JPWO2009060875A1 - Manufacturing method of glass plate - Google Patents

Abstract

The present invention provides a glass plate for a display substrate without generating a local raised shape on the surface of the glass plate by laser beam irradiation, generating a local residual stress or birefringence in the glass plate, etc. In particular, the present invention provides a method for producing a glass plate, which can produce a glass plate that is free from bubbles that are problematic in use as a glass plate for a flat panel display substrate or a glass plate for a photomask. In the present invention, the glass plate (or glass ribbon in the glass plate production process) containing bubbles has an absorptivity to the glass plate (or glass ribbon) at a temperature at which the viscosity of the glass is 10 7 to 10 14.5 dPa · s. The present invention relates to a method for producing a glass plate, wherein the bubbles in the glass plate (or glass ribbon) are irradiated with a laser beam having a wavelength of 30% or more to reduce or eliminate the bubbles.

Description

  The present invention relates to a method for producing a glass plate. Specifically, when used as a glass plate for a display substrate, particularly a glass plate for a flat panel display substrate or a glass plate for a photomask, the surface of the glass plate or the inside of the glass plate, preferably the surface of the glass plate Further, the present invention relates to a method for producing a glass plate in which bubbles having a size that causes a problem for these applications do not exist inside the glass plate.

  Currently, glass plates for display substrates, especially glass plates for flat panel display substrates such as liquid crystal displays, plasma displays, organic EL displays, field emission displays, glass plates used for windows of buildings such as houses and buildings, automobiles, railways A glass plate is used as an opening member in many fields, such as a glass plate used for a window of a transportation engine such as an aircraft or a ship. Such glass plates are manufactured from molten glass using a float process, a fusion process or a downdraw process.

  The bubbles present inside these glass plates are problematic because they hinder visibility. For example, a glass plate having a thickness of 3 mm or less is used as a glass plate for a display substrate. If bubbles of a certain size or more are present in the glass plate, white spots appear on the display screen. Occurs, hindering the visibility of the display. In addition, a glass plate having a thickness of 7 mm or less is used as a photomask. However, when bubbles of a certain size or more are present in the glass plate, the photomask becomes a defect.

When the raw material batch is vitrified in the melting process, gases such as CO ₂ , H ₂ O, O ₂ and SO ₂ are released, and a part of this gas remains as bubbles in the molten glass. When the molten glass is formed into a plate shape, the bubbles present in the molten glass are stretched in the horizontal direction and become substantially elliptical. A substantially elliptical bubble has a particularly large adverse effect on the visibility of the glass plate because the maximum diameter of the bubble is larger than the spherical bubble before being stretched.

  Conventionally, in order to reduce the amount of bubbles present inside the glass plate, the melting tank structure and the stirring mechanism inside it are improved, the selection of a glass composition that suppresses the generation and growth of bubbles, or the generation and growth of bubbles. Methods such as the addition of trace trace additives to suppress are being implemented. However, although these methods can reduce the amount of bubbles present inside the glass plate, it has been difficult to reduce the amount of bubbles to zero as much as possible. In addition, improvement of the apparatus and change of the glass composition have many problems to be studied, and this is reflected in the manufacturing cost of the glass plate.

  Patent Document 1 discloses a method for repairing defects in glass for photomasks, which comprises removing small defects present in glass for photomasks, and then filling glass fragments and liquid curable resin at positions where the defects existed. Is disclosed. However, this method is troublesome because the glass chip and the liquid curable resin are filled at the position where the minute defect is scraped off with a drill or the like. For example, it is necessary to prepare a glass piece of a desired size in order to fill a position cut by a drill. Further, after filling the glass pieces and the liquid curable resin, a polishing operation of the photomask surface is required to achieve a desired flatness. These problems are particularly difficult when repairing a defect existing near the center of the glass sheet in the thickness direction. Furthermore, it is difficult to make the optical characteristics of the glass piece and the portion filled with the liquid curable resin completely match the optical characteristics of the other portion, and the glass piece and the portion filled with the liquid curable resin may become a new defect. There is.

  In order to solve the above-described problems of the prior art, the present inventors have reduced the diameter of bubbles existing inside a glass plate, and the light beam is emitted from the light source toward the bubbles existing inside the glass plate. The diameter of the bubbles existing inside the glass plate is reduced by reducing the maximum diameter of the bubbles by setting the temperature of the glass near the bubbles to be equal to or higher than the softening point of the glass. A method has been disclosed (see Patent Document 2).

  According to the method described in Patent Document 2, the diameter of bubbles present inside a glass plate, particularly a glass substrate for a display, particularly a glass substrate for a flat panel display or a glass plate used as a photomask, is visually recognized by the glass plate. It can be reduced to the extent that it does not interfere with sex. Thereby, it is possible to obtain a glass substrate for display with reduced white spots and excellent visibility, and it is possible to obtain a photomask in which defects due to the presence of bubbles are eliminated.

According to the method described in Patent Document 2, since the diameter of the bubble is reduced by locally raising the temperature of the glass near the bubble above the softening point, the shape of the glass plate itself is not impaired. For this reason, a possibility that a new defect may arise in the glass plate after a process is reduced.
However, since the method described in Patent Document 2 irradiates a glass plate with a high-intensity laser beam or the like, the effect on the glass plate due to the light irradiation becomes a problem.

First, as in the CO ₂ laser beam, using a ray wavelength region that is mostly absorbed by the glass, most of the CO ₂ laser beam near the surface of the glass plate is absorbed. As a result, the temperature near the surface of the glass plate irradiated with the laser beam rises. The glass near the surface expands due to this temperature rise, and a local raised shape may occur on the surface of the glass plate. When a raised shape is generated on the surface of the glass plate, the appearance and optical characteristics of the glass plate may be adversely affected.

Secondly, changes in the density of the glass and changes in the network structure are induced in the portion of the glass plate where the laser beam is condensed. Due to this change, there is a possibility that residual stress or birefringence is locally developed inside the glass plate. If local residual stress or birefringence develops inside the glass plate, the optical properties of the glass plate may be adversely affected.
Therefore, when carrying out the method described in Patent Document 2, a problem such as the above-described raised shape of the surface of the glass plate or local residual stress or birefringence inside the glass plate does not occur, or It is necessary to select light irradiation conditions (light source intensity, wavelength, irradiation time, irradiation site, etc.) so as to be as light as possible.

In addition, regarding the raised shape on the surface of the glass plate, it is necessary to select a position where the light beam is irradiated so that the position where the raised shape is generated does not cause a problem in using the glass plate.
Further, the raised shape generated on the surface of the glass plate needs to be removed by polishing the surface of the glass plate. On the other hand, it is necessary to eliminate the change in the density of the glass and the change in the network structure at the portion where the light beam is condensed by gradually heating the glass plate after the light beam irradiation with an electric furnace or the like and then gradually cooling it.

Japanese Patent Laid-Open No. 10-239828 International Publication No. 2006-112415 Pamphlet

  In order to solve the above-described problems of the prior art, the present invention has a problem caused by irradiation with a laser beam, specifically, generation of a local raised shape on the surface of the glass plate, and local residual inside the glass plate. Without producing stress, birefringence, etc., a glass plate that does not have bubbles that cause problems in use as a glass plate for a display substrate, particularly as a glass plate for a flat panel display substrate or a glass plate for a photomask. The object is to provide a method of manufacturing.

The present invention relates to a method for producing a glass plate, comprising heating a glass plate containing bubbles to a specific temperature and irradiating the bubbles in the glass plate with a laser beam to reduce or eliminate the bubbles.
That is, in the present invention, a glass plate containing bubbles is heated to a temperature at which the viscosity of the glass is 10 ⁷ to 10 ^14.5 dPa · s, and the absorptivity with respect to the glass plate is 30% or more at the heating temperature. Provided is a method for producing a glass plate, wherein a bubble in the glass plate is irradiated with a laser beam having a wavelength to reduce or eliminate the bubble.

In the above invention, the temperature at which the viscosity of the glass is 10 ⁷ to 10 ^14.5 dPa · s is preferably a temperature not lower than the strain point of the glass and not higher than the softening point. Moreover, it is preferable that the maximum diameter D of the laser beam on the surface of the glass plate satisfies the following formula.
d ₂ ≦ D ≦ 4 d ₁
(In the formula, d ₁ and d ₂ represent the maximum diameter and the minimum diameter, respectively, in a shape in which the bubbles are projected in the normal direction of the glass plate surface.)
Furthermore, in the said invention, it is preferable that the largest diameter of the bubble which exists in the said glass plate after irradiation of the said laser beam is less than 350 micrometers.

The present invention also provides a glass plate characterized in that, in a state where the glass ribbon in the glass plate production process is in a specific temperature range, the bubbles in the glass ribbon are irradiated with a laser beam to reduce or eliminate the bubbles. It relates to a manufacturing method.
That is, the present invention is a method for producing a glass plate, which includes a forming step of forming molten glass into a glass ribbon, a cooling step of cooling the glass ribbon, and a cutting step of cutting the cooled glass ribbon into a glass plate. Then, in the temperature range where the glass ribbon has a glass viscosity of 10 ⁷ to 10 ^14.5 dPa · s, the bubbles in the glass ribbon are irradiated with a laser beam in a wavelength range where the absorption rate for the glass ribbon is 30% or more. Also provided is a method for producing a glass plate, comprising a step of reducing or eliminating the bubbles.

Further, in the above-described invention in which the glass ribbon is irradiated with a laser beam, the following aspect is preferably employed.
The temperature range in which the viscosity of the glass is 10 ⁷ to 10 ^14.5 dPa · s is preferably a temperature range from the strain point of the glass ribbon to the softening point. The maximum diameter D of the laser beam on the surface of the glass ribbon preferably satisfies the following formula.

d ₂ ≦ D ≦ 4 d ₁
(In the formula, d ₁ and d ₂ represent the maximum diameter and the minimum diameter, respectively, in a shape in which the bubbles are projected in the normal direction of the glass ribbon surface.)
Furthermore, it is more preferable that the above D satisfies the following formula.
d ₁ ≦ D ≦ 2d ₁
(Wherein, d ₁ represents the maximum diameter of the shape obtained by projecting the bubbles in the normal direction of the glass ribbon surface.)
Moreover, it is preferable that the distance E between the central axis of the laser beam on the glass ribbon surface and the central axis of the shape obtained by projecting the bubbles in the normal direction of the glass ribbon surface satisfies the following formula.

0 ≦ E ≦ d _2/2
(In the formula, d ₂ represents the minimum diameter in the shape in which the bubble is projected in the normal direction of the glass ribbon surface. The central axis of the shape is an arbitrary orthogonal passing through a certain point in the shape. (This represents the axis where the secondary moment of inertia is zero with respect to the axis.)
The wavelength of the laser beam is preferably 10 to 360 nm or 2700 to 10600 nm, and the thickness of the glass ribbon at the laser beam irradiation position is preferably 0.05 to 25 mm.

Furthermore, in the said manufacturing method, it has a procedure which detects the bubble in a glass ribbon, and it is preferable to irradiate a laser beam to the bubble detected by this procedure.
Further, after the laser beam irradiation, it is preferable that the maximum diameter of bubbles in the glass ribbon is less than 350 μm, and further, bubbles having a maximum diameter of 80 μm or more are substantially within a depth of 10 μm from the surface of the glass ribbon. Preferably not present.

The light source of the laser beam is preferably at least one selected from the group consisting of a CO ₂ laser, a YAG laser, an excimer laser, and a YVO ₄ laser.

According to the method for producing a glass plate of the present invention, a glass plate for a display substrate, particularly a glass plate for a flat panel display substrate, or a glass plate free from bubbles that cause a problem in use as a glass plate for a photomask is produced. can do.
Moreover, according to the method of the present invention, it is possible to obtain a glass plate for a display substrate with reduced white spots and excellent visibility.

Furthermore, according to the method of the present invention, a photomask in which defects due to the presence of bubbles are eliminated can be obtained.
In the method of the present invention, a glass plate or glass ribbon is irradiated with a laser beam at a temperature where the viscosity of the glass is 10 ⁷ to 10 ^14.5 dPa · s. There is no fear that a local raised shape is generated on the surface of the ribbon, or a local residual stress or birefringence is expressed inside the glass.

  When a molten glass with fluidity is irradiated with a laser beam, the position of bubbles in the molten glass may change. For this reason, it is necessary to irradiate the laser beam in consideration of the change in the position of the bubble in the molten glass, and the operation of irradiating the laser beam toward the bubble becomes complicated. However, in the method of the present invention, since the laser beam is irradiated to the bubbles existing in the glass having substantially no fluidity, it is necessary to consider the change in the position of the bubbles in the glass plate or the glass ribbon. However, the operation of irradiating the laser beam toward the bubbles is relatively easy.

Moreover, in the method for producing a glass plate of the present invention, the operation of condensing the laser beam on the bubble is easy in consideration of the position of the bubble in the thickness direction, compared with the case of irradiating the molten glass with the laser beam. It is.
Furthermore, in the method for producing a glass plate by irradiating the glass ribbon of the present invention with a laser beam, the laser beam irradiation is performed only by irradiating the bubble with a laser beam having an absorption rate of 30% or more with respect to the glass ribbon. Due to the bubble reduction action by the laser beam, or the bubble floating action by laser beam irradiation, there is no bubble that poses a problem in use as a glass plate for a display substrate, particularly a glass plate for a flat panel display substrate or a glass plate for a photomask. Can be in a state. For this reason, man-hours can be reduced as compared with the conventional method described above as the background art, and the operation is easy.

  Furthermore, in the manufacturing method of the glass plate of this invention, the bubble which exists in a glass plate or a glass ribbon can not only reduce to the magnitude | size which does not have a problem in quality, but can also be substantially lose | disappeared.

FIG. 1 is a plan view schematically showing bubbles present inside a glass plate (glass ribbon).

Explanation of symbols

1: Bubble 10: Glass plate (glass ribbon)

  In the present invention, “reducing bubbles” means reducing the maximum diameter of bubbles. As described above, most of the bubbles in the glass plate and the glass ribbon have a substantially elliptical shape that is stretched in the horizontal direction. A substantially elliptical bubble has a particularly large adverse effect on the visibility of the glass plate because the maximum diameter is larger than a spherical bubble of the same volume. Therefore, this adverse effect can be reduced by reducing the maximum bubble diameter. Therefore, in the present invention, even when the volume of the foam does not change, when the maximum diameter of the foam is reduced, it corresponds to “reduce the foam”. Of course, the case where the volume of the foam is reduced and the maximum diameter is reduced corresponds to “reducing the foam”.

  Furthermore, in this invention, while reducing a bubble, a bubble can also be moved inside glass. By melting the glass around the bubbles to provide fluidity, the bubbles can be moved upward (upward in the vertical direction) in the glass by the buoyancy of the bubbles. When bubbles are present in the vicinity of the upper surface of the glass plate or glass ribbon, the bubbles can be moved to the upper surface by this buoyancy and broken on the upper surface to disappear. When bubbles are present near the lower surface of the glass plate or glass ribbon, the bubbles can be kept away from the lower surface by buoyancy. In the case of a glass ribbon, it is difficult, but in the case of a glass plate, even when bubbles are present near the other surface, the bubbles can be eliminated by inverting the glass plate and irradiating a laser beam, Or it can be kept away from the surface.

FIG. 1 is a plan view schematically showing bubbles present inside a glass plate or glass ribbon, and the bubbles are shown in a shape projected in the normal direction of the glass plate surface or glass ribbon surface. The bubbles 1 existing inside the glass plate (glass ribbon) 10 are stretched in the horizontal direction at the time of glass forming and have a substantially elliptical shape. In the following description, as shown in the figure, in the shape in which bubbles are projected in the normal direction of the glass plate surface, the maximum bubble diameter is represented by d ₁ and the minimum bubble diameter is represented by d ₂ . Since it is considered that a substantially elliptical bubble is formed by stretching a spherical bubble in one direction, the thickness of the bubble shown in the figure (the size in the direction perpendicular to the paper surface of FIG. 1) is the minimum bubble diameter. It is considered to be almost equal to d _2. That is, it is considered that the bubble 1 has a shape substantially equal to a spheroid.

In the manufacturing method of the glass plate of this invention, a laser beam is irradiated to a bubble under the temperature whose viscosity of glass is 10 < ⁷ > ^-10 < ^14.5 > dPa * s. The temperature at which the viscosity of the glass is 10 ^14.5 dPa · s corresponds to the strain point of the glass. Therefore, in the manufacturing method of the glass plate of this invention, since a glass plate and a glass ribbon irradiate a laser beam to a glass plate or a glass ribbon on the conditions which are the temperature more than the strain point of the glass, it is described in patent document 1. Problems caused by irradiating the glass plate with light from a high-intensity light source, such as the generation of raised shapes on the surface of the glass plate, local residual stress or birefringence in the glass plate Problems such as occurrence are reduced.

The temperature at which the glass has a viscosity of 10 ⁷ dPa · s corresponds to a temperature at which the glass does not substantially flow. Therefore, below this temperature, the position of bubbles in the glass plate or glass ribbon does not substantially change, and it becomes easy to irradiate the bubbles with a laser beam. A more preferable upper limit of the temperature is a temperature at which the viscosity of the glass is 10 ^7.6 dPa · s, and this temperature corresponds to the softening point of the glass.

The temperature of the glass corresponding to the viscosity is a value measured according to the method of JIS R3103-1: 2001 near the lower limit of the viscosity, and based on the method of JIS R3103-2: 2001 near the upper limit of the viscosity. .
A laser beam having a wavelength at which the absorptivity with respect to the glass plate or the glass ribbon is 30% or more is used to efficiently heat and melt the glass in the vicinity of the bubbles. If the absorptivity is too low, the ratio of light rays that pass through the glass increases, and the glass around the bubbles cannot be efficiently heated. The laser beam needs to have sufficient strength to heat and melt the glass in the vicinity of the bubbles. In addition to the absorptance, the intensity of the laser beam required to melt the glass near the bubble is the bubble position (distance from the irradiated surface), the bubble size, and the cross-sectional area of the laser beam. The laser beam intensity of the light source is determined in consideration of the irradiation time. In the present invention, the amount of energy given by the laser beam can be reduced compared to the invention described in Patent Document 2, because the temperature of the glass plate or the glass ribbon is higher than the strain point at the time of laser beam irradiation, It is possible to melt the glass in the vicinity of the bubbles in a short time with a lower strength.

  The laser beam is preferably applied from above the glass plate or glass ribbon. When the laser beam is applied to the bubble, the glass of the portion irradiated with the laser beam is heated, so that the glass of the portion where the laser beam is prevented from entering by the bubble (the portion that becomes the shadow of the bubble) is not easily heated. . In order to move the bubbles in the molten glass by buoyancy, the glass above the bubbles needs to be a molten glass having a sufficiently low viscosity. When the laser beam is irradiated from below the glass plate or the glass ribbon, the upper part of the bubble tends to be a shadow of the laser beam. When the movement of bubbles is not the main purpose or when the glass around the bubbles can be sufficiently heated with a high-intensity laser beam, the laser beam may be irradiated from below the glass plate or glass ribbon.

  When irradiating a bubble with a laser beam, it is preferable to adjust the size and shape of the irradiated surface according to the size and shape of the bubble. Since the bubbles are inside the glass plate or glass ribbon, the size and shape of the laser beam irradiation surface are adjusted by the size and shape of the projection of the bubble on the surface of the glass plate or glass ribbon (laser beam entry side surface). It is preferable. The maximum diameter D of the laser beam on the glass plate surface or the glass ribbon surface preferably satisfies the following formula.

d ₂ ≦ D ≦ 4 d ₁
More preferably, d ₂ ≦ D ≦ 2d ₁
According to the production method of the present invention, the maximum diameter of bubbles present in the glass plate obtained by the present invention (which also means a glass plate cut out from a glass ribbon after laser beam irradiation) is set to a desired size or less. Can be reduced. In the case of a glass plate used as a display substrate, the maximum bubble diameter after laser beam irradiation is preferably reduced to less than 350 μm, more preferably reduced to less than 200 μm, and further preferably reduced to less than 100 μm. . In the case of a high-definition display device and a glass plate for a monitor for a personal computer, it is desirable that acceptable bubbles fall within the above-mentioned preferable range. In the case of a glass plate used as a photomask, the maximum diameter of bubbles present inside is preferably reduced to 50 μm or less, and more preferably 20 μm or less.

  The maximum diameter of bubbles in the glass before laser beam irradiation varies depending on the production method and production conditions, but is about 150 to 1000 μm in the case of a glass substrate for a liquid crystal display and about 200 to 1000 μm in the case of a glass substrate for a plasma display. is there. Therefore, in the display substrate, the maximum diameter of the bubble after irradiation with the laser beam with respect to the maximum diameter of the bubble before irradiation with the laser beam is preferably 60% or less, and more preferably 30% or less. In particular, it is preferably 10% or less. As described above, the required quality (the size and number of bubbles) may vary depending on the use of the glass plate. In the present invention, the maximum bubble diameter can be reduced according to such required quality from the maximum bubble diameter that does not satisfy the quality requirement before laser beam irradiation to the maximum diameter that satisfies the quality requirement. Can be eliminated. Therefore, the reduction ratio of the maximum value of the foam is not limited to the above reduction ratio as long as the maximum diameter after the reduction is the maximum diameter that satisfies the quality requirement.

  In addition, although the above description focused on one bubble and demonstrated this invention, this invention is in a glass plate (The glass plate cut out from the glass ribbon after irradiation of a laser beam is also meant). All the bubbles are not limited to those described above. For example, some bubbles in the glass plate may not be the target of laser beam irradiation. In the glass plate, when bubbles having a size satisfying a certain standard (the above-mentioned required quality or the like) are present, the bubbles need not be the target of laser beam irradiation in the present invention. In the present invention, reducing or eliminating bubbles means reducing or eliminating the number of bubbles having a size that does not satisfy a certain standard (such as the required quality) as the whole glass plate.

  It is preferable that this invention is a manufacturing method of plate glass which shrinks | disappears or lose | disappears the bubble in a glass ribbon by irradiating a laser beam to the glass ribbon in a glass plate manufacturing process. The manufacturing method of irradiating the glass ribbon at the temperature with the laser beam is compared with the manufacturing method in which the glass plate obtained by cooling and cutting the glass ribbon is then heated to the temperature and irradiated with the laser beam. This is advantageous in terms of energy utilization efficiency. In addition, detecting bubbles in a glass ribbon that flows at a constant speed and irradiating with a laser beam means that operations such as setting a glass plate are more difficult than detecting bubbles in individual glass plates and irradiating a laser beam. It is not necessary and is easy and efficient to operate. On the other hand, in the case of manufacturing a variety of products in small quantities, it is often preferable to heat individual glass plates and perform laser beam irradiation.

Hereinafter, the manufacturing method of the present invention (hereinafter also referred to as a glass ribbon irradiation method) in which the glass ribbon is irradiated with a laser beam to reduce or eliminate bubbles in the glass ribbon will be described in more detail. The following description can also be applied to the description of the production method of the present invention in which individual glass plates are heated and irradiated with a laser beam, unless specific to the glass ribbon irradiation method.
The manufacturing method of the glass plate of the present invention in the glass ribbon irradiation method includes a forming step of forming molten glass into a glass ribbon, a cooling step of cooling the glass ribbon, and a cutting step of cutting the cooled glass ribbon into a glass plate. In the method for producing a glass plate containing the glass ribbon, the bubble in the glass ribbon in the temperature range where the glass ribbon has a viscosity of 10 ⁷ to 10 ^14.5 dPa · s is irradiated with the laser beam to reduce or eliminate the bubble. It is a manufacturing method of a glass plate. This method is not particularly different from a normal glass plate manufacturing method except that the laser beam is irradiated on bubbles in the glass ribbon in the temperature range. Similar to the ordinary glass plate manufacturing method, before the above forming step, as a general procedure, a melting step of melting glass raw material by heating to form molten glass, and foaming in the molten glass by volatilization or the like Usually has a clarification step to remove.

In the molding process, fluid molten glass at a temperature above the softening point is molded into a continuous plate shape (ribbon shape) with a constant thickness, and in the cooling process, the glass ribbon formed in the molding process is formed at a constant speed. Gradually cool while moving to bring the molten glass to a temperature with less fluidity or lower than the softening point, further lower the temperature of the glass ribbon to less than the strain point of the glass, and further cool to a temperature close to room temperature, and then cut Cut into individual glass plates in the process. In the present invention, the laser beam is irradiated in a temperature range in which the glass ribbon has a viscosity of 10 ⁷ to 10 ^14.5 dPa · s in the cooling process from the forming process. Various molding methods, such as a float method, a down draw method, and a fusion method, can be used for the molding method of the molten glass in the molding step. In these molding methods, the tensile stress in the length direction is applied to the glass ribbon to be molded, so that the bubbles in the glass ribbon have the substantially elliptical shape described above.

  As will be described in detail later, as described above, when the bubbles in the glass ribbon in the predetermined temperature range are irradiated with the laser beam, the bubbles and the glass in the vicinity thereof absorb the laser beam and are heated. As a result, the diameter of the bubbles present in the glass ribbon is reduced or eliminated. Furthermore, the bubbles can be moved up inside the glass ribbon. By these actions, it is possible to make a bubble that causes a problem in use as a glass plate for a display substrate, particularly a glass plate for a flat panel display substrate or a glass plate for a photomask, not present. Hereinafter, in this specification, the effect of reducing the diameter of bubbles present in the glass ribbon by irradiating the laser beam is referred to as “bubble reducing effect by laser beam irradiation”, and by irradiating the laser beam, The action of causing bubbles present in the vicinity of the lower surface of the glass ribbon to float and move to the inside of the glass ribbon is referred to as “bubble lifting action by laser beam irradiation”.

Although the substantially elliptical shape formed by the bubbles shown in FIG. 1 varies depending on the molding method, the maximum diameter (major axis) d ₁ and the minimum diameter (minor axis) of the bubble 1 are taken as an example of the glass ribbon 10 molded by the float process. ) The relationship of d ₂ is generally as follows.
d ₁ / d ₂ = 1.5~10
As is clear from this relationship, the problem with the diameter of the bubble 1 existing inside the glass ribbon 10 is the maximum diameter of the bubble 1, that is, the major axis d ₁ of the bubble 1 having an approximately elliptical shape. In addition, even in a glass ribbon molded by another molding method such as the fusion method or the downdraw method, bubbles existing inside the glass ribbon are stretched in the length direction of the glass ribbon at the time of molding and become substantially elliptical. There are many.

  In addition, in the molding method such as the fusion method and the downdraw method, the glass ribbon is moved in a direction other than the horizontal direction (usually the vertical direction). Not effective. However, since the major axis of the substantially elliptical bubble in the glass ribbon formed by these molding methods exists in a substantially vertical direction, the maximum diameter of the bubble can be effectively reduced by the buoyancy of the bubble. it is conceivable that. In the following description, a method of manufacturing a glass plate that moves and cools a glass ribbon in the horizontal direction, such as a float method, will be described.

In the method of the present invention, the following three principles can be considered as the principle of the bubble reducing action by laser beam irradiation.
As a first principle, when a laser beam is irradiated toward the bubble 1 existing in the glass ribbon 10, the glass near the bubble 1, more specifically, the glass near the interface with the bubble 1 is heated. The glass near the boundary surface with the bubble 1 has fluidity. At this time, the shape of the bubble 1 changes from a substantially elliptical shape to a spherical shape so that the pressure at the interface of the bubble 1 becomes uniform. As a result, when the shape of the bubble 1 changes to a spherical shape, the maximum diameter of the bubble 1 is reduced compared to the case of a substantially elliptic shape.

  As a second principle, when the bubble 1 is present near the upper surface of the glass ribbon 10 (in this case, it is assumed that the laser beam is irradiated from the upper part of the figure), the region extending from the vicinity of the bubble 1 to the surface of the glass ribbon 10 The glass is heated and the glass in this region becomes fluid. Thereby, the bubble 1 floats to the surface of the glass ribbon 10. The bubble 1 that reaches the surface of the glass ribbon 10 is broken and disappears. That is, in this principle, the bubble 1 inside the glass ribbon 10 substantially disappears, so the maximum diameter of the bubble 1 inside the glass ribbon 10 becomes zero.

  As a third principle, the glass in the vicinity of the bubble 1, more specifically, the glass in the vicinity of the interface with the bubble 1 is heated, so that the glass in the vicinity of the interface with the bubble 1 expands. Due to the expansion of the glass near the boundary surface with the bubble 1, the bubble 1 is crushed and the volume of the bubble 1 is reduced. Thereby, the maximum diameter of the bubble 1 is reduced. When the temperature of the glass near the bubble 1 rises, the bubble 1 also tries to expand, but the expansion force of the bubble 1 which is a gas is much weaker than the expansion force of the glass. As a result, the volume of the bubble 1 decreases due to the expansion of the nearby glass, so that the maximum diameter of the bubble 1 is reduced.

In the method of the present invention, the maximum diameter of the bubbles 1 existing in the glass ribbon 10 can be reduced to a desired size or less by any one of the above three principles or a combination thereof. As described above, in the case of the glass ribbon 10 used as a display substrate, the maximum diameter of the bubble 1 after laser beam irradiation is preferably reduced to less than 350 μm, more preferably less than 200 μm, and less than 100 μm. More preferably, it is reduced.
In the case of a glass ribbon 10 for a monitor with a higher definition and a personal computer, it is desirable that acceptable bubbles fall within the above-described preferable range. In the case of the glass ribbon 10 used as a photomask, the maximum diameter of the bubbles 1 existing inside is preferably reduced to 50 μm or less, and more preferably reduced to 20 μm or less.

On the other hand, the following principle is considered about the bubble floating effect by laser beam irradiation.
When the bubble 1 exists in the vicinity of the lower surface of the glass ribbon 10, by irradiating the laser beam from the upper surface side of the glass ribbon 10, the glass in the vicinity of the bubble 1, particularly the upper glass with respect to the bubble 1, is heated. To have. Thereby, the bubble 1 floats upward and moves to the inside of the glass ribbon 10.

In the case of a liquid crystal display substrate, even if the maximum diameter is less than 100 μm, if an open bubble with a maximum diameter of 80 μm or more exists on the substrate surface, the wiring formed on the substrate surface of the liquid crystal display is disconnected.
Therefore, the glass plate for a liquid crystal display substrate should not have open bubbles having a maximum diameter of 80 μm or more on the surface. Moreover, the glass plate for the liquid crystal display substrate may be etched in order to remove the defects existing on the surface, and even if there are no open bubbles on the surface in the manufacturing stage, it is near the surface. If bubbles having a maximum diameter of 80 μm or more are present, an opening bubble having a maximum diameter of 80 μm or more may be generated on the surface of the glass plate by the etching treatment. For this reason, the glass plate for a liquid crystal display substrate should not have bubbles having a maximum diameter of 80 μm or more in the range of 10 μm depth from the surface.

  In the method of the present invention, even when bubbles having a maximum diameter of 80 μm or more exist within a depth of 10 μm from the back surface of the glass ribbon, the bubbles are moved into the glass ribbon by the bubble floating action by laser beam irradiation. By making it, it can be set as the state where the bubble whose maximum diameter is 80 micrometers or more does not exist in the range of 10 micrometers in depth from the back surface of a glass ribbon. On the other hand, in the case where bubbles with a maximum diameter of 80 μm or more exist within a depth of 10 μm from the surface of the glass ribbon, the bubbles are broken and extinguished by the second principle of the bubble reduction action by laser beam irradiation. Further, it is possible to make a state where bubbles having a maximum diameter of 80 μm or more do not exist in the range of 10 μm depth from the surface of the glass ribbon.

  In the method of the present invention, the reason for using a laser beam in a wavelength region where the absorption rate for the glass ribbon is 30% or more is that the bubbles and the glass in the vicinity thereof absorb the laser beam and need to raise the temperature in a short time. It is. The laser beam absorptance with respect to the glass ribbon varies depending on the glass composition, thickness, and wavelength range of the laser beam, so the wavelength range of the laser beam to be used is appropriately selected according to the glass composition and thickness of the glass ribbon. There is a need. For example, when the thickness is 2 mm with soda lime glass, the absorptance with respect to the laser beam is 30% or more in two regions having a wavelength of 360 nm or less, preferably 330 nm or less, and a wavelength of 2500 nm or more. For example, in the case of alkali-free glass having a thickness of 0.7 mm, the absorptance with respect to the laser beam is 30% or more in two regions having a wavelength of 360 nm or less, preferably 330 nm or less and a wavelength of 2700 nm or more. As the thickness of the glass ribbon increases, the absorptance with respect to the same wavelength increases. Therefore, the wavelength range where the above absorptance is 30% or more is expanded. It is preferable for it to be at least 2700 nm because soda-lime glass and alkali-free glass can be shared.

In the method of the present invention, the lower limit of the lower region of the two regions of the wavelength of the laser beam is preferably not less than the X-ray range but 10 nm or more, more preferably 100 nm or more in consideration of laser handling. Preferably, 150 nm or more is more preferable.
In the method of the present invention, the upper limit value in the higher region of the two regions of the laser beam wavelength is preferably 10600 nm, which is the wavelength of the CO ₂ laser.

In the method of the present invention, in consideration of irradiating a moving glass ribbon with a laser beam, in order to increase the temperature in a short time, it is possible to use a laser beam in a wavelength region in which the absorption rate for the glass ribbon is 50% or more. preferable.
Since the strain point and softening point of the glass irradiated with the laser beam vary depending on the glass composition, it is necessary to appropriately select the temperature range for irradiating the laser beam according to the glass composition. Specifically, for example, a certain soda lime glass has a strain point and a softening point of 510 ° C. and 729 ° C., respectively. A certain glass for a plasma display substrate has a strain point and a softening point of 570 ° C. and 830 ° C., respectively. Some alkali-free glass has a strain point and a softening point of 670 ° C. and 950 ° C., respectively. These temperatures naturally vary depending on the glass composition of each target glass. The glass in the present invention is preferably a glass having a strain point of 450 to 750 ° C., a softening point of 650 to 1100 ° C., and a difference between the two being 150 ° C. or more. In particular, a glass having a strain point of 500 to 700 ° C., a softening point of 700 to 1000 ° C., and a difference between the two of 200 to 350 ° C. is preferable.

In the method of the present invention, since the glass ribbon is irradiated with a laser beam in a temperature range below the temperature at which the viscosity of the glass becomes 10 ⁷ dPa · s, the bubbles present in the glass in a state having substantially no fluidity A laser beam is emitted toward the head. This is important in performing an operation of irradiating a laser beam toward bubbles present in the glass ribbon.
In the cooling step, the glass formed into the glass ribbon is conveyed to a slow cooling kiln and gradually cooled while moving in the slow cooling kiln. Therefore, in the method of the present invention, when the bubbles existing in the glass ribbon are irradiated with a laser beam, the bubbles are moved toward the bubbles in the glass ribbon on the way to the slow cooling kiln or in the slow cooling kiln. A laser beam is irradiated toward the bubbles in the glass ribbon. That is, in order to irradiate the laser beam toward the bubbles in the glass ribbon, it is necessary to scan the laser beam along the moving direction of the glass ribbon. Therefore, the operation of irradiating the laser beam toward the bubble is complicated as compared with the case of irradiating the bubble in the stationary glass plate with the laser beam. However, the operation of irradiating the laser beam is easier than the case of irradiating the bubble in the molten glass flowing with the laser beam. In the case of molten glass flowing in a certain direction from upstream to downstream, in addition to the flow of the molten glass, the operation of irradiating the laser beam toward the bubbles by changing the position of the bubbles inside the molten glass Is even more complicated.

On the other hand, in the method of the present invention, the laser beam is irradiated in a temperature range equal to or lower than the temperature at which the glass has a viscosity of 10 ⁷ dPa · s, so that it is directed toward bubbles in the glass ribbon in a substantially non-fluid state. Although it is necessary to scan the laser beam along the moving direction of the glass ribbon, it is not necessary to consider the change in the position of the bubble inside the glass ribbon, and the laser beam is directed toward the bubble. Irradiation operation is relatively easy.

Furthermore, when the bubble in the molten glass is irradiated with a laser beam, even if the bubble reducing effect by the laser beam irradiation is exerted, the bubble is formed in the length direction of the glass ribbon when the molten glass is formed into a glass ribbon. There is a high possibility that the film will be stretched to become a substantially oval shape. For this reason, there is a possibility that the maximum diameter of the foam once reduced is enlarged by molding and does not satisfy the required quality.
In the method of the present invention, such a fear does not occur by irradiating a glass ribbon having substantially no fluidity after molding molten glass with a laser beam.

  Since the bubbles are present inside the glass ribbon, in the method of the present invention, it is necessary to focus the laser beam on the bubbles in consideration of the position of the bubbles in the thickness direction of the glass ribbon. However, the thickness of the glass ribbon has a thickness approximately equal to the thickness of the glass plate of the product, and since it is relatively thin, the operation of condensing the laser beam on the bubble in consideration of the position of the bubble in the thickness direction. Is easy. The thickness of the glass plate of the product varies depending on its use, but is usually 0.05 to 25 mm, preferably 0.1 to 25 mm. Therefore, the thickness of the glass ribbon at the laser beam irradiation position in the method of the present invention is 0.05 to 25 mm, and further 0.1 to 25 mm, although it differs slightly from the thickness of the product glass plate depending on the temperature at that position. It is preferable that Since the thickness of many product glass plates is 0.1 to 10 mm, the thickness of the glass ribbon at the laser beam irradiation position is more preferably 0.1 to 10 mm. For example, since the thickness of the glass plate for a display substrate is usually 0.1 to 6 mm, the thickness of the glass ribbon at the laser beam irradiation position when producing it is preferably 0.1 to 6 mm. .

In the method of the present invention, the diameter of the laser beam irradiated toward the bubble 1 existing inside the glass ribbon 10, specifically, the maximum diameter D of the laser beam on the surface (irradiation surface) of the glass ribbon 10 is as follows. It is preferable to satisfy the formula (1).
d ₂ ≦ D ≦ 4 d ₁ (1)
More preferably, d ₂ ≦ D ≦ 2d ₁
By irradiating the laser beam with the maximum diameter D of the laser beam on the surface of the glass ribbon 10 satisfying the above formula, the bubble 1 and the glass in the vicinity thereof absorb the laser beam, and the bubble reducing action by the laser beam irradiation or laser The bubble floating effect by light irradiation is preferably exhibited.

As for the maximum diameter D of the laser beam in the surface of the glass ribbon 10, it is more preferable to satisfy | fill following formula (2).
d ₁ ≦ D ≦ 2d ₁ (2)
In the method of the present invention, the distance E between the central axis of the laser beam on the surface (irradiation surface) of the glass ribbon 10 and the central axis of the shape in which bubbles are projected in the normal direction of the surface (irradiation surface) of the glass ribbon 10. However, it is preferable to satisfy | fill following formula (3).

_{0 ≦ E ≦ d 2/2} (3)
If the laser beam and the bubble present in the glass ribbon satisfy the relationship represented by the above formula, the bubble 1 and the glass in the vicinity thereof absorb the laser beam, and the bubble reducing action by laser beam irradiation, or laser The bubble floating effect by light irradiation is preferably exhibited.
The laser beam used in the method of the present invention is not particularly limited as long as it is a laser beam in a wavelength region where the absorption rate for the glass ribbon is 30% or more. As the laser light source, a known laser light source such as a CO ₂ laser, a YAG laser, an excimer laser, and a YVO ₄ laser can be used. These laser light sources may be used alone or in combination with a plurality of laser light sources. However, a CO ₂ laser, a YAG laser, or an excimer laser is preferable because it is generally used widely and a high-intensity light source can be obtained.

In a CO ₂ laser, a light beam having an oscillation wavelength of 10600 nm is the most common. Light in this wavelength region has an absorptivity of 90% or more with respect to glass ribbons of almost all glass compositions, regardless of the thickness of the glass ribbon.
In the excimer laser, light beams having oscillation wavelengths of 157, 193, 248, 308, and 351 nm are generally used. In this wavelength region, the absorptance changes depending on the thickness of the glass ribbon, but the absorptance is 30% or more with respect to the glass ribbon having the above-described thickness of almost all glass compositions.

On the other hand, the YAG laser can use light beams of 355 nm and 266 nm, which are the harmonics, excluding light beams of 1064 nm, which is the fundamental wavelength. Similarly, the YVO ₄ laser also has an absorptance of 30% or more by using harmonic light.
However, depending on the relationship between the oscillation wavelength and the composition of the glass ribbon, the absorptivity with respect to the glass ribbon may be low and may be less than 30%. Therefore, it is necessary to appropriately select the oscillation wavelength of the laser light according to the composition of the glass ribbon so that the absorption rate for the glass ribbon is 30% or more.

The intensity of the laser light source used in the method of the present invention depends on the size of bubbles present in the glass ribbon, the thickness of the glass ribbon, the composition of the glass ribbon, the type of laser light source used (oscillation wavelength, oscillation mode, etc.), etc. Although it can select suitably according to it, in order to exhibit the effect intended by irradiation of a laser beam, the one where the intensity | strength of a light source is higher is preferable.
However, if an extremely high-intensity light source is used, there is a risk of deterioration or evaporation of the glass, a protruding shape on the surface of the glass ribbon, local residual stress or birefringence inside the glass ribbon. May occur.

For this reason, it is preferable to use a laser light source with an average output of 0.1 to 100 W, more preferably 0.5 to 50 W, and even more preferably 1 to 30 W. Note that the preferable range of the intensity of the light source varies depending on the type of laser light source used. For example, in the case of a CO ₂ laser, it is preferable to use a laser light source having an average output of 0.1 to 50 W, more preferably 0.5 to It is 30W, and it is further more preferable that it is 1-20W. On the other hand, in the case of a YAG laser or a YVO ₄ laser, depending on the relationship between the oscillation wavelength and the composition of the glass ribbon, it is preferable to use a laser light source with an average output of 1 to 100 W because the absorption rate for the glass ribbon is low. More preferably, it is 2-50W, and it is still more preferable that it is 5-30W.

  The oscillation form of the laser light source is not particularly limited, and may be continuous wave light (CW light) or pulsed light. Also, when using a continuous laser light source, for example, in order to prevent the temperature of the portion of the glass ribbon irradiated with the laser beam from excessively rising, for example, after irradiation for 0.1 second, irradiation for 0.05 second You may irradiate a laser beam intermittently by the irradiation cycle of stopping.

The irradiation time of the laser beam can also be appropriately selected according to the position and size of the bubble, the glass composition of the glass ribbon, and the like.
In general, the shape of the laser beam at the irradiation site, for example, the glass ribbon surface (irradiation surface) is circular, but a laser beam having a cross-sectional shape matched to a substantially elliptical bubble may be irradiated. For example, the laser beam may be irradiated using an elliptical lens so that the shape of the laser beam at the irradiation site becomes an elliptical shape. Further, by using an optical system such as a dichroic mirror, the laser beam may be scanned so that the shape of the laser beam at the irradiation site is elliptical. Furthermore, you may irradiate a several laser beam so that the whole shape in an irradiation site | part may make elliptical shape.

  Also in these cases, the maximum diameter D of the laser beam on the surface of the glass ribbon 10 and the distance between the central axis of the laser beam on the surface of the glass ribbon and the central axis of the shape in which bubbles are projected in the normal direction of the glass ribbon surface. It is preferable that the laser beam is irradiated so that E satisfies the above formulas (1) to (3). Here, the maximum diameter D and the distance E of the laser beam are the maximum diameter of the elliptical laser beam, and the shape in which the center axis and bubbles of the elliptical laser beam are projected in the normal direction of the glass ribbon surface. This is the distance from the central axis.

  In the method of the present invention, it is preferable to provide a procedure for detecting bubbles in the glass ribbon and irradiate the bubbles detected by the procedure with a laser beam. Detect bubbles present on the glass ribbon in the procedure for detecting bubbles, determine the necessity of laser beam irradiation based on the size and position of the detected bubbles, and irradiate the laser beam toward the determined bubble Is preferred. Examples of the method for detecting the size and position of bubbles present on the glass ribbon include a method of directly observing with a camera, or a laser beam for inspection that is irradiated onto the glass ribbon, and scattered light from bubbles present on the glass ribbon. Can be detected by a camera. There is also a method called the PIV method in which the particle location and velocity are simultaneously measured, which can be preferably used for detecting bubbles present in the glass ribbon.

The present invention will be further described below with reference to examples.
A glass plate in which bubbles were present was prepared. The glass plate was a 3 cm × 3 cm glass substrate for liquid crystal display (trade name AN100, manufactured by Asahi Glass Co., Ltd., strain point 670 ° C., softening point 950 ° C.), and thickness was 0.7 mm. The bubbles in the glass plate had a substantially elliptical shape and the maximum diameter was 400 μm. This glass plate was put into a heating furnace, the temperature of the glass plate was set to 800 ° C., and then irradiated to bubbles in the glass plate from a CO ₂ laser light source under the following conditions.
Ray form: continuous wave light (CW light)
Maximum diameter of light beam on glass plate surface: 1.4mm
Average output: 5W
Irradiation time: 10 seconds The maximum diameter of bubbles after irradiation is reduced from the initial 400 μm to about 200 μm. Further, when the vicinity of the irradiation region on the glass plate and the periphery thereof are visually confirmed, changes in the shape of the glass plate surface, changes in the refractive index, and the like cannot be confirmed.

  Similarly, prepare a foam glass with a maximum diameter of 300 μm (the same glass as above except for the maximum diameter of the foam) and irradiate a laser with a maximum diameter of 0.5 mm (other than the maximum diameter of the light is the same as above) Laser irradiation conditions). The maximum diameter of the bubbles is reduced from the initial 300 μm to about 150 μm. Further, even if the vicinity of the irradiation region on the glass plate and the vicinity thereof are visually confirmed, no change in the shape of the glass plate surface, change in the refractive index, or the like is confirmed.

Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
This application is based on Japanese Patent Application No. 2007-290652 filed on Nov. 8, 2007, the contents of which are incorporated herein by reference.

  As described above, the glass plate for display substrate, particularly the glass plate for flat panel display substrate, and the advantages in the case of producing the glass plate for photomask have been described for the method of the present invention. Even when glass plates used for windows of buildings such as houses, buildings, etc. or glass plates used for windows of automobiles, railways, aircraft, ships, etc. are manufactured in glass plates It is preferable to reduce the existing bubbles because visibility and appearance are improved.

Claims (15)

The glass plate containing bubbles is heated to a temperature at which the glass has a viscosity of 10 ⁷ to 10 ^14.5 dPa · s. Under the heating temperature, a laser beam having a wavelength at which the absorptivity with respect to the glass plate is 30% or more is used. A method for producing a glass plate, comprising: irradiating bubbles in the glass plate to reduce or eliminate the bubbles. The temperature at which the viscosity of the glass becomes 10 ⁷ ~10 ^14.5 dPa · s is a temperature below the strain point not more than the softening point of the glass, a manufacturing method of a glass plate according to claim 1. The manufacturing method of the glass plate of Claim 1 or 2 with which the maximum diameter D of the said laser beam in the surface of the said glass plate satisfy | fills a following formula.
d ₂ ≦ D ≦ 4 d ₁
(In the formula, d ₁ and d ₂ represent the maximum diameter and the minimum diameter, respectively, in a shape in which the bubbles are projected in the normal direction of the glass plate surface.)   The method for producing a glass plate according to any one of claims 1 to 3, wherein a maximum diameter of bubbles existing in the glass plate is less than 350 µm after irradiation with the laser beam. A method for producing a glass plate comprising a forming step of forming molten glass into a glass ribbon, a cooling step for cooling the glass ribbon, and a cutting step for cutting the cooled glass ribbon into a glass plate,
In the temperature range where the glass ribbon has a viscosity of 10 ⁷ to 10 ^14.5 dPa · s, the bubbles in the glass ribbon are irradiated with a laser beam in a wavelength range where the absorption rate for the glass ribbon is 30% or more, A method for producing a glass plate, comprising a step of reducing or eliminating bubbles. Temperature range the viscosity of the glass is 10 ⁷ ~10 ^14.5 dPa · s is a temperature range below the strain point not more than the softening point of the glass of the glass ribbon, a manufacturing method of a glass plate according to claim 5. The manufacturing method of the glass plate of Claim 5 or 6 with which the maximum diameter D of the said laser beam in the surface of the said glass ribbon satisfy | fills a following formula.
d ₂ ≦ D ≦ 4 d ₁
(In the formula, d ₁ and d ₂ represent the maximum diameter and the minimum diameter, respectively, in a shape in which the bubbles are projected in the normal direction of the glass ribbon surface.) The manufacturing method of the glass plate of Claim 5 or 6 with which the maximum diameter D of the said laser beam in the surface of the said glass ribbon satisfy | fills a following formula.
d ₁ ≦ D ≦ 2d ₁
(Wherein, d ₁ represents the maximum diameter of the shape obtained by projecting the bubbles in the normal direction of the glass ribbon surface.) The distance E between the center axis of the laser beam on the glass ribbon surface and the center axis of the shape obtained by projecting the bubble in the normal direction of the glass ribbon surface satisfies the following formula. The manufacturing method of the glass plate of description.
0 ≦ E ≦ d _2/2
(In the formula, d ₂ represents the minimum diameter in the shape in which the bubble is projected in the normal direction of the glass ribbon surface. The central axis of the shape is an arbitrary orthogonal passing through a certain point in the shape. (This represents the axis where the secondary moment of inertia is zero with respect to the axis.)   The method for producing a glass plate according to any one of claims 5 to 9, wherein the wavelength of the laser beam is 10 to 360 nm or 2700 to 10600 nm.   The thickness of the glass ribbon of the said laser beam irradiation position is 0.05-25 mm, The glass plate manufacturing method in any one of Claims 5-10.   It has the procedure which detects the bubble in a glass ribbon, The glass plate manufacturing method in any one of Claims 5-11 which irradiates a laser beam to the bubble detected by this procedure.   The glass plate manufacturing method according to any one of claims 5 to 12, wherein a maximum diameter of bubbles in the glass ribbon is less than 350 µm after the laser beam irradiation.   The method for producing a glass plate according to any one of claims 5 to 13, wherein, after irradiation with the laser beam, bubbles having a maximum diameter of 80 µm or more are not substantially present within a depth of 10 µm from the surface of the glass ribbon. The glass plate manufacturing method according to claim 5, wherein the light source of the laser beam is at least one selected from the group consisting of a CO ₂ laser, a YAG laser, an excimer laser, and a YVO ₄ laser.

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