Apparatus for fabricating a perforated web by light

Abstract: An apparatus for fabricating a perforated web comprises an endless masking plate (4) arranged above a continuously conveyed web (5). The masking plate has a plurality of apertures (34) arranged in a predetermined pattern, the masking plate being adapted so as to be continuously circulated. The light is irradiated to the web via the masking plate so that apertures or slits are formed in the web corresponding to the apertures of the masking plate. The light source (1) may be a laser, an infrared light, or an ultraviolet light, and the light from the source is diverged transversely about the web and converged longitudinally about the web.

Description: The present invention relates to an apparatus for fabricating a perforated web by a light, and in particular, the present invention relates to an apparatus for continuously forming apertures or slits in a moving web by the energy of a light, according to the preamble of claim 1 (see US-A-4 507 535). There are known apparatuses and methods for forming apertures or slits in a continuously moving web using razor edges, needles, or rotatable blades (cf, for example, Japanese Examined Patent Publication (Kokoku) No. 60-37786 filed by the inventors of this application). The method of forming apertures or slits in a wide web using a sharp cutting edge has a shortcoming in that the life of the cutting edge is short due to wear thereof and it is difficult to accurately arrange a plurality of cutting edges in position. Apparatuses and methods for forming apertures or slits in a continuously moving web using hot cutting edges to melt the web (cf, for example, Japanese Examined Patent Publication (Kokoku) No. 61-11757) are also known. The method of forming apertures or slits using heat has a problem in that margins of apertures or slits melt to a greater extent and the shape of the margins is not clear, in addition to the above described problem concerning the cutting edges. Denaturalization of the margins of apertures or slits is not preferable when the resultant perforated web is to be subsequently stretched. Laser techniques are being developed and used in a variety of fields, and heat energy is being used for cutting with the development of carbon dioxide lasers or YAG (yttrium, aluminum and garnet) lasers. The conventional cutting method using the laser beam is to continuously cut a web longitudinally, or to perforate holes regularly along the length of the web (cf, for example, Japanese Examined Patent Publication (Kokoku) No. 1-46236). Also, laser beams are used for engraving or forming holes in wood or plastic plates, using a masking plate of a predetermined size (cf, for example, Japanese Unexamined Patent Publication (Kokai) No. 58-15232). Also, as an example of a laser beam applied to a moving web, the use of heat energy of a laser beam for drying the web (cf, for example, Japanese Examined Patent Publication (Kokoku) No. 3-54053) is known. Heat energy of the laser beam is also used to dry paintings or to weld plates by concentrating the laser beam at a point. However, the laser beam is not used for perforating a moving web since it is difficult to concentrate the laser beam at a point on the moving web, and the power of the laser beam is insufficient. Also, ultraviolet light such as used in an eximer laser is used for precision procedures in semiconductor devices, but perforating a moving web using ultraviolet light is not known. The present invention is directed to an apparatus for continuously perforating a moving web using a light such as a laser beam, infrared light, or ultraviolet light. In the afore-mentioned prior art, it is not possible to continuously form a plurality of discontinuous holes in a moving web having a width in a non-contact manner and at an economical speed, and though there has been a demand for continuously forming a plurality of holes along the width of a web using a masking plate, it has not been possible to continuously form a plurality of holes in the moving web because the masking plate of a predetermined size in the prior art cannot follow the moving web. Recently, in the field of non-woven fabrics, a large amount of cross-laminated non-woven fabric comprising a warp web and a weft web have been manufactured. The warp web is fabricated by forming slits in a web so that the slits extend longitudinally about the web and by stretching the web in the direction of the slits; the weft web is fabricated by forming slits in a web so that the slits extend transversely about the web and by stretching the web in the direction of the slits; and the warp and weft webs are laminated one above the other so that the stretching directions are held crosswise to each other. Also, a reinforced film, in which a film is stretched uniaxially or biaxially and the stretched film is perforated, is used in a variety of fields. There is also known from US-A-4,302,654, an apparatus for forming perforations in cigarette tipping paper. The apparatus involves use of driven cylindrical masks and a laser beam. A similar apparatus is known from US-A-4 507 535. It is an object of the present invention to provide an apparatus for fabricating a perforated web using a light, by which apertures or slits are clearly formed in the intended shape and the film is not affected during the perforating step. According to the present invention there is provided an apparatus for fabricating a perforated web comprising: conveying means for conveying a web along a predetermined path and in a predetermined direction, the web having a longitudinal direction in correspondence with the conveying direction and a width; an endless masking plate arranged along the predetermined path and having a plurality of apertures arranged in a predetermined pattern, the masking plate being adapted so as to be continuously circulated around a fixed point at the same conveying speed as the web; a source of light; and an optical means for directing the light from the source to the masking plate to form apertures in the web, characterised in that said predetermined pattern is formed by a plurality of transversely-spaced-apart apertures and extends across the width of the masking plate and in that said source of light and said optical means are arranged such that light is irradiated onto a continuous area of the masking plate containing said plurality of transversely-spaced-apart apertures. The optical means may be arranged to diverge light from said source transversely with respect to the web. This is called the system M hereinafter. Preferably, the optical means includes a second optical means for converging the light from the source longitudinally about the web. Preferably, the optical means includes a third optical means arranged between the second optical means and the masking plate for gathering the light. The optical means can be arranged so that the light impinges upon the masking plate at an area having a width corresponding to the width of the web (called the system M-1). Also, the optical means can be arranged so that the light impinges upon the masking plate at an area having a width smaller than the width of the web (called the system M-2). In the latter case, the optical means includes a traversing means for traversing the light transversely about the masking plate. Preferably, the masking plate is supported at one side thereof by a rotatable body, and at least a part of the optical means is stationary and arranged within the masking plate, the light from the source being passed from the other side of the masking plate to at least a part of the optical means in the masking plate and to the masking plate. In this case, the rotatable body is preferably supported on a stationary shaft by a bearing, the stationary shaft extending in the mask plate and supporting at least a part of the optical means. The source of light may comprise a plurality of elements emitting divergent light, respectively, to cover the width of the web. The beam diameter may be narrowed as small as possible, for example, several tens to one hundred of microns in the case of a laser beam. A plurality of such beams may be used together to increase the efficiency of the operation. The source of light may be a source of infrared light, and in this case, a conventionally available halogen lamp my be preferable for a light having high energy. A usual halogen lamp emits a light in the bandwidth of a wavelength having a peak near 1 micron, which is scarcely absorbed in a polymer material, but it has been found that when a halogen lamp is controlled to emit a light of approximately 700°C the peak of the wavelenth thereof becomes approximately 3.5 microns and the energy of such a light is effectively absorbed in a polymer material having a C-C bond. It is also possible to use a light of medium or long wavelength (a far infrared light) longer than that of the infrared light, using a ceramic heater or the like. The infrared light is thus advantageous since a major wavelength can be selectively used. It is also possible to turn off an unnecessary wavelength component using a filter. It is possible to use the heat energy of a combustion gas or an electric heater as a source of infrared light, as well as an infrared heater or an infrared lamp. The infrared light emitting device is cheaper, easier to handle, and has a larger energy effect than a laser emitting device. Also, it is possible to provide a linearly patterned light or a spot light. It is also possible to use a gas laser such as a carbon dioxide laser or a carbon monoxide laser, a solid laser such as YAG (ytrium, aluminum and garnet) laser, or a liquid laser. The laser has a single wavelength; the wavelength of the carbon dioxide laser is 10.6 microns and the wavelength of the YAG laser is 1.06 microns, these lasers being preferable for perforating a web that absorbs a light of such wavelength. The laser emitting device is preferably a high or low speed axial flow type but in many cases, a low speed axial flow type provides a stably divergent light. It is also possible to use an ultraviolet light as a source of light for the present invention. The infrared heater or the infrared laser functions based on heat energy but the ultraviolet light functions base on a chemical action that severs or denatures molecular chains. Therefore, it is sufficient that apertures not be opened at the time when the ultraviolet light irradiates the web but the apertures be subsequently opened at the time the web is stretched. It is possible for the ultraviolet light alone to irradiate the web but the ultraviolet light should be used in combination with the laser or the infrared heater so that the ultraviolet light first severs molecular chains thereby denaturing the web and subsequently the infrared light irradiates the web to effectively form holes thereat. The ultraviolet light has a shorter wavelength and it is convenient to concentrate the ultraviolet light at a specific spot or form precise holes. It is also possible to use an excimer laser, a mercury lamp, a metal halide lamp, or an xenon lamp as a source of ultraviolet light. As a masking plate material, a metallic material that does not easily melt is preferable. But, an organic material such as a fabric or a plastic can be used with a suitable coating by metal depositing, ceramic coating, or a heat-resistant coating, to provide a heat-resistant property or reflect light. It is most preferable to plate the masking plate with gold to reflect light at the surface of the masking plate. A highly bright aluminum, copper or chrome plating with a polished surface, or other metals with a mirror finishing are advantageous. It is preferable to arrange the masking plate close to the web to form the apertures exactly corresponding to the apertures of the masking plate. To this end, a close adhesive agent is used or a vacuum is used between the web and the masking plate. It is preferable that the web be preheated to increase the speed of the manufacturing line. The preheating not only assists in increasing the temperature but has an effect such that the molecules of the web oscillate intensely and absorb light easier even if the web may be of a transparent material, such as polyethylene or polypropylene. However, the preheating must be carried out below a melting point if the web has a melting point, or at a softening temperature if the web is an amorphous polymer or a thermosetting polymer since the shape of the web becomes unstable if the web is heated excessively. The web may comprise a film, a paper, a fabric, a non-woven fabric, a metal foil such as a thin copper or a thin aluminum. The film may comprise a thermoplastic resin such as polyethylene, polypropylene, polyvinyl chloride, polyamide, or polyester, or a thermosetting resin such as epoxy, unsaturated polyester, urea, or phenol. It is also possible to add an organic or an inorganic filler or a reinforcing material to the base polymer. If these additives absorb light, the ability to form apertures may be enhanced. When the web is of a material such as polyethylene, which does not have an absorbing wavelength corresponding to the wavelength of the light such as a laser, it is preferable to add a light absorbable material to the web by blending, coating, laminating or printing so that the web as a whole can absorb the light; it is also preferable to preheat the web, as described. As a light absorbable material, there are silicon containing compounds such as silicon carbide and silicon oxide, titanium compounds such as titanium oxide, aluminum compounds such as aluminum oxide, calcium compounds such as calcium carbonate, sulfur compounds, phosphatic manganese, talc, organic or inorganic pigment, pigment or dye such as carbon black and aniline black, tackifier resin such as rosin, and powder resin such as phenol. The solution of the light absorbable material (for example, sodium silicate) can be used as an adhesive material. The thermoplastic film used in the present invention is preferably a stretched film. For example, when a biaxially stretched film such as polypropylene, polyester, polystyrene, polyvinylidene chloride is perforated, the margins of the apertures or the resultant film are melted by heat and are not easily torn, and thus it is possible to obtain a strong perforated film. The films perforated by the light can be used for fabricating a non-woven fabric comprising the lamination of a warp web and a weft web. In fabricating a non-woven fabric, not-stretched or partly stretched films (including a film stretched between a pair of stretching rollers placed a short distance apart) have perforated slits, are stretched longitudinally or transversely so as to obtain a warp or weft webs, and are laminated one above the other with stretching directions crosswise to each other. It is also possible for the fully stretched film to be perforated. The cross-laminated non-woven fabric not only has a strength 3 to 5 times larger than that of a normal nonwoven fabric but can be manufactured at a high productivity rate, for example, a productivity 100 times higher than a weaving machine. A film for forming a weft web having a width of 250 to 300 millimeters is perforated at a line speed of 20 to 100 meters per minute. The warp web having a width of 1 to 3 meters is perforated at a line speed of 5 to 30 meters per minute. Accordingly, the films or webs must be perforated at a rate of 10 to 100 square meters per minute, which is realized by the present invention. It is necessary to use an adhesion to adhere the warp and weft webs. The adhesion is applied to the film when the web is formed by co-extruding, extruding coating, or laminating. It is also advisable that a light absorbable material be mixed in the adhesion. The present invention will become more apparent from the following description of the preferred embodiments, with reference to the accompanying drawings, in which: Fig 1 is a diagrammatic side view of the apparatus according to the first embodiment of the present invention; Fig 2 is a diagrammatic side view of the apparatus according to the second embodiment of the present invention; Fig 3 is a perspective view of the apparatus of Fig. 1; Fig 4 is a cross-sectional view of the apparatus of Fig. 3; Fig 5 is a view illustrating an example of a means for obtaining a divergent light; Fig 6 is a view illustrating another example of a means for obtaining a divergent light; Figs 7 to 10 are views illustrating further examples of means for obtaining a divergent light; Fig 11 is a plan view illustrating the third embodiment according to the present invention; Figs 12 and 13 are views of further examples of means for traversing the light, respectively; Figs 14A to 14C are views of examples of the light irradiated on the masking plate; Fig 15 is a perspective view illustrating the fourth embodiment according to the present invention; Fig 16 is a view illustrating means for obtaining a convergent light; Figs 17A to 17C are views illustrating light absorption in the web in relation to wavelength; Figs. 18A to 18D are views illustrating examples of apertures formed in the web according to the present invention; Figs. 19A and 19B are views illustrating an example of slits formed in the web and the slits when the web is subsequently stretched; Figs. 20A and 20B are views illustrating another example of slits formed in the web and the slits when the web is subsequently stretched; Figs. 21A and 21B are views illustrating another example of slits formed in the web and the slits when the web is subsequently stretched; Figs. 22A and 22B are views illustrating still another example of slits formed in the web and the slits when the web is subsequently stretched; Figs. 23A and 23B are views illustrating still another example of slits formed in the web and the slits when the web is subsequently stretched; and Fig. 24 is a view of the cross-laminated non-woven fabric obtained from the lamination of the webs of Figs. 19A to 23B. Figure 1 shows the first embodiment according to the present invention, concerning the system M-1. The apparatus for fabricating a perforated web comprises conveying rollers 90 for conveying a web 5 along a predetermined path and in a predetermined direction A, an endless ring-shaped masking plate 4 arranged along the predetermined path and having a plurality of apertures 34 (Fig. 3) arranged in a predetermined pattern, a source of light 1, and optical means for directing the light from the source 1 to the masking plate 4 so as to form holes or slits 77 (Fig. 3) in the web 5. The endless masking plate 4 is circulated in the direction of the arrow B. In Figs. 1 and 3, the source of light 1 is arranged outside the masking plate 4 and a concave mirror 3 is arranged inside the masking plate 4. The source of light 1 comprises a plurality of laser emitting devices 1a to 1d each of which emits a laser beam 2a, 2b, 2c, or 2d with a small beam diameter. Convex lenses 91a to 92d are arranged on the optical axes of the laser emitting devices 1a to 1d, respectively, to deliver the divergent light (the divergent beam 2b is shown by hatching in Fig. 3) to the concave mirror 3. The light is reflected at the concave mirror 3 toward the inner surface of the masking plate 4 so that the light, as the total of the beams 2a, 2b, 2c, and 2d, is diverged to the width of the web 5. The concave mirror 3 serves to converge the light from the source 1 longitudinally about the web 5 so that the light in the shape of a narrow belt impinges upon the masking plate 4 In addition, an additional mirror(s) 6 is arranged near the inner surface of the masking plate 4 to gather the light that is reflected at the inner surface of the masking plate 4, the gathered light being again directed to the inner surface of the masking plate 4. It is possible to use other optical means other than the illustrated means to obtain a divergent light corresponding to the width of the web 5 and to converge the light longitudinally about the web 5. Mirrors can be plated with gold, high bright aluminum, copper, and finished to a mirror surface. Also, when the source of light 1 emits a light having a sufficient width corresponding to the width of the web 5, for example, when an infrared light, an ultraviolet light or a mercury lamp is used, it is possible to omit the light diverging means. A spray nozzle 7 is arranged above the masking plate 4 to supply cooling water to cool the masking plate 4. The cooling water flows to a gap between the masking plate 4 and the web 5 to provide surface tension acting so as to maintain close contact between the web 5 and the masking plate 4 and form holes or slits 77 exactly coinciding with the apertures 34 of the masking plate 4. It is possible to mix a tacky agent to a light absorbable agent and when cooling and a supply of the light absorbable agent are required, it is possible to arrange the spray nozzle 7 inside the masking plate 4 so as to hold the light absorbable agent in the apertures 34 of the masking plate 4. However, it should be noted that the masking plate 4 should not be excessive since a preheating of the web 5 is preferable for increasing the speed of the manufacturing line. Also, a vacuum box 8 is arranged below the web 5 to draw a smoke occurring when the web 5 is burned by the light when forming the holes or slits 77. The smoke may reduce the efficiency of the laser beam, soil the mirrors and lenses, and store the heat thereby adversely affecting the performance of the system. In Figs. 3 and 4, the masking plate 4 is supported at one side thereof by a cylindrical rotatable body 92 having a gear 93. The rotatable body 92 is supported on a stationary shaft 94 by bearings 95. The stationary shaft 94 extends in the masking plate 4 and supports the concave mirror 3 and the mirror 6. Another gear 96 is supported to a shaft 97 and engages with the gear 93. An electric motor 98 drives the shaft 97 and thus the masking plate 4. As shown in Fig. 3, the masking plate 4 has a plurality of apertures 34 arranged in rows in a staggered manner. The masking plate is made, for example, from high bright aluminum or copper having a high reflecting surface, and it is possible to plate the inner surface of the masking plate 4 with gold or chrome. As one example, the masking plate 4 has a width of 400 millimeters including a central region of 350 millimeters in which apertures 34 are arranged. The masking plate 4 is cylindrical and has a diameter of 350 millimeters. The masking plate 4 has a thickness of 0.5 millimeters, and when the masking plate 4 has a thickness less than the above dimension (for example, 0.3 millimeters), it may be preferable to arrange a reinforcing rib at the free end of the masking plate 4. Each of the apertures 34 has a dimension of 10 millimeters in the transverse direction of the web 5, and a dimension of 0.2 millimeters in the longitudinal direction of the web 5. The apertures 34 are arranged at a pitch of 2 millimeters in the longitudinal direction of the web 5. Figure 2 shows the second embodiment according to the present invention. In Fig. 2, elements similar to those of Fig. 1 are deleted. The endless masking plate 4 of this embodiment is formed in the shape of a polygonal cylinder and guided by guide rollers 10a to 10d. The web 5 is conveyed in the direction of the arrow A, and the endless masking plate 4 is circulated in the direction of the arrow B, and it is possible to arrange appropriate elements inside the masking plate 4. Vacuum boxes 11a and 11b are arranged inside the masking plate 4 to extract the smoke and to maintain contact between the masking plate 4 and the web 5. A backup roll 12 is arranged below the web 5 to maintain contact between the masking plate 4 and the web 5 to improve the accuracy of the perforated hole and the efficiency of the perforation at the backup roll 12. Also, the web can be preheated by an infrared heater 13 but it is possible to preheat the web 5 by other means such as hot air or a hot cylinder. A portion of the inner surface of the masking plate 4 where the light impinges, is concave in Fig. 1, and flat in Fig. 2, but there is a case in which a portion of the inner surface of the masking plate 4 where the light impinges is convex, thereby efficiently recovering the light reflected at the masking plate 4 by mirrors. Figure 5 shows a modification of an optical means for obtaining a divergent light. This embodiment comprises an integrating sphere 15 having an internal surface plated with gold, an inlet 16, and a narrow and elongated outlet 17. The light enters the integrating sphere 15 from the inlet 16, repeats diffused reflections within the integrating sphere 15 many times, and exits from the integrating sphere 15 in a uniform distribution. Figure 6 shows a modification of an optical means for obtaining a divergent light. This embodiment comprises a box 18 having an internal surface plated with gold, an inlet 19, and a narrow and elongated outlet 20. A square pyramid mirror 80 is inserted in the box 18 so as to create diffused reflections of light. The light exits from the box 18 in an elongated and narrow form. The box 18 may be oval shaped having one end collapsed and elongated. The integrating sphere 15 and the box 18 may be cooled. Figures 7 to 10 show further modifications of an optical means for obtaining a divergent light. The embodiment of Fig. 7 comprises a convex lens L-1 to obtain the convergent light appearing at a position other than the focus thereof. A pair of mirrors M-1 and M-2 are arranged opposite each other to convert the divergent light 2 in an elongated and narrow form. The mirrors M-1 and M-2 are not necessarily symmetrically arranged and are not necessarily flat mirrors. It is also possible to constitute the mirrors M-1 and M-2 from the composite mirrors. The embodiment of Fig. 8 comprises a concave lens L-2 to obtain the convergent light 2'. In this case, it is possible to use mirrors M-1 and M-2, as in the previous case. The embodiment of Fig. 9 comprises a cylindrical lens (a sector of a cylinder) L-2 to obtain the convergent light 2'. The embodiment of Fig. 10 comprises a combination mirror comprising a plurality of segment mirrors M-a, M-b, M-c, ..., arranged to obtain the convergent light 2'. The above examples are shown in a simplified manner and additional optical elements and cooling means (not shown) can be used with the illustrated optical elements. It is possible to use the concave mirror 3 of Fig. 1 and elements of Figs. 7 to 10 individually and it is possible to use these elements in combination. The lens used in the present invention must absorb the light which is determined according to the characteristic of the used light, and if there is an unnecessary component of light, as described later, it is possible to use filtered light or to coat or attach by baking a material to reflect the unnecessary wavelength component of the light to the lens. It is preferable that the lens is capable of being cooled. Figure 11 shows the third embodiment according to the present invention, concerning the system M-2. The apparatus of this embodiment comprises a means (not shown) for conveying a web 5 in the direction A, an endless masking plate 4 circulated in the direction B and having a plurality of apertures 34, a source of light 1, and an optical means for directing the light from the source 1 to the masking plate 4. In this example, the source of light 1 comprises an infrared lamp, and the optical means for directing the light from the source 1 to the masking plate 4 comprises a concave mirror 21 and a mechanism traversing or scanning the light reflected at the concave mirror 21. The concave mirror 21 causes light 2' to impinge upon the masking plate 4 at an area having a width smaller than the width of the web. The concave mirror 21 is traversed by the traversing mechanism comprising a support block 21a supporting the concave mirror 21, a pair of guide rails 24a and 24b for reciprocatingly guiding the support block 21a transversely about the web 5, as shown by the arrow C, a crank 23 having one end connected to the support block 21a and the other end connected to an electric motor 22. The motor 22 causes the support block 21a with the concave mirror 21 to move transversely about the web 5 so that the light reflected at the concave mirror 21 traverses the width of the web 5 to form the holes or slits in the web depending on the apertures 34 of the masking plate 4. It is possible to use other elements for the traversing mechanism, for example, cams or electromagnetic elements can be used. It is also possible for several lights to be arranged along the width of the web 5, and in this case, each of the lights is traversed along a fraction of the width of the web 5. Figs. 12 and 13 are views of further examples of the traversing means. In Fig. 12, a plurality of mirrors 21a to 21c are attached to a belt 26 travelling between pulleys 25a and 25b. One of the mirrors 21a to 21c, which is above the belt 26, receives and reflects the light 2 so that the light traverses the web 5. When optical fibers can be used, for example, with the YAG laser, or when the light is guided by a flexible tube, as in a laser scalpel for a medical application, it is possible to traverse the optical fibers or the flexible tube. Fig. 13 shows an example in which a bundle of optical fibers 27 is traversed depending on the rotation of a cam 28. It is also possible to use an oscillating mirror in Fig. 16 or a polygonal mirror in Fig. 17. Figs. 14A to 14C are views of examples of preferable patterns of the light irradiated on the masking plate in the system M. Opposite sides 31a and 31b of the masking plate 4 are reinforced and have holes 32 for engagement with a sprocket wheel to drive the masking plate 4. A plurality of apertures 34 are formed in the central portion of the masking plate 4. The apertures 34 are shown in a circular shape in this example, but the apertures 34 can be formed in a variety of shapes, as shown in Figs. 27A to 32A. The masking plate 4 can be made from copper or iron, and the apertures 34 can be formed in the masking plate 4 by a chemical etching process or by a laser cutting. As shown in Fig. 14A, in the system M-1, the light 2 has a constant width corresponding to the width of the web 5. The light 2 is narrowed longitudinally about the web 5 as small as possible so that the intensity of the light per unit area becomes large and the efficiency of the perforation is high. Fig. 14B also concerns the system M-1, in which a plurality of spaced light 2a to 2d having respective impinging areas are arranged to cover the width of the web 5. This example is advantageous when it is difficult to manufacture a single, large source of light 1. Figure 14C concerns the system M-2, in which the light 2 traverses the width of the web 5. The light 2 is extended longitudinally about the web 5 and it is possible to increase the line speed without excessively increasing the traversing speed. Figure 15 shows the fourth embodiment according to the present invention, concerning the system M-1. The apparatus of this embodiment comprises a means (not shown) for conveying a web 5 in the direction A, an endless masking plate 4 circulated in the direction B and having a plurality of slits 34 arranged in transverse rows (the slits 34 are shown partly in the masking plate 4), a source of light, and an optical means for directing the light from the source to the masking plate 4. In this example, the source of light comprises an ultraviolet lamp 35 having an elongated shape along the width of the web 5 and an infrared lamp 38 having an elongated shape along the width of the web 5 and arranged on the downstream side of the ultraviolet lamp 35. The ultraviolet lamp 35 is covered by a cover 36 that reflects the light from the ultraviolet lamp 35 to the masking plate 4 to direct a thick irradiation pattern 37 to the masking plate 4. The ultraviolet beam gives the web 5 and optical-chemical action via the slits 34. The infrared lamp 38 is also covered by a cover 39 that reflects the light from the infrared lamp 38 to the masking plate 4 so as to direct a narrow irradiation pattern 40 to the masking plate 4 to form slits in the web 5 via the slits 34. It is possible to use a filter to select a desirable wavelength of the infrared light, thereby reducing the temperature rise of the masking plate 4 while providing necessary energy to the web 5 for forming slits. The irradiation pattern 40 of the infrared light is preferably as narrow as possible in the longitudinal direction of the web 5 so as to concentrate the energy of the infrared light applied to the web 5. In this regard, it is advantageous to use a cylindrical mirror for the cover 39 to collect the light in a linear pattern on the masking plate 4. It is also possible to arrange a plurality of infrared light emitting devices in multiple stages. It is also possible to arrange a pluralty of infrared light emitting devices to irradiate the light in a linear pattern on the masking plate 4. In the case that the ultraviolet light is used with the infrared light, the molecules of the web 5 are denatured by the optical-chemical action of the ultraviolet light so as to easily absorb the infrared light and decompose the web 5, resulting in increased efficiency. The system M using the ultraviolet light is advantageous when the property of the web 5 changes upon the masking plate 4 overheating, or when the web 5 absorbs less infrared light. Figure 16 shows an embodiment to produce a convergent light using a rotated ellipsoidal body. This embodiment comprises a box 60a and 60b having an internal rotated ellipsoidal surface having focuses F1 and F2, and a lamp 51 arranged on one of the focuses F1, so that the light emitting from the lamp 51 is collected at the other focus F2. The position of the lamp 51 can be adjusted by a screw 61. Water is introduced in the box 60a and 60b from inlets 62a and 62b and discharged from outlets 63a and 63b to cool the interior of the box 60a and 60b. The light collected at the focus F2 exits the box 60a and 60b from an exit pipe 64m which is tapered. The interiors of the box 60a and 60b and the exit pipe 64 are plated with gold, and the converged light emitting from the exit pipe 64 is further converged by a lens 65. Figure 17A shows the transmittance of polyethylene versus the wavelength and Figure 17C shows the transmittance of polypropylene versus the wavelength. It is known that polyethylene and polypropylene have light absorbing ranges at a wavelength of approximately 3.5 and 7 microns. The transmittance of polyethylene and polypropylene by the light having a wavelength of approximately 1 micron is approximately 95 percent, although this is not shown in these Figures. Dioxide laser has a wavelength of 10.6 microns and a YAG laser has a wavelength of 1.06 microns, and accordingly, polyethylene and polypropylene do not absorb any of these laser beams. Figure 17C shows the radiation energy of a lamp such as a halogen lamp the wavelength at the temperature of 1100°C, 900°C, and 700°C. It has been found that the lower the temperature of the heater, the lower the radiation energy but the peak of the radiation energy shifts to the long wavelength side. The curve with the hatching shows that the radiation energy is relatively high and the peak of the radiation energy is shifted to the long wavelength side, which is attained by producing the surface of the heater from a ceramic material. Figures 18A to 18D show examples of a perforated web having holes 77 formed in a uniaxially or biaxially stretched film. The biaxially stretched film has strength in a longitudinal and transverse direction and has a resistance to tearing since the margins around the holes 77 are sealed by heating and it is possible to provide a good design appearance, as shown in Figs. 18A to 18D. Figures 19A to 23B show examples of perforated webs for fabricating a cross-laminated non-woven fabric. In Figs. 19A and 20A, longitudinal slits 77 are formed in a non-stretched or partly stretched web 5. Figs. 19B and 20B show that the web 5 having the longitudinal slits 77 are stretched longitudinally, as shown by the arrow in Figs. 19A and 20A. The web is preferably stretched by a pair of stretching rollers arranged a short distance therebetween to form a network structure having widely open apertures. In Fig. 19A, s1 and s2 represent slits (apertures), and m1 and m2 represent unslit portions between the slits. To form the stretched web, it is important that the unslit portions in one row do not coincide with the unslit portions in the transversely adjacent rows. The unslit portions are precisely arranged in a staggered manner in the embodiment, but it is not always necessary to arrange as such. In Figs. 21A, 22A, and 23A transverse slits 77 are formed in a non-stretched or partly stretched web 5. In this case too, the unslit portions in one row do not coincide with the unslit portions in the longitudinally adjacent rows. Figs. 21B and 23B show that the web 5 having the transverse slits 77 are stretched transversely, as shown by the arrow in Figs. 21A to 23A. According to the present invention, the slits 77 are formed by the light and it is possible to obtain slits arranged in a complex pattern, as shown in Figs. 20A and 23A. Figure 24 shows a non-woven fabric 100 comprising the warp web 5A and the weft web 5b. The warp web 5a corresponds to the web 5 of Fig. 19B or 20B, and the weft web 5b corresponds to the web 5 of Fig. 21B or 22B. It is possible that one of the warp and weft webs 5a and 5b is formed by the light according to the present invention and the other web is formed conventionally by slitting edges. It is also possible to form slits in an uniaxially stretched film. As described in greater detail, according to the present invention, it is possible to continuously form apertures or slits in a web continuously conveyed at high speed and the margins of the apertures or slits thus formed are clear.

Claims: An apparatus for fabricating a perforated web comprising: conveying means (90) for conveying a web (5) along a predetermined path and in a predetermined direction, the web (5) having a longitudinal direction in correspondence with the conveying direction and a width; an endless masking plate (4) arranged along the predetermined path and having a plurality of apertures (34) arranged in a predetermined pattern, the masking plate (4) being adapted so as to be continuously circulated around a fixed point at the same conveying speed as the web (5); a source of light (1;35,38); and an optical means (91a-91d;21,22,23;36,39) for directing the light from the source (1;35,38) to the masking plate (4) to form apertures in the web (5), characterised in that said predetermined pattern is formed by a plurality of transversely-spaced-apart apertures and extends across the width of the masking plate (4) and in that said source of light (1;35,38) and said optical means (91a-91d; 21,22,23; 36,39) are arranged such that light is irradiated onto a continuous area of the masking plate (4) containing said plurality of transversely-spaced-apart apertures. An apparatus according to claim 1, wherein said optical means (91a-91d) is arranged to diverge light from said source (1) transversely with respect to the web (5). An apparatus according to claim 2, wherein the optical means includes second optical means (3) for converging the light from the source (1) longitudinally of the web (5). An apparatus according to claim 3, wherein the optical means includes third optical means (6) arranged between the second optical means (3) and the masking plate (4) for gathering the light. An apparatus according to claim 1, wherein the optical means is arranged so that the light impinges upon the masking plate (4) at an area having a width corresponding to the width of the web (5). An apparatus according to claim 1, wherein the optical means comprises a body (15,18) having a cavity with an inlet (16,19) and outlet (17,20), the cavity having an internal reflecting surface at which the light incident from the inlet (16,19) is subjected to diffused reflections and existing from the outlet (17,20) in the pattern in conformity of the shape of the outlet (17,20). An apparatus according to claim 1, wherein means (7) for cooling the circulating masking plate (4) is provided. An apparatus according to claim 1, wherein means (8;11a,11b) for extracting a smoke is provided. An apparatus according to claim 1, wherein means (13) for preheating the web (5) is provided. An apparatus according to claim 1, wherein the source of light (1) comprises means (35) generating an ultraviolet light and means (38) for generating an infrared light. An apparatus according to claim 1, wherein the masking plate (4) has a portion that contacts the web (5) and moves with the web (5). An apparatus according to claim 11, wherein the said portion that contacts the web (5) is a curved portion. An apparatus according to claim 11, wherein the said portion that contacts the web (5) is a generally planar portion. An apparatus according to claim 1, wherein the optical means is arranged so that the light impinges upon the masking plate (4) at an area having a width smaller than the width of the web (5). An apparatus according to claim 14, wherein the optical means includes a traversing means (21a,22,23, 24a,24b) for traversing the light transversely with respect to the masking plate (4). An apparatus according to claim 1, wherein the masking plate (4) is formed in the shape of a cylinder. An apparatus according to claim 16 wherein the masking plate (4) is formed in the shape of a circular cylinder. An apparatus according to claim 16, wherein the masking plate (4) is formed in the shape of a polygonal cylinder. An apparatus according to claim 1, wherein the masking plate (4) is supported at one side thereof by a rotatable body (92), and at least a part (3,6) of the optical means is stationary and arranged within the masking plate (4), the light from the source (1) being passed from the other side of the masking plate (4) to at least a part of the optical means (3) in the masking plate (4) and to the masking plate (4). An apparatus according to claim 19, wherein the rotatable body (92) is supported on a stationary shaft (94) by a bearing (95), the stationary shaft (94) extending in the masking plate (4) and supporting at least a part (3,6) of the optical means. An apparatus according to claim 1, wherein the source (1) of the light emits at least one of a laser beam, an infrared light beam, and an ultraviolet beam. An apparatus according to claim 1, wherein the apertures formed in the web (5) comprise transverse slits and the web (5) is arranged to be stretched in the transverse direction.

Inventors: KURIHARA KAZUHIKO, KUROIWA YUKI, MURAKAMI SHUICHI, YAZAWA HIROSHI, YAZAWA SHOICHI, KURIHARA, KAZUHIKO, KUROIWA, YUKI,, MURAKAMI, SHUICHI,, YAZAWA, HIROSHI, YAZAWA, SHOICHI,
Applicants: NIPPON PETROCHEMICALS CO LTD, POLYMER PROCESSING RES INST, NIPPON PETROCHEMICALS COMPANY, LIMITED, POLYMER PROCESSING RESEARCH INSTITUTE LIMITED
Application year: 1992
Main classification: B23K26
IPC codes: D06C23, D06M101, D06M10, B23K26, D04H13