The present invention relates to a technique for forming a three-dimensional light reflector plate adapted to allow thickness reduction and enhancement of the brightness and efficiency of backlights and lighting boxes for use with illumination signboards, liquid crystal displays, lighting fixtures, and the like.
Conventionally proposed light reflector plates for use with illumination signboards, liquid crystal displays, lighting fixtures, and the like include those fabricated as follows: a light-reflecting film having a thickness of about 200 μm is laminated on an aluminum or steel plate, and the resultant reflector plate material is formed into a three-dimensional shape to thereby yield a light reflector plate; and a reflector plate of resin is formed into a three-dimensional shape to thereby yield a light reflector plate (refer to, for example, Japanese Patent Application Laid-Open (kokai) No. 6-260010).
However, fabrication of the former light reflector plate—fabricated in a manner such that a light-reflecting film is laminated on an aluminum or steel plate, and the resultant reflector plate material is formed into a three-dimensional shape—involves a number of press dies and a number of working steps, resulting in high die cost, increased man-hours, and high cost of working. Fabrication of the latter light reflector plate—fabricated in a manner such that a reflector plate of resin is formed into a three-dimensional shape—involves thermal molding that uses a molding die or the like. However, this fabrication method involves poor working accuracy caused by, for example, shrinkage after thermal molding, as well as high molding die cost and cost of working.
The present invention has been accomplished in view of the foregoing, and an object of the invention is to provide a light reflector plate including a bent light-reflecting film or sheet of resin and having the following advantages A to D:
To achieve the above object, the present invention provides the following methods 1 to 5 for manufacturing a light reflector plate:
Also, the present invention provides a light reflector plate characterized by being manufactured by the method for manufacturing a light reflector plate as described above in any one of 1 to 5. Specifically, the light reflector plate of the present invention is a light reflector plate characterized by being fabricated by a method such that narrow cuts are intermittently formed in a light-reflecting plastic foam film or sheet along a straight line in such a manner as to penetrate from one side surface of the film or sheet to the opposite side surface thereof, and subsequently the film or sheet is bent along the cuts, as well as a light reflector plate fabricated such that the thus-obtained light reflector plate is fixed on an aluminum or steel plate by the method described above in 4.
As mentioned previously, conventionally, in order to form, into a three-dimensional shape, a reflector plate material including an aluminum or steel plate having a thickness of about 200 μm and a light-reflecting film laminated on the aluminum or steel plate, fabrication involves a number of press dies and a number of working steps. As a result, die cost is high, and the number of working man-hours is large, resulting in high cost of working. Also, in order to form a reflector plate of resin into a three-dimensional shape, a thermal molding method that uses a molding die or the like has been employed. However, this method involves poor working accuracy caused by, for example, shrinkage after thermal molding, as well as high molding die cost and cost of working.
By contrast, according to the present invention described above in 1 to 3, cuts are formed in a plastic foam film or sheet in the form of perforations in rows, whereby the film or sheet can be readily and accurately formed into a three-dimensional shape by bending it inward and outward along the cuts. Thus, the need to use expensive dies is eliminated, and bending work can be performed at low cost by use of simple jigs or the like. Also, according to the present invention described above in 4 and 5, the shape of a three-dimensional light reflector plate formed through the bending work can be retained practically, readily, and accurately.
The present invention will next be described in detail. According to the present invention, narrow cuts are formed in a light-reflecting plastic foam film or sheet in the form of perforations in straight rows in such a manner as to penetrate from one side surface of the film or sheet to the opposite side surface thereof, and subsequently the film or sheet is bent inward and outward along the cuts in the form of perforations in rows, whereby the planar film or sheet can be readily formed into a three-dimensional shape. Preferably, the film or sheet is a thermoplastic polyester or cyclopolyolefin film or sheet having therein a number of fine bubbles or pores having an average diameter not greater than 50 μm.
According to the present invention, preferably, each of the cuts to be formed in the plastic foam film or sheet has a width not greater than 3 mm and a length not longer than 10 mm, and an uncut portion located between two adjacent cuts has a length not shorter than 1 mm. In order to prevent the initiation of breakage of material from a cut portion at the time of bending the film or sheet along a line of cuts, an uncut portion located between intermittently arranged cuts preferably has a length not shorter than 1 mm. The length of a cut is determined on the basis of the following: use of a commercially available cutting tool that has cutting blades arranged intermittently at a pitch not greater than 10 mm so as to cut a row of perforations is inexpensive and practical.
In the case where, instead of the above-mentioned cuts, depressed ruled lines are formed straight on the surface of a film or sheet, and subsequently bending the film or sheet inward and outward along the lines is attempted, the bending work is hard to carry out, since a force required for bending is large, and the film or sheet is not necessarily bent along the ruled lines.
Also, use of an unfoamed plastic sheet or film involves the following problem: in the case of involving a large number of bending lines or a large area subjected to bending (e.g., the case shown in
According to the present invention, after a step of bending the above-mentioned light-reflecting plastic foam film or sheet along the cuts to thereby obtain a bent reflector plate, there is performed a step of inserting, into a hole or slit portion provided on the bent reflector plate, a claw-like standing portion having a width of 1 mm to 5 mm and a length of 3 mm to 20 mm and formed on an aluminum or steel plate having a thickness not greater than 1 mm, and bending the claw-like standing portion to thereby fixedly join together the bent reflector plate and the aluminum or steel plate. That is, preferably, in order to retain the shape of a three-dimensionally bent film or sheet, a claw-like bend portion is provided on an aluminum or steel plate; after insertion of the claw into a corresponding hole or slit portion provided on the film or sheet, the claw is, for example, bent forward or backward to thereby attach the film or sheet to the aluminum or steel plate. In this case, preferably, in order to facilitate bending of the claw, the thickness of the aluminum or steel plate is not greater than 1 mm; the width of the claw is 1 mm to 5 mm, and the length of the claw is 3 mm to 20 mm; and the claw is formed through slit cutting because of easiness of machining.
Preferably, claw clamp portions formed through insertion of the claw-like standing portions into the corresponding holes or slit portions mentioned above are arranged at a pitch not greater than 300 mm. That is, by arranging the clamping claws in a planar direction at a pitch not greater than 300 mm, even when the completed reflector plate is put into actual used or tested at high temperature, at high humidity, or under thermal cycle conditions, the shape can be retained with a desired dimensional accuracy. The bent film or sheet can be attached to the aluminum or steel plate by means of pressure sensitive adhesive double coated tape. However, this method is disadvantageous in that positioning between the bent film or sheet and the metal plate to which the film or sheet is to be attached is difficult. Attachment by screws is also possible. However, when a number of fastening positions are involved, cost tends to increase, and thus the method becomes impractical.
Next, embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited thereto. A light-reflecting plastic foam sheet having a thickness of 1 mm and an internal bubble diameter not greater than 50 μm (e.g., MCPET (registered trademark) from The Furukawa Electric. Co., Ltd.) is commercially available and is formed as follows: an extruded sheet of thermoplastic polyester is impregnated with carbon dioxide gas under high pressure, and the resultant sheet is foamed through application of heat. Also commercially available is a light-reflecting plastic foam film formed from cyclopolyolefin and having a thickness of 0.5 mm and an internal bubble diameter not greater than 50 μm. The examples below are offered to illustrate a method for manufacturing, from the light-reflecting sheet and film and by use of the present invention, a three-dimensional light reflector plate to be placed behind fluorescent lamps that serve as light sources for backlight of a liquid crystal display unit.
As shown in
Next, as shown in
When, as shown in
8) formed through foaming eightfold and having an average bubble diameter not greater than 50 μm and a thickness of 0.5 mm was to be attached onto a formed aluminum article 26 (
Subsequently, the film 22 was bent along perforation portions 28, which correspond to the standing portions 24 of the formed aluminum article 26. Claw-like standing portions 30 each having a width of 2 mm and a length of 4 mm were formed on the formed aluminum article 26 at a pitch of 200 mm at positions selected so as to avoid contact with a fluorescent lamp at the time of application of vibration. U-shaped slit portions 32 each having a side length of 3 mm as shown in
The present invention yields the following effects:
Number | Date | Country | Kind |
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2002301828 | Oct 2002 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP03/12956 | 10/9/2003 | WO | 7/5/2005 |