JP2009023885A - Repairing method of part of surface scar on surface of glass substrate by laser irradiation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new method of smoothing a glass substrate, which is used as a glass plate substrate for a flat display, by instantly softening only in the vicinity of the part of surface scar while decreasing residual stress. <P>SOLUTION: This smoothing method of the surface scar of a glass plate is a smoothing method by heating the part of the surface scar by irradiating both a continuous-wave laser and a pulsed oscillation laser on the part of surface scar of the glass, and first the continuous-wave laser is irradiated on a larger cross section of the surface than the part of the surface scar of the glass plate, then the pulsed oscillation laser is irradiated on the cross section smaller than the cross section where the continuous-wave laser was irradiated. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method of repairing a surface by smoothing a surface scratch on the surface of a glass plate.

  The glass plate is generally manufactured using a float method, a fusion method, a down draw method, or the like. Glass plates produced by these production methods are used for glass substrates for flat panel displays such as liquid crystal displays, plasma displays, organic EL displays, and field emission displays.

  It is known that the presence of a surface flaw on the surface of the glass plate described above deteriorates the visibility. In the case of a glass substrate for display, there is a problem that the surface flaw affects the display. In particular, it is often a problem that minute surface scratches present on the glass substrate for display cause disconnection during electrode formation. As a result, the yield of the glass plate is reduced.

  As a method for repairing a surface flaw, mechanical polishing or fire polishing of a glass substrate is generally known. However, in mechanical polishing of the glass substrate, it is necessary to hold the glass substrate and control the movement of the polishing pad with high accuracy. Moreover, the removal work of the slurry used for grinding | polishing and the glass fine particles generated by grinding | polishing is needed, and a process becomes complicated. Fire polish can melt a glass surface with a flame to obtain a smooth surface. However, it is difficult to bring a flame into contact with a minute surface scratch with high accuracy, and it is impossible to melt only the surface scratch.

Patent Document 1 discloses a method of repairing a crack on the surface of a glass plate without using mechanical polishing and increasing the strength. The above method is a method in which the entire glass is preheated in a furnace until the viscosity of the glass reaches 10 ¹⁵ poise, and the surface scratch is repaired by melting the surface scratch with the carbon dioxide laser. In the above method, since the entire glass is inserted into the furnace and heated, it takes a long time to heat the glass, and further, it is necessary to combine the glass heating furnace and the laser irradiation apparatus, so the apparatus and operation are large and complicated. It will be a thing.

  Patent Document 2 discloses a method of repairing a crack by forming a metal thin film on a crack on a display glass surface, absorbing and heating a YAG laser beam having a wavelength of 1 μm to the metal thin film, and melting the glass with the heat. Has been. However, this method uses a YAG laser having a low absorption efficiency for glass, and requires a complicated process for producing a metal thin film on the glass. For this reason, in order to use as an opening member after crack repair, a metal film removal process etc. are needed, and a process becomes complicated.

  Patent Document 3 discloses that a surface flaw is repaired by filling the surface flaw of the glass substrate with a resin and then solidifying it and polishing the surface. However, since this method uses a resin for repairing the surface scratch, there is a problem that the substrate after the repair cannot be used in a process such as a high-temperature heat treatment process or an etching process.

JP-T-57-501326 JP 2006-206372 A Japanese Patent Laid-Open No. 5-150205

  An object of the present invention is to provide a method for smoothing a surface scratch on a glass plate, particularly a glass substrate for display, for solving these problems.

The present invention is a method for heating and smoothing the surface flaws by irradiating the surface flaws of the glass plate with continuous wave laser light and pulsed laser light, and includes the following steps A to C: Provided is a method for smoothing a surface flaw of a glass plate.
Step A: A step of irradiating the surface flaw portion of the glass plate with the continuous wave laser beam and heating the surface flaw portion of the glass plate.
Step B: While irradiating the continuous wave laser light, an irradiation area of the pulsed laser light on the glass plate is less than or equal to an irradiation area of the continuous wave laser light on the glass plate, and the pulsed laser light Irradiating the surface scratch so as to be included in the irradiation surface of the continuous wave laser, and heating the surface scratch to the softening point temperature or higher.
Step C: a step of irradiating the surface scratch portion of the glass plate with the continuous wave laser light even after the irradiation with the pulsed laser light.

  The present invention also provides a method for smoothing a surface scratch on the glass plate, wherein the wavelength of the pulsed laser beam is 3 to 11 μm.

  The present invention also provides a method for smoothing a surface flaw of the glass plate, wherein the pulse width of the pulsed laser beam is 1 μsec to 500 msec.

In the glass plate according to the present invention, an average power density defined by average wattage / irradiation area is 1 to 100 W / mm ² on an irradiation surface of the pulsed laser beam on the glass plate. Provided is a method for smoothing a surface flaw.
The present invention provides a method for smoothing a surface flaw of the glass plate, wherein the wavelength of the continuous wave laser beam is 3 to 11 μm.

The present invention also provides a method for smoothing a surface scratch on a glass plate, wherein the power density defined by the wattage of the continuous wave laser beam / irradiation area is 0.05 to 5 W / mm ^2. provide.

  Further, the present invention irradiates the pulsed laser beam 1 to 100 seconds after the start of continuous wave laser beam irradiation, and stops the continuous wave laser beam irradiation 1 to 1000 seconds after the pulsed laser beam irradiation. A method for smoothing a surface scratch on the glass plate is provided.

  The present invention also provides a method for smoothing a surface scratch on the glass plate, wherein the pulse profiles of the pulsed laser beam and the continuous wave laser beam are flat-top type intensity distributions.

  According to the method of the present invention, the surface scratches are smoothed by smoothing the surface scratches present on the surface of the glass plate, in particular, the glass substrate for display, particularly the glass substrate for flat panel displays, in a state of low residual stress. Can be reduced.

  The present invention smoothes the surface scratches of a glass substrate produced during the production of a glass substrate used for flat panel displays such as liquid crystal displays, plasma displays, organic EL displays, and field emission displays, and ensures mass productivity. A method for improving the yield is provided.

  Although the size of the surface scratches on these glass plates varies depending on their origin, the surface scratches on the glass plate surface in the present invention refer to those having a width of several μm to several 100 μm and a depth of several tens of μm or less. . The length of these surface scratches ranges from several μm to several mm. For example, surface scratches produced when manufactured by the float process, or foreign matter containing tin of several μm to several tens of μm adheres to the surface of the glass substrate, and the foreign matter is YAG laser, femtosecond laser, etc. These surface scratches are also included in the removal marks after the removal with.

  The present invention heats and smoothes the surface flaws by irradiating the surface flaws of the glass plate of the surface of the glass substrate by laser irradiation with continuous wave laser light and pulsed laser light. Is the method.

  In step A of the present invention, a continuous wave laser beam is irradiated to a surface scratch on the glass plate, and the surface scratch on the glass plate is heated. This step is a step necessary to prevent cracking and breakage due to rapid heating due to irradiation with pulsed laser light by heating the surface scratches with continuous wave laser light.

In step A, it is preferable to heat the surface scratches of the glass plate to a strain point temperature or higher. When heated above the strain point temperature, the flaw expands, is restrained by the surrounding unheated glass, the heated flaw is compressed, and a continuous stress laser is generated by generating compressive stress on the surface flaw of the glass plate. This is because it can play a role of preventing damage caused by the pulsed gas laser irradiated after the light. Moreover, it has the objective of making it easy to deform | transform a flaw by the pulse laser to irradiate by heating more than strain point temperature. Here, the strain point temperature is a temperature at which the internal strain of the glass can be substantially removed in 4 hours, and the viscosity coefficient of the glass has a value of η = 10 ^14.5 . Since the structural change of the glass can be induced practically above the strain point temperature, it is necessary to heat the glass to a temperature higher than the temperature.

  Moreover, in the process A, it is preferable to heat to less than the glass transition temperature. This is because if the surface flaws of the glass plate are heated to a temperature higher than the glass transition temperature, a strong strain is generated by such heating. Here, the glass transition point temperature is a temperature measured by differential thermal analysis, and since a rapid expansion derived from the structural change of the glass is induced compared to the expansion up to that temperature, strong strain, excessive expansion This is the temperature at which breakage can be induced.

  In step A, the surface of the glass plate is irradiated with continuous-wave laser light, and the scratches and the vicinity of the scratches are preliminarily heated, whereby the scratches and the glass near the scratches easily flow. For this reason, it is possible to erase and smooth a larger flaw by using continuous oscillation carbon dioxide laser light irradiation in combination as compared with the case where irradiation with only pulse oscillation carbon dioxide laser light having the same power density is performed.

  The irradiation area of the continuous-wave laser beam in the process A irradiated on the surface flaw of the glass plate is not necessarily equal to or larger than the flaw. The reason why it is necessary to keep the temperature above the strain point temperature and below the transition point temperature on the glass plate surface by the continuous wave laser light is that the area larger than the irradiation area of the pulsed laser light applied to the scratched portion may be used. is there. However, in the process A, since it is necessary to heat a range wider than the range irradiated with the pulsed laser beam in the process B described later, when the irradiation area of the continuous wave laser beam is smaller than the wound to be smoothed Therefore, it is necessary to irradiate the entire scratched portion to be smoothed by scanning with a continuous wave laser beam. Therefore, it is preferable that the irradiation area of the continuous-wave laser beam irradiated on the surface scratch portion of the glass plate is larger than the scratch portion. This is because the above-described scanning is not necessary, and the scratches can be smoothed more easily.

In step B, while irradiating the continuous wave laser beam, an irradiation area of the pulsed laser beam on the glass plate is less than or equal to an irradiation area of the continuous wave laser beam on the glass plate, and the pulsed laser beam is The surface flaws are irradiated so as to be included in the irradiation surface of the continuous wave laser, and the surface flaws are melted and smoothed by heating to the softening point temperature or higher. Here, the softening point temperature is a temperature at which the viscosity coefficient of the glass corresponds to η = 10 ^7.6 and can substantially induce the deformation of the glass.

  As described above, heating the surface scratch on the glass plate in step A makes the surface scratch on the glass plate easy to flow and generates compressive stress on the surface scratch, followed by irradiation in step B. This is to help melt by the pulsed laser and prevent damage.

  Therefore, the irradiation area on the glass plate of the pulsed laser irradiated in the process B needs to be less than or equal to the irradiation area on the glass plate of the continuous wave laser beam. For the same reason, the pulsed laser light is applied to the surface scratches so as to be included in the irradiation surface of the continuous wave laser with respect to the area heated in advance by the continuous wave laser light irradiation in step A. Irradiation is necessary.

  When the irradiation surface on the glass plate of the pulsed laser beam is not included in the irradiation surface on the glass plate of the continuous wave laser beam, there is a possibility that the surface flaws cannot be appropriately heated. When the glass plate is partially softened and the surface scratches are smoothed by the pulsed laser light irradiation, a steep temperature distribution is formed around the optical axis of the laser light. Therefore, normally, stress derived from the temperature distribution remains during cooling after smoothing the surface scratches. If this steep temperature distribution is smoothed, the residual stress after cooling can be reduced. For this purpose, a wide range than the temperature distribution formed by the pulsed laser light irradiated to the surface scratches is heated by continuous wave laser beam irradiation to reduce the steep temperature distribution generated in the smoothed surface scratches. There is a need. In order to sufficiently reduce the steep temperature distribution generated in the smoothed surface scratches, the irradiation area on the glass plate of continuous wave laser light is larger than the irradiation area on the glass plate irradiated with pulsed laser light. Also need to be big.

  In step C, the continuous wave laser beam is irradiated on the surface scratch of the glass plate even after the pulsed laser beam is irradiated. Step C is a step necessary for causing stress relaxation by heating the surface scratches of the glass plate even after irradiation with the pulsed laser beam. In step C, it is preferable to heat the surface scratches of the glass plate to a temperature above the strain point temperature and below the glass transition temperature. As in step A, it is possible to induce relaxation of strain caused by melting of the surface flaw of the glass plate by pulsed laser irradiation by heating the surface flaw of the glass plate to a temperature above the strain point temperature. is there. In addition, it is preferable to heat the glass sheet to a temperature lower than the glass transition temperature in Step C. When the surface scratch portion of the glass plate is heated to a temperature higher than the glass transition temperature, a strong strain is generated by itself, resulting in a strong residual stress. This is because there is a risk of losing. Therefore, by heating the surface scratch portion of the glass plate to a temperature equal to or higher than the strain point temperature and lower than the glass transition temperature, stress relaxation of the scratch portion smoothed in step B can be suitably performed in step C.

  The wavelength of the continuous wave laser light to be irradiated is preferably 3 to 11 μm. If the wavelength is shorter than 3 μm, the laser beam may enter the inside of the glass plate and heat up to the inside of the glass plate. On the other hand, if it is longer than 11 μm, it is difficult to obtain a laser beam oscillator. More preferably, it is 10.6 μm which is the oscillation wavelength of the carbon dioxide laser.

  The irradiation time of the continuous oscillation laser beam for preventing cracking during the irradiation of the pulse oscillation laser beam by heating the surface scratches before the irradiation of the pulse oscillation laser beam is 1 μsec to 100 seconds. Is desirable. If the irradiation time is shorter than 1 μsec, there is a possibility that a temperature above the strain point cannot be obtained. If it is longer than 100 seconds, there is a risk of heating more than necessary, or heating beyond the glass point transfer. More preferably, it is 10 seconds or more and 60 seconds or less.

Moreover, it is preferable that the power density of the continuous wave laser beam to irradiate is 0.05-5 W / mm < ² >. If it is smaller than 0.05 W / mm ² , there is a possibility that a temperature above the strain point cannot be obtained. If it is larger than 5 W / mm ² , the range more than necessary may be heated, or the glass point may be transferred beyond the transfer. More preferably, it is 0.14-1.4 W / mm < ² >.

  The wavelength of the pulsed laser beam in the present invention is preferably 3 to 11 μm. When the wavelength is less than 3 μm, the laser light enters the inside of the glass plate and heats an unnecessary range of the glass plate, making it difficult to use in the present invention. If it exceeds 11 μm, it becomes difficult to obtain a laser. Therefore, it is particularly preferable to use a carbon dioxide laser with a wavelength of 10.6 μm.

  The pulse width of the pulsed laser beam is preferably 1 μs to 500 milliseconds. This is because it is difficult to obtain a laser device having a pulse width of less than 1 μsec, and if the pulse width exceeds 500 msec, a strong residual stress is generated. A more preferable range is 1 to 100 milliseconds from the viewpoint of suppressing residual stress and smoothing by melting.

The average power density of the pulsed laser beam is 1 to 100 W / mm ² . In this method of irradiating laser light of average power density and smoothing the surface flaws, the surface flaws and the vicinity thereof are irradiated with pulsed laser light to heat above the softening point and smooth the surface flaws. It becomes possible to make it. If the average power density is less than 1 W / mm ² , the surface flaws may not be sufficiently smoothed because they are not melted. If the average power density is more than 100 W / mm ² , the glass may be damaged by residual stress exceeding the ability of stress relaxation by a continuous wave laser described later. From the viewpoint of smoothing being induced and suppressing residual stress, the preferred range is ² to 14 W / mm ² .

  In the present invention, it is necessary for stress relaxation to continue irradiation with a continuous wave laser even after pulse laser irradiation. It is preferable that the continuous wave laser beam continuously irradiated after the pulse laser irradiation is stopped after 1 second to 1000 seconds from the end of the pulse laser irradiation. If the irradiation time is less than 1 second, a temperature higher than the strain point cannot be obtained at the surface flaw portion and the vicinity thereof, and there is a possibility that sufficient stress relaxation may not be performed. Moreover, there exists a possibility that the unnecessary range of a glass plate may be heated as it exceeds 1000 second, or it may heat to more than glass point transfer. More preferably, it is 5 to 100 seconds, More preferably, it is 10 to 60 seconds.

  More preferably, it is preferable that the pulsed laser beam and the continuous wave laser beam have a flat-top type intensity distribution because the surface scratches in a desired range can be smoothed with a minimum energy. In order to obtain a flat-top intensity distribution, a uniform intensity distribution region near the center of a laser beam having a Gaussian distribution may be cut out and used, or a diffractive optical element such as a hologram may be used. When the surface scratch is larger than the irradiation area of the pulsed laser beam, the laser pulse may be irradiated in a plurality of times while moving the irradiation site of the pulsed laser beam.

  Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows an example of a method for smoothing a surface flaw on a glass substrate surface by laser irradiation according to the present invention. A continuous wave carbon dioxide laser beam 3 is generated from a laser oscillator 4 on a surface flaw 2 existing on the surface of the glass plate 1 and is irradiated to an area larger than the surface flaw 2 by a lens 5 so as to have a glass transition point higher than the strain point temperature. Heat to a temperature below the temperature. In this example, the irradiation area of the continuous wave carbon dioxide laser beam 3 on the glass plate 1 is larger than the surface flaw 2, so that it is not necessary to scan the continuous wave carbon dioxide laser beam 3 to the size of the flaw.

  Next, the pulse oscillation carbon dioxide laser beam 6 generated from the laser oscillator 7 is applied to the surface flaw 2 heated by the continuous oscillation carbon dioxide laser beam 3 more than the irradiation area of the continuous oscillation carbon dioxide laser beam 3 on the glass plate 1. Irradiate the surface scratch so as to have a small cross-sectional area and be included in the irradiation cross section of the continuous wave laser. At this time, the pulsed carbon dioxide laser beam is condensed to a power density that can induce melting of the surface flaw 2 using the lens 8, and is melted and smoothed by heating the surface flaw 2 to a temperature equal to or higher than the softening point temperature. . The stress induced by the pulsed carbon dioxide laser light irradiation can be relieved by continuously heating the continuous wave carbon dioxide laser light 3 after the pulsed carbon dioxide laser light 6 is irradiated. The continuous carbon dioxide laser beam 3 and the pulsed carbon dioxide laser beam 6 may be irradiated coaxially using a beam combiner or the like.

  Hereinafter, the present invention will be further described by examples. Example 1 is an example and Example 2 is a comparative example.

(Example 1)
The entire surface of a glass substrate for plasma display (product name: PD200, manufactured by Asahi Glass Co., Ltd.) having a size of 5 cm × 5 cm and a thickness of 2.8 mm is rubbed in various directions with a diamond paste of 15 μm, and is linear with a width of 10 μm and a depth of 100 nm. A glass plate with a uniform scratch on the surface was prepared. The width and depth of the linear scratches were measured with a micromap (manufactured by Ryowa Systems). A continuous wave carbon dioxide laser beam (wavelength 10.6 μm) having a power density of 0.7 W / mm ² and an irradiation sectional area of 7.1 mm ² on the surface irradiated to the glass plate is applied to the scratched portion uniformly attached to the surface of the glass. Irradiated for 2 seconds. Thereafter, a single pulse of pulsed carbon dioxide laser light having a pulse width of 50 milliseconds and an irradiation cross-sectional area of 0.07 mm ² was irradiated. The irradiation cross section of the surface irradiated to the glass plate of the pulsed laser beam was included in the irradiation cross section of the surface irradiated to the glass plate of the continuous wave carbon dioxide laser beam irradiated previously.

At this time, in order to investigate the relationship between the irradiation power density and the size of the retardation and scratches removed and smoothed, the pulsed carbon dioxide laser beam with irradiation power densities of 2.8, 8.4 and 14.2 W / mm ² Was irradiated. The continuous oscillation carbon dioxide laser light was irradiated so that the irradiation cross section of the surface of the continuous oscillation carbon dioxide laser light irradiated on the glass plate included the irradiation cross section of the surface of the pulse oscillation laser light irradiated on the glass plate.

  Furthermore, irradiation of the continuous oscillation carbon dioxide laser was stopped 60 seconds after the completion of the pulse oscillation carbon dioxide laser light irradiation. The surface of the glass after irradiation was observed with an optical microscope, and the size of the scratch removed and smoothed was measured. Moreover, the retardation used as an index of the residual stress value was measured by applying a cenalmon method using a polarizing microscope.

(Example 2)
In the same manner as in Example 1, a glass plate having a similar scratch on the surface was prepared. A single pulse of pulsed carbon dioxide laser light having a pulse width of 50 milliseconds and an irradiation cross-sectional area of 0.07 mm ² was irradiated on the scratched part uniformly on the surface of the glass plate. At this time, pulses having irradiation power densities of 2.8, 8.4, 11.3, and 14.2 W / mm ² are used in order to examine the relationship between the irradiation power density and the size of the retardation and scratches removed and smoothed. Oscillation carbon dioxide laser light was irradiated. In the same manner as in Example 1 after irradiation, the size and retardation of scratches removed and smoothed were measured.

  The results of Examples 1 and 2 of the present invention are shown in FIGS. FIG. 2 shows the relationship between the irradiation power density and the size at which the scratches are erased, and FIG. 3 shows the relationship between the irradiation power density and the retardation. From FIG. 2, it can be seen that, when pulsed carbon dioxide laser light irradiation with the same power density is performed, it is possible to erase and smooth larger scratches by using continuous wave carbon dioxide laser light irradiation together. Further, FIG. 3 shows that when pulsed carbon dioxide laser light irradiation with the same power density is performed, the retardation can be reduced by using continuous wave carbon dioxide laser light irradiation together. That is, it is shown that stress can be reduced in smoothing the surface flaws of the glass plate by using the continuous oscillation carbon dioxide laser beam irradiation in combination.

  From the above results, by using the method of the present invention in combination with continuous wave carbon dioxide laser light irradiation, the surface scratched part of the glass plate can be smoothed with a wider range and with lower stress than the conventional method of irradiating only the pulsed carbon dioxide laser light. It can be seen that the surface scratches on the glass plate can be smoothed.

  The surface scratches on the glass plate substrate for display are smoothed to improve the yield.

The conceptual diagram which shows the laser irradiation method for smoothing the surface crack part of the glass plate of this invention The figure which shows the relationship between the average power density and the size where scratches are erased and smoothed Diagram showing the relationship between average power density and retardation

Explanation of symbols

1: Glass plate 2: Surface scratch 3: Continuous oscillation carbon dioxide laser beam 4: Continuous oscillation carbon dioxide laser oscillator 5: Lens 6: Pulse oscillation carbon dioxide laser beam 7: Pulse oscillation carbon dioxide laser beam oscillator 8: Lens

Claims (8)

A method for heating and smoothing a surface flaw by irradiating a surface flaw of a glass plate with a continuous wave laser beam and a pulsed laser beam, comprising the following steps A to C: A method for smoothing a surface scratch on a plate.
Step A: A step of irradiating the surface flaw portion of the glass plate with the continuous wave laser beam and heating the surface flaw portion of the glass plate.
Step B: While irradiating the continuous wave laser light, an irradiation area of the pulsed laser light on the glass plate is less than or equal to an irradiation area of the continuous wave laser light on the glass plate, and the pulsed laser light Irradiating the surface scratch so as to be included in the irradiation surface of the continuous wave laser, and heating the surface scratch to the softening point temperature or higher.
Step C: a step of irradiating the surface scratch portion of the glass plate with the continuous wave laser light even after the irradiation with the pulsed laser light.   The method for smoothing a surface scratch on a glass plate according to claim 1, wherein the pulsed laser beam has a wavelength of 3 to 11 μm.   The method for smoothing a surface flaw of a glass plate according to claim 1 or 2, wherein a pulse width of the pulsed laser beam is 1 µs to 500 milliseconds. 4. The glass plate according to claim 1, wherein an average power density defined by average wattage / irradiation area is 1 to 100 W / mm ² on an irradiation surface of the pulsed laser beam on the glass plate. Method for smoothing surface scratches on the surface.   The method for smoothing a surface scratch on a glass plate according to any one of claims 1 to 4, wherein the wavelength of the continuous wave laser beam is 3 to 11 µm. Surface flaws of the smoothing method of the glass plate according to any one of claims 1 to 5 power density is 0.05~5W / mm ² as defined in watts / irradiation area of the continuous wave laser beam.   The pulsed laser light irradiation is performed 1 to 100 seconds after the start of the continuous wave laser light irradiation, and the continuous wave laser light irradiation is stopped 1 to 1000 seconds after the pulsed laser light irradiation. The smoothing method of the surface flaw part of the glass plate in any one.   The method of smoothing a surface flaw of a glass plate according to any one of claims 1 to 7, wherein beam profiles of the pulsed laser beam and the continuous wave laser beam are flat-top type intensity distributions.

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