Coating processes – Electrical product produced – Fluorescent or phosphorescent base coating
Reexamination Certificate
2000-05-11
2001-09-11
Beck, Shrive (Department: 1762)
Coating processes
Electrical product produced
Fluorescent or phosphorescent base coating
C427S066000, C427S071000, C427S073000, C427S469000, C427S472000, C427S218000, C427S256000
Reexamination Certificate
active
06287629
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a color cathode ray tube and a method of producing it, and more particularly to a color cathode ray tube in which fluorescent substance forming a fluorescent substance film on an inner surface of a glass panel is coated with a layer having a wave length selective characteristic and a method of producing it.
2. Description of the Prior Art
Conventionally, the color cathode ray tube has been used in color TV, color display and the like. In the color cathode ray tube, a fluorescent substance film is formed on an inner surface of a glass panel. In the fluorescent film, respective patters are formed for green, blue and red with a predetermined positional relation. On an electron gun side of this fluorescent substance film, attachment is made of color selective electrodes, such as shadow mask or the like, left a predetermined interval therebetween. By this structure, it is adapted in such a manner that electron beams corresponding to green, blue and red are applied onto the fluorescent substances for respectively corresponding colors on the fluorescent substance film, and a light emission is performed.
Generally in the color cathode ray tube, non-luminous absorptive substance such as graphite or the like is loaded between respective color fluorescent substance luminous pixels of green, blue and red (hereinafter referred to as G, B and R) in order to improve contrast which is a basic performance as an image display. This non-luminous absorptive substance film is called black matrix film (hereinafter referred to as BM film). Further on a whole surface of the fluorescent screen which is opposite to the display surface, a film is formed for reflecting light in the form separated from the fluorescent screen. This film consists, for example, of aluminum film and will be called metal back film.
As described above, contrast is one of the important characteristics of the color cathode ray tube. This contrast is a characteristic which is determined by a ratio between brightness and external light reflection of the fluorescent screen. As a means for improving the contrast, it can be considered to increase a current amount of electron beam from the cathode or raise an anode high voltage. However, this method is not preferable because power consumption of the cathode ray tube becomes large.
Further, it can be considered as other method to increase a light emission performance of the fluorescent substance and a light transmittance of the glass panel. However, the light emission performance of the fluorescent substance has already been at a high level. Further, the light transmittance has almost reached its limit in the glass panel. Thus, it is difficult to improve these characteristics.
By the way, a method of lowering a reflectance of the fluorescent screen is disclosed in Japanese Unexamined Patent Publication No. 8-7800 (hereinafter referred to as prior art 1). In the method, use is generally made of a mixture of fluorescent substance with pigments. This mixture is produced by attaching inorganic pigment particles having selective absorption property in a region other than luminous wave length of respective color to the whole surfaces of the fluorescent substance particles for blue color and red color. On the other hand, the fluorescent substance for green color is yellowish in itself and absorbs lights other than the luminous wave length to some extent, so that ordinary pigment is not used. Such mixtures exert an effective absorbing action to external light coming from the glass panel side. However, the pigments are placed on a side of fluorescent substance onto which the electron beams will impinge, so that the pigments does not only contribute to absorption of external light but also prevents the electron beams from reaching the fluorescent substance, thereby reducing brightness.
As a means for improving the brightness and contrast, technique for a micro-filter tube (Toshiba) has been introduced in “Electronics” November 1995 (hereinafter referred to as prior art 2). In this technique, a screen of the micro-filter tube comprises color filters (hereinafter referred to as M filters) disposed between an inner surface of a glass panel and fluorescent substance films which respectively consist of fluorescent substance of G, B, R and which are formed between BM films, and a color filter (hereinafter referred to as BE filter) disposed on an outer surface of the glass panel.
The M filters consists of respective colors of G, B, R selectively and absorb wave length regions other than the luminous portion of the fluorescent substance and so absorb external lights effectively without deteriorating the brightness, thereby improving the contrast. On the other hand, the BE filter acts as an common filter for respective colors, so that it can selectively absorb external light energy having luminosity peak, thereby achieving improvement in the contrast and color purity.
However, the color cathode ray tube described above is produced by coating the M filters consisting of respective colors of G, B, R after the BM film has been formed and thereafter forming respective fluorescent substance films at positions corresponding to respective colors. Therefore, the conventional color cathode ray tube has disadvantages in that the production process becomes complicated thereby leading to a drop of yield and that a large equipment investment is needed.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a color cathode ray tube capable of extracting the characteristics of brightness and contrast to a maximum extent.
It is another object of the present invention to provide a color cathode ray tube capable of suppressing a large equipment investment for production to a minimum extent.
It is still another object of the present invention to provide a method of producing a color cathode ray tube having the aforementioned advantages.
According to one aspect of the present invention, there is provided a color cathode ray tube comprising black matrix films formed on an inner surface of a glass panel with a predetermined positional relation and having a plurality of light transmission window portions, and fluorescent substance films formed by fluorescent substance particles of green, blue and red at the light transmission window portions. In the aspect of the present invention, the fluorescent substance films have wave length selective layers partly coated on a surface of at least one kind of the fluorescent substance particles of green, blue and red and having a wave length selective characteristic.
Here in the above aspect of the present invention, it is preferable that the wave length selective layer consists of a pigment formed on a surface of at least one kind of the fluorescent substance particles.
Further in the above aspect of the present invention, it is more preferable that the wave length selective layer consists of a pigment coated over a nearly half range of a total surface area of the fluorescent substance particles.
Furthermore in the above aspect of the present invention, it is most preferable that the fluorescent substance particles are formed in such a manner that the wave length selective layer is oriented toward the light transmission window portions on an inner surface of the glass panel.
According to another aspect of the present invention, there is provided a method of producing a color cathode ray tube comprising the steps of forming black matrix films formed on an inner surface of a glass panel with a predetermined positional relation and having light transmission window portions, and forming fluorescent substance films formed by fluorescent substance particles of green, blue and red at the light transmission window portions. In the aspect of the present invention, use is made as the fluorescent substance of one consisting of at least one kind of the fluorescent substance particles of green, blue and red, whose respective surface is partly coated with a wave length selective lay
Beck Shrive
Cleveland Michael
McGuireWoods LLP
NEC Corporation
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