This application claims priority to and the benefit of Korean Patent Application No. 10-2004-0049411 filed on Jun. 29, 2004 in the Korean Intellectual Property Office, the entire content of which is incorporated herein by reference.
The present invention relates to a cathode ray tube, and in particular, to a cathode ray tube which has a panel with an improved inner surface and a shadow mask.
Generally, a cathode ray tube (CRT) includes a panel with an inner phosphor screen, a funnel connected to the rear of the panel with a deflection yoke mounted around the outer circumference thereof, and a neck connected to the rear of the funnel with an electron gun mounted therein.
The phosphor screen has red, green and blue phosphor layers, and the electron gun emits three rays of electron beams toward the phosphor screen corresponding to respective three colors, red, green, and blue. The deflection yoke deflects the electron beams progressing in the funnel such that they scan the phosphor screen.
A shadow mask is fitted within the panel as a color selection electrode while being spaced apart from the phosphor screen. The shadow mask has a plurality of electron beam passage holes, and selects the three rays of electron beams emitted from the electron gun such that they land on the appropriate phosphor layer.
With the above-structured cathode ray tube, the panel may have a flat outer surface and a curved inner surface with a predetermined curvature. It has been proposed that the central thickness of the panel should be reduced to enhance the screen brightness and reduce the weight. However, in this case, X rays harmful to human body are emitted from the cathode ray tube due to the reduced central thickness. Therefore, a limit is imposed on reducing the thickness of the panel.
Furthermore, when the inner surface of the panel is varied in shape, the curvature characteristic of the shadow mask should be varied accordingly. However, the curvature characteristic of the shadow mask is related to the impact resistance characteristic thereof with respect to the external impact, such as accidental dropping of the panel. Consequently, when the inner surface of the panel and the curvature characteristic of the shadow mask are determined without considering the impact resistance characteristic of the shadow mask, the impact resistance characteristic is deteriorated, and thus decreasing the reliability of the device.
In one exemplary embodiment of the present invention, there is provided a cathode ray tube including a panel which improves the shape of the inner surface of the panel to reduce the weight of the panel while maintaining the X ray interception function thereof and enhancing the impact resistance characteristic of the shadow mask.
In an exemplary embodiment of the present invention, the cathode ray tube includes a panel with inner and outer surfaces, a funnel connected to the panel, a neck connected to the rear of the funnel, and a shadow mask mounted within the panel. The inner surface of the panel satisfies the following condition:
0.2≦Px≦0.4, 0.3≦Py≦0.6
where when the inner surface of the panel is expressed by the following biquadratic:
based on the inner central point of the panel with the three-dimensional orthogonal coordinates system defined by the x, y and z axes, Px and Py are defined by the following formula:
In one embodiment, the outer surface of the panel is substantially flat, and the panel has an effective portion with a diagonal length of 580 mm or more.
In one embodiment, the panel has a center with a thickness of 12 mm or more.
In one embodiment, the shadow mask has an effective portion with electron beam passage holes, and when the horizontal pitch of the electron beam passage holes at the center of the effective portion is indicated by Ph1 and the horizontal pitch of the electron beam passage holes at the ends of the effective portion by Ph2, the ratio of Ph2/Ph1 is established to exceed 1.4.
In one embodiment, the panel satisfies the following condition:
0.25≦Px≦0.35, 0.35≦Py≦0.45.
The above and other advantages of the present invention will become more apparent by describing embodiments thereof in detail with reference to the accompanying drawings in which:
As shown in the
As shown in
A shadow mask 16 is fitted within the panel 6 while being spaced apart from the phosphor screen 4 with a predetermined distance Q0. The shadow mask 16 has a plurality of electron beam passage holes 16a. The three rays of electron beams emitted from the electron gun 12 are converged at the electron beam passage holes 16a of the shadow mask 16 while passing through them, and land on the relevant phosphor layers. Thus, the electron beam passage holes 16a function as color selection electrodes.
Referring back to
The outer surface of the panel 6 is substantially flat, and the inner surface is curved with a predetermined curvature. The panel 6 has an improved shape (described below) to reduce its weight while maintaining the interception of the X rays harmful to the human body.
As shown in
Such a shape variation reduces the thickness of the panel 6 at the outer surface without largely reducing the minimal thickness of the panel 6, thereby decreasing the volume of the panel 6 in an effective manner. As a result, the weight of the panel 6 is reduced while preventing the X rays harmful to the human body from being emitted to the outside of the cathode ray tube.
The diagonal size D (shown in
Furthermore, the curvature of the shadow mask 16 is determined depending upon the shape of the inner surface of the panel 6, which in turn, is determined depending upon the impact resistance of the shadow mask 16. The shape of the inner surface of the panel 6 is expressed by the biquadratic equation 1, based on the inner central point ◯ of the panel 6 by way of the three-dimensional orthogonal coordinates system defined by the x, y and z axes.
Where, (x, y) represent coordinates of a predetermined position, z is the displacement measured from the inner central point ◯ at the predetermined (x, y) position, and Ai,j are constants for determining the displacement and inner curvature of the panel.
Based on the equation 1, the factors Px and Py influencing the inner curvature of the panel 6 can be defined by the following formula:
The impact resistance values of the shadow mask 16 designed in accordance with the shape of the inner surface of the panel 6 as a function of the values of Px and Py are illustrated in
As listed in Table 1, when Px is in the range of 0.2-0.4 and Py in the range of 0.3-0.6, the impact resistance of the shadow mask 16 is in the range of 14-16.7G. Particularly, when Px is in the range of 0.25-0.35 and Py in the range of 0.35-0.45, it turns out that the impact resistance of the shadow mask 16 exceeds 15G, and involves excellent characteristic.
The optimal value of Px derived from
Meanwhile, when the panel 6 is structured to satisfy the above conditions, the typical electron beam landing characteristic can be maintained to be as usual by varying the horizontal pitch of the electron beam passage holes 16a formed at the shadow mask 16 without varying the curvature of the shadow mask 16.
As shown in the
In
In equation 3, because Lsg and Sg are constants with a predetermined value during the manufacturing of the cathode ray tube, it can be seen that Qo and Pm are proportional to each other. Accordingly, when the horizontal pitch Pm of the electron beam passage holes 16a at the center of the screen is reduced by the same amount that the Q value at the center of the screen is reduced due to the variation in the inner surface shape of the panel 6, the usual electron beam landing characteristic is maintained, without varying the curvature characteristic of the shadow mask 16.
The values of Px and Py of a panel according to a prior art (Comparative Example), and a panel according to the present embodiment (Example), the ratio of Ph2 to Ph1 of the shadow mask, and the weight of the panel are compared, and illustrated in Table 2.
As listed in Table 2, it can be seen that the weight of the panel in the cathode ray tube according to the Example is reduced by 1 kg, compared to that in the cathode ray tube according to the Comparative Example.
With the inventive cathode ray tube, the shape of the inner surface of the panel is improved to reduce the volume of the panel while maintaining its function of intercepting the X rays harmful to the human body, considering the impact resistance characteristic of the shadow mask. Consequently, the inventive cathode ray tube is advantageous in reducing the production cost due to the reduced weight of the panel, and the impact resistance characteristic thereof is enhanced while ensuring the easy handling thereof.
Although some embodiments of the present invention have been described in detail hereinabove, it should be clearly understood that many variations and/or modifications of the basic inventive concept herein taught which may appear to those skilled in the art will still fall within the spirit and scope of the present invention, as defined in the appended claims.
Number | Date | Country | Kind |
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10-2004-0049411 | Jun 2004 | KR | national |