Electric lamp and discharge devices – Cathode ray tube – Screen
Reexamination Certificate
2000-06-26
2001-09-04
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Screen
C313S463000, C313S466000, C313S469000, C313S471000, C313S402000
Reexamination Certificate
active
06285122
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a color cathode ray tube and, more particularly, to a color cathode ray tube having a high resolution and an external size suited for use as a display monitor of the desktop size.
The color cathode ray tube is frequently employed as a TV receiver and as a display monitor for various information terminals, such as personal computers or workstations. In particular, the cathode ray tube for a color display monitor of the so-called “desktop terminal” type, such as a personal computer to be mounted on a desk for use by a user, is required to have a display performance of high resolution on a large screen and to be mounted compactly in a restricted space.
At present, the typical large size color cathode ray tube to be used as a display monitor of a desktop terminal of this kind is the 17 type (the effective display area of which has a diagonal size of about 41 cm) and the 21 type (with a diagonal size of about 51 cm). The 17 type color display monitor has a display performance of 1.3 M pixels. For a higher resolution, the 21 type color display monitor is used (which has a display performance of 2 M pixels: a horizontal dot number of not less than 1,450/line, preferably 1,600/line).
From the point of view of size, the 21 type color display cathode ray tube has an overall length of more than 450 mm, so that the length of the display monitor exceeds 500 mm. On the other hand, the typical table or desk has a top which is as deep as about 700 mm. If the depth of the keyboard is 150 mm, and if the area for accommodating the hands of the user is as deep as 100 mm, the usability of the display monitor becomes undesirable, if it is to be employed in a desktop size terminal.
If the display resolution of 2 M pixels is to be realized in the screen size of a 20 type color display monitor (corresponding to a 20 type color cathode ray tube having a panel unit with a diagonal diameter of 52 cm) or less, on the other hand, the hole pitch of the shadow mask must be reduced, which causes a problem in that the allowance for adjusting the color purity is deteriorated. In order to compensate for this, the transmittance of the holes of the shadow mask has to be lowered, which causes a drop in the brightness of the color cathode ray tube. Moreover, the color irregularity at the central portion and the peripheral portion of the screen becomes so serious as to cause a practical problem in the image quality.
Thus, a display monitor employing the color cathode ray tube of the prior art does not have a resolution corresponding to 2 M pixels and is not able to meet the size requirements necessary for desktop use.
In this kind of color cathode ray tube, on the other hand, a glass material forming the panel unit of the color cathode ray tube is a so-called “tinted material” or “dark tinted material” for improving the contrast and preventing the reflection of incoming light. In addition, the glass panel unit of the color cathode ray tube of the prior art is thinner at the central portion of its effective display area and thicker at the corner portion thereof, and this thickness difference is 1.7 mm or more. This makes a luminance difference due to the optical transmittance difference of the glass between the central portion and the corner portion irregular, causing a deterioration in the image quality.
SUMMARY OF THE INVENTION
An object of the invention is to solve the aforementioned several problems of the prior art and to provide a color cathode ray tube which has a resolution corresponding to 2 M pixels for a screen size of 20 type or less, but which has no irregularity in the display luminance and which can be adopted for use in a desktop terminal.
In order to achieve the above-specified object, the invention sets the size of the screen and the entire length of a color cathode ray tube for realizing the display performance of 2 M pixels (e.g., a horizontal dot number of 1,450/line or more, preferably 1,600/line) for the so-called “19 type size”.
According to a first aspect of the invention, more specifically, there is provided a color cathode ray tube comprising a vacuum enclosure including: a panel unit having a fluorescent film formed on its inner face in the form of densely arrayed three color dot trios of a fluorescent material, with a shadow mask being mounted in the vicinity of the fluorescent film; a neck unit housing an electron gun for emitting three electron beams; and a funnel unit for jointing the panel unit and the neck unit; wherein, the panel unit has a diagonal diameter of not more than 52 cm, the effective display area on the outer face of the panel unit has a diagonal radius of curvature of not less than 1,000 mm, and the dot trios of the fluorescent material are horizontally arrayed in a number not less than 1,450 (preferably 1,600).
According to a second aspect, the diagonal radius of curvature is not less than 1,300 mm.
According to a third aspect, the diagonal diameter is not less than 49 cm and not more than 50 cm.
According to a fourth aspect, the diagonal diameter of the effective display area of the panel unit is not more than 482 mm, and wherein the radius of curvature of the corner portion of the effective display area is not more than 5 mm.
According to a fifth aspect, the radius of curvature of the corner portion of the effective display area is not more than 3 mm.
According to a sixth aspect, the difference (Td-To) is not more than 1.7 mm if the center portion of the effective display area of the panel unit has a thickness To and if the diagonal end portion of the effective display area has a thickness Td.
According to a seventh aspect, the difference (Td-To) is not more than 1.5 mm.
According to an eighth aspect, the panel unit is made of a tinted glass material.
According to a ninth aspect, the panel unit is made of a dark tinted glass material.
According to a tenth aspect, a cover film having at least one of an antistatic effect and an antireflection effect is formed on the outer surface of the panel unit, and wherein the green spectrum of the cover film has an optical absorptivity of 10 to 20%.
According to an eleventh aspect, the optical absorptivity of the green spectrum is 14 to 16%.
According to a twelfth aspect, the dot trios of the fluorescent material has a horizontal pitch not more than 0.22 mm.
According to a thirteenth aspect, three electron beams to be emitted from the electron gun have a mutual spacing not more than 5.5 mm.
According to a fourteenth aspect, three electron beams to be emitted from the electron gun have a mutual spacing not more than 5.0 mm.
According to a fifteenth aspect, a plurality of electrodes forming the main lens of the electron gun have an outer circumference shared among the three electron beams at their confronting portions.
According to a sixteenth aspect, the electron gun is a dynamic focus type electron gun having an electrostatic quadruplex lens.
According to a seventeenth aspect, the electron gun is a dynamic focus type electron gun having a plurality of electrostatic quadruplex lenses.
By the aforementioned individual aspects of the invention, the color cathode ray tube can be given an overall length of about 420 mm, so that the monitor will have a length of about 450 mm for a convenient desktop size, and the cathode ray tube can realize a display performance matching 2 M pixels (having a horizontal dot number of 1,450/line or more, preferably 1,600/line).
REFERENCES:
patent: 5660876 (1997-08-01), Kojima et al.
patent: 5869929 (1999-02-01), Eida et al.
patent: 6114803 (2000-09-01), Hosotani
patent: 6140756 (2000-10-01), Hosotani
“Hitachi Color Display Tubes”, Hitachi, Ltd., Sep. 1995.
“M48KFH60X”, Registration/Registration Format, World Type Designation System, pp. 1-3.
“M41KSX60X”, Registration/Registration Format, World Type Designation System, pp. 1-3.
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Patel Nimeshkumar D.
Quarterman Kevin
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