Curved lamp manufacturing method, curved lamp, and backlight unit

Abstract

A curved lamp manufacturing method including a curving process in which a straight glass tube sealed with reduced pressure inside is heated and curved. The curving process includes: a first step of holding a predetermined portion of the glass tube using a first chuck, and holding one end portion of the glass tube using a second chuck such that the second chuck can slide in a longitudinal direction of the glass tube; and a second step of, while heating a planned curved portion of the glass tube positioned between the predetermined portion and the end portion by a heater, curving the planned curved portion by moving the second chuck relative to the glass tube. The end portion is moved in the second step so that a weight of the end portion is applied to the planned curved portion that has been softened by the heater.

Description

[0001]This application is based on applications No. 2004-083635, No. 2004-096767 and No. 2004-100958 filed in Japan, the contents of which are hereby incorporated by reference.BACKGROUND OF THE INVENTION[0002](1) Field of the Invention[0003]The present invention relates to a curved lamp manufacturing method for manufacturing a curved lamp by curving a straight glass tube, a curved lamp, and a backlight unit.[0004](2) Description of the Related Art[0005]Cold-cathode fluorescent lamps (hereinafter referred to as fluorescent lamps) used in backlight units for liquid crystal display screens are one example of conventional curved lamps. The fluorescent lamps are in the shape of character “U” or “L”. When they are used in a direct-below-type backlight unit, a plurality of fluorescent lamps in the shape of character “U” are arranged at the back of the screen. When they are used in an edge-light-type backlight unit, the fluorescent lamps in the shape of character “L” are attached to the rim...

AI Technical Summary

Benefits of technology

[0013]The object of the present invention is therefore to provide a curved lamp manufacturing method for manufacturing a curved lamp by locally heating a glass tube, the method being efficient even if the glass tube to be curved is narrow in diameter and has been sealed with inside thereof being under reduced pressure; a curved lamp that contributes to downsizing of the backlight unit, enables the light emitted therefrom to be used effectively, and has improved brightness and light distribution; and a backlight unit using the curved lamp.

[0015]The above-stated construction provides an advantageous effect that the method is efficient even if the glass tube to be curved by local heating is narrow in diameter and has been sealed with inside thereof being under reduced pressure. This is because with above-stated construction, the planned curved portion is curved while it is softened by heat and compressed by the weight of the moved portion of the glass tube. This enables the amount of extension of the curved portions to be suppressed, and makes the outer sides of the curved portions thicker than the conventional method in which the glass tube is curved along a horizontal plane. The glass tube curved by this method has higher strength than the glass tube curved by the conventional method. This enables even a glass tube, which has a small diameter and was sealed with its inside being under reduced pressure, to be partially curved by heat. This method therefore provides an advantageous effect of manufacturing the curved lamps with high efficiency.

[0017]With the above-stated construction in which the curvature radius of an inner side of the curved portion is equal to or larger than 0.5 mm and smaller than 4.0 mm, it is possible to downsize the backlight unit without decreasing the strength of the outer sides of the curved portions, and to use the light emitted from the lamp effectively. Also, with the outer diameter of the straight glass tube being set to 1.8 mm or more in the above-stated construction, the electrodes, which, for example, to be attached to the glass tube at the ends thereof, can be manufactured more easily. This is another advantageous effect provided by the present invention. Also, with the outer diameter of the straight glass tube being set to 6.5 mm or less in the above-stated construction, it is possible to decrease the backlight unit in thickness, namely, in length perpendicular to screen, enabling the backlight unit to be made thinner. The distance between the inner surface of the glass tube and the discharge path is shortened by this. As a result, for example, in the case where a fluorescent substance is applied to the inner surface of the glass tube, the light emitted from the fluorescent substance is increased in brightness and the light-emitting efficiency is improved. Also, with the thickness of the straight glass tube being set to a range from 0.2 mm to 0.6 mm inclusive, it is possible to prevent the curved portion from being deformed during the curving process, reduce the time required for the curving process, and reduce the manufacturing cost.

Problems solved by technology

If there is a great distance between the fluorescent lamps and the optical waveguide, only a small amount of light enters the optical waveguide, the light distribution characteristics is deteriorated, and the backlight unit becomes large in size.

As a result, if the curvature radius of the curved portion is increased, the curved portion outside the screen display area is extended as much, and a large amount of light, among the light emitted from the lamp, is wasted (not illuminating the screen).

However, the above-described conventional method has a problem in manufacturing such narrow lamps.

That is to say, the conventional method cannot be used to curve such narrow glass tubes, or such narrow lamps are manufactured at extremely low manufacturing efficiency.

As a result, when such a narrow glass tube is partially curved, the curved portion becomes weak, and by the negative pressure inside the glass tube and the atmospheric pressure, the weak portion is collapsed.

This prevents the backlight unit from being made compact, and also prevents the improvement in the brightness and light distribution.

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