Method of manufacturing light transmission tubes

Abstract

A light transmission tube includes a tubular clad and a core section having a higher refractive index than that of the tubular clad, said light transmission tube is characterized in that a belt-like reflecting layer is formed between the tubular clad and the core section, extending in the longitudinal direction of the tubular clad, in a manner such that a light passing through the core section is reflected and scatterred by the reflecting layer and then emitted from an outer surface area of the tubular clad, which outer surface area is located opposite to one side of the tubular clad where the reflecting layer has been formed. Further, the reflecting layer may be so formed that a light is allowed to be emitted in a plurality of directions. Moreover, the belt-like reflecting layer may be formed into a spiral configuration. The width of the belt-like reflecting layer may be changed in the longitudinal direction of the light transmission tube. The tubular clad is allowed to have a non-circular cross section. The clad formation material may contain an ultraviolet light shielding material or an ultraviolet light absorbing material.

Description

BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT[0001] The present invention relates to light transmission tubes and methods for manufacturing the light transmission tubes. Each of the light transmission tubes to which the present invention relates is comprised of a transparent tubular clad and a transparent core section having a higher refractive index than the transparent tubular clad. In particular, this invention relates to light transmission tubes and methods for manufacturing said tubes each of which is capable of emitting a light having a predetermined directivity from one side of the clad (a part of its outer surface area).[0002] In general, if a light transmission tube is comprised of a tubular clad and a core section having a higher refractive index than the tubular clad, a usually adopted method for the use of it is that a large amount of light be sent toward the front end of the light transmission tube. As a result, a brightness on the circumferential surface area o...

AI Technical Summary

Benefits of technology

[0013] It is a still further object of the present invention to provide a light transmission tube and a method for manufacturing said tube which is capable of being manufactured with an improved productivity and is allowed to be installed in position in a desired place with a great ease and a reduced cost.

[0045] In the light transmission tube made according to a sixth aspect of the present invention, a belt-like reflecting layer is formed between the tubular clad and the core section and extending in the longitudinal direction of the light transmission tube. Therefore, a light passing through the core section (having the largest light amount than other portions in the light transmission tube) is reflected by the belt-like narrow reflecting layer, thus it is possible to give out a strong light having a high directivity from an outer surface area of the tubular clad (which outer surface area is located opposite to one side of the tubular clad where the reflecting layer has been formed). As a result, it is sure for the light transmission tube to provide a remarkably higher brightness, enabling a place equipped with such light transmission tube to be illuminated very brightly. In particular, since the tubular clad formation material contains an ultraviolet light shielding material or an ultraviolet light absorbing material, an obtained light transmission tube has an excellent ultraviolet light resistance, so that it is suitable for use in an outdoor environment. Therefore, it has become possible to provide, with a low manufacturing cost, a light transmission tube having a simple structure without a necessity to use some other specific protection materials. For this reason, it is allowed to use a core section formation material which has only a low resistance against an ultraviolet light.

Problems solved by technology

As a result, a brightness on the circumferential surface area of the light transmission tube is usually not very high.

However, if a light transmission tube has a structure which is formed by filling the internal space of the tubular clad with a liquid state polymerizable monomer (for forming the core section), followed by applying a pressure to effect a predetermined polymerization of the monomer, the formation of the irregular convex and concave portions on the internal surface of the clad will cause the clad to be easily broken, hence making it difficult to manufacture a light transmission tube in the above manner.

However, when using a neon tube or a fluorescent tube, since a high voltage is needed to be applied to a neon tube or a fluorescent tube, there is a danger that an electric shock or an electric leakage may happen.

As a result, such a neon tube or a fluorescent tube can not be used under water, not is it suitable for them to be used in a place where rain water or snow frequently occur.

Further, since a neon tube or a fluorescent tube has been formed into a tubular shape, they do not have a desired impact resistance.

However, since in use of such a light transmission tube, a light will be caused to emit from the circumferential surface area of the tube in every direction along the cross sectional plane, it is impossible to obtain a light emission having a sufficiently high brightness in a predetermined desired direction.

But, a problem with such a light directing rod is that if some dust or small rubbish have attached to the outer circumferential surface of the light directing rod, such dust or small rubbish will cause a deterioration in the light transmissibility of the transparent rod.

As a result, a desired brightness will be decreased and / or a brightness distribution in the longitudinal direction of the transparent rod will have an undesired variation.

Because of this, such a light directing transparent rod can only be used in a very clean environment free of dust or small rubbish.

In fact, since a relatively long time is required in a subsequent drying process for drying the printed coating material, and since the whole manufacturing process has to involve at least two steps including rod formation and coating material printing, an industrial productivity is low and its manufacturing cost is high.

In addition, since the above printing process is performed on a rod-like member, a desired reflective layer can only be formed on one side of the outer circumferential surface thereof, hence undesirably causing an emitted light to receive a restriction in its emitting direction.

As may be understood from the above discussion, in any of the related prior art techniques, there has not been provided a light transmission tube whose brightness may be increased by emitting a light from a circumferential surface of said tube in a specifically determined direction, which light transmission tube is capable of being used without a problem that its light emitting performance will be possibly deteriorated because of an attachment of dust or small rubbish thereto.

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