LASER PROCESSING METHOD FOR PLASTIC FILM, AND PLASTIC FILM

Abstract

A laser processing method is disclosed which is capable of easily reducing contamination on a plastic film surface, and also capable of cutting a plastic film in a free-form shape. A laser processing method includes a process of pulsing a laser beam L having a wavelength in the infrared region from a laser beam source 1 and causing a plastic film F to be irradiated with the laser beam L to cut the plastic film. The peak energy density of the laser beam with which the plastic film is irradiated is 70 J/cm.sup.2 or more and 270 J/cm.sup.2 or less.

Claims

1. A laser processing method for a plastic film, comprising: a process of pulsing a laser beam having a wavelength in an infrared region and causing a plastic film to be irradiated with the laser beam to cut the plastic film, wherein a peak energy density of the laser beam with which the plastic film is irradiated is 70 J/cm.sup.2 or more and 270 J/cm.sup.2 or less.

2. The laser processing method for a plastic film according to claim 1, wherein: a pulse energy of the laser beam with which the plastic film is irradiated is 3.4 mJ/pulse or more and 8 mJ/pulse or less.

3. A laser processing method for a plastic film comprising: a process of, with respect to a plastic film in which at least a protective film, an adhesive and a base material are laminated in that order, pulsing a laser beam having a wavelength in an infrared region from the protective film side and causing the plastic film to be irradiated with the laser beam to cut the plastic film, wherein a thickness of the adhesive is 20 m or less.

4. The laser processing method for a plastic film according to claim 1, wherein: a wavelength of the laser beam is 5 m or more and 11 m or less.

5. The laser processing method for a plastic film according to claim 1, wherein: a cut form of the plastic film is a full cut or a half cut.

6. The laser processing method for a plastic film according to claim 1, wherein: the plastic film is cut in a free-form shape by two-dimensionally scanning the laser beam and the plastic film relative to each other.

7. A plastic film in which at least a protective film, an adhesive and a base material are laminated in that order, wherein a width of contamination caused by components derived from the adhesive that adhere to the protective film surface is 0.3 mm or less.

8. The plastic film according to claim 7, wherein: a thickness of the adhesive is 20 m or less.

9. The plastic film according to claim 7, wherein: the plastic film is a polarizing film.

10. The plastic film according to claim 8, wherein: the plastic film is a polarizing film.

11. The laser processing method for a plastic film according to claim 2, wherein: a wavelength of the laser beam is 5 m or more and 11 m or less.

12. The laser processing method for a plastic film according to claim 2, wherein: a cut form of the plastic film is a full cut or a half cut.

13. The laser processing method for a plastic film according to claim 2, wherein: the plastic film is cut in a free-form shape by two-dimensionally scanning the laser beam and the plastic film relative to each other.

14. The laser processing method for a plastic film according to claim 3, wherein: a wavelength of the laser beam is 5 m or more and 11 m or less.

15. The laser processing method for a plastic film according to claim 3, wherein: a cut form of the plastic film is a full cut or a half cut.

16. The laser processing method for a plastic film according to claim 3, wherein: the plastic film is cut in a free-form shape by two-dimensionally scanning the laser beam and the plastic film relative to each other.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0042] FIG. 1 is a diagram that schematically illustrates one example of a laser processing apparatus used in a laser processing method according to one embodiment of the present invention.

[0043] FIG. 2 FIGS. 2A to 2C are diagrams that schematically illustrate cross sections of plastic films used in tests according to Examples and Comparative Examples.

[0044] FIG. 3 is an explanatory drawing for describing a method for evaluating the contamination of a plastic film surface.

[0045] FIG. 4 is a table showing various conditions of laser processing methods according to Examples and Comparative Examples, and contamination widths W that were evaluated.

DESCRIPTION OF EMBODIMENTS

[0046] Hereunder, a laser processing method for a plastic film according to one embodiment of the present invention is described with reference being made as appropriate to the attached drawings.

[0047] FIG. 1 is a diagram that schematically illustrates one example of a laser processing apparatus used in a laser processing method according to one embodiment of the present invention.

[0048] As illustrated in FIG. 1, a laser processing apparatus 100 of the present embodiment includes a laser beam source 1, an optical element 2, reflection mirrors 3 and 4, a galvanometer mirror 5, a telecentric f lens 6, an X-Y dual-axis stage 7 and a control device 8.

[0049] Although the laser beam source 1 is not particularly limited as long as it is a laser beam source that pulses a laser beam L having a wavelength in the infrared region, preferably a laser beam source is used in which the wavelength of the laser beam L that is pulsed from the laser beam source 1 is 5 m or more and 11 m or less. Specifically, a CO laser beam source (oscillation wavelength: 5 m) or a CO.sub.2 laser beam source (oscillation wavelength: 9.3 to 10.6 m) is used. In the case of using a CO laser beam source, the optical path of the laser beam L may be purged using an inert gas such as nitrogen.

[0050] The optical element 2 is constituted by various optical components such as an acousto-optic modulator (AOM) for controlling the power (intensity) of the laser beam L, an expander or condenser lens or aperture for condensing the laser beam L, and a homogenizer for flattening the spatial beam profile of the laser beam L.

[0051] The laser beam L that is oscillated from the laser beam source 1 and passes through the optical element 2, is reflected and deflected at the reflection mirrors 3 and 4, respectively, and is incident on the galvanometer mirror 5.

[0052] The laser beam L incident on the galvanometer mirror 5 is reflected and deflected by the galvanometer mirror 5 to be incident on the telecentric f lens 6. The galvanometer mirror 5 is capable of changing the deflection direction of the reflected laser beam L by pivoting. In the example illustrated in FIG. 1, the deflection direction of the laser beam L is changed in the X-direction of an X-Y two-dimensional plane (the deflection direction of the laser beam L indicated by the arrow mark of the straight line in FIG. 1 is sequentially changed to the deflection directions indicated by the arrow marks of the dashed lines) by the galvanometer mirror 5. That is, the laser beam L is scanned in the X-direction.

[0053] The laser beam L that is incident from the galvanometer mirror 5 and exits from the telecentric f lens 6 is emitted onto a plastic film F from a direction perpendicular to the surface of the plastic film F at each of the scanning positions in the X-direction, and is also emitted with a uniform spot diameter at each of the scanning positions.

[0054] The plastic film F is placed on and fixed (fixed by suction) to the X-Y dual-axis stage 7, and the X-Y dual-axis stage 7 changes the position on the X-Y two-dimensional plane of the plastic film F.

[0055] The control device 8 of the present embodiment coordinates and controls the galvanometer mirror 5 and the X-Y dual-axis stage 7. Specifically, a desired cutting shape of the plastic film F is input in advance into the control device 8. The control device 8 outputs a control signal for cutting the plastic film F in accordance with the input cutting shape (scanning the laser beam L at cutting positions in accordance with the desired cutting shape), to the galvanometer mirror 5 and the X-Y dual-axis stage 7. The galvanometer mirror 5 and the X-Y dual-axis stage 7 each operate in accordance with the input control signal, and the laser beam L is sequentially scanned at the cutting positions of the plastic film F in accordance with the desired cutting shape by co-operation between the galvanometer mirror 5 and the X-Y dual-axis stage 7.

[0056] Further, the control device 8 outputs a control signal to the laser beam source 1 to control settings with respect to the on/off timing, repetition frequency, and power of the laser beam L that is oscillated from the laser beam source 1.

[0057] A laser processing method according to the present embodiment that uses the laser processing apparatus 100 having the above configuration is described hereunder.

[0058] The laser processing method according to the present embodiment includes a process of pulsing the laser beam L from the laser beam source 1 and causing the plastic film F to be irradiated with the laser beam L to thereby cut the plastic film F. At such time, by the control device 8 controlling the galvanometer mirror 5 and the X-Y dual-axis stage 7, the laser beam L and the plastic film F are two-dimensionally scanned relative to each other so that the plastic film F is cut into a desired free-form shape. The cut form with respect to the plastic film F is not limited to a full cut, and it is also possible to adopt a half cut as the cut form.

[0059] Examples of the plastic film F that is the cutting object in the laser processing method according to the present embodiment include a single-layer film or a laminated film composed of multiple layers which is formed of polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), an acrylic resin such as polymethyl methacrylate (PMMA), a cyclic olefin polymer (COP), a cyclic olefin copolymer (COC), a polycarbonate (PC), a urethane resin, a polyvinyl alcohol (PVA), a polyimide (PI), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polystyrene (PS), triacetylcellulose (TAC), polyethylene naphthalate (PEN), ethylene vinyl acetate (EVA), a polyamide (PA), a silicone resin, an epoxy resin, a liquid crystal polymer, or a plastic material such as various kinds of resin foam.

[0060] The plastic film F adopted as the cutting object in the laser processing method according to the present embodiment preferably has an absorptivity of 15% or more with respect to the wavelength of the laser beam L with which it is irradiated.

[0061] In a case where the plastic film F is a laminated film composed of multiple layers, various kinds of adhesive such as acrylic adhesive, urethane adhesive, or silicone adhesive, or a bonding agent may be interposed between the layers.

[0062] Further, an electroconductive inorganic membrane composed of indium tin oxide (ITO), Ag, Au, or Cu or the like may be formed on the surface of the plastic film F.

[0063] The laser processing method according to the present embodiment is favorably used for various kinds of optical films such as a polarizing film or a phase contrast film to be particularly used in a display.

[0064] The thickness of the plastic film F is preferably made to fall within the range of 20 to 500 m. Regarding the form of the plastic film F, the plastic film F may be in a sheet-like form as in the present embodiment or may be in the form of a raw film that is wound in a roll shape.

[0065] In the laser processing method according to the present embodiment, the peak energy density of the laser beam L oscillated from the laser beam source 1 and causing the plastic film F to be irradiated with the laser beam L (peak energy density at the irradiated position on the film F) is set to 70 J/cm.sup.2 or more and 270 J/cm.sup.2 or less. Further, the pulse energy of the laser beam L with which the plastic film F is irradiated (pulse energy at the irradiated position on the film F) is set to 3.4 mJ/pulse or more and 8 mJ/pulse or less. The optical components such as the AOM constituting the optical element 2 are adjusted so that the aforementioned peak energy density and pulse energy are obtained.

[0066] In the laser processing method according to the present embodiment, the control device 8 controls the galvanometer mirror 5 and the X-Y dual-axis stage 7 so that a shot pitch of the laser beam L is smaller than the spot diameter on the plastic film F of the laser beam L. The shot pitch is a value obtained by dividing the scanning speed of the laser beam L (relative movement speed between the laser beam L and the plastic film F) by the repetition frequency (equivalent to the number of pulses of the oscillated laser beam L per unit time), and means the interval between a laser beam L emitted by a certain pulsing and a laser beam L emitted by the next pulsing.

[0067] Hereunder, examples of results of tests in which a plastic film F was cut using laser processing methods according to the present embodiment (Examples) and Comparative Examples are described.

[0068] FIGS. 2A to 2C are diagrams that schematically illustrate cross sections of plastic films F used in tests according to the Examples and Comparative Examples. FIG. 2A illustrates the cross section of a plastic film F to which laser processing methods according to Examples 1 to 13 and Comparative Examples 1 and 2 were applied. FIG. 2B illustrates the cross section of a plastic film F to which laser processing methods according to Examples 14 and 15 were applied. FIG. 2C illustrates the cross section of a plastic film F to which laser processing methods according to Examples 16 and 17 were applied.

[0069] As illustrated in FIG. 2A, as the plastic film F of Examples 1 to 13 and Comparative Examples 1 and 2, a laminated film was used in which, in order from the top (in order from the side irradiated with the laser beam L), a protective film, a base material and a release liner were laminated. A carrier tape for conveying was attached to the undersurface of the laminated film F, and the laminated film F was subjected to half-cut processing that cut the laminated film F except for the carrier tape.

[0070] Polyethylene terephthalate (PET) was used as the material for forming the protective film, and an acrylic adhesive (not illustrated) was applied to the undersurface of the protective film. A polarizing film was used as the base material. A laminated film composed of triacetylcellulose (TAC) and polyvinyl alcohol (PVA) was used as the polarizing film, and an acrylic adhesive (not illustrated) was applied to the undersurface of the polarizing film. Polyethylene terephthalate (PET) was used as the material for forming the release liner, and an acrylic adhesive (not illustrated) was applied to the top surface of the release film. Polyethylene terephthalate (PET) was used as the material for forming the carrier tape, and an acrylic adhesive (not illustrated) was applied to the top surface of the carrier tape.

[0071] As illustrated in FIG. 2B, a single-layer film composed of only a base material was used as the plastic film F in Examples 14 and 15, and full-cut processing to cut the single-layer film was performed. A single-layer film formed from polyimide (PI) was used as the plastic film F in Example 14. A single-layer film formed from polypropylene (PP) was used as the plastic film F in Example 15.

[0072] As illustrated in FIG. 2C, as the plastic film F in Examples 16 and 17, a laminated film was used in which, in order from the top (in order from the side irradiated with the laser beam L), a protective film, an adhesive and a base material were laminated. The laminated film F was subjected to half-cut processing that cut the protective film and adhesive of the laminated film F. A protective film that was the same as in Examples 1 to 13 and Comparative Examples 1 and 2 was used. Polyethylene terephthalate (PET) was used as the material for forming the base material of Examples 16 and 17. Instead of the acrylic adhesive used in Examples 1 to 13 and Comparative Examples 1 and 2, a urethane adhesive was used as the adhesive in Example 16. Instead of the acrylic adhesive used in Examples 1 to 13 and Comparative Examples 1 and 2, a silicone adhesive was used as the adhesive in Example 17.

[0073] Each of the plastic films F described above was subjected to a cutting process to cut the plastic film F into a rectangular shape of 50 mm50 mm using a CO.sub.2 laser beam source (oscillation wavelength: 9.4 m) as the laser beam source 1, under a condition whereby the peak energy density of the laser beams L with which the respective plastic films F was irradiated was changed to various values.

[0074] Contamination of the surface of each plastic film F after cutting was then evaluated.

[0075] FIG. 3 is an explanatory drawing for describing the method for evaluating contamination of the surface of the plastic film F.

[0076] As illustrated in FIG. 3, the surface of the plastic film F (surface on the side irradiated with the laser beam L) was observed using an optical microscope, and the length (maximum length) to which scattered matter was adhered from the edge of the cutting position was measured and taken as a contamination width W.

[0077] Although the plastic film F shown in FIG. 2A is illustrated in FIG. 3, the contamination width W was also measured by the same method for the plastic films F shown in FIG. 2B and FIG. 2C.

[0078] FIG. 4 is a table showing various conditions of the laser processing methods according to the Examples and Comparative Examples, as well as the contamination widths W that were evaluated. Note that, the numerical value described in the Adhesive thickness column shown in FIG. 4 means the thickness of an acrylic adhesive applied to the undersurface of the protective film (acrylic adhesive applied between the protective film and the base material).

[0079] As illustrated in FIG. 4, in Examples 1 to 17, by setting the peak energy density of the laser beam L with which the plastic film F is irradiated to a value of 70 J/cm.sup.2 or more and 270 J/cm.sup.2 or less, the contamination width W was reduced to 0.3 mm or less that is the upper limit value of the specification. Further, in Examples 8 to 13, because the thickness of the adhesive (acrylic adhesive) that was applied between the protective film and the base material was 20 m or less, the contamination width W was decreased to 0.3 mm or less. Further, the thinner the thickness of the adhesive was, the smaller the contamination width W became.

[0080] In contrast, in Comparative Example 1, because the peak energy density was less than 70 J/cm.sup.2, the contamination width W was more than 0.3 mm. Further, in Comparative Example 2, because the peak energy density was more than 270 J/cm.sup.2, a state was entered in which the protective film peeled off from the polarizing film that was the base material.

[0081] As described above, according to the laser processing method according to the present embodiment, because the peak energy density of the laser beam L with which the plastic film F is irradiated is 70 J/cm.sup.2 or more, a temperature increase accompanying infrared absorption of the plastic film F is activated. By this means, the kinetic energy of scattered matter that arises when the plastic film F melts and gasifies increases, and it is possible to reduce scattered matter that adheres to the surface of the plastic film F in the vicinity of the cutting position. As a result, contamination of the surface of the plastic film F can be reduced.

[0082] Further, according to the laser processing method according to the present embodiment, because the peak energy density of the laser beam L with which the plastic film F is irradiated is 270 J/cm.sup.2 or less, there is no risk of the laser beam L leading to a decrease in the quality of the end face of the plastic film F at the cutting position.

REFERENCE SIGNS LIST

[0083] 1 Laser Beam Source [0084] 2 Optical Element [0085] 3, 4 Reflection Mirror [0086] 5 Galvanometer Mirror [0087] 6 Telecentric f Lens [0088] 7 X-Y Dual-axis Stage [0089] 8 Control Device [0090] 100 Laser Processing Apparatus [0091] F Plastic Film [0092] L Laser Beam