JP2009221046A - Laser-processed object - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-strength laser-processed object obtained by irradiating an object to be processed with laser light to make higher the fracture stress and/or flexural strength of the object to be processed. <P>SOLUTION: The laser-processed object 1 has a thermally deteriorated layer 1b in which compressive stress is produced by irradiating the object to be processed with the converged laser light. It is preferable that the thermally deteriorated layer 1b is formed in the range of ≥10% from the irradiation position of the laser light toward the inside of the object to be processed on the basis of 100% thickness of the object to be processed. It is much preferable that the thermally deteriorated layer 1b is formed in the range of ≥30% from the irradiation position of the laser light toward the inside of the object to be processed on the basis of 100% thickness of the object to be processed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a laser processed product in which a laser beam irradiation site is processed with high intensity.

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 on which a switching element such as a thin film transistor (hereinafter referred to as “TFT”) is disposed, and a red (R), green (G), and blue (G) for each predetermined pixel facing the substrate. B) a substrate on which the color filter layer is arranged, and the two substrates are held at a predetermined interval via a spacer, and the liquid crystal layer is held between them.
The organic EL panel includes a TFT substrate on which a TFT is disposed, 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, and a color filter. It has a structure in which a substrate on which layers are arranged is laminated.

In order to improve the production efficiency of liquid crystal panels and organic EL panels, for example, a plurality of display elements constituting the screen of each device such as a mobile phone are formed on a large area substrate of 600 mm length × 700 mm width. A large-area substrate is divided into small substrates that constitute the screen of each device.
As a material for a substrate on which a TFT and a color filter layer are disposed, which is used for a liquid crystal panel and an organic EL panel, a glass material such as quartz glass or inorganic glass that generally transmits light is used.

As a method of dividing (breaking down) a large substrate into a small substrate, for example, a method is generally used in which a groove (scribe) is formed on the surface of a substrate such as a glass substrate, and the substrate is divided (breaked) using this as a starting point. is there.
For example, there is a method in which a scribing of an appropriate depth is formed using a mechanical blade (tool) such as a super steel cutter or a diamond cutter, and the substrate is divided by forming a vertical crack starting from the scribe. Can be mentioned. However, the mechanical method has a problem that microcracks are generated in the horizontal direction in the vicinity of the surface of the substrate, and the bending strength of the workpiece is lowered.

In addition to the mechanical method, there is a method of using a heating laser such as a carbon dioxide (CO ₂ ) gas laser and irradiating the glass substrate with a laser beam of about 500 ° C. to divide the glass substrate.
As an example of this method, first, an initial crack is formed with a mechanical blade in advance using a continuous wave or pulsed CO ₂ gas laser with a wavelength of 1060 nm and a focused spot diameter (diameter) of 2 to 3 mm. Irradiate the planned processing line of the glass substrate. The glass substrate is melted by the irradiation of the CO ₂ gas laser, and the irradiated portion is thermally expanded.
Then, cooling water or the like is sprayed, the glass substrate is rapidly cooled, the glass substrate is thermally contracted, and initial cracks previously formed with a mechanical blade are developed to divide the glass substrate.

As a method of using laser light, using a Nd: YAG laser or the like, a glass substrate is irradiated with a laser beam to heat the glass substrate, and a cut portion of the glass substrate is rapidly cooled to form a microcrack. A method for cutting a glass substrate provided with a cooling step is disclosed (Patent Document 1).
This method irradiates a laser beam having a uniform energy density in a vertically long shape, thereby suppressing natural cooling caused by the difference in energy density and increasing the thermal shock in the cooling process, thereby increasing the surface of the glass substrate and Microcracks are generated inside to increase the cutting speed of the glass substrate.

Also, using a long wave YAG laser or the like, the focusing means for aligning the focal point with a predetermined position inside the object to be processed, and the focal point is relatively moved along the planned cutting line of the object to be processed. A laser processing apparatus including a moving unit is disclosed (Patent Document 2).
This laser processing device irradiates a workpiece with pulsed laser light having a wavelength in the ultraviolet region, causes a multiphoton absorption phenomenon inside the workpiece, and forms a modified portion in the vicinity of the surface of the workpiece. Then, the workpiece is cleaved along the planned cleaving line with a small force.

Also, using a light source with an infrared wavelength such as Nd: YAG (wavelength: 1064 nm) or Ti: Sapphire (wavelength: 800 nm) at a first harmonic, a short pulse laser beam with a pulse width of 100 picoseconds or less is swept onto the glass surface. A method of forming a cutting groove on the glass surface by irradiation is also disclosed (Patent Document 3).
This method reduces the influence of thermal vibration by setting the pulse width of the short pulse laser beam to 100 picoseconds or less, and does not cut the bond by a thermal process, but directly bonds glass molecules without heat. The object to be processed (glass substrate) is cleaved by making the process of cutting dominant.

JP 2000-219528 A JP 2006-315031 A JP 2007-331983 A

In the method of cutting a glass substrate using a CO ₂ gas laser, since the glass substrate is cleaved by rapid thermal conversion, the larger the volume of the glass substrate, that is, the greater the thickness of the substrate, the higher the accuracy. It is cleaved.
In recent years, mobile phones and the like have a strong tendency to be reduced in size and thickness, and liquid crystal panels and the like are desired to be thin and have high bending strength. Therefore, for example, a conventional method using a CO ₂ gas laser is not suitable as a method for cleaving a thin substrate of 200 μm or less. Further, when a thin substrate is cleaved with a CO ₂ gas laser, thermal strain may remain on a small substrate cleaved by rapid thermal conversion.
Furthermore, the method of cleaving a substrate using a CO ₂ gas laser is a method of causing thermal damage to a color filter material such as a liquid crystal panel, a liquid crystal material, a sealing resin, and the like due to rapid thermal conversion, and these display elements are destroyed. There is also a risk.

  In the method of cutting a glass substrate of Cited Document 1, since the glass substrate was heated and cut by irradiating a laser beam, the cut portion was rapidly cooled to generate a microcrack, and thus the glass substrate was cut due to the presence of the microcrack. There exists a problem that the bending strength of a glass substrate falls.

  If the laser processing apparatus of cited document 2 or the scribing method of cited document 3 is used, it is possible to cleave the substrate without abrupt thermal conversion, so the thermal strain and heat remaining on the cleaved small substrate Damage can be avoided. However, in order to sever the substrate without rapid thermal conversion, no compressive stress is generated inside the substrate, and the strength of the substrate (particularly the glass substrate), such as tempered glass, for example, fracture stress, The bending strength cannot be increased.

  The present invention has been made paying attention to the above-described conventional problems, and by irradiating a laser beam onto a workpiece, the fracture stress and / or bending strength is increased, and a high-strength laser workpiece is obtained. The purpose is to provide.

  As a result of intensive studies to achieve the above object, the inventors of the present invention formed a thermally deteriorated layer in which compressive stress was generated at the irradiated portion of the laser beam by irradiating the focused laser beam on the workpiece. It has been found that a high-strength laser processed product with increased fracture stress and / or bending strength can be obtained, and the present invention has been completed.

  The laser processed product of the present invention is characterized by having a thermally altered layer in which a compressive stress is generated by irradiating a processed laser beam with a focused laser beam.

  In the laser processed product of the present invention, by irradiating the focused laser beam, the processed object is locally heated and cooled above the softening point or melting point of the material constituting the processed object, and the compressive stress is increased. It has the produced | generated heat-altered layer, It is characterized by the above-mentioned.

  The laser-processed product of the present invention irradiates a focused laser beam on a workpiece, thereby forming a thermally deteriorated layer in which a compressive stress is generated at the laser beam irradiation site. Since the laser-processed product of the present invention has a thermally deteriorated layer in which a compressive stress is generated, a high-strength laser-processed product having high fracture stress and / or bending strength can be provided.

Hereinafter, the present invention will be described in detail.
The laser processed product of the present invention has a thermally deteriorated layer in which a compressive stress is generated by irradiating the processing target with a focused laser beam.
When an object to be processed such as a glass substrate is irradiated with a focused laser beam in a predetermined wavelength region, a laser beam irradiation site (processing site) of the object to be processed (that is, a laser spot portion) is locally processed. It is heated to a temperature above the softening point or above the melting point, softened or melted, and thermally expanded.
Since the laser beam irradiation part (processing part) is local, the laser spot part is uniformly heated and softened or melted, and the softened or melted irradiation part (processing part) is immediately and uniformly cooled, A thermally deteriorated layer in which a substantially uniform compressive stress is generated is formed at the thermally expanded portion.
In the present specification, the thermally deteriorated layer of the laser processed product refers to a portion where a substantially uniform compressive stress is generated. The substantially uniform compressive stress is generated by heating the workpiece to a temperature equal to or higher than the softening point or melting point of the material constituting the workpiece, and then cooling the workpiece.
The laser-processed product having a thermally deteriorated layer is not only formed with a microcrack that is the starting point of fracture, like a scribe formed by a mechanical method, but also has a compressive stress generated in the thermally affected layer. Therefore, the fracture stress and / or the bending strength is remarkably increased.
In addition, since the focused laser beam in a predetermined wavelength region is irradiated locally on the workpiece, the thermal distortion of the laser workpiece is suppressed, and the thermal damage that the laser workpiece receives is reduced. Can do.

  The laser processed product of the present invention absorbs laser light in a specific wavelength region with high efficiency, and is used as a TFT substrate or a color filter layer substrate such as a liquid crystal panel or an organic EL panel. It is preferable that it consists of glass materials, such as.

The laser beam applied to the object to be processed is a wavelength region suitable for the light absorption characteristics of the object to be processed, and is preferably a wavelength region that can be easily condensed and irradiated with an optical lens. Therefore, it is preferable that a laser beam is a wavelength range of 200-2000 nm (0.2-2.0 micrometers) which satisfy | fills these requirements.
When a transparent substrate used as a substrate for a liquid crystal panel or the like, for example, a substrate made of a glass material, is a processing target, accurate focus control is required to locally raise the temperature of only the laser spot portion. In order to enable such precise focus control, it is desirable to use laser light in a wavelength region having a high transmittance with respect to transparent glass.
Therefore, when the object to be processed is a transparent substrate made of a glass material, it is more preferable to use laser light having a wavelength range of 266 to 532 nm with high transmittance.

  An appropriate driving frequency is selected as the driving frequency of the laser light source that oscillates the laser light in a specific wavelength region depending on the processing speed and the like. From the viewpoint of increasing the processing speed, the driving frequency of the laser light source is preferably 1 Hz to 500 MHz. In order to ensure more stable processing characteristics, the driving frequency of the laser light source is preferably 20 KHz to 200 KHz.

  The laser light source only needs to oscillate a laser beam having a wavelength region of 200 to 2000 nm (0.2 to 2.0 μm), and oscillates a pulse laser that oscillates intermittent laser light and a continuous laser beam. A CW (continuous wave) laser, an excimer laser in which the medium is a gas, a solid laser in which the medium is solid and using harmonics, a semiconductor laser using a short wavelength, or the like can be used.

Next, a method for processing an object to be processed using a laser processing apparatus will be described.
FIG. 1 shows an example of a laser processing apparatus suitably used for forming the laser processed product of this example, and is a diagram illustrating a schematic configuration of the laser processing apparatus 10. FIG. 1 shows an example in which the object to be processed is a large liquid crystal panel 4.
As shown in FIG. 1, the laser processing apparatus 10 includes a laser light source 2 that oscillates laser light having a wavelength region of 200 to 2000 nm, laser processing means that includes an objective lens 3 that condenses the laser light, 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 (not shown) is provided for driving the objective lens 3 to adjust the focal length so that the focal point is included in a predetermined range inside the substrate from the substrate surface constituting 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.
FIG. 2 is a plan view for explaining a schematic configuration of the laser processing apparatus 10 shown in FIG.
As shown in FIG. 2, the square frame provided on the large-sized liquid crystal panel 4 shows one display element, and shows the size divided by the small-sized 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 10 of this example uses the laser displacement meter 5 to accurately determine the distance between the objective lens 3 and the upper or lower substrate surface of the large liquid crystal panel 4 along the planned processing line 4d. taking measurement. In this example, the distance between the objective lens 3 and the surface (lower surface) of the lower substrate 4b of the large liquid crystal panel 4 is measured.
Based on this measurement result, the objective lens 3 is driven by adjusting means (not shown) so that the focal point of the laser beam is at a predetermined position, and the focal length between the substrate 4b and the objective lens 3 is adjusted.
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.

  As shown in FIGS. 1 and 2, the laser light oscillated from the laser light source 2 is transmitted through the mirror 8 for a long distance in the horizontal direction, and converted into the direction of the large liquid crystal panel 4 by the mirror 9. The light is condensed by the objective lens 3 and irradiated to the large liquid crystal panel 4.

  The focal point of the laser beam is preferably 5% or more inside the processing object from the surface of the processing object, more preferably 10% or more inside the processing object from the surface of the processing object, with respect to the thickness of the processing object 100%. More preferably, it is set at a position of 30% or more inside the processing object from the surface of the processing object. In addition, from the viewpoint of improving the processing accuracy, the focal point of the laser light is preferably set at a position of 50% or less inside the substrate with respect to the thickness of the substrate that is the processing target 100%.

When the laser beam focus is set within the above range and the laser beam is irradiated, the substrate absorbs the laser beam, and the laser spot portion inside the substrate locally exceeds the softening point or the melting point of the material constituting the substrate. Is softened or melted and thermally expanded.
Since the irradiation site (processing site) of the laser beam is local, the irradiation site (processing site) is uniformly heated and softened or melted, and the softened or melted irradiation site (processing site) is immediately and uniformly cooled. A thermally deteriorated layer in which a substantially uniform compressive stress is generated is formed at the thermally expanded portion.
That is, the thermally deteriorated layer of the laser processed product is formed by being heated and cooled locally and uniformly above the softening point or melting point of the material constituting the processing target by irradiation with laser light.
The heat-affected layer of the laser processed product is not heated unevenly, such as a modified part formed by causing a multiphoton absorption phenomenon in the processed object by irradiation with pulsed laser light. Therefore, horizontal microcracks are not generated in the thermally deteriorated layer.

The focal point set inside the substrate is correlated with the depth of scribe after laser processing (Depth profile). In addition, the scribe depth and the thickness of the thermally altered layer formed on the laser processed product are almost the same.
The greater the thickness of the thermally affected layer formed on the laser processed product, the greater the fracture stress and bending strength of the laser processed product, so that the focal point and depth of focus set inside the substrate are preferably large.
However, if the focal point set inside the substrate is too large, high-precision processing becomes difficult.
Therefore, the focal point of the laser beam is preferably set at a position of 5 to 50% inside the processing object from the processing object surface with respect to the thickness of the processing object of 100%.
If the focus of the laser beam is set at a position of less than 5% from the surface of the workpiece to the inside of the workpiece with respect to the thickness of the workpiece, the scribe is too shallow to divide the substrate. In addition, the processing accuracy may be reduced and chipping may occur, which is not preferable because the thickness of the heat-affected layer formed becomes small.
If the focal point of the laser beam is set at a position exceeding 50% of the inside of the object to be processed from the surface of the object to be processed, although the thickness of the thermally deteriorated layer is increased, the processing accuracy is lowered and chipping may occur. Therefore, it is not preferable.

The heat-affected layer formed on the laser workpiece may be formed in a range of 10% or more from the laser light irradiation portion toward the inside of the workpiece with respect to the thickness of the workpiece 100%. preferable.
FIG. 3 schematically shows the range of the thermally altered layer 1b formed on the substrate 1 when the focal point is set at a predetermined position of the substrate 1 to be processed and laser light is irradiated to form the scribe 1a. They are (a) sectional drawing and (b) top view shown in figure.
That is, when the object to be processed is the substrate 1 having a thickness of 100 μm, the heat-affected layer 1b formed on the substrate 1 has a depth approximately equal to the depth of 10 μm of the scribe 1a in the Y (vertical) direction. It is formed in the range of 10 μm. The heat-affected layer 1b is formed in the X (horizontal) direction within a range of about 10 μm in width, which is about the same as the depth of the scribe 1 a of 10 μm.
When the heat-affected layer of the laser workpiece is formed in a range of 10% from the laser beam irradiation site to the inside of the workpiece with respect to the thickness of the workpiece 100%, Although it depends on the material and the wavelength region of the laser beam to be irradiated, the focal point of the laser beam is set at a position of about 10% from the surface of the workpiece to the inside of the workpiece with respect to the thickness of the workpiece. It is preferable.

The thermally deteriorated layer formed on the laser workpiece may be formed in a range of 30% or more from the laser light irradiation portion toward the inside of the workpiece with respect to the thickness of the workpiece 100%. More preferred.
When the workpiece is a substrate having a thickness of 100 μm, the laser beam is focused from the substrate surface to 30% from the substrate surface to the substrate thickness so that a scribe with a depth of 30 μm or more is formed. It is preferable to set to the above positions.
When the scribe depth formed on a substrate having a thickness of 100 μm is 30 μm or more, the substrate has a thickness of 30 μm or more in the Y (vertical) direction from the substrate surface and a width of 30 μm or more in the X (horizontal) direction from the scribe. The heat-affected layer is formed.

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)
The depth of focus of the laser light is preferably set so as to fall within a range of 5 to 50% from the surface of the workpiece to the inside of the workpiece with respect to the thickness of the workpiece.

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 is difficult to perform high-precision processing.
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)

Next, a method of processing the large liquid crystal panel 4 which is a processing object with the laser processing apparatus shown in FIGS. 1 and 2 will be described.
As shown in FIG. 2, the large liquid crystal panel 4 fixed to the movable stage 7 is moved in the W direction, and the lasers are arranged in an array along the planned processing line (cutting pitch) 4d of the large liquid crystal panel 4. The displacement meter 5 accurately measures the distance between the objective lens 3 and the surface of the lower substrate 4b of the large liquid crystal panel 4 (the lower surface of the large liquid crystal panel 4). This measurement result is stored in an electronic control component (not shown) as sequential data according to the movement path of the objective lens 3, that is, the planned processing path.
The laser processing apparatus 1 shown in FIG. 1 and FIG. 2 includes a plurality of laser displacement meters 5 installed in an array corresponding to the planned processing line 4 d of the large liquid crystal panel 4. Therefore, the distance information between the objective lens 3 and the large-sized liquid crystal panel 4 can be obtained only by moving the movable stage once in one direction, and the measurement time can be greatly shortened.

Next, according to the sequential data, the position of the objective lens 3 is adjusted by adjusting means (for example, a piezo element) to accurately control the focal length, and the surface of the lower substrate 4b (large liquid crystal panel). 4), a laser beam is irradiated to a predetermined position inside the substrate.
By laser beam irradiation, the laser spot portion of the substrate (lower substrate) 4b is locally heated, and a scribe is formed along the planned processing line (cutting pitch) 4d.
Along with the formation of the scribe, the laser irradiation portion of the substrate (lower substrate) 4b, that is, the processed portion where the scribe is formed, generates compressive stress due to local temperature rise and cooling of the laser spot portion, and the substrate 4b. A thermally altered layer is formed in a predetermined region inside.

  Next, the distance between the objective lens 3 and the surface of the upper substrate 4a of the large liquid crystal panel 4 (the upper surface of the large liquid crystal panel 4) is again measured by the laser displacement meter 5 without inverting the upper and lower surfaces of the large liquid crystal panel 4. Measure accurately. This measurement result is stored in an electronic control component (not shown) as sequential data according to the movement path of the objective lens 3, that is, the planned processing path.

Then, according to the sequential data, the position of the objective lens 3 is adjusted by an adjusting means (for example, a piezo element) to accurately control the focal length, and the surface of the substrate 4a on the upper side of the large liquid crystal panel 4 (the large liquid crystal panel 4). A laser beam is irradiated from a top surface to a predetermined position inside the substrate.
By irradiating the laser beam, the upper substrate 4a is locally heated at the laser spot portion to form a scribe, a crack progresses from the bottom of the scribe to the scribe of the lower substrate 4b, and a large liquid crystal panel 4 is divided along a processing scheduled line (cutting pitch) 4d.
Along with the division of the large liquid crystal panel 4, the laser irradiation portion of the upper substrate 4a, that is, the processing portion where the scribe is formed, generates compressive stress due to local temperature rise and cooling of the laser spot portion, and the inside of the substrate 4a. A thermally deteriorated layer is formed in a predetermined region.

When the object to be processed is a substrate obtained by bonding the upper and lower substrates together like the large liquid crystal panel 4 of this example, the lower substrate is processed first, and then the upper substrate is mounted. It is preferable to process. If the upper substrate is irradiated with laser light first, it becomes difficult to accurately focus the laser light on the lower substrate due to the scribe formed on the upper substrate, and the processing reliability decreases. .
When the object to be processed is a substrate obtained by bonding the upper and lower substrates together, first measure the distance between the surface of both the lower and lower substrates and the objective lens, The measurement result of the substrate and the measurement result of the upper substrate may be stored in this order, the lower substrate may be irradiated with laser light in accordance with the stored order, and then the upper substrate may be irradiated with laser light.

  FIG. 4 is a diagram illustrating a schematic configuration of the laser processing apparatus 10, showing another example of a laser processing apparatus suitably used for forming the laser processed product of this example. FIG. 5 is a plan view showing a part of the laser processing apparatus shown in FIG. 4 and 5, the same members as those in FIGS. 1 and 2 are denoted by the same reference numerals.

  As shown in FIGS. 4 and 5, 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) is provided that drives the objective lens 3 to adjust the focal length so that the focal point and the focal depth are included in a predetermined range from the substrate surface of the large liquid crystal panel 4 to the inside of the substrate. ing.

FIG. 6 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 this example, four laser displacement meters 5 are installed at symmetrical positions on the X axis and the Y axis with the objective lens 3 as the center.
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 substrate surface and the objective lens 3 can be accurately measured.

Next, a process of processing the large liquid crystal panel 4 which is a processing object with the laser processing apparatus 10 shown in FIGS.
As shown in FIG. 5, the large liquid crystal panel 4 fixed to the movable stage 7 is moved in the W direction, and the four laser displacement meters 5 are moved along the planned processing line (cutting pitch) 4 d of the large liquid crystal panel 4. The distance between the surface of the substrate 4b on the lower side of the large liquid crystal panel 4 (the lower surface of the large liquid crystal panel 4) and the objective lens 3 is accurately measured.
Based on the measurement result, the position of the objective lens 3 is adjusted by an adjusting means (for example, a piezo element) to accurately control the focal length, and the surface of the substrate 4a on the lower side of the large liquid crystal panel 4 (large liquid crystal panel). 4), a laser beam is irradiated to a predetermined position inside the substrate.
As a result of the laser light irradiation, the laser spot portion of the lower substrate 4b is locally heated, and a scribe line is formed along the planned processing line (cutting pitch) 4d.
Along with the formation of the scribe, the laser irradiation portion of the lower substrate 4b, that is, the processing portion where the scribe is formed, generates compressive stress due to local temperature rise and cooling of the laser spot portion. A heat-affected layer is formed in the region.

Next, without moving the large liquid crystal panel 4 fixed to the movable stage 7 upside down, the movable stage is moved by the laser displacement meter 5 along the planned processing line (cutting pitch) 4d of the large liquid crystal panel 4. The distance between the surface of the upper substrate 4a of the large liquid crystal panel 4 (the upper surface of the large liquid crystal panel 4) and the objective lens 3 is accurately measured.
Based on the measurement result, the position of the objective lens 3 is adjusted by an adjusting means (for example, a piezo element) to accurately control the focal length, and the surface of the upper substrate 4a of the large liquid crystal panel 4 (the large liquid crystal panel 4). The laser beam is irradiated to a predetermined position inside the substrate from the upper surface of the substrate.
By irradiating the laser beam, the upper substrate 4a is locally heated at the laser spot portion to form a scribe, a crack progresses from the bottom of the scribe to the scribe of the lower substrate 4b, and a large liquid crystal panel 4 is divided along a processing scheduled line (cutting pitch) 4d.
Along with the division of the large liquid crystal panel 4, the laser irradiation portion of the substrate (upper substrate) 4 a, that is, the processing portion where the scribe is formed, generates compressive stress due to local temperature rise and cooling of the laser spot portion. A thermally deteriorated layer is formed in a predetermined region inside 4a.

  The laser processing apparatus 10 shown in FIGS. 4 to 6 measures the distance between the objective lens 3 and the large liquid crystal panel 4 with the laser displacement meter 5 as the movable stage 7 moves, and based on the measurement result, the movable stage 7. Since the laser beam can be irradiated by adjusting the focal length in real time in accordance with the movement, the processing time can be remarkably shortened.

The laser processed product of the present invention has a thermally altered layer in which a compressive stress is generated at a laser beam irradiation site (worked site), and the laser processed product having this thermally altered layer has a fracture stress and / or bending. Strength increases.
For example, a small liquid crystal panel divided by irradiating a large liquid crystal panel with laser light has a heat-affected layer in which compressive stress is generated at the laser light irradiation part (processed part), and thus has high strength. It can be suitably used as a display element constituting the screen of a device such as a mobile phone.

Hereinafter, the present invention will be described based on examples. The present invention is not limited to the following examples.
Example 1
With the laser processing apparatus shown in FIG. 1, a non-alkali glass substrate having a length of 300 mm × width of 350 mm and a thickness of 200 μm was processed under the following conditions.
A UV-YAG laser having a wavelength of 355 nm was used as the laser light source. This laser light source has a laser output of 5.0 W and a drive frequency of 40 KHz. The numerical aperture (NA) of the objective lens is 0.1.
The focal point of the laser beam was set at a position of 15% (30 μm) from the substrate surface to the inside of the substrate with respect to the substrate thickness of 100% (200 μm).
The depth of focus of the laser beam was set at a position included in a range of 5 to 25% (30 μm ± 20 μm) from the substrate surface to the inside of the substrate with respect to the substrate thickness of 100% (200 μm).
Based on the measurement result of the laser displacement meter, the position of the objective lens is adjusted, and the focused laser beam is processed at a speed of 50 mm / sec (mm / sec), a laser spot diameter of 2.3 μm, and a processing line (cutting pitch). The substrate was irradiated along a width of 15 μm, and the substrate was divided into 12 small substrates (laser processed products) of 35 mm length × 50 mm width.
FIG. 7 shows an optical micrograph (a: plan view, b: cross-sectional view) of a laser irradiation site (processed site) of a small substrate cut.
Further, the fracture stress was measured for each of the 12 divided small substrates by the four-point bending strength evaluation method shown in FIG. The results are shown in FIG. In FIG. 13, reference numeral 1 denotes a substrate that is a workpiece, and reference numeral 11 denotes a fulcrum.

(Comparative Example 1)
Using a wheel-shaped super steel mechanical blade, an alkali-free glass substrate similar to that of Example 1 was divided into 12 small substrates having a cutting pitch width of 50 μm and a length of 35 mm and a width of 50 mm.
FIG. 9 shows an optical micrograph (plan view) of a processed portion of a small substrate cut.
For each of the 12 divided small substrates, the fracture stress was measured by the 4-point bending strength evaluation method shown in FIG. The results are shown in FIG.

(Comparative Example 2)
Using a CO ₂ gas laser, the same alkali-free glass substrate as in Example 1 was irradiated with laser light under the following conditions to divide the substrate into 12 small substrates of 35 mm length × 50 mm width.
A CO ₂ gas laser having a wavelength of 1060 nm (10.6 μm) was used as the laser light source. This laser light source has a laser output of 120 W and a drive frequency of 10 KHz.
The substrate was irradiated with a laser beam at a speed of 50 mm / sec (mm / sec) and a laser spot diameter of 2 to 3 mm along a planned processing line (cutting pitch width 50 μm). Divided into small substrates.
FIG. 11 shows an optical microscope photograph (plan view) of a laser irradiation site (processed site) of a divided small substrate.
Further, for each of the 12 divided small substrates, the breaking stress was measured by the 4-point bending strength evaluation method shown in FIG. The results are shown in FIG.

As shown in FIG. 7 (a: plan view, surface observation image), the small substrate (laser processed product) of Example 1 was processed in a straight line with high accuracy without causing chipping or the like at the processing site. Further, as shown in FIGS. 7A and 7B, in the small substrate (laser processed product) of Example 1, a portion having a clearly different interference color is observed in the irradiated portion (processed portion) of the laser beam. It was confirmed that a thermally altered layer in which compressive stress was generated was formed.
Further, from FIGS. 7A and 7B, it was confirmed that the depth of the scribe formed on the small substrate and the thickness of the thermally deteriorated layer almost coincided with each other.
In addition, as shown in FIG. 8, among the 12 processed small substrates, the breaking stress of 5 or more substrates is 250 MPa or more, and the strength of the small substrate (laser processed product) is improved. It could be confirmed.

On the other hand, as shown in FIG. 9, the small substrate of Comparative Example 1 that was divided using a mechanical blade had chipping at the processing site. Moreover, as shown in FIG. 10, all the 12 processed small substrates had a small fracture stress of 50 MPa.
Further, as shown in FIG. 11, the small substrate of Comparative Example 2 divided by the CO ₂ gas laser had a slight chipping at the processing site. Moreover, as shown in FIG. 12, all the 12 processed small substrates had a small fracture stress of 150 MPa or less. The laser spot portion of the CO ₂ gas laser can only be heated to a temperature below the softening point of glass (about 700 to 800 ° C.) (about 500 ° C.), and the fracture stress of the processed small substrate is as low as 150 MPa or less. From the results, it was estimated that the workpiece of Comparative Example 2 generated almost no compressive stress and did not have a heat-affected layer in which compressive stress was generated.

(Examples 2 to 5)
(A) About 55 μm (Example 2), (B) About 65 μm (Example 3), (C) About 70 μm (Example 4), (D) About 75 μm (D) The four positions in Example 5) are set to 12 small substrates in the same manner as Example 1 from one alkali-free glass substrate similar to Example 1 for each focal point (A to D). It was divided.
The focal point of each laser beam is (A) about 28%, (B) about 33%, (C) about 35%, (D) from the substrate surface to the inside of the substrate with respect to the substrate thickness of 100% (200 μm). The position is about 38%.
The depth of focus of each laser beam is (A) about 23 to 33%, (B) 28 to 38%, (C) 32 to 38%, and (D) 35 to 41% with respect to the substrate thickness of 100%. It is a position included in the range.
Twelve small substrates (48 in total) separated by the laser light set at each focal point (A to D) are the distance between the focal point inside the substrate from the substrate surface and the scribe depth formed on the substrate. And the thickness of the heat-affected layer almost coincided.
The 12 small substrates divided at each focal point (A to D) were measured for bending strength by the four-point bending strength evaluation method shown in FIG. 13, and 12 small substrates for each scribe depth (Depth Profile). The average value of the substrate was calculated. The results are shown in FIG.

As shown in FIG. 14, the laser processed product is set at a position of 35% or more when the scribe depth, that is, the focal point is set at a position near 30% from the substrate surface to the inside of the substrate (A, B). In the case of (C, D), the average value of the bending strength is different. When the scribe depth, that is, the focal point was set at a position of 35% or more from the substrate surface to the inside of the substrate (C, D), the bending strength of the laser processed product (substrate) suddenly increased.
When the focal point is set at a position of 35% or more inside the substrate, the thermally deteriorated layer becomes thick and the bending strength increases accordingly. Therefore, the presence of the thermally affected layer clearly contributes to the improvement of the bending strength of the glass substrate. I found out.

(Example 6)
The internal stress of the thermally altered layer formed on the laser processed product (glass substrate) was simulated by the finite element method under the following conditions in consideration of the effects of temperature rising, melting, sublimation, cooling, and creep.
A non-alkali glass substrate having a length of 300 mm × width of 350 mm and a thickness of 200 μm was processed under the following conditions. Glass density of glass substrate 2.51 g / cm ³ , specific heat 837 J / Kg · K, thermal conductivity 1.089 W / m · ° C., thermal expansion coefficient 3.8 × 10 ⁻⁶⁰ C ⁻¹ , thermal diffusion coefficient 1.21 × 10 ⁻⁶ m ² / s, Young's modulus 6.75 × 10 ⁴ N / mm ² , Poisson's ratio 0.22 and melting temperature 950 ° C. were set.
A UV-YAG laser having a wavelength of 355 nm was used as the laser light source. This laser light source has a laser output of 5.0 W, a drive frequency of 40 KHz, and a laser spot diameter of 2.3 μm. The aperture ratio (NA) of the objective lens 3 is 0.15.
The focal point of the laser beam was set at a position of 15% (30 μm) from the substrate surface to the inside of the substrate with respect to the substrate thickness of 100% (200 μm).

As shown in FIGS. 15 (a) and 15 (b), from the result of calculation by the finite element method, in the thermally altered layer of the laser processed product, the compressive stress in the X (horizontal) direction component and the Y (vertical) direction The component compressive stress was generated, and it was found that this compressive stress is a factor showing a large fracture stress and bending strength by the same principle as that of the tempered glass.
Regarding the calculation result of the Y (vertical) direction component of the internal stress, the outermost surface portion showed tensile stress, but this portion was 5% or less of the entire thermally deteriorated layer even when converted into a volume component.
From the above simulation results, compressive stress can be obtained by irradiating laser light in a specific wavelength region, locally raising the temperature of the laser spot to a temperature above the softening point of the workpiece or above the melting point, and cooling it. It was confirmed that a laser-processed layer in which fracture strength and / or bending strength was significantly obtained can be obtained.

(Example 7)
With the laser processing apparatus shown in FIG. 1, a non-alkali glass substrate having a length of 300 mm × width of 350 mm and 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. This laser light source 2 has a laser output of 3.0 W and a driving frequency of 40 KHz. The aperture ratio (NA) of the objective lens 3 is 0.1.
The focal point of the laser beam was set at a position of 15% (30 μm) from the substrate surface to the inside of the substrate with respect to the substrate thickness of 100% (100 μm).
Based on the measurement result of the laser displacement meter, the position of the objective lens is adjusted, and the focused laser beam is processed at a speed of 50 mm / sec (mm / sec), a laser spot diameter of 2.3 μm, and a processing line (cutting pitch). The substrate was irradiated along a width of 10 μm, and the substrate was divided into a square small substrate (laser processed product) having a length of 250 μm × 250 μm. FIG. 16 shows an optical micrograph (plan view) of a small substrate (Example 7) divided.

(Example 8)
In the same manner as in Example 7, two scribes were formed by irradiating a laser beam to a non-alkali glass substrate with an interval of 100 μ. FIG. 17 shows an optical microscope photograph (plan view) of a substrate (Example 8) on which two scribes are formed at intervals of 100 μm.

As shown in FIGS. 16 and 17, the small substrate (Example 7) or the substrate (Example 8) having the thermally altered layer in which the compressive stress is generated can be accurately obtained even in a minute part of 250 μm × 250 μm or 100 μm, And it was processed with good reproducibility.
As described above, the laser processed product having the thermally deteriorated layer in which the compressive stress is generated has higher accuracy and the strength than the processed product processed by the conventional CO ₂ gas laser having a laser beam diameter of 2 to 3 mm. It was also confirmed that

It is explanatory drawing which shows an example of a laser processing apparatus typically. It is a top view which shows a part of laser processing apparatus shown in FIG. It is (a) sectional drawing and (b) top view which show typically the laser beam product of the present invention. It is explanatory drawing which shows the other example of a laser processing apparatus typically. It is a top view which shows a part of laser processing apparatus shown in FIG. It is explanatory drawing which shows schematic structure of the objective lens and laser displacement meter of the laser processing apparatus of FIG.4 and FIG.5. It is (a) top view and (b) sectional view which show the optical microscope photograph of the laser beam product (small substrate) of the present invention. It is a graph which shows the fracture stress of the laser processed product (small board | substrate) of this invention (Example 1). It is a top view which shows the optical microscope photograph of the processed material of the comparative example 1 (mechanical blade). It is a graph which shows the fracture stress of the workpiece of the comparative example 1. Is a plan view showing an optical microscope photograph of the workpiece of Comparative Example 2 (CO ₂ gas laser). It is a graph which shows the fracture stress of the workpiece of the comparative example 2. It is explanatory drawing of a 4-point bending strength evaluation method. It is a graph which shows each focal point (AD), ie, each scribe depth (Depth Profile), and the average value of the bending strength of 12 small substrates processed by each scribe depth (Depth Profile). It is explanatory drawing which shows the state (a: X (horizontal) direction, b: Y (vertical) direction) in the thermal alteration layer of the laser processed product simulated by the finite element method. It is a top view which shows the optical microscope photograph of the laser processed product (250 micrometer x 250 micrometer small board | substrate) of this invention. It is a top view which shows the optical microscope photograph of the laser processed material of this invention (The board | substrate which formed two scribes with a space | interval of 100 micrometers).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser processed material, 1a ... Scribe, 1b ... Thermal alteration layer, 2 ... Laser light source, 3 ... Objective lens, 4 ... Large liquid crystal panel, 4a ... Upper substrate, 4b ... Lower substrate, 4c ... Spacer, 4d ... Processing scheduled line (cutting pitch), 4e ... small liquid crystal panel, 5 ... laser displacement meter, 5a ... detection position of laser displacement meter, 6 ... arm, 7 ... movable stage, 8,9 ... mirror, 10 ... laser machining device 11 ... fulcrum

Claims (7)

  A laser processed product having a thermally altered layer in which a compressive stress is generated by irradiating a focused laser beam on a processing target.   By irradiating the condensed laser light, the processing object is locally heated and cooled above the softening point or melting point of the material constituting the processing object, thereby having a thermally altered layer in which compressive stress is generated. Laser processed product characterized by that.   The heat-altered layer is formed in a range of 10% or more from a laser beam irradiation portion toward the inside of the processing object with respect to a thickness of 100% of the processing object. The laser workpiece described.   The heat-altered layer is formed in a range of 30% or more from a laser beam irradiation site toward the inside of the processing object with respect to a thickness of 100% of the processing object. The laser workpiece described.   The laser processed product according to claim 1, wherein a wavelength region of the laser beam is 200 to 2000 nm.   The laser processed product according to claim 1, wherein a wavelength region of the laser beam is 266 to 532 nm.   The laser workpiece according to claim 1, wherein the workpiece is made of a glass material.

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