JP2009220142A - Laser beam machining apparatus and laser beam machining method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam machining apparatus capable of efficiently and highly strongly machining a large substrate of a low profile such as a liquid crystal panel and an organic EL panel, and a laser beam machining method. <P>SOLUTION: The laser beam machining apparatus 1 includes: a laser beam source 2 which oscillates a laser beam having a wavelength region of 200-2,000 nm; a laser beam machining means which has an objective lens 3 for condensing the laser beam; at least two laser displacement gauges 5 which measure a distance between the objective lens 3 and the surface of a substrate as a workpiece; and an adjusting means which, on the basis of the measurement by the laser displacement gauges 5, drives the objective lens 3 to adjust a focal distance so that the depth of focus of the laser beam is included within the range of 5-50% inside the substrate from the surface of the substrate relative to the entire thickness 100% of the substrate. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a laser processing apparatus and a laser processing method for processing a display panel for image display.

In recent years, active matrix type image display devices such as liquid crystal panels and organic EL (Electroluminescence) panels have been developed as devices for display panels that express high-quality moving images.
A liquid crystal panel has a substrate in which a switching element such as a thin film transistor (hereinafter abbreviated as “TFT”) is disposed on a light-transmitting substrate or the like, and a red (R) for each predetermined pixel facing the substrate. , A bonded substrate having a counter substrate on which color filter layers of green (G) and blue (B) are arranged. The two substrates are kept at a predetermined interval via a spacer, and the liquid crystal layer is held between them. , Constituting one display element.
The organic EL panel includes a TFT substrate on which a TFT is formed, and an organic EL substrate having a multilayer structure in which an organic hole transport layer, an organic electron transport layer, an organic light emitting layer, etc. are laminated between a cathode and an anode. The counter substrate on which the color filter is formed is laminated to constitute one display element.

In consideration of production efficiency, a liquid crystal panel or an organic EL panel has a plurality of display elements formed on a large area substrate of, for example, 600 mm in length × 700 mm in width, and a predetermined display element including each display element from the large area panel. A small-sized panel is cut out, and this small panel is used as a display panel for each device such as a mobile phone. Therefore, technology for cutting a substrate from a large panel having a large area into a small panel has become important.

As a method of dividing (breaking down) a large panel into a small panel, for example, a method of forming a groove (scribe) on the surface of a substrate such as a glass substrate, and dividing the substrate (breaking) from this is generally used. ing.
For example, a general method is to form a scribe with an appropriate depth using a mechanical blade (tool) made of super steel or diamond cutter, and divide the substrate by forming a vertical crack starting from this scribe. It is. However, such a mechanical method has a problem that horizontal cracks are generated in the vicinity of the surface of the substrate and the bending strength is lowered.

In recent years, a method of cutting using a laser beam such as a carbon dioxide (CO ₂ ) gas laser is also used. For example, there is a method in which a focal point is set at a predetermined distance in the tangential direction of the cleaving line at the starting point or tip from the cleaving starting point or crack tip, and a laser beam is irradiated (Patent Document 1). In this method, a compressive stress against the tensile force generated by thermal expansion of the substrate by irradiating a laser beam (heat source; 800 to 850 ° C.) with a focal point set at a predetermined distance from the cleaving line. Use to cut the workpiece.

As a method using both a laser beam and a mechanical blade (tool), an initial crack (scribe line) is mechanically formed on one surface of the substrate with a scribing roller, and the other side of the substrate is then moved along the scribe line. For example, a method of cleaving the substrate by irradiating the surface with a heating laser such as a CO ₂ gas laser (Patent Document 2).
In this method, when a scribe is formed by the irradiation of a heating laser, the compressive stress generated against the force that the thermally expanded part of the workpiece expands the surroundings acts on the bottom of the scribe (groove) and cleaves it. Considering the point of reducing the efficiency, a scribe by a mechanical blade (tool) is formed facing a scribe by a heating laser so that a linear crack is formed in the thickness direction.

In addition to the CO ₂ gas laser, a laser processing apparatus using an Nd: YAG laser or the like is also used (Patent Document 3).

Japanese Patent Publication No. 3-13040 JP 2001-26435 A JP 2006-315031 A

In general, a method using a CO ₂ gas laser generates a compressive stress against the thermal expansion by irradiation with a gas laser, and then rapidly cools the substrate by spraying cooling water or the like to cool the substrate. A tensile stress against thermal contraction is generated to develop initial cracks and divide the substrate. As described above, the method using the rapid stress change caused in the substrate by the rapid thermal change enables the cleaving with higher accuracy as the volume of the substrate is larger, that is, as the substrate is thicker. When the plate thickness is reduced, it becomes difficult to cleave with high accuracy.
In recent years, mobile phones and the like have a strong tendency toward miniaturization and thinning, and liquid crystal panels and the like are also desired to be thin and have high bending strength. Therefore, the conventional method using a gas laser is thin, for example, about 200 μm. It is not suitable as a substrate cleaving method.

  In addition, there is no problem in terms of strength in the method of irradiating the substrate with a gas laser, raising the temperature of the substrate above the softening point of the glass constituting the substrate (for example, 800 to 850 ° C.), and then rapidly cooling and cleaving. However, a color filter material such as a liquid crystal panel, a liquid crystal material, a sealing resin, or the like may be damaged by heat to destroy the display element.

  The present invention has been made paying attention to the above-described conventional problems, and a laser processing apparatus and laser capable of processing a thin large substrate such as a liquid crystal panel and an organic EL panel efficiently and with high strength. An object is to provide a processing method.

  As a result of intensive studies to achieve the above object, the present inventors have accurately measured the distance to the object to be processed using a laser displacement meter, and irradiating the laser beam so as to have a predetermined depth of focus. The inventors have found that the above object can be achieved and have completed the present invention.

  The laser processing apparatus of the present invention includes a laser light source that oscillates a laser beam having a wavelength region of 200 to 2000 nm, a laser processing unit that includes an objective lens that condenses the laser beam, the objective lens, and an object to be processed. Based on two or more laser displacement meters that measure the distance to the surface of the substrate and the measurement results measured by the laser displacement meter, the focal depth of the laser light is 100% of the total thickness of the substrate. An adjusting means for adjusting the focal length by driving the objective lens so as to be included in a range of 5 to 50% from the surface of the substrate to the inside of the substrate is provided.

  Measures the distance between the laser light source that oscillates laser light having a wavelength region of 200 to 2000 nm, laser processing means having an objective lens for condensing the laser light, and the objective lens and the surface of the substrate that is the object to be processed. And driving the objective lens so that the focal depth of the laser light is included in a predetermined range from the surface of the substrate to the inside of the substrate based on two or more laser displacement meters and the measurement result of the laser displacement meter. , A laser processing method for processing a large substrate into a small substrate using a laser processing apparatus having an adjusting means for adjusting the focal length, wherein the objective lens and the large substrate are Based on the step of measuring the distance to the surface and the measurement result, the focal depth of the laser beam is based on the surface of the substrate with respect to 100% of the total thickness of the substrate. Driving the objective lens to include 5 to 50% of the internal and adjust the focal length, characterized in that a radiation step of irradiating a laser beam.

According to the present invention, the distance to the workpiece is accurately measured, and based on the measurement result, the focal length is adjusted so that the focal depth is included in the predetermined range inside the substrate, and the laser beam is irradiated. Thus, the strength of the cut edge portion that becomes the processing site can be improved without damaging the processing object, and a large substrate can be processed into a small substrate with excellent accuracy.
Further, according to the present invention, by using two or more laser displacement meters, it is possible to shorten the time for measuring the distance between the object to be processed having a plurality of processing lines and the objective lens.
Furthermore, according to the present invention, since a large substrate can be processed without being turned upside down, the production efficiency can be greatly improved.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a plan view schematically showing an example of a preferred embodiment of the laser processing apparatus of the present invention, and FIG. 2 is a plan view showing a part of the laser processing apparatus shown in FIG.

  As shown in FIGS. 1 and 2, the laser processing apparatus 1 of this example includes a laser light source 2 that oscillates laser light having a wavelength region of 200 to 2000 nm and an objective lens 3 that condenses the laser light. Based on the measurement results of the means, two or more laser displacement meters 5 that measure the distance between the objective lens 3 and the surface of the large liquid crystal panel 4 that is the object to be processed, Adjustment means (not shown) that drives the objective lens 3 to adjust the focal length so that the focal depth of the emitted laser light is included in a predetermined range from the surface of the large liquid crystal panel 4 to the inside of the substrate of the large liquid crystal panel 4 ).

  The laser displacement meter 5 is arranged in an array of equal intervals on a linear arm 6 on which the objective lens 3 is installed so as to face a plurality of processing lines (cutting pitch) 4d set in parallel on the large liquid crystal panel 4. Is installed.

As shown in FIG. 1, the large liquid crystal panel 4 is fixed on a movable stage 7 that is movable in the horizontal direction.
The large liquid crystal panel 4 has an upper substrate 4a on which switching elements of TFTs (not shown) are arranged, and R, G, B color filter layers (not shown) are arranged for each predetermined pixel. And a lower substrate 4b. The upper substrate 4a and the lower substrate 4b are maintained at a predetermined interval via a spacer 4c, a liquid crystal layer (not shown) is held at this interval, and one display is provided between the spacer 4c and the spacer 4c. Consists of elements. A portion where the spacer 4c is arranged becomes a processing planned line (cutting pitch) 4d.
As shown in FIG. 2, the square frame provided on the large liquid crystal panel 4 represents one display element and has a size divided into the small liquid crystal panel 4e. An interval between the small liquid crystal panels 4e and 4e is a processing planned line (cutting pitch) 4d.

The laser processing apparatus 1 of this example uses the laser displacement meter 5 to accurately measure the distance from the surface of either the upper or lower substrate of the large liquid crystal panel 4 along the planned processing line 4d. In this example, the distance between the surface (lower surface) of the substrate 4b on the lower side of the large liquid crystal panel 4 and the objective lens 3 is measured.
Based on this measurement result, adjustment is made so that the focal depth of the laser light is included in a range of 5 to 50% inside the substrate from the surface (lower surface) of the substrate 4b with respect to 100% of the total thickness of the substrate 4b. The objective lens 3 is driven by means (not shown) to adjust the focal length.
As the adjusting means, for example, a piezo element can be used. Further, as the laser displacement meter, for example, a non-contact type laser displacement meter such as a heterodyne method or a triangulation method can be used.
The focal length can be adjusted by finely moving the objective lens 3 in the vertical direction (Z-axis direction) by controlling the voltage to the piezo element based on the measurement result of the laser displacement meter 5.

The depth of focus (DF) of the laser beam is a numerical value represented by the following equation (1). In the equation (1), k is a process constant, λ is the wavelength of the laser beam, and N.I. A. Is the numerical aperture (NA) of the objective lens. The depth of focus is represented by the length in the optical axis direction (Z-axis direction).
± D (μm) = kλ / (NA) ² (1)
Focusing is performed so that the depth of focus represented by the above formula (1) is included in a range of 5 to 50% from the front surface (lower surface) of the substrate 4b to the inside of the substrate with respect to 100% of the total thickness of the substrate 4b. Adjust the distance.

The focal length so that the depth of focus represented by the above formula (1) is included in the range of 5 to 50% from the surface (lower surface) of the substrate 4b to the inside of the substrate with respect to 100% of the total thickness of the substrate 4b. Is adjusted, the substrate absorbs the laser beam, and only the central portion of the laser spot inside the substrate is locally heated above the softening point of the material constituting the substrate.
A crack is generated by a local temperature rise in the laser spot portion inside the substrate, and a linear scribe with a constant width and high accuracy is formed without causing chipping or the like.
By forming scribes on both the upper and lower substrates of the large liquid crystal panel, cracks develop in the vertical direction, and the large panel can be accurately cut into small panels.
If the focal length is adjusted so that the focal depth of the laser beam is less than 5% from the surface of the substrate with respect to the total thickness of 100% of the substrate, the scribe may be too shallow to divide the substrate. In some cases, the machining accuracy is lowered and chipping or the like occurs.
On the other hand, when the focal length is adjusted so that the focal depth of the laser light is within 50% from the surface of the substrate with respect to 100% of the total thickness of the substrate, the processing accuracy decreases and chipping occurs. There is.

When the large-sized liquid crystal panel 4 is irradiated with the laser beam condensed by adjusting the focal length so that the depth of focus represented by the above formula (1) is included in the above range, the laser spot portion is formed inside the substrate. Compressive stress that counteracts the tensile force to destroy the substrate is generated by local temperature rise, and this compressive stress can improve the strength such as bending strength and fracture strength of the cutting edge part that becomes the processing site. it can. When the breaking strength is high, the bending strength is also increased.
In the conventional processing apparatus, it was difficult to process the fractured small liquid crystal panel so that the breaking strength exceeds 250 MPa. However, when the laser processing apparatus 1 of this example is used, the large liquid crystal panel is cleaved with high accuracy. Thus, a high-strength small liquid crystal panel having a breaking strength exceeding 250 MPa can be obtained.
In addition, even if the temperature inside the substrate is locally raised to near the softening point of the material constituting the substrate, the TFT, liquid crystal material, and color filter material constituting the large liquid crystal panel are thermally damaged by the local temperature rise. Therefore, a large substrate can be cleaved into a small substrate without degrading quality.

  As the laser light source 2, any laser light source that oscillates laser light in the wavelength region of 200 to 2000 nm (0.2 to 2.0 μm) may be used. Pulse laser that oscillates intermittent laser light, continuous laser light may be used. An oscillating CW (continuous wave) laser, a gas excimer laser, a solid medium that uses a harmonic wave and a semiconductor laser that uses a short wavelength, or the like can be used. Specifically, a YAG laser having a wavelength of 355 nm and a third harmonic is used.

  The laser light oscillated from the laser light source 2 is transmitted through the mirror 8 for a long distance in the horizontal direction, converted into the direction of the large liquid crystal panel 4 by the mirror 9, condensed by the objective lens 3, and large liquid crystal. The panel 4 is irradiated.

The laser light oscillated from the laser light source 2 is 200 to 2000 nm (0.2 to 2.0 μm).
When the wavelength of the laser light oscillated from the laser light source is a short wavelength of less than 200 nm, the transmission efficiency of the laser light in the air is significantly reduced.
On the other hand, if the wavelength of the laser light oscillated from the laser light source exceeds 2000 nm (2.0 μm), the material of the objective lens for condensing such long-wavelength laser light becomes expensive, and the condensed laser light Therefore, it is difficult to control the depth of focus within a range of 5 to 50% from the surface of the substrate to the inside of the substrate with respect to 100% of the total thickness of the substrate.
For example, in a transparent substrate such as glass that absorbs laser light with a wavelength of 200 to 2000 nm with high efficiency, the laser spot portion inside the substrate is locally heated above the softening point of the glass by laser light irradiation, and the predetermined A scribe with a precise depth and width within the range can be formed.

The drive frequency of the laser light source 2 is preferably 1 to 500 KHz.
If the driving frequency of the laser light source 2 is less than 1 KHz, the pulse oscillation interval becomes longer relative to the moving speed in the case of a pulse laser when the moving speed of the substrate that is the object to be processed is increased. Is impossible and the processing speed cannot be increased, resulting in a decrease in productivity.
On the other hand, when the driving frequency of the laser light source 2 exceeds 500 KHz, the pulse output characteristics are remarkably deteriorated in the case of a pulse laser, and the quality of the processed product is remarkably deteriorated.

The aperture ratio (NA) of the objective lens 3 is preferably 0.01 to 0.5.
When the aperture ratio (NA) of the objective lens is less than 0.01, the focal length becomes long, which is not practical for mounting on an engineering processing machine, and further the laser spot diameter is set to 50 μm or less. It becomes difficult.
On the other hand, when the numerical aperture (NA) of the objective lens exceeds 0.5, the focal length is shortened, and scattered workpieces adhere to the objective lens when the substrate is processed by irradiating laser light. Thus, the light transmittance of the lens is significantly reduced.
The numerical aperture (NA) of the objective lens is a numerical value represented by the following equation (2). In the formula (2), n is the refractive index of the medium between the objective lens and the object to be processed. When the medium is air, n = 1.0. In the equation (2), θ is an angle formed between a light beam passing through the outermost side of the objective lens and the center (optical axis) of the objective lens.
N. A. = N · sin θ (2)

3-6 is explanatory drawing which shows one process which processes the large sized liquid crystal panel 4 with the laser processing apparatus shown in FIG.1 and FIG.2, and the arrow fixes the large sized liquid crystal panel 4 in FIGS. The direction in which the movable stage 7 is moved is shown.
Based on FIGS. 3-6, an example in the case of processing the large sized liquid crystal panel 4 using the laser processing apparatus 1 is demonstrated.
As shown in FIG. 3, the movable stage 7 to which the large liquid crystal panel 4 is fixed is moved in the Y direction (arrow direction in FIG. 3) to correspond to the processing line (cutting pitch) 4 d of the large liquid crystal panel 4, The distance between the objective lens 3 installed on the same arm 6 and the surface of the large liquid crystal panel 4 is accurately measured by a laser displacement meter 5 (see FIGS. 1 and 2) installed in an array on the arm 6.
The measurement result (focal length) measured by the laser displacement meter 5 is sent to an electronic control component (not shown) as sequential data according to the processing sequence of the processing scheduled line 4d, that is, the movement path that reciprocates the movable stage 7 in the Y direction. To store.
Since the laser processing apparatus 1 of this example includes a plurality of laser displacement meters 5 arranged in an array corresponding to the planned processing line 4d of the large liquid crystal panel 4, the movable stage is moved once in one direction. Only the distance information between the objective lens 3 and the large liquid crystal panel 4 can be obtained, and the measurement time can be greatly shortened.

Next, as shown in FIG. 4, the positions of the objective lens 3 (not shown) and one processing scheduled line 4d of the large liquid crystal panel 4 are aligned.
Then, the movable stage 7 is moved in the Y direction so that the movable stage 7 moves at the shortest distance along the processing line 4d, and then the movable stage 7 is moved in the X direction by an interval of the small liquid crystal panel 4a to be divided. After the movement, the movable stage 7 is reciprocated in the Y direction again.
As the movable stage 7 reciprocates in the Y direction, the movable stage 7 is adjusted while adjusting the focal length of the objective lens 3 with an adjusting means such as a piezo element based on the sequential data of the focal length stored in the electronic control component. The large liquid crystal panel 4 is irradiated with laser light by reciprocating in the Y direction.

  Next, the movable stage 7 is rotated by 90 °. Then, as shown in FIG. 5, the movable stage 7 is moved once in the Y direction (in the direction of the arrow in FIG. 8) to correspond to the planned machining line 4d orthogonal to the planned machining line 4d that has already been irradiated with the laser beam. The distance between the objective lens 3 and the surface of the large liquid crystal panel 4 is accurately measured by the laser displacement meter 5 installed in an array on the arm 6.

Thereafter, as shown in FIG. 6, the objective lens 3 and the planned processing line 4d are aligned, and the movable stage 7 is moved in the Y direction so that the movable stage 7 moves along the planned processing line 4d with the shortest distance. After the movement, the movable stage 7 is moved in the X direction by an interval of the small liquid crystal panel 4a to be cleaved, and then the movable stage 7 is reciprocated in the Y direction again. Simultaneously with the movement of the movable stage 7, the focal length of the objective lens is adjusted based on the measurement result of the laser displacement meter 5 stored as sequential data, and the large liquid crystal panel 4 is irradiated with laser light.
By laser light irradiation, the laser spot portion inside the substrate is locally heated, and a scribe is formed along the planned processing line 4d.

In the case where the object to be processed is a bonded substrate in which the upper and lower substrates are bonded together like the large liquid crystal panel shown in FIGS. After irradiating laser light in the order shown in FIG. 6, it is preferable to similarly irradiate the upper substrate with laser light in the order shown in FIGS.
If the upper substrate is irradiated with laser light first, scribing is formed on the surface of the upper substrate by this laser light irradiation, and even if the lower substrate is irradiated with laser light after that, The scribing formed on the substrate makes it difficult to focus the laser beam accurately, and the processing reliability is lowered.

When using the laser processing apparatus of this example, first, by irradiating the lower substrate of the large liquid crystal panel with laser light, the laser spot portion is locally heated, and the lower substrate is scribed. It is formed. Next, by irradiating the upper substrate of the large liquid crystal panel with laser light, a scribe is formed on the upper substrate due to local temperature rise in the laser spot portion, and the crack propagates vertically from the bottom of the scribe. The large liquid crystal panel can be cleaved into small liquid crystal panels with high accuracy without causing chipping or the like.
In this way, when the laser processing apparatus of this example is used, the large liquid crystal panel can be cleaved into a small liquid crystal panel without flipping the bonded substrate like the large liquid crystal panel up and down, greatly increasing the production efficiency. Can be improved.

The laser processing apparatus of this example locally raises the temperature of the laser spot inside the substrate by irradiating laser light, but the temperature rise is small, so the temperature rises without spraying cooling water or the like. The applied part is rapidly cooled. Therefore, the thermal damage accompanying a rapid temperature change can be reduced and the quality of a processed product can be improved.

In the laser processing apparatus 1 of this example, a preferable example of processing conditions is as follows.
The wavelength of the laser light source is 200 to 2000 nm, the laser power is preferably 1 to 30 W, the driving frequency is preferably 10 to 500 KHz, and the processing rate (NA) of the objective lens is preferably 0.01 to 0. 5. If the moving speed of the movable stage is preferably 10 to 500 mm / sec (mm / sec), for example, even if the substrate thickness is 500 μm or less, the quality accuracy of the processed product is improved. Thus, good processing can be performed.

The wavelength of the laser light source is preferably an appropriate wavelength depending on the light absorption characteristics of the object to be processed. When the object to be processed is a transparent glass substrate, the laser light source has a high glass transmittance of 266 to 532 nm. It is more preferable to use one having a wavelength.
The driving frequency of the laser light source can be selected more appropriately depending on the processing speed, that is, the moving speed of the movable stage 7. From the viewpoint of increasing the processing speed, the driving frequency of the laser light source is more preferably 20 to 200 KHz.

Next, another example of a preferred embodiment of the laser processing apparatus of the present invention will be described.
FIG. 7 is a plan view schematically showing another example of the preferred embodiment of the laser processing apparatus 1 of this example, and FIG. 8 is a plan view showing a part of the laser processing apparatus shown in FIG. 7 and 8, the same members as those in FIGS. 1 and 2 are denoted by the same reference numerals.

  As shown in FIGS. 7 and 8, the laser processing apparatus 1 of this example includes a laser light source 2 that oscillates laser light having a wavelength region of 200 to 2000 nm, laser processing means including an objective lens 3, and an objective lens 3. And two or more laser displacement meters 5 for measuring the distance between the surface of the large liquid crystal panel 4 to be processed and the measurement result of the laser displacement meter 5, the laser light condensed by the objective lens 3 Adjustment means (for example, a piezo element, not shown) that drives the objective lens 3 to adjust the focal length so that the depth of focus is included in a predetermined range within the substrate of the large liquid crystal panel 4 from the surface of the large liquid crystal panel 4 It has.

FIG. 9 is a plan view showing the laser displacement meter 5 installed in the laser processing apparatus 1 of this example.
The laser displacement meter 5 is installed at a symmetrical position in the horizontal direction around the laser processing means provided with the objective lens 3. In the laser processing apparatus 1 of the present example, four laser displacement meters 5 are installed on a common arm 6 on which the objective lens 3 is installed at symmetrical positions on the X axis and the Y axis with the objective lens 3 as the center. .

The laser processing apparatus 1 of the present example has one of the upper side and the lower side of the large liquid crystal panel 4 by four laser displacement meters 5 installed at symmetrical positions on the X axis and the Y axis with the objective lens 3 as the center. The distance between the surface of the substrate and the objective lens 3 is accurately measured along the planned processing line 4 d of the large liquid crystal panel 4.
The laser processing apparatus 1 of this example includes four laser displacement meters 5 installed at symmetrical positions on the X axis and the Y axis with the objective lens 3 as the center, and the objective lens 3 and the large liquid crystal according to the movement of the movable stage 7. The distance to the panel 4 is accurately measured, and based on the measurement result, the objective lens 3 is driven in the Z-axis direction with a piezo element, so that the focal depth of the laser beam is 100% of the total thickness of the substrate 4b. On the other hand, the focal length is adjusted so as to fall within the range of 5 to 50% of the inside of the substrate from the surface (lower surface) of the substrate 4b.
The laser processing apparatus 1 of this example measures the distance between the objective lens 3 and the large liquid crystal panel 4 along with the movement of the movable stage 7, and based on this measurement result in real time according to the movement of the movable stage 7, Since the laser beam can be irradiated by adjusting the focal length, the processing time can be remarkably shortened.
In addition, since the laser displacement meter 5 of this example is installed at a symmetrical position on the X axis and the Y axis with the objective lens 3 as the center, the distance between the surface of the substrate and the objective lens 3 can be accurately measured. .

10 and 11 illustrate an example of a direction in which the movable stage 7 to which the large liquid crystal panel 4 is fixed is moved by arrows when the large liquid crystal panel 4 is processed by the laser processing apparatus 1 illustrated in FIGS. FIG.
First, as shown in FIG. 10, the positions of the objective lens 3 (not shown) and one processing scheduled line 4 d of the large liquid crystal panel 4 are aligned. The movable stage 7 is moved in the Y direction so that the movable stage 7 moves at the shortest distance along the planned processing line 4d, and then the movable stage 7 is moved in the X direction by an interval of the small liquid crystal panel 4a to be divided. Thereafter, the movable stage 7 is reciprocated in the Y direction again.
As the movable stage 7 reciprocates, the surface (lower surface) of either the upper or lower substrate (the lower substrate 4b in this example) of the large liquid crystal panel 4 by the four laser displacement meters 5 described above. ) And the objective lens 3 are accurately measured. Based on the measurement result, the objective lens 3 is driven in the Z-axis direction by adjusting means such as a piezo element while the movable stage 7 is reciprocated, and the focal depth of the laser beam is 100% of the total thickness of the substrate 4b. On the other hand, the focal length is adjusted so as to fall within the range of 5 to 50% of the inside of the substrate from the surface (lower surface) of the substrate 4b, and laser light is irradiated to form a scribe on the lower substrate 4b.
The large liquid crystal panel 4 is preferably processed first on the lower substrate. If the upper substrate is irradiated with the laser beam first, it becomes difficult to accurately irradiate the predetermined portion inside the lower substrate with the laser beam due to the scribe previously formed on the upper substrate. This is because reliability is lowered.

Next, the movable stage 7 is rotated by 90 °. As shown in FIG. 11, the movable stage 7 is moved while moving the movable stage 7 in the X direction by an interval of the small liquid crystal panel 4a to be divided so that the movable stage 7 moves along the planned processing line 4d at the shortest distance. Is reciprocated in the Y direction.
And while moving the movable stage 7, the distance between the surface (upper surface) of the upper substrate 4a and the objective lens 3 is accurately measured by the laser displacement meter 5, and the objective lens 3 is moved to Z based on the measurement result. Driven in the axial direction, the focal length is adjusted so that the focal depth of the laser beam is included in a predetermined range, and the laser beam is irradiated to form a scribe on the upper substrate 4a.
When the scribe is formed on the upper substrate 4a, cracks develop in the scribe direction (vertical direction) of the lower substrate 4b, and the large liquid crystal panel 4 can be divided into small panels with high accuracy.

Next, an example of a preferred embodiment of the laser processing method of the present invention will be described.
The laser processing method of this example is a laser light source that oscillates laser light having a wavelength region of 200 to 2000 nm, laser processing means including an objective lens that condenses the laser light, the objective lens, and an object to be processed. Two or more laser displacement meters that measure the distance to the surface of the substrate and the depth of focus of the laser light are included in a predetermined range from the surface of the substrate to the inside of the substrate based on the measurement result of the laser displacement meter. A laser processing method for processing a large substrate into a small substrate using a laser processing apparatus equipped with an adjusting means for adjusting the focal length by driving the objective lens as described above. Based on the step of measuring the distance between the objective lens and the surface of the large substrate and the measurement result, the focal depth of the laser beam is 100% of the total thickness of the substrate. Performing an irradiation step of adjusting the focal length by driving the objective lens to include 5 to 50% of the inner substrate from the surface of the substrate is irradiated with laser light it is.

Further, in the laser processing method of this example, when the substrate to be processed is a bonded substrate such as a large liquid crystal panel, as the irradiation step, the focal depth of the laser beam is below the bonded substrate. The objective lens is driven to adjust the focal length so as to be included in the range of 5 to 50% of the inside of the substrate from the lower surface of the lower substrate with respect to the total thickness of 100% of the substrate, and the laser beam is irradiated. The first irradiation step and the depth of focus of the laser beam are included in a range of 5 to 50% from the upper surface of the upper substrate to the inside of the substrate with respect to 100% of the total thickness of the upper substrate of the bonded substrate. Thus, the objective lens is driven, the focal length is adjusted, and the second irradiation step of irradiating the laser beam is included.
The laser processing method of this example includes a color filter on the lower substrate and a TFT on the upper substrate when the object to be processed is a bonded substrate such as a large organic EL panel or a large liquid crystal panel. Suitable for processing things.
If the upper substrate is irradiated with the laser beam first, it becomes difficult to accurately irradiate the predetermined portion inside the lower substrate with the laser beam due to the scribe previously formed on the upper substrate. This is because reliability is lowered.

According to the laser processing apparatus and the laser processing method of the present invention, a large substrate is processed into a small substrate by improving the strength of a cutting edge portion serving as a processing portion without damaging the material constituting the panel. Therefore, it is suitable as an apparatus and method for dividing a large liquid crystal panel or a large organic EL panel into small sizes for each device.
Further, according to the present invention, by using two or more laser displacement meters, it is possible to shorten the time for measuring the distance between the object to be processed having a plurality of processing lines and the objective lens, Since the substrate can be processed without being turned upside down, the production efficiency can be greatly improved.

Hereinafter, the present invention will be described based on examples. The present invention is not limited to the following examples.
(Example)
With the laser processing apparatus shown in FIG. 1, a non-alkali glass substrate having a thickness of 100 μm was processed under the following conditions.
As the laser light source 2, a UV-YAG laser having a wavelength of 355 nm was used. The laser light source 2 has a laser power of 5 W and a driving frequency of 50 KHz. The aperture ratio (NA) of the objective lens 3 is 0.1, and the moving speed of the movable stage 7 is 50 mm / sec (mm / sec).
The focal point of the laser beam is set at a position 30 μm from the surface of the substrate to the inside of the substrate, and the focal depth of the laser beam is 50% from the surface of the substrate to the inside of the substrate with respect to the total thickness of 100% (100 μm). The focal length of the objective lens 3 was adjusted so as to be included in the range of 50 μm), and laser light was irradiated.

FIG. 12: shows the optical microscope photograph of the glass substrate processed with the laser processing apparatus and processing method of an Example, and is the top view (a) and sectional drawing (b) of a glass substrate.
As shown in FIG. 12, the glass substrate processed by the laser processing apparatus and processing method of the example has a fine linear shape with a depth of 44.1 μm and a width of 17.6 μm without causing chipping or the like. A scribe was formed. In addition, vertical cracks progressed from the surface of the glass substrate to a depth of 70 μm inside the substrate due to the formation of the scribe.
Moreover, the cutting edge part which is a site | part (processed site | part) in which the scribe was formed had a fracture stress exceeding 250 MPa and a bending strength exceeding 30N. The fracture stress was measured by a four-point bending strength evaluation method.
From this result, due to the local temperature rise of the laser spot portion on the glass substrate, a compressive stress that counteracts the tensile force to destroy the glass substrate is generated, and a thermally deteriorated layer is formed. It was confirmed that the fracture stress at the cutting edge portion was improved. In addition, according to the laser processing apparatus and the processing method of this example, it was possible to improve the quality of a processed product with excellent accuracy and process a large substrate into a small substrate.

(Comparative example)
The focal point of the laser beam is set at a position of 70 μm inside the substrate from the surface of the glass substrate, and the focal depth of the laser beam is 70% from the substrate surface to the inside of the substrate with respect to the total thickness of the substrate 100% (100 μm). A glass substrate was processed in the same manner as in the example except that the focal length of the objective lens 3 was adjusted and the laser beam was irradiated so as to include the position (70 μm).

  FIG. 13: shows the optical microscope photograph of the glass substrate of the comparative example 1, (a) Top view and (b) Sectional drawing. As shown in FIG. 13, the depth of focus of the laser beam is included outside the range of 5 to 50% in the substrate from the surface of the substrate with respect to the total thickness of the substrate of 100% (specifically, 70%). When the focal length was adjusted in this way, chipping occurred in the processed portion, and accurate processing could not be performed.

It is a top view which shows typically an example of the laser processing apparatus of this invention. It is a top view which shows a part of laser processing apparatus shown in FIG. It is explanatory drawing which shows the process using the laser processing apparatus of FIG.1 and FIG.2. It is explanatory drawing which shows the process using the laser processing apparatus of FIG.1 and FIG.2. It is explanatory drawing which shows the process using the laser processing apparatus of FIG.1 and FIG.2. It is explanatory drawing which shows the process using the laser processing apparatus of FIG.1 and FIG.2. It is a top view which shows typically the other example of the laser processing apparatus of this invention. It is a top view which shows a part of laser processing apparatus shown in FIG. It is a top view which shows schematic structure of the objective lens and laser displacement meter of the laser processing apparatus of FIG.7 and FIG.8. It is explanatory drawing which shows the process using the laser processing apparatus of FIG.7 and FIG.8. It is explanatory drawing which shows the process using the laser processing apparatus of FIG.7 and FIG.8. It is the (a) top view and (b) sectional view of the glass substrate processed by the laser processing apparatus and laser processing method of the present invention. It is the (a) top view and (b) sectional view of the glass substrate processed by the laser processing apparatus and laser processing method of the comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser processing apparatus, 2 ... Laser light source, 3 ... Objective lens, 4 ... Large liquid crystal panel, 4a ... Upper board | substrate, 4b ... Lower board | substrate, 4c ... Spacer, 4d ... Processing planned line (cutting pitch), 4e ... small liquid crystal panel, 5 ... laser displacement meter, 6 ... arm, 7 ... movable stage, 8,9 ... mirror

Claims (10)

A laser light source that oscillates a laser beam having a wavelength region of 200 to 2000 nm;
A laser processing means comprising an objective lens for condensing the laser beam;
Two or more laser displacement meters that measure the distance between the objective lens and the surface of the substrate that is the workpiece;
Based on the measurement result measured by the laser displacement meter, the depth of focus of the laser beam is included in the range of 5 to 50% inside the substrate from the surface of the substrate with respect to 100% of the total thickness of the substrate. And an adjusting means for adjusting the focal length by driving the objective lens. The laser displacement meter measures the distance between the objective lens and the upper and lower surfaces of the substrate,
Based on the measurement result of the laser displacement meter, the adjusting means has a focal depth of the laser beam of 5 to 50% from the upper and lower surfaces of the substrate to 100% of the total thickness of the substrate. The laser processing apparatus according to claim 1, wherein the focal length is adjusted by driving the objective lens so as to be included in the range.   The laser processing apparatus according to claim 1, wherein the laser displacement meter is installed at a symmetrical position in a horizontal direction around the objective lens.   The laser processing apparatus according to claim 1, wherein the laser displacement meters are arranged in an array on a processing target line of a processing object.   The laser processing apparatus according to claim 1, wherein the adjusting means is a piezo element.   The numerical aperture of the objective lens A. The laser processing apparatus according to claim 1, wherein is 0.01 to 0.5.   The laser processing apparatus according to claim 1, wherein a driving frequency of the laser light source is 1 to 500 KHz. A laser light source that oscillates a laser beam having a wavelength region of 200 to 2000 nm;
A laser processing means comprising an objective lens for condensing the laser beam;
Two or more laser displacement meters that measure the distance between the objective lens and the surface of the substrate that is the workpiece;
Adjusting means for driving the objective lens and adjusting the focal length so that the focal depth of the laser light is included in a predetermined range inside the substrate from the surface of the substrate based on the measurement result of the laser displacement meter. A laser processing method for processing a large substrate into a small substrate using the laser processing apparatus,
Measuring the distance between the objective lens and the surface of the large substrate with the laser displacement meter;
Based on the measurement result, the objective lens is driven so that the focal depth of the laser light is included in the range of 5 to 50% from the surface of the substrate to the inside of the substrate with respect to 100% of the total thickness of the substrate. A laser processing method comprising: an irradiation step of adjusting a focal length and irradiating a laser beam. The substrate is a bonded substrate,
In the irradiation step, the depth of focus of the laser beam is included in a range of 5 to 50% inside the substrate from the lower surface of the lower substrate with respect to 100% of the total thickness of the lower substrate of the bonded substrate. A first irradiation step of driving the objective lens and adjusting the focal length to irradiate the laser beam,
The objective lens is driven so that the focal depth of the laser beam is within a range of 5 to 50% of the inside of the substrate from the upper surface of the upper substrate with respect to 100% of the total thickness of the upper substrate of the bonded substrate. The laser processing method according to claim 8, further comprising a second irradiation step of adjusting the focal length and irradiating the laser beam.   The laser processing method according to claim 9, wherein the lower substrate includes a color filter, and the upper substrate includes a thin film transistor.

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