1. Field of the Invention
The present invention relates to a sealed container, a manufacturing method therefor, a gas measuring method, and a gas measuring apparatus for implementing the gas measuring method. More specifically, the invention relates to a sealed container used for a flat panel display, a manufacturing method for the sealed container, a gas measuring method used for measuring a gas rate of an emission gas, a leakage gas, or the like or measuring a life of a getter, and a gas measuring apparatus for implementing the gas measuring method.
2. Related Background Art
Examples of self-light emitting flat panel displays include a plasma display, an EL display device, and an image display device using an electron beam. An image display device using a sealed container that maintains its inside to a lower pressure than the atmospheric pressure is represented by a cathode ray tube (hereinafter, referred to as “CRT”) of a television set, but devices and apparatuses including the plasma display and a flat panel display using an electron beam also utilize the sealed container that has a pair of plates and maintains its inside to a lower pressure than the atmospheric pressure. Currently, there are increasing demands for the display devices to have a larger screen and a higher definition, and there are ever-growing needs for the self-light emitting flat panel displays.
Such image display devices face a major problem of an image display life. This is because, while having a gas source that may be hit by electrons and ions, the image display device must maintain a high vacuum for as long as several tens of thousands of hours by limited exhaust means, making it necessary for electron radiation from an electron source to be conducted in a stable manner over a long period of time. The radioactivity of the electrons from the electron source is largely influenced by an emission gas inside the image display device. For example, the CRT may involve a problem of damage caused by Ar (JP 10-269930 A).
Accordingly, it is necessary to grasp types of gases causing damage to an electron source in an operation state and a gas generation rate (gas emission from a member) to reduce the damage to the electron source.
Further, in order to maintain a pressure inside a panel by the limited exhaust means, it is necessary to exhaust the emission gas emitted from the member. As the exhaust means, a barium getter is conventionally known, and almost all of its basic properties have become apparent. However, a gas absorbing power of the barium getter inside an actual panel is hard to estimate from the basic properties. This is because the absorbing power of a getter film largely differs according to a fine structure of the getter film inside the panel, the amount and type of the emission gas inside the panel (generation of a reaction product), and the like. Therefore, the absorbing power of a getter inside an actual panel can be only directly measured with respect to a subject panel.
Accordingly, as a method of measuring a life of an image display device, it is a problem of urgency to establish a method of measuring a life of a getter, in which an influence of a gas exerted to a device when an image is displayed is evaluated (an emission gas rate is accurately measured for each type of gas) while a vacuum state of the image display device is maintained.
On the other hand, known as a conventional gas measuring method is a method of measuring a gas partial pressure using a quadrupole mass spectrometer (Q-Mass) as a mass spectrometer for analyzing gases inside a vacuum apparatus and a process chamber (JP 2952894 B).
Proposed as a method of measuring an emission gas rate and an adsorption gas rate for each gas is a measuring method using a partial pressure gauge provided to each of two chambers that are connected to each other through an orifice (JP 05-072015 A). Also, for a CRT, plural methods of measuring an emission gas rate and an adsorption gas rate are proposed as the method of measuring a life of a getter. Examples of the proposed plural methods include: a method of heating a CRT to 150° C. to 250° C. and measuring an emission gas rate while cooling the CRT (JP 07-226159 A); a method of measuring a gas absorbing power of a getter film after the CRT is caused to run for a predetermined period of time, calculating an amount of an emission gas from a built-in member of the CRT, and estimating a long-term life of a getter based on the calculated amount (JP 10-208641 A); and a method of finding a relationship between an amount of a getter and a life of a CRT by setting the amount of the getter to a small amount (JP 2000-076999 A).
Further, JP 2000-340115 A discloses a manufacturing method for an image display device in which a manufacturing process is performed while a state of an atmosphere is being monitored by using an orifice having a known conductance and installed in part of an exhaust channel of a manufacturing apparatus for vacuum pumping.
According to the gas measuring methods disclosed in JP 2952894 B and JP 05-072015 A, a gas measurement is performed by placing a measurement sample inside a vacuum chamber and using a mass spectrometer, enabling the measurement for each type of gas. Particularly in JP 05-072015 A, a vacuum chamber having an orifice is used, enabling the measurement of an emission gas rate for each type of gas as well. However, it is difficult to place a large apparatus such as a flat panel display inside the vacuum chamber for the measurement. If the measuring apparatus is manufactured to be adapted for such a large apparatus, a huge manufacturing cost is required, making it hard to implement such arrangement.
The gas measurement for a CRT has long been performed. However, in JP 07-226159 A, a mass spectrometer is not used for the gas measurement, thereby making it impossible to measure an emission gas rate for each type of gas, and a gas to be adsorbed to a getter cannot be supplied, thereby making it impossible to accurately evaluate a life of a CRT. Further, in JP 10-208641 A, there are included an orifice and a total pressure gauge for measuring an emission gas rate, and a gas supply system for measuring a gas adsorbing power of a getter. However, a mass spectrometer is not used for a partial pressure measurement, thereby making it impossible to measure an emission gas rate for each type of gas. Also, it is possible to supply to the CRT a gas to be adsorbed to a getter through the orifice at a constant rate. However, lack of a chamber for adjustment of a pressure makes it difficult to adjust a pressure of the supplied gas, resulting in a long-time measurement. Further, according to the method of JP 2000-076999 A, which serves to measure the relationship between an amount of a getter and a life of a CRT by setting the amount of the getter to a small amount, the measurement requires a long period of time, and the gas measurement cannot be performed for a type of gas that is actually generated in the CRT. Therefore, it is difficult to accurately predict the life of the CRT.
The manufacturing method for an image display device disclosed in JP 2000-340115 A is suitable for a gas measuring method during the manufacturing, but is difficult to use as a gas measuring method for an image display device that has become a vacuum container.
Alternatively, as the gas measuring method for a CRT that has been manufactured, there is a method in which a hole is opened by a punch when a pipe for a measurement is connected to a funnel of the CRT.
However, according to this method, in the case of an apparatus using a thin glass plate such as a flat panel display, a crack easily develops, increasing the possibility of generating a leak.