Laser processing method and land laser processed product

Abstract

There is provided a laser beam processing method in which generation of foreign substances from cut can be suppressed and contamination of a surface of a work can be decreased when performing the processing method using a laser beam on the work made of a polymer material, and a laser processed product. Further, the present invention is to provide a laser beam processing apparatus that is used in the laser beam processing method. The present invention relates to a laser beam processing method for processing the work made of a polymer material using a laser beam, wherein the work is irradiated with a laser beam in a state that the optical axis of the laser beam is tilted in the advancing direction of processing by a prescribed angle with respect to the vertical direction of the work.

Claims

1. A half-cut laser beam processing method for processing a work made of a polymer material using a laser beam, the method comprising: partially cutting the work by irradiating the work with a laser beam in a state that the optical axis of the laser beam is tilted in an opposite direction to the advancing direction of the work by a prescribed angle with respect to the vertical direction of the work such that the laser beam is tilted toward a cutting surface of the work, and the angle between the optical axis of the laser beam and the vertical direction of the work is in the range of 20 to 45; wherein the processing method is a half cut method, and the work is an optical film, and the optical film is installed in a liquid crystal display device; wherein the laser beam is a Gaussian beam having a rectangular profile; wherein polymer material decomposes to form a gas upon irradiation with the laser beam, and a second portion of the polymer material melts without decomposing upon irradiation with the laser beam, and a maximum height of a raised portion of the second portion of the polymer material that is extruded to an outside of a cut portion after the cut processing is 30 m or less; and wherein the gas diffuses in a direction opposite to the advancing direction of the work.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic drawing explaining a laser beam processing method according to the embodiment of the present invention, FIG. 1 (a) is a sectional drawing showing a state of irradiating a laser beam onto a work, and FIG. 1 (b) is a drawing of its upper surface view.

(2) FIG. 2 is a sectional schematic drawing explaining a conventional laser beam processing method.

(3) FIG. 3 is a sectional schematic drawing explaining a conventional laser beam processing method.

EXPLANATION OF THE REFERENCE NUMERALS

(4) 1 Work 2 Laser beam 3 Gas

BEST MODE FOR CARRYING OUT THE INVENTION

(5) The embodiment of the present invention is explained below by referring to FIG. 1. FIG. 1 is a schematic drawing explaining a laser beam processing method according to the present embodiment, FIG. 1 (a) is a sectional drawing showing a state of irradiating a laser beam onto a work, and FIG. 1 (b) is a drawing of its upper surface view. The laser beam processing method according to the present invention is a processing method that is performed using a laser beam 2 on a work 1 made of a polymer material, and the laser beam is irradiated in a state that the optical axis of the laser beam 2 is tilted in the advancing direction of processing by a prescribed angle with respect to the vertical direction of the work 1.

(6) The laser processing method of the present invention is suitable for performing a shape processing such as a cut processing, a marking, a hole-opening processing, a groove processing, a scribing processing, and a trimming processing. The present invention is preferably applied to cut processing among these processings.

(7) The cut processing can be applied for any of half cut or full cut. However, the effect of the present invention is exhibited furthermore in the case of a half cut.

(8) When the cut processing is performed by fixing the work 1 and scanning with the laser beam 2, the optical axis of the laser beam 2 is tilted in the same direction as the advancing direction of the laser beam 2. Further, when the cut processing is performed by fixing the laser beam 2 and moving the work 1, the optical axis of the laser beam 2 is tilted in the opposite direction as the advancing direction of the work 1. Accordingly, the optical axis of the laser beam 2 can be tilted in the advancing direction of processing by a prescribed angle with respect to the vertical direction of the work 1. Examples of a method that can be adopted to moving a laser irradiation position along a prescribed processing line include a galvano scan and an X-Y stage scan.

(9) The angle (the incident angle) between the optical axis of the laser beam 2 and the vertical direction of the work 1 is preferably 10 to 45, and more preferably 15 to 40. When the angle is less than 10, a gas 3 that is generated diffuses into the direction parallel to the surface of the work 1, and the surface contamination tends to increase. On the other hand, when the angle exceeds 45, the incident angle to the work 1 becomes excessively small. Accordingly, the irradiation of the laser beam 2 at the focus of the lens becomes difficult, and processing accuracy of the cut processing part decreases. Moreover, when the angle is negative, that is, when the optical axis of the laser beam 2 is tilted in the direction opposite to the advancing direction of processing, the gas 3 diffuses along the horizontal direction and the contamination on the surface of the work increases (refer to FIG. 3).

(10) Next, the laser beam 2 that is used in the present embodiment is explained. The laser beam 2 is not especially limited, and it can be appropriately selected depending on the processing method. Specific examples include a CO.sub.2 laser, a YAG laser, and a UV laser. Among these, the CO.sub.2 laser is preferable in the viewpoints that it is applicable over a range of thicknesses of the work, that cracking and breaking of markings do not occur, etc. The output of the laser beam irradiation is in the range of 10 to 800 W, for example, and preferably in the range of 100 to 350 W when cutting the work with one irradiation, and preferably in the range of 50 to 200 W when cutting with two times of irradiation.

(11) The laser beam that is generated from various laser beams described above is basically a Gaussian beam having a maximum value of the beam intensity at the center of the laser spot. Because the beam intensity has a Gaussian distribution, it has a characteristic that the beam intensity is large at the center of the beam spot, and the beam intensity gradually decreases toward the outside from the center. Therefore, when the Gaussian beam is used for cutting the work 1, a component of the work is first decomposed and vaporized and the cutting is initiated at the center of the beam spot. However, the beam intensity becomes small toward the outside of the center of the beam spot, and therefore, the work component is gradually melted and decomposed. At this time, an outward stress is generated when the work component is decomposed and vaporized at the center of the beam spot, and the work component that is melted but not yet decomposed and vaporized at the outside of the center of the beam spot is pushed away toward the outside due to such stress. As a result, a raised portion of the melted component is generated at the cut surface of the work 1. Therefore, when an optical film as the work is integrated into a liquid crystal panel, etc. for example, poor adhesion, etc. are generated at the edge portion of the liquid crystal panel and various optical malfunctions are ultimately generated.

(12) In the present embodiment, the profile of such Gaussian beam is preferably shaped into a rectangular profile. Such a rectangular profile can be made by providing a diffraction optical element to the laser beam generator for example. By controlling the diffraction optical element, the rising angle expressing the beam intensity distribution from the beam edge in the rectangular profile of the laser beam can be appropriately set. For the condition of a laser beam shaped into a rectangular profile, the beam intensity distribution can be expressed with a value with the intensity of the center of the laser beam being 1 within a half value width of the rectangular profile. The smaller the a value, the sharper the rising of the rectangular profile becomes, and the larger the value, the duller the rectangular profile becomes and the closer to a Gaussian beam it becomes.

(13) The concentrated diameter of the laser beam 2 can be appropriately set depending on the type of processing that is performed on the work 1. In the case of cut processing, the cut width approximately matches the concentrated diameter of the laser beam 2. Therefore, by adjusting the concentrated diameter, the cut width can be controlled. The concentrated diameter (the cut width) is normally preferably 50 to 500 m, and more preferably 150 to 300 m. When the concentrated diameter is less than 50 m, there is a case that the cutting speed becomes low. On the other hand, when it exceeds 500 m, there is a case that deposits are increased.

(14) The power density of the laser beam 2 can be appropriately set depending on the physical properties of the work 1 and the cutting speed in the case of cut processing. The photo-absorption rate of the work 1 is affected by the wavelength of the laser beam 2. The laser beam 2 can oscillate the wavelength from an ultraviolet ray to a near-infrared ray by selecting an oscillation medium or a crystal. Therefore, the processing can be performed effectively with a low power density.

(15) The decomposed and melted substances may be scattered and removed by blowing an assist gas in the same axial direction as the focused laser beam 2 onto a laser beam processing portion with a high flow. Examples of the assist gas include helium, nitrogen, and oxygen.

(16) The work 1 is not especially limited as long as it is made of a polymer material, and a conventionally known substance can be used. Specific examples include various pressure-sensitive adhesive films and an optical film.

(17) The pressure-sensitive adhesive film is not especially limited, and an example includes an acrylic pressure-sensitive adhesive.

(18) The optical film is not especially limited, and an example includes a polarizing plate.

EXAMPLES

(19) Preferred examples of the present invention will be explained in detail hereinafter.

(20) (Pressure-Sensitive Adhesive Film)

(21) The pressure-sensitive adhesive film that was used in the present example has a structure in which a pressure-sensitive adhesive layer is provided between a pair of separators. A PET (polyethylene terephthalate) base having a thickness of 75 m was used as each separator. An acrylic pressure-sensitive adhesive having a thickness of 200 m was used as the pressure-sensitive adhesive layer.

(22) (Optical Film)

(23) The optical film that was used in the present example has a structure in which a surface protective film is provided on one surface of a polarizing plate (manufactured by Nitto Denko Corporation) and a separator is laminated on the other surface with the pressure-sensitive adhesive layer in between. The surface protective film consists of a film in which a pressure-sensitive adhesive is applied onto a PET base, and the thickness was about 63 m. An acrylic pressure sensitive adhesive having a thickness of 23 m was used as the pressure-sensitive adhesive layer. Each separator consists of a PET base having a thickness of 38 m. The thickness of the polarizing plate was about 200 m.

(24) (Cutting Condition by Laser Beam)

(25) The cutting condition of the pressure-sensitive adhesive film was as follows.

(26) Light source: carbon dioxide gas laser beam

(27) Wavelength of the laser beam: 10.6 m

(28) Spot diameter: 150 m

(29) Cutting speed: 24 m/min

(30) Power of the laser beam: 43 W (half cut), 52 W (full cut)

(31) The cutting condition of the optical film was as follows.

(32) Light source: carbon dioxide gas laser beam

(33) Wavelength of the laser beam: 10.6 m

(34) Spot diameter: 150 m

(35) Cutting speed: 24 m/min

(36) Power of the laser beam: 32 W (half cut), 41 W (full cut)

Example 1

(37) In the present example, the laser beam processing was performed using the above-described optical film and pressure-sensitive adhesive film as the work and with half cut and full cut on each as the cutting method. The laser beam was irradiated in a condition that the optical axis of the laser beam is tilted in the advancing direction of cutting with an incident angle of 10 with respect to the vertical direction of the optical film. The result is shown in Table 1.

Comparative Example 1

(38) The cut processing was performed on each optical film and pressure-sensitive adhesive film in the same manner as Example 1 except the incident angle was made to be 0 in Comparative Example 1. The result is shown in Table 1.

Examples 2 to 6

(39) The cut processing was performed on each optical film and pressure-sensitive adhesive film in the same manner as Example 1 except the incident angle was made to an angle shown in Table 1 in each of Examples 2 to 6. The result is shown in Table 1.

(40) (Evaluation Method and Results)

(41) <Range of Contamination (mm)>

(42) The range of the contamination means the maximum width of the range where the decomposed substances from the cut portion are attached in the vicinity of the cut portion after the cut processing of the work.

(43) <Height of Raised portion (m)>

(44) The height of a raised portion means the maximum height of the raised portion of the melted component that is melted without decomposing and vaporizing and that is extruded to the outside of the cut portion after the cut processing of the work.

(45) <Results>

(46) The adhesion of contaminants was observed on the surface of the pressure-sensitive adhesive film and the optical film after the cut processing. As shown in Table 1, when the laser beam processing is performed at an incident angle of the laser beam being in the range of 10 to 45, it was confirmed that the contamination on the surface or the backside of the work was decreased. When the incident angle is in the range of 15 to 40, the amount of smoke that diffuses along the surface of the work (also along the backside in the case of full cut) can be decreased, and the surface or the backside of the work can be maintained in an extremely clean state. Especially when the incident angle is in the range of 20 to 40, it was found that the range of contamination can be kept to 0.5 mm or less, and at the same time, the height of the raised portion of the melted component can be decreased to 30 m or less.

(47) On the other hand, because the smoke that is generated by the irradiation of the laser beam diffused along the surface of the work in Comparative Example 1, the surface was extremely contaminated. In the case of Example 6 with the incident angle of 45, the irradiation of the laser beam at the lens focal point became difficult and the processing accuracy of the cut surface decreased.

(48) When the region of the contamination is 0.5 mm or less, a step of removing the contaminated portion can be omitted after the cut processing, and a large effective area as a product can be taken. When the height of the raised portion of the melted component is 30 m or less, when installing the optical film in a liquid crystal display device for example, it becomes an advantage in the respect that avoidance of poor adhesion at the edge of the liquid crystal panel can be sufficiently attempted.

(49) TABLE-US-00001 TABLE 1 Optical Film Half Cut Pressure-sensitive adhesive film Height Full Cut Half Cut Full Cut Con- of Con- Con- Con- Con- Con- tami- raised tami- Height tami- Height tami- Height tami- Height tami- Height nation portion nation of raised nation of raised nation of raised nation of raised nation of raised Incident Range (m) Range portion Range portion Range portion Range portion Range portion Angle (mm) Back- (mm) (m) (mm) (m) (mm) (m) (mm) (m) (mm) (m) () Surface side Surface Backside Surface Backside Surface Backside Surface Backside Surface Backside Example 1 10 0.9 22 1 1.1 25 30 0.85 32 1.6 1.1 35.5 35.5 Comparative 0 1.65 21 2.1 1.05 21.5 31 1.5 30.5 1.3 1.45 31 33 Example 1 Examples 2 15 0.8 20 0.95 0.75 22.5 26.5 0.7 31.5 0.55 0.45 31 31.5 Examples 3 20 0.35 18.5 0.4 0.5 20.5 27.5 0.25 27.5 0.2 0.15 28 28 Examples 4 30 0.1 20.5 0.1 0 20.5 27 0.25 27 0.1 0.25 26.5 25.5 Examples 5 40 0 19 0.1 0 21 29.5 0.4 27 0.2 0.25 29.5 21 Examples 6 45 0 21 0.05 0.05 23 30.5 0.25 28 0.25 0.25 27.5 21.5