1. Field of the Invention
The present invention relates to a cathode ray tube (CRT) display apparatus including an FBT (flyback transformer) having a plurality of high voltage output terminals, and more particularly, to a CRT display device including an electric field shielding member easily shielding an electric field from an FBT.
2. Description of the Related Art
Recently, harmful electromagnetic waves radiated by electronic appliances have become an issue. Thus, limits on the harmful electromagnetic waves are internationally standardized and the electronic appliances are produced meeting the standard. Particularly, in a display apparatus using a CRT, the electromagnetic waves are not only harmful to humans, but are also likely to distort a displayed picture such that the reliability of the display device is deteriorated.
For example, the MPR-II standard established in Sweden prescribes the limits on the harmful electromagnetic waves in ELF (Extremely low frequency) and VLF (Very Low Frequency) ranges, and regulates devices radiating the harmful electromagnetic waves such as a television, a monitor, etc. The limits prescribed by the MPR-II standard are shown in a following Table 1.
TABLE 1Limit Standard (at a distanceFrequency Bandof 50 cm)Electric fieldELF (5 Hz~2 kHz)25 V/m and belowVLF (2 kHz~400 kHz)2.5 V/m and belowMagnetic fieldELF (5 Hz~2 kHz)2.50 mG and belowVLF (2 kHz~400 kHz)0.25 mG and below
As shown in Table 1, the limit in the ELF range is relatively high. Thus, a device using general CRT is capable of meeting the limit in the ELF range.
However, in the case of the VLF range, the limit is relatively low. Thus, it is difficult for the general CRT (except a high quality CRT) to meet the limit in the VLF range.
Here, the magnetic field due to voltage applied to a deflection coil can be easily shielded by compensating the deflection coil attached to an electron gun of the CRT or by separately adding an offset coil to the deflection coil. However, it is not easy to shield the electric field due to high voltage outputted from the FBT, including voltage applied to an anode. Therefore, there have been proposed various methods to shield the electric field due to the FBT. As general methods, the electric field is shielded by separately mounting a filter to a front of the CRT or by specially coating the inside of the CRT. However, such methods involve problems that there are stumbling blocks to mass production and production cost is increased because of complicated processes, technological difficulties, etc.