabe Shinya
Yoshida Shigeyoshi
Leurig Sharlene
NEC Tokin Corporation
Patel Vip
Ruben Bradley N.
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