JP2000102889A - Laser processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser processing device for enabling high precision laser processing almost without distortion by restraining interference of the laser beam with a pair of fly's eye lenses at a minimum level. SOLUTION: A beam shape restoration part 6 comprises, from an incident side, a cylindrical concave lens 21 and a cylindrical convex lens 22, and is rotatable around an optical axis of a laser beam A by a rotation means 23 composed of gears 24 and 25. By rotating the beam shape restoration part 6, the cylindrical face is inclined against the laser beam A with a rectangle cross sectional shape, whereby the interference of the laser beam on the fly's eye lenses is restrained and energy density variation of the laser beam due to the position on a workpiece becomes small. Therefore, processing accuracy variation and distortion due to the difference of the position on the workpiece become small, resulting in improvement of the processing accuracy all over the workpiece.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing apparatus provided with a beam shaping section for shaping and introducing a laser beam into a pair of fly-eye lenses. The present invention relates to a laser processing apparatus capable of minimizing interference of a laser beam passing through a pair of fly-eye lenses when performing a plurality of hole processing.

[0002]

2. Description of the Related Art As shown in FIG. 1, a conventional general laser processing apparatus for processing the above-described ink jet nozzle hole includes a laser beam oscillator 1 and a beam shaping unit 5 for shaping a laser beam A. , A beam expander 7 for expanding the laser beam A, and a pair of fly-eye lenses 8, 8 as a beam flattening optical system (homogenizer).
The fly-eye lenses 8, 8 disperse the laser beam A into a number of elongated beams and condense them by the condenser lens 9 to make the beam intensity uniform and control the light output. . The work piece B is provided on the mask 11 disposed on the downstream side of the condenser lens 9.
A laser processing shape, that is, a hole pattern (not shown) in which a plurality of nozzle holes are arranged in a row, is provided. Light is focused at the position (hole pattern position).

[0003] The laser beam A transmitted through the mask 11 is processed by an imaging lens 12 as projection optical means at a predetermined magnification (for example, 1/4 or 1/5) at a workpiece made of a polymer such as polyimide. Imaged on B, mask 1
A plurality of nozzle holes corresponding to one hole pattern (not shown)
Is drilled on the workpiece B. Here, the laser beam A is output again by the laser beam oscillator 1 while the workpiece B is moved by a predetermined dimension in the X direction or the Y direction by the XY table 5 on which the workpiece B is placed, and irradiated. By doing so, the nozzle hole group is formed with a certain pitch. Reference numerals 2, 3, and 4 in the figure are total reflection mirrors.

[0004]

However, the above-mentioned conventional laser processing apparatus has room for improvement in the following points. That is, as shown in FIG.
Nozzle plate of inkjet printer (workpiece)
When a plurality of nozzle holes C for ink ejection are laser-processed on B, each nozzle hole C is formed in a truncated conical shape in which the diameter gradually decreases from the side where the ink enters to the side where the ink exits. The phenomenon that the emission side shape Co of the nozzle hole C is distorted and does not become a perfect circle occurs. This phenomenon occurs regularly in the plurality of nozzle holes C on the workpiece B. In other words, when a plurality of nozzle holes C are simultaneously laser-processed on the workpiece B by transmitting the hole pattern of the mask 11 (FIG. 1), the emission side shape Co is periodically distorted depending on the position of the nozzle holes C. Or not distorted. This is because the laser beam A interferes with the pair of fly-eye lenses 8 and 8,
In addition, it is considered that the interference of the laser beam A causes distortion at the time of processing due to the periodic change of the interference position. That is, since there is a distance corresponding to the thickness of the workpiece B (100 μm in this example) between the front and the back of the workpiece B, the laser beam A Is less likely to be affected by light interference within the depth of focus, but the light-collecting characteristics change on the exit side that deviates from the focal depth, so that the influence of light interference increases and the exit-side shape Co is distorted.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and minimizes laser beam interference between the pair of fly-eye lenses, thereby enabling high-precision laser processing with almost no distortion. It is intended to provide a processing device.

[0006]

In order to achieve the above object, a laser processing apparatus according to the present invention forms a laser beam having a substantially rectangular cross section output from a laser oscillator by a beam shaping section including a cylindrical lens. In the laser processing apparatus provided with a pair of fly-eye lenses, the cylindrical surface of the cylindrical lens in the beam shaping unit around the optical axis with respect to a substantially rectangular laser beam output from the laser oscillator It is characterized by being inclined.

According to the laser processing apparatus of the first aspect having the above structure, the cylindrical surface of the cylindrical lens in the beam shaping unit is tilted around the optical axis with respect to the substantially rectangular shape of the laser beam.
Light interference generated when a laser beam passes through a pair of fly-eye lenses is reduced, and processing accuracy can be improved.

Preferably, the laser beam is an excimer laser beam. The cross-sectional shape of the laser beam emitted from the laser oscillator of the excimer laser is substantially rectangular, and can be suitably implemented in the configuration of the first aspect.

Preferably, the beam shaping unit is an optical system that changes a laser beam from a substantially rectangular shape to a substantially rhombic shape. A laser beam having a substantially rectangular cross section emitted from a laser oscillator is shaped into a roughly rhombic shape by a beam shaping unit, and then dispersed into a number of elongated beams when passing through a pair of fly-eye lenses, resulting in a uniform beam intensity. Is effectively achieved.

According to a fourth aspect of the present invention, it is preferable that the beam shaping unit includes a cylindrical concave lens and a cylindrical convex lens, and is inclined around the optical axis.

[0011] According to the laser processing apparatus of the fourth aspect,
2 of cylindrical concave lens and cylindrical convex lens
With the configuration in which the two lenses are inclined around the optical axis, the configuration of claim 1 can be easily realized.

Preferably, the beam shaping section is provided with a rotating means for rotating the beam shaping section around the optical axis. According to this, by rotating the beam shaping unit according to the magnitude of the interference,
By selecting a range in which the energy loss is small and the interference is small, efficient laser processing can be performed.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the laser processing apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 is an overall schematic view showing a laser processing apparatus to which the present invention is applied, and FIG. 2 is an enlarged perspective view showing a beam shaping unit in the processing apparatus shown in FIG. FIG. 3 is a schematic front view of the beam shaping unit of FIG. 2 as viewed from the downstream side, and FIG. 4 is a diagram illustrating the inclination angle θ of the beam shaping unit of FIG. Diagram (graph) showing the relationship with the position of the workpiece (exit side), FIG.
FIG. 6 is a diagram showing the relationship between the shape of the nozzle hole formed on the emission side on the workpiece for each inclination angle θ of the beam shaping unit in FIG. 2, and FIG. FIG. 5 is a perspective view in which a nozzle hole is machined by applying a pressure.

As shown in FIG. 1, in the laser processing apparatus 20 of the present embodiment, an excimer laser beam (KrF laser beam) A having a wavelength of, for example, 248 nm output (emitted) from the laser oscillator 1 has three beams. Through the total reflection mirrors 2, 3, and 4 arranged at an angle of 45 °, the light is refracted in the right-angle direction, and reaches the processing table 5 that supports the workpiece B. Between the laser oscillator 1 and the first mirror 2, a beam shaping unit 6 for shaping the rectangular cross section of the laser beam A into a predetermined shape is arranged.

The laser beam A is refracted at right angles by the first mirror 2 and travels straight upward in the figure. First mirror 2 and second
A beam expander (Beam Expander) 7 for expanding the laser beam A is arranged between the mirror 3 and the beam expander 7. In this example, the beam expander 7 includes a pair of convex lenses. Downstream of the second mirror 3, a pair of fly-eye lenses (Fly-eye-Lenz) as a homogenizer
8, 8 are arranged so as to face each other. Second mirror 3
The laser beam A, which is refracted in a right angle direction and travels rightward in the horizontal direction to the right in the figure, is dispersed by the fly-eye lenses 8 and 8 into a plurality of elongated beams, and a condenser lens as a condensing optical means. By condensing a large number of elongate beams by the method 9, uniform beam intensity and output control can be achieved.

A mask 11 is arranged downstream of the condenser lens 9, and the condensed laser beam A is applied to the mask 1.
The light is condensed at one predetermined position (hole pattern position).

The mask 11 is provided with a shape for laser processing the workpiece B, that is, a hole pattern corresponding to a plurality of nozzle holes, and the mask 11 is held by a mask holder (not shown). The laser beam A transmitted through the hole pattern of the mask 11 is refracted by the third mirror 4 in the right-angle direction, and goes straight down in the figure. On the downstream side of the third mirror 4, a workpiece B is placed on a processing table 5 that is movable in the horizontal direction. The processing table 5 can be moved up and down in the vertical direction so that the laser beam is focused on the workpiece B. Further, an imaging lens (also referred to as a projection lens) 12 is arranged between the third mirror 4 and the processing table 13. The image forming lens 12 forms an image of the laser beam A (image of the laser beam A) transmitted through the hole pattern of the mask 11 on the workpiece B by reducing it to a predetermined magnification (in this example, 1/5). Laser processing is performed corresponding to the 11 hole patterns. In this example, the workpiece B is a polyimide sheet (100 μm thick) which is a polymer material in this example.
m) is used, and a plurality of nozzle holes (diameter: 30 μm) are formed in a row by the laser beam A.

After a group of nozzle holes are formed at one location, the processing table 5 is moved horizontally to make the next processing area on the workpiece B face directly below the imaging lens 12,
By outputting the laser beam A, a large number of groups of nozzle holes can be sequentially formed.

As shown in FIG. 2, the beam shaping unit 6 includes:
From the incident side, a cylindrical concave lens 21 and a cylindrical convex lens 22 are arranged in the optical axis direction. In a conventional general laser processing apparatus, each of the cylindrical lenses 21 and 22 has an axial direction of its cylindrical surface defined by a rectangular cross section of a laser beam (8 m in this example).
(m × 24 mm).
As described later, in the present embodiment, the axial direction of the cylindrical surface is used with a slight inclination.

In this embodiment, the two cylindrical lenses 21 and 22 are configured to be rotatable around the optical axis A ′ of the laser beam A by the rotating means 23. That is, the beam shaping unit 6 is attached to a large-diameter gear 24 so as to be able to rotate integrally with the large-diameter gear 24, and a small-diameter drive gear 25 rotated by a motor 26 is meshed with the large-diameter gear 24. Although a stepping motor that rotates forward and backward is used as the motor 26, any device that can stop and hold the beam shaping unit 6 at an arbitrary position may be, for example, a manual rotating unit. In this example, reference numeral 24
26 to 26 constitute the rotating means 23.

In FIG. 2, both cylindrical lenses 2
When the axial directions of the cylindrical surfaces 1 and 22 are placed parallel to the longitudinal direction of the rectangular shape of the laser beam as in the related art,
Laser beam A emitted from laser oscillator 1 (FIG. 1)
In the figure, the short side direction of the rectangle is enlarged by the cylindrical concave lens 21, the enlarged optical path is parallelized by the cylindrical convex lens 22, and the laser beam A is shaped into a square. Then, the light is incident on the pair of fly-eye lenses 8. In this case, depending on the position on the workpiece B among the plurality of nozzle holes that are simultaneously processed, FIG.
As shown in (a), the emission side shape Co of the nozzle hole C is formed with distortion. This is because, due to the interference of the laser beams between the pair of fly-eye lenses 8, 8, the energy density periodically changes greatly as shown in FIG. .

Since there is a distance corresponding to the thickness of the workpiece B (100 μm in this example) between the front and the back of the workpiece B, the surface on the laser beam incident side of the workpiece B is:
Since the laser beam A falls within the depth of focus and is hardly affected by interference, the incident side shape Ci of the nozzle hole C is circular without being distorted. However, on the back surface of the workpiece B that is out of the range of the depth of focus of the laser beam A, the influence of the interference by the pair of fly-eye lenses 8, 8 appears as described above, and the emission side shape Co of the nozzle hole C is distorted. .

On the other hand, according to the laser processing apparatus 20 of the present embodiment, the beam shaping unit 6 is rotated to incline the axial direction of the cylindrical surface with respect to the longitudinal direction of the rectangular cross section of the laser beam. The laser beam A emitted from the part 6 has a rhombus shape as shown by a two-dot chain line in FIG. When the tilt angle θ of the beam shaping unit 6 becomes, for example, 5 °, the influence of the laser beam interference between the pair of fly-eye lenses 8 is reduced, and as shown in FIG. The change in energy density due to the difference in position on the emission side of the laser beam with respect to
As shown in FIG. 5B, the distortion of the emission side shape Co of the nozzle hole C is reduced. Further, when the inclination angle θ becomes 10 °, FIG.
As shown in FIG. 5, there is almost no change in the energy density, and the emission side shape Co of the nozzle hole C is changed as shown in FIG.
Around a perfect circle, a plurality of nozzle holes are formed substantially uniformly.

In the case of this embodiment, the inclination angle θ is 10 °.
Before and after, the interference of the laser beam A was reduced to almost the minimum, and the exit side shape Co of the nozzle hole C at each position became almost a perfect circle as shown in FIG. 5 (c). Even if it exceeds, the interference of the laser beam A is reduced. However, when the laser beam A is incident on the fly-eye lens 8, the cross-sectional shape is substantially rhombic as described above,
When the light enters the fly-eye lens 8, a portion to be deleted may occur, resulting in energy loss. In the experiment of this example, favorable results could be obtained when the inclination angle θ was around 10 °. Note that the tilt angle θ may be determined based on the degree of interference of the laser beam A in the fly-eye lens and the energy efficiency.

As described above, the laser processing apparatus 20 of the present invention
Although one embodiment of the beam shaping unit 6 has been particularly described, the present invention can be implemented as follows.

(1) The beam shaping unit 6 may be a combination of a concave lens and a convex lens, or may be a combination of any other number of lenses.

(2) The beam shaping unit 6 may not be arbitrarily rotatable but may be fixed at a desired angle.

(3) The imaging lens 12 is omitted, and the mask 11
Can be similarly implemented in a contact mask method in which is fixed directly on the workpiece B.

(4) In addition to the processing of the nozzle holes of the ink jet printer, the present invention can be applied to, for example, changing the workpiece B to another material such as ceramics, or groove processing.

[0031]

As is apparent from the above description,
The laser processing apparatus according to the present invention has the following excellent effects.

(1) According to the first aspect of the present invention, the addition of a simple structure minimizes the interference of the laser beam at the fly-eye lens, and achieves high-precision laser processing over the entire workpiece with almost no distortion. Can be. For example, in processing the nozzle holes for ink ejection, the emission side shape can be processed to be almost a perfect circle, and when processing a plurality of nozzle holes, the processing can be performed substantially uniformly.

(2) According to the second aspect of the present invention, since the laser beam is an excimer laser, the cross-sectional shape of the laser beam emitted from the laser oscillator is substantially rectangular, which can be suitably implemented in the configuration of the first aspect. .

(3) According to the third aspect of the present invention, since the beam shaping unit is an optical system that changes a laser beam from a substantially rectangular shape to a substantially rhombic shape, a laser beam having a substantially rectangular cross section emitted from a laser oscillator is used. After being shaped substantially into a rhombus by the beam shaping unit, when the beam passes through a pair of fly-eye lenses, the beam is dispersed into a large number of elongated beams, and the beam intensity is effectively made uniform.

(4) According to the fourth aspect of the present invention, the cylindrical concave lens and the cylindrical convex lens are used in the first aspect.
Can easily be realized.

(5) According to the fifth aspect of the present invention, the beam shaping section is rotated around the optical axis, thereby selecting a range in which the energy loss is small and the interference is small, and performs efficient laser processing. be able to.

[Brief description of the drawings]

FIG. 1 is an overall schematic diagram showing a laser processing apparatus provided with a beam shaping unit to which the present invention is applied.

FIG. 2 is an enlarged perspective view showing an embodiment of the present invention of a beam shaping unit in the processing apparatus of FIG. 1;

FIG. 3 is a schematic front view of the beam shaping unit of FIG. 2 viewed from a downstream side.

4 is a diagram (graph) showing a relationship between an inclination angle θ of a beam shaping unit in FIG. 2, an energy density of a laser beam on an emission side on a workpiece, and a position of a workpiece (emission side). is there.

5 is a diagram illustrating a relationship between an inclination angle θ of a beam shaping unit in FIG. 2 and a shape of a nozzle hole formed on an emission side on a workpiece.

FIG. 6 is a perspective view of a workpiece in which a laser beam is applied to the workpiece from below in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser oscillator 2, 3, 4 Total reflection mirror 5 Processing table 6 Laser shaping part 7 Beam expander 8 Fly eye lens (homogenizer) 9 Condenser lens 11 Mask 12 Imaging lens 20 Laser processing device 21 Cylindrical concave lens 22 Cylindrical convex lens 23 Rotation Means 24 Large diameter gear 25 Small diameter gear 26 Motor A Laser beam B Workpiece C Nozzle hole

Claims (5)

[Claims] 1. A laser processing apparatus for shaping a laser beam having a substantially rectangular cross section output from a laser oscillator by a beam shaping unit including a cylindrical lens and introducing the laser beam to a pair of fly-eye lenses. A laser processing apparatus wherein a cylindrical surface of a lens is inclined around an optical axis with respect to a substantially rectangular shape of a laser beam output from the laser oscillator. 2. The laser processing apparatus according to claim 1, wherein the laser beam is an excimer laser beam. 3. The beam shaping unit is an optical system that changes a laser beam from a substantially rectangular shape to a substantially rhombic shape.
The laser processing apparatus according to item 1. 4. The laser processing apparatus according to claim 1, wherein the beam shaping unit includes a cylindrical concave lens and a cylindrical convex lens, and is inclined around the optical axis. 5. The laser processing apparatus according to claim 1, wherein the beam shaping unit is provided with a rotating unit that rotates the beam shaping unit around an optical axis.