KR101271292B1 - Glass plate manufacturing method - Google Patents

Abstract

The present invention is a glass plate for a display substrate, in particular a flat panel display, without generating a local raised shape on the surface of the glass plate by laser beam irradiation, or developing a local residual stress or birefringence within the glass plate. It is providing the manufacturing method of the glass plate which can manufacture the glass plate which does not exist foam which becomes a problem in use as a glass plate for board | substrates or a photomask glass plate. Absorption rate of the present invention, in the glass (or glass ribbon in the glass manufacturing process) to include a foam at a temperature that the viscosity of the glass is of 10 ⁷ to 10 ^14.5 dPa · s, and the glass sheet (or the glass ribbon) A laser beam having a wavelength of 30% or more is irradiated to bubbles in the glass plate (or glass ribbon) to reduce or eliminate the bubbles.

Description

Glass plate manufacturing method {GLASS PLATE MANUFACTURING METHOD}

The present invention relates to a method of manufacturing a glass plate. Specifically, when used as a glass plate for a display substrate, especially a glass plate for a flat panel display substrate, or a glass plate for a photomask, the use of these on the surface of the glass plate or the inside of the glass plate, preferably the surface of the glass plate and the inside of the glass plate The present invention relates to a method for producing a glass plate in which bubbles of a size in question are not present.

Currently, glass plates for display substrates, in particular, glass plates for flat panel display substrates such as liquid crystal displays, plasma displays, organic EL displays, field emission displays, glass plates used in windows of buildings such as houses, buildings, or automobiles, railways, aircrafts, In practice, glass plates are used as opening members in many fields, such as glass plates used in windows of transport engines such as ships. Such a glass plate is manufactured from molten glass using the float method, the fusion method, or the downdraw method.

Since the foam which exists in these glass plates interferes with visibility, it becomes a problem. For example, a glass plate having a thickness of 3 mm or less is used for a glass plate for a display substrate. However, if bubbles of a predetermined size or more exist in the glass plate, pinholes are generated on the screen of the display to hinder the visibility of the display. Moreover, although the glass plate of thickness 7mm or less is used as a photomask, when the bubble of a predetermined size or more exists in a glass plate, it becomes a defect of the said photomask.

When vitrifying the raw material batch in the melting process, gases such as CO ₂ , H ₂ O, O ₂ , and SO ₂ are released, and a part of the gas remains as bubbles in the molten glass. When the molten glass is shaped into a plate shape, bubbles present in the molten glass extend in the horizontal direction to become an approximately elliptic shape. The substantially elliptic bubble has a particularly large influence on the visibility of the glass plate since the maximum diameter of the bubble is larger than that of the spherical bubble before stretching.

Conventionally, in order to reduce the amount of foam existing inside the glass plate, improvement of the structure of the dissolution tank and the stirring mechanism therein, selection of the glass composition which suppresses the generation and growth of bubbles, or suppressing the generation and growth of bubbles Methods such as addition of trace additives have been carried out. However, by these methods, even if the amount of foam existing in the inside of a glass plate can be reduced, it was difficult to make the amount of foam completely zero. Moreover, there are many examination subjects actually in improvement of an apparatus and a change of glass composition, and are reflected in the manufacturing cost of a glass plate by that much.

Patent Literature 1 discloses a method for repairing defects in glass for photomasks, wherein after removing the micro defects present in the glass for photomasks, the glass fragments and the liquid curable resin are filled at positions where the defects exist. . However, this method is cumbersome because the glass fragments and the liquid curable resin are filled at positions where the microscopic defects are scraped off by a drill or the like. For example, in order to fill the position cut out by a drill, it is necessary to prepare glass fragments of a desired size. In addition, after the glass fragment and the liquid curable resin are filled, in order to achieve a desired flatness, polishing operation of the surface of the photomask is required. These problems become especially difficult when repairing the fault which exists in the vicinity of the center of the thickness direction of a thin glass plate. Moreover, it is difficult to make the part which filled glass small piece and liquid curable resin, and the optical characteristic of another part completely match, and the part which filled glass piece and liquid curable resin may become a new defect.

MEANS TO SOLVE THE PROBLEM This invention is a method of reducing the diameter of the bubble which exists in the inside of a glass plate, in order to solve the above-mentioned problem of the prior art, and irradiates a light beam from a light source toward the bubble which exists in the inside of a glass plate, By making the temperature of glass more than the softening point of the said glass, the method of reducing the diameter of the bubble which exists in the inside of a glass plate characterized by reducing the largest diameter of the said bubble was disclosed (refer patent document 2).

According to the method of patent document 2, the diameter of the foam which exists in the inside of a glass plate, especially a glass substrate for a display, especially a glass substrate for flat panel displays, or a photomask, is to the extent that it does not interfere with the visibility of the said glass plate. Can be reduced. Thereby, the glass substrate for a display which is excellent in visibility which pinhole was reduced can be obtained, and the photomask in which the defect by the presence of a bubble was eliminated can be obtained.

According to the method of patent document 2, since the diameter of a bubble is reduced by raising the temperature of the glass near a bubble locally more than a softening point, it does not damage the shape of the glass plate itself. For this reason, the possibility that a new defect arises in the glass plate after a process is reduced.

However, since the method of patent document 2 irradiates a glass plate with a high intensity laser beam etc., the influence on the glass plate by light irradiation becomes a problem.

First, as shown in the CO ₂ laser beam, in the case of using a light beam of a wavelength region that is mostly absorbed in the glass, most of the CO ₂ laser light is absorbed near the surface of the glass plate. As a result, the temperature near the surface of the glass plate to which the laser beam was irradiated rises. The glass in the vicinity of the surface expands due to this temperature rise, and a locally raised shape may occur on the surface of the glass plate. When raised form arises on the surface of a glass plate, there exists a possibility that it may adversely affect the external appearance and optical characteristic of a glass plate.

Second, in the site | part which collected the laser beam of the glass plate, the density change of a glass and the change of a mesh structure are caused. By this change, there exists a possibility that residual stress and birefringence may express locally in a 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 implementing the method of patent document 2, so that problems, such as a raised shape of the surface of the said glass plate, or local residual stress or birefringence in the inside of a glass plate, may not arise or become as light as possible, It is necessary to select the irradiation conditions (light intensity, wavelength, irradiation time, irradiation site, etc.) of the light beam.

Moreover, also about the raised shape of the surface of a glass plate, it is necessary to select the position which irradiates a light beam so that the position which a raised shape generate | occur | produces may become a position which does not have a problem in use of a glass plate.

In addition, it is necessary to remove the ridge shape which generate | occur | produced on the surface of a glass plate by grinding the surface of a glass plate. On the other hand, the density change of the glass in the site | part which light-condensed light, and the change of a mesh structure need to be eliminated by heating a glass plate after light irradiation gradually in an electric furnace etc., and slow cooling after that.

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

SUMMARY OF THE INVENTION In order to solve the problems of the prior art described above, the present invention relates to a problem caused by laser beam irradiation, specifically, the occurrence of local ridge shapes on the surface of the glass plate, local residual stress and birefringence in the interior of the glass plate. It is an object of the present invention to provide a method for producing a glass plate free of foam, which is a problem in use as a glass plate for a display substrate, in particular, a glass plate for a flat panel display substrate, or a glass plate for a photomask, without generating expression.

This invention relates to the manufacturing method of the glass plate characterized by heating the glass plate containing foam to specific temperature, and irradiating a laser beam to the said bubble in a glass plate, and shrink | condensing or disappearing the said foam.

That is, the wavelength of the present invention, in a glass sheet comprising a foam under the viscosity of the glass is heated to a temperature that is 10 ⁷ to 10 ^14.5 dPa · s, and the heating temperature, which is the absorption rate for the glass sheet to at least 30% The laser beam is irradiated to the bubbles in the glass plate to provide a method for producing a glass plate, characterized in that the bubble is reduced or lost.

In the above invention, the temperature, the viscosity of the glass is 10 ⁷ to 10 ^14.5 dPa · s is preferably at least while the distortion point of the glass at a temperature below the softening point. Moreover, it is preferable that the largest diameter D of the said laser beam in the surface of the said glass plate satisfy | fills following formula.

Wherein, d ₁ and d ₂ represents the maximum diameter and the minimum diameter in the shape respectively projected onto the foam in the normal direction of the glass plate surface.

Moreover, in the said invention, after irradiation of the said laser beam, it is preferable that the largest diameter of the bubble which exists in the said glass plate is less than 350 micrometers.

The present invention further provides a method for producing a glass plate, characterized in that the bubble in the glass ribbon is irradiated with a laser beam in a state where the glass ribbon in the glass plate manufacturing process is in a specific temperature region to reduce or eliminate the bubble. It is about.

That is, this invention is a manufacturing method of the glass plate containing the shaping | molding process which shape | molds a molten glass with a glass ribbon, the cooling process which cools a glass ribbon, and the cutting process which cuts the cooled glass ribbon and makes it into a glass plate, and glass of a glass ribbon In a temperature range of 10 ⁷ to 10 ^14.5 dPa · s, a step of irradiating a bubble in the glass ribbon with a laser beam in a wavelength range where the absorption rate with respect to the glass ribbon becomes 30% or more is reduced or eliminated. It also provides a manufacturing method of the provided glass plate.

Moreover, in the said invention which irradiates a laser beam to a glass ribbon, employment of the following forms is preferable.

It is the viscosity of the glass 10 ⁷ to 10 ^14.5 dPa · s or higher temperature region, yet the distortion of the glass of the glass ribbon preferably has a temperature range of less than the softening point. Moreover, it is preferable that the largest diameter D of the said laser beam in the surface of the said glass ribbon satisfy | fills following formula.

Wherein, d ₁ and d ₂ represents the maximum diameter and the minimum diameter in the respective shape of the foam projected in the normal direction of the glass ribbon surface.

More preferably, D satisfies the following equation.

Wherein, d ₁ is the maximum diameter in a projection shape the bubble in the normal direction of the glass ribbon surface.

Moreover, it is preferable that the distance E between the central axis of the said laser beam in the said glass ribbon surface, and the central axis of the shape which projected the said bubble in the normal direction of the glass ribbon surface satisfy | fills the following formula.

In the formula, d ₂ represents the smallest diameter of the projection in the shape of the bubble in the normal direction of the glass ribbon surface. Further, the central axis of the shape refers to the axis where the cross-sectional secondary moments become zero with respect to any orthogonal axis through any point in the shape.

It is preferable that the wavelength of the said laser beam is 10-360 nm or 2700-10600 nm, and it is preferable that the thickness of the glass ribbon of the said laser beam irradiation position is 0.05-25 mm.

Moreover, in the said manufacturing method, it is preferable to have a procedure which detects the bubble in a glass ribbon, and to irradiate a laser beam to the bubble detected by the said order.

Moreover, after irradiation of the said laser beam, it is preferable that the largest diameter of the bubble in the said glass ribbon is less than 350 micrometers, and the bubble which has a maximum diameter of 80 micrometers or more substantially in the range of 10 micrometers depth from the surface of a glass ribbon does not exist substantially. It is preferable.

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 manufacturing method of the glass plate of this invention, the glass plate which does not exist the bubble which becomes a problem in use as a glass plate for display substrates, especially the glass plate for flat panel display substrates, or the glass plate for photomasks can be manufactured.

Moreover, according to the method of this invention, the glass plate for display substrates excellent in visibility which pinhole was reduced can be obtained.

Further, according to the method of the present invention, it is possible to obtain a photomask in which defects due to the presence of bubbles are eliminated.

In the method of the present invention, for a glass sheet or the glass ribbon, and therefore the viscosity of the glass irradiated with the laser beam under the 10 ⁷ to 10 ^14.5 dPa · s temperature, localized on the surface of the glass sheet or glass ribbon by the irradiation of the laser beam There is no fear that raised shapes or local residual stress or birefringence are expressed in the glass.

When the laser beam is irradiated to the molten glass with flowability, the position of the bubble in the molten glass may change. For this reason, it is necessary to irradiate a laser beam in consideration of the change of the position of the bubble in a molten glass, and the operation which irradiates a laser beam toward a bubble becomes complicated. However, in the method of the present invention, since the laser beam is irradiated to the bubbles present in the glass in a substantially non-flowable state, it is not necessary to consider the change in the position of the bubbles in the glass plate or the glass ribbon, and the laser beam is directed toward the bubbles. The operation to irradiate is relatively easy.

Moreover, in the manufacturing method of the glass plate of this invention, compared with the case of irradiating a laser beam with respect to a molten glass, the operation which condenses a laser beam into a bubble in consideration of the position of a bubble in the thickness direction is easy.

Moreover, in the method of manufacturing a glass plate by irradiating a laser beam with respect to the glass ribbon of this invention, the bubble reduction effect | action by laser beam irradiation only by irradiating a laser beam of 30% or more of absorption rate with respect to a glass ribbon toward a bubble, Or the bubble which becomes a problem in use as a glass plate for display substrates, especially a glass plate for flat panel display substrates, or a glass plate for photomasks by a bubble floating action by laser beam irradiation can be made into the state which does not exist. For this reason, compared with the conventional method mentioned above as a background art, process number becomes small and operation is easy.

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

1: is a top view which shows typically the foam which exists in the inside of a glass plate (glass ribbon).

In the present invention, the term "reducing foam" means reducing the maximum diameter of the foam. As described above, most of the bubbles in the glass plate or the glass ribbon have a substantially elliptical shape extending in the horizontal direction. Since the substantially elliptic bubble has a larger maximum diameter compared to the spherical bubble having the same volume, the bubbles have a particularly bad effect on the visibility of the glass plate. Therefore, this adverse effect can be reduced by reducing the maximum diameter of foam. Therefore, in this invention, even if the volume of a bubble does not change, it shall correspond to "reducing a bubble" when the maximum diameter of a bubble is reduced. Of course, the case where the volume of the foam is reduced and the maximum diameter is smaller also corresponds to "reducing the foam".

In the present invention, the bubbles can be reduced and the bubbles can be moved inside the glass. By dissolving the glass around the bubble to make it flowable, the bubble can be moved upwards (upward in the vertical direction) in the glass by buoyancy of the bubble. When bubbles exist near the upper surface of the glass plate or the glass ribbon, the buoyancy forces the bubbles to move to the upper surface, and the bubbles can be destroyed at the upper surface to dissipate the bubbles. When foam exists in the vicinity of the lower surface of a glass plate or a glass ribbon, a bubble can be made to move away from a lower surface by buoyancy. In the case of a glass ribbon, it is difficult, but in the case of a glass plate, even if a bubble exists in the vicinity of the other surface, by inverting a glass plate and irradiating a laser beam, the said bubble may be lost or it may be far from the surface. .

FIG. 1 is a plan view schematically showing bubbles existing inside a glass plate or a glass ribbon, and the bubbles are shown in a shape projected in the normal direction of the glass plate surface or the glass ribbon surface. The foam 1 existing inside the glass plate (glass ribbon) 10 extends in the horizontal direction at the time of glass shaping, and forms an substantially elliptical shape. In the following description, as shown in the figure, in a shape in which the foam is projected in the normal direction of the glass plate surface, the maximum diameter of the foam is denoted by d ₁ , and the minimum diameter of the foam is denoted by d ₂ . Since the substantially elliptic bubble is thought to be formed by extending the spherical bubble in one direction, the thickness of the bubble (size perpendicular to the surface of Fig. 1) shown in the drawing is approximately equal to the minimum diameter d ₂ of the bubble. I think. That is, the bubble 1 is considered to have a substantially identical shape with a rotating ellipse.

In the production method of the glass plate of the present invention, in the viscosity of the glass under the 10 ⁷ to 10 ^14.5 dPa · s at a temperature and applying a laser beam to the foam. The temperature at which the glass has a viscosity of 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 laser beam is irradiated to a glass plate or a glass ribbon on the conditions that a glass plate and a glass ribbon are at the temperature more than the distortion point of the glass, it is from the high intensity light source like the method of patent document 1 The problem which arises by irradiating a glass plate with a light ray, ie, generation | occurrence | production of the raised shape in the surface of a glass plate, a problem, such as local residual stress or birefringence generation in the inside of a glass plate, is alleviated.

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

In addition, the temperature of the glass corresponding to the said viscosity is what was measured based on the method of JIS R3103-1: 2001 by the method of JIS R3103-1: 2001 near the lower limit of a viscosity, and the vicinity of the upper limit of viscosity.

A laser beam having a wavelength of 30% or more with respect to the glass plate or the glass ribbon is used for efficiently heating and melting the glass near the bubble. When the absorptivity is too low, the ratio of light rays passing through the glass becomes high and the glass around the bubble cannot be efficiently heated. In addition, the laser beam needs to have sufficient intensity to heat and melt the glass near the bubbles. It is thought that the intensity of the laser beam required to melt the glass near the bubble depends not only on the absorption rate but also on the position of the bubble (distance from the irradiated surface), the size of the bubble, the size of the cross-sectional area of the laser beam, the irradiation time, and the like. In consideration of these, the laser beam intensity of the light source is determined. In this invention, since the temperature of a glass plate or a glass ribbon is more than a distortion point at the time of irradiation of a laser beam, compared with the invention of the said patent document 2, the amount of energy given by a laser beam becomes small, and it is small in intensity It is possible to melt the glass near the bubbles in a short time.

It is preferable to irradiate a laser beam from the upper side of a glass plate or a glass ribbon. When the laser beam is irradiated to the bubble, the glass of the portion to which the laser beam is irradiated is heated, so that the glass of the portion where the entry of the laser beam is prevented by the bubble (part of the shadow of the bubble) is difficult to be sufficiently heated. In order to move a bubble by buoyancy in the molten glass, the glass above the bubble needs to be a sufficiently low viscosity molten glass. When a laser beam is irradiated from below a glass plate or a glass ribbon, the upper direction of a bubble will become the shadow of a laser beam easily. In the case where the movement of the bubbles is not the main purpose or when the glass around the bubbles can be sufficiently heated by a high-intensity laser beam, the laser beam may be irradiated from below the glass plate or the glass ribbon.

When irradiating a bubble with a laser beam, it is preferable to adjust the size or shape of an irradiation surface according to the size and shape of a bubble. Since the bubbles are inside the glass plate or the glass ribbon, it is preferable to adjust the size and shape of the irradiation surface of the laser beam according to the size or shape of the projection of the bubble onto the surface of the glass plate or the glass ribbon (surface of the laser beam entry side). . It is preferable that the largest diameter D of the laser beam in a glass plate surface or a glass ribbon surface satisfy | fills following formula.

More preferably, d ₂ ≤ D ≤ 2d ₁

According to the manufacturing method of this invention, the largest diameter of the bubble which exists in the glass plate obtained by this invention (it also means the glass plate cut out from the glass ribbon after irradiation of the laser beam) can be reduced to below a desired size. In the case of a glass plate used as a display substrate, the maximum diameter of the bubbles after laser beam irradiation is preferably reduced to less than 350 µm, more preferably less than 200 µm, and even more preferably less than 100 µm. In the case of a more precise display apparatus and the glass plate for monitors for personal computers, it is preferable that an allowable foam becomes the said more preferable range. In the case of the glass plate used as a photomask, it is preferable that the largest diameter of the bubble existing inside is reduced to 50 micrometers or less, and more preferably to 20 micrometers or less.

Although the maximum diameter of the bubble in glass before irradiation of a laser beam differs according to a manufacturing method and manufacturing conditions, it is about 150-1000 micrometers in the case of the glass substrate for liquid crystal displays, and about 200-1000 micrometers in the case of the glass substrate for plasma displays. . Therefore, in the display substrate, it is preferable that the maximum diameter of the said bubble after irradiation of the laser beam with respect to the maximum diameter of the bubble before irradiation of a laser beam is 60% or less, and it is more preferable that it is 30% or less. In particular, it is preferable that it is 10% or less. As mentioned above, the quality (size and number of bubbles) required may differ according to the use of a glass plate. In the present invention, the maximum diameter of the foam can be reduced from the maximum diameter of the foam which does not satisfy the quality requirement before the irradiation of the laser beam to the maximum diameter that satisfies the quality requirement, and also the foam disappears according to the required quality. You can. Therefore, the reduction ratio of the maximum value of the foam is not limited to the reduction ratio as long as the maximum diameter after the reduction is such that the maximum diameter satisfies the quality requirements.

In addition, although the above description demonstrated this invention focusing on one bubble, this invention is that all the bubbles in a glass plate (it also means the glass plate cut out from the glass ribbon after irradiation of the laser beam) are the foam of the said description. It is not limited. For example, depending on the bubble in the glass plate, there may be a thing which is not the object of laser beam irradiation. In a glass plate, when there exists a bubble of the magnitude | size which satisfy | fills a certain criterion (the said quality requirements etc.), it is not necessary to make it the object of laser beam irradiation in this 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 criterion (such as the required quality or the like) as a whole of the glass plate.

It is preferable that this invention is a manufacturing method of the plate glass which irradiates a laser beam to the glass ribbon in a glass plate manufacturing process, and shrinks or loses the bubble in a glass ribbon. The manufacturing method of irradiating a laser beam to the glass ribbon at the said temperature is compared with the manufacturing method of irradiating a laser beam by heating to the said temperature the glass plate obtained by cooling and cutting a glass ribbon after that, and the aspect of utilization efficiency of thermal energy. Is advantageous in In addition, detecting the bubbles in the glass ribbon flowing at a constant speed and irradiating the laser beam does not require an operation such as setting the glass plate as compared to the case of detecting bubbles in each plate glass and irradiating the laser beam. As easy and efficient as possible. On the other hand, in the case of manufacture of small quantity of many kinds, it is not preferable that heating each glass plate and irradiating a laser beam is few.

Hereinafter, the manufacturing method (henceforth a glass ribbon irradiation method) of this invention which irradiates a glass ribbon with a laser beam and shrinks or loses the bubble in a glass ribbon is demonstrated in more detail. The following description is applicable also to description of the manufacturing method of this invention which heats each glass plate and irradiates a laser beam, unless it is peculiar to a glass ribbon irradiation method.

The manufacturing method of the glass plate of this invention in a glass ribbon irradiation method includes the shaping | molding process which shape | molds a molten glass into a glass ribbon, the cooling process which cools a glass ribbon, and the glass plate which cuts the cooled glass ribbon and makes it into a glass plate. in the production method of, and the bubbles in the glass ribbon in a temperature range that the viscosity of the glass of the glass ribbon 10 ⁷ to 10 ^14.5 dPa · s irradiating the laser beam, a method for manufacturing a glass plate to collapse or disappearance of the bubble . This method is not particularly different from the manufacturing method of a normal glass plate except for irradiating the said laser beam to the bubble in the glass ribbon in the said temperature range. Like the manufacturing method of a normal glass plate, before the said shaping | molding process, as a general procedure, it has a dissolution process which heat-dissolves a glass raw material to make molten glass, and a clarification process which removes the bubble in a molten glass by volatilization etc. normally.

In the said molding process, the molten glass of fluid which exists at the temperature more than a softening point is shape | molded to continuous plate shape (ribbon shape) of constant thickness, and in a cooling process, the molten glass is cooled slowly by moving the glass ribbon formed in the molding process at a constant speed. The fluidity is set to a temperature lower than the softening point or lower, and the temperature of the glass ribbon is lower than or equal to the strain point of the glass, and further cooled to a temperature close to room temperature, and cut into respective glass plates in the cutting step. In the present invention, a laser beam in a temperature range ^{of 7} to 10, a viscosity of 10 ^14.5 dPa · s of the glass of the glass ribbon in the cooling process from the molding process. The shaping | molding method of the molten glass in a shaping | molding process can use various shaping | molding methods, such as the float method, the downdraw method, and the fusion method. In these shaping | molding methods, the tensile stress of the longitudinal direction is added to the glass ribbon shape | molded, and the bubble in a glass ribbon becomes said substantially oval shape.

Although mentioned later in detail, as above-mentioned, when a laser beam is irradiated to the bubble in the glass ribbon in a predetermined | prescribed temperature range, the bubble and the glass of its vicinity will absorb and heat a laser beam. As a result, the diameter of the bubbles present in the glass ribbon is reduced or lost. Bubbles can also be floated and moved inside the glass ribbon. By these actions, it can be set as the state in which the foam which becomes a problem in use as a glass plate for display substrates, especially the glass plate for flat panel display substrates, or the glass plate for photomasks does not exist. Hereinafter, in this specification, the effect | action which reduces the diameter of the bubble which exists in a glass ribbon by irradiating a laser beam is called the "foam reduction effect by laser beam irradiation", and especially the lower part of a glass ribbon by irradiating a laser beam The action of floating the bubbles existing near the surface and moving them inside the glass ribbon is referred to as "bubble floating action by laser light irradiation".

Although the substantially elliptic shape formed by the foam shown in FIG. 1 differs depending on the molding method, for example, the glass ribbon 10 molded by the float method may be used, for example, the maximum diameter (long diameter) d ₁ and the minimum diameter of the foam 1. relationship (short diameter) d ₂ are as follows in general.

d ₁ / d ₂ = 1.5 to 10

As evident from this relationship, a problem in the diameter of the foam 1 present inside the glass ribbon 10 is that the maximum diameter of the foam 1, that is, the length of the foam 1 having an approximately elliptic shape. Diameter d ₁ . Moreover, also in the glass ribbon shape | molded by another shaping | molding method, such as a fusion method or the downdraw method, the foam which exists in the inside of a glass ribbon often extends in the longitudinal direction of a glass ribbon at the time of shaping | molding, and it becomes an almost elliptical shape in many cases.

In addition, in a molding method such as a fusion method or a downdraw method, the glass ribbon is moved in a direction other than the horizontal direction (usually a vertical direction), so that the bubble breakage caused by the above-mentioned bubbles rises or the bubble is separated from the surface. Action is not valid. However, since the long diameter of the substantially elliptic bubble in the glass ribbon formed by these molding methods exists in the substantially vertical direction, it is thought that the maximum diameter of the bubble can be reduced more effectively to the buoyancy of the bubble. In the following description, the manufacturing method of the glass plate which cools by moving a glass ribbon in a horizontal direction, such as a float method, is demonstrated.

In the method of this invention, the following three principles can be considered as a principle of the bubble shrinkage | action action by laser beam irradiation.

As a first principle, when the laser beam is irradiated toward the bubble 1 present in the glass ribbon 10, the glass near the bubble 1, more specifically, the glass near the interface with the bubble 1 is heated. As a result, the glass near the interface with the foam 1 has fluidity. At this time, the shape of the bubble 1 changes from an approximately elliptical shape to a spherical shape so that the pressure in the interface of the bubble 1 becomes uniform. As a result, since the shape of the bubble 1 changes to spherical shape, the largest diameter of the bubble 1 is reduced compared with the time of substantially ellipse shape.

As a second principle, when the bubble 1 is present near the upper surface of the glass ribbon 10 (in this case, to be irradiated with a laser beam from above the drawing), the glass ribbon 10 from the vicinity of the bubble 1 The glass of the area | region across the surface of is heated, and the glass of this area will have fluidity. As a result, the bubble 1 floats to the surface of the glass ribbon 10. The foam 1 that has reached the surface of the glass ribbon 10 is broken and lost. That is, in this principle, since the bubble 1 inside the glass ribbon 10 is substantially lost, 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 interface with the foam 1 is expanded by heating the glass near the foam 1, more specifically, in the vicinity of the interface with the foam 1. The expansion of the glass near the interface with the foam 1 causes the foam 1 to crush, resulting in a decrease in the volume of the foam 1. This reduces the maximum diameter of the foam 1. When the temperature of the glass near the bubble 1 rises, the bubble 1 also tries to expand, but the expansion force of the gas bubble 1 is much weaker than that of the glass. As a result, the volume of the foam 1 is reduced by the expansion of the nearby glass, so that the maximum diameter of the foam 1 is reduced.

In the method of the present invention, by any of the above three principles, or a combination thereof, the maximum diameter of the foam 1 present in the glass ribbon 10 can be reduced to the desired size or less. As described above, in the case of the glass ribbon 10 used as the display substrate, the maximum diameter of the bubble 1 after the laser beam irradiation is preferably reduced to less than 350 µm, more preferably less than 200 µm, More preferably, the shrinkage is less than 100 µm.

In the case of the higher-definition display device and the glass ribbon 10 for monitors for personal computers, it is preferable that an allowable foam becomes the said more preferable range. In the case of the glass ribbon 10 used as a photomask, it is preferable that the largest diameter of the bubble 1 existing inside is reduced to 50 micrometers or less, and it is more preferable to shrink to 20 micrometers or less.

On the other hand, the following principle can be considered about the bubble floating action by laser beam irradiation.

When the bubble 1 is present near the lower surface of the glass ribbon 10, by irradiating a laser beam from the upper surface side of the glass ribbon 10, it is near the bubble 1, in particular above the bubble 1. The glass is heated to make it fluid. As a result, the bubble 1 floats upward and moves to the inside of the glass ribbon 10.

In the case of a liquid crystal display board | substrate, even if it is a bubble whose maximum diameter is less than 100 micrometers, if the open bubble which has a maximum diameter of 80 micrometers or more exists in a board | substrate surface, the wiring formed in the board | substrate surface of a liquid crystal display will be disconnected.

Therefore, in the glass plate for liquid crystal display substrates, the opening bubble whose maximum diameter is 80 micrometers or more should not exist. In addition, in order to remove the defect which exists in the surface, the glass plate for liquid crystal display substrates may be etched, and even if an opening bubble does not exist in a surface at the manufacturing stage, the maximum diameter is 80 micrometers or more in the vicinity of a surface. When foam exists, opening bubble of 80 micrometers or more of maximum diameters may generate | occur | produce on the surface of a glass plate by an etching process. For this reason, in the glass plate for liquid crystal display substrates, the bubble whose maximum diameter is 80 micrometers or more should not exist in the range of 10 micrometers from the surface.

In the method of the present invention, even when a bubble having a maximum diameter of 80 µm or more exists in a range of 10 µm in depth from the rear surface of the glass ribbon, by moving the foam into the glass ribbon by a bubble floating action by laser beam irradiation, The maximum diameter of 80 micrometers or more can be made into the state which does not exist in the range of 10 micrometers in depth from the back surface of a glass ribbon. On the other hand, when a bubble having a maximum diameter of 80 μm or more exists in a range of 10 μm in depth from the surface of the glass ribbon, by bubble breaking and extinguishing the bubble by the second principle of bubble shrinkage by laser beam irradiation, It can be set as the state in which the bubble whose maximum diameter is 80 micrometers or more does not exist in the range of 10 micrometers in depth from the surface of a glass ribbon.

In the method of the present invention, the reason for using the laser beam in the wavelength region in which the absorptivity of the glass ribbon is 30% or more is that the bubble and the glass in the vicinity thereof need to absorb the laser beam and increase the temperature in a short time. Because. Since the absorption rate of a laser beam with respect to a glass ribbon changes with glass composition, thickness, and the wavelength region of a laser beam, it is necessary to suitably select the wavelength region of the laser beam to be used according to the glass composition and thickness of a glass ribbon. For example, when the soda-lime-based glass is 2 mm in thickness, the absorption of 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, when alkali-free glass and thickness are 0.7 mm, the absorption rate with respect to a laser beam will be 30% or more in two areas of wavelength 360 nm or less, Preferably it is 330 nm or less and wavelength 2700 nm or more. Moreover, when the thickness of a glass ribbon increases, the absorption rate with respect to the same wavelength increases, and the range of the wavelength by which the said absorption rate becomes 30% or more is expanded. If it is 2700 nm or more, since a soda-lime type glass and an alkali free glass can be shared, it is preferable.

In the method of the present invention, the lower limit in the lower region of the above two regions of the wavelength of the laser beam is not in the range of X-rays, preferably 10 nm or more, more preferably 100 nm or more, in consideration of handling of the laser. Preferably, 150 nm or more is more preferable.

In the method of the present invention, the upper limit in the higher region of the two regions of the wavelength of the laser beam is preferably 10600 nm, which is the wavelength of the CO ₂ laser.

In the method of this invention, in consideration of irradiating a laser beam to a moving glass ribbon, in order to raise temperature in a short time, it is preferable to use the laser beam of the wavelength range whose absorption rate with respect to a glass ribbon becomes 50% or more.

Since the strain point and the softening point of the glass to which the laser beam is irradiated vary depending on the composition of the glass, it is necessary to appropriately select a temperature region for irradiating the laser beam according to the glass composition. Specifically, in some soda-lime glass, a strain point and a softening point are 510 degreeC and 729 degreeC, respectively. In some glass for plasma display substrates, the strain point and the softening point are 570 ° C and 830 ° C, respectively. In some alkali free glass, the strain point and softening point are 670 ° C and 950 ° C, respectively. These temperatures fluctuate naturally by the difference in the glass composition of each object glass. As glass in this invention, glass with a strain point of 450-750 degreeC and a softening point of 650-1100 degreeC, and the difference of both is 150 degreeC or more is preferable. In particular, glass with a strain point of 500 to 700 ° C and a softening point of 700 to 1000 ° C and a difference between them is 200 to 350 ° C.

In the method of the present invention, since the laser beam is irradiated to the glass ribbon in a temperature range below the temperature at which the viscosity of the glass becomes 10 ⁷ dPa · s, the laser beam is directed toward the bubbles present in the glass in a substantially non-flowable state. I will investigate. This is important in performing the operation of irradiating a laser beam toward the bubbles present in the glass ribbon.

In a cooling process, the glass shape | molded by the glass ribbon is conveyed to a slow cooling kiln, and is cooled slowly, moving in the said slow cooling kiln. Therefore, in the method of this invention, when irradiating a laser beam to the bubble which exists in a glass ribbon, it lasers toward the bubble in the glass ribbon on the way to the slow cooling kiln, or toward the bubble in the glass ribbon moving in the slow cooling kiln. The beam is irradiated. That is, in order to irradiate a laser beam toward the bubble in a glass ribbon, it is necessary to scan a laser beam along the moving direction of a glass ribbon. Therefore, compared with the case where a laser beam is irradiated to the bubble in the stopped glass plate, the operation which irradiates a laser beam toward a bubble becomes complicated. However, compared with the case where the bubble in the molten glass which flows is irradiated with a laser beam, operation to irradiate a laser beam is easy. In the case of the molten glass which flows in a fixed direction from the upstream to the downstream, in addition to the flow of the molten glass, the operation of irradiating a laser beam toward the bubble becomes more complicated because the position of the bubble changes inside the molten glass.

On the other hand, in the method of the present invention, since the laser beam is irradiated in a temperature range below the temperature at which the viscosity of the glass becomes 10 ⁷ dPa · s, the laser beam is irradiated toward the bubbles in the glass ribbon in a substantially non-flowable state. In addition, although it is necessary to scan a laser beam along the moving direction of a glass ribbon, it is not necessary to consider the change of the position of the bubble in the inside of a glass ribbon, and the operation which irradiates a laser beam toward a bubble is comparatively easy.

In addition, when irradiating a laser beam to the bubble in a molten glass, even if the bubble reduction effect | action by a laser beam irradiation is exhibited, when shape | molding the molten glass with a glass ribbon, a bubble will expand in the longitudinal direction of a glass ribbon, and will be in substantially ellipse shape. There is a big concern. For this reason, there exists a possibility that the largest diameter of the bubble once contracted may expand by shaping | molding, and it may not satisfy a required quality.

In the method of this invention, since a laser beam is irradiated to the glass ribbon of the substantially non-flowable state after shape | molding a molten glass, such a concern does not arise.

Since the bubble exists inside the glass ribbon, in the method of the present invention, it is necessary to focus the laser beam on the bubble in consideration of the position of the bubble in the thickness direction of the glass ribbon. However, since the thickness of a glass ribbon has the thickness substantially the same as the thickness of the glass plate of a product, and it is comparatively thin, the operation which condenses a laser beam into a bubble in consideration of the position of a bubble in the thickness direction is easy. Although the thickness of the glass plate of an article varies with the use, it is usually 0.05-25 mm, Preferably it is 0.1-25 mm. Therefore, although the thickness of the glass ribbon in the laser beam irradiation position in the method of this invention is a little different from the thickness of the product glass plate by the temperature of the position, it is preferable that it is 0.05-25 mm, and also it is 0.1-25 mm. Do. Since the thickness of most product glass plates is 0.1-10 mm, it is more preferable that the thickness of the glass ribbon in a laser beam irradiation position is 0.1-10 mm. For example, since the thickness of the glass plate for display substrates is 0.1-6 mm normally, it is preferable that the thickness of the glass ribbon in the laser beam irradiation position at the time of manufacturing it is 0.1-6 mm.

In the method of this invention, the diameter of the laser beam irradiated toward the bubble 1 which exists in the inside of the glass ribbon 10, specifically, the maximum of the laser beam in the surface (irradiation surface) of the glass ribbon 10. It is preferable that diameter D satisfies following formula (1).

More preferably, d ₂ ≤ D ≤ 2d ₁

When the maximum diameter D of the laser beam in the surface of the glass ribbon 10 irradiates the laser beam which satisfy | fills the said Formula, the bubble 1 and the glass of its vicinity absorb a laser beam, and are irradiated by laser beam irradiation The bubble shrinking action or the bubble floating action by laser beam irradiation is preferably exhibited.

As for the largest diameter D of the laser beam in the surface of the glass ribbon 10, it is more preferable to satisfy following formula (2).

In the method of this invention, the central axis of the laser beam in the surface (irradiation surface) of the glass ribbon 10, and the central axis of the shape which projected the bubble in the normal direction of the surface (irradiation surface) of the glass ribbon 10 It is preferable that the distance E to satisfy the following expression (3).

If the laser beam and the bubble present in the glass ribbon satisfy the relationship represented by the above equation, the bubble 1 and the glass in the vicinity thereof absorb the laser beam, and the bubble shrinkage action by the laser beam irradiation or the laser The bubble floating action by light irradiation is preferably exhibited.

The laser beam used by the method of this invention is not specifically limited as long as it is a laser beam of the wavelength range in which the absorption rate with respect to a glass ribbon becomes 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 of a plurality of laser light sources. However, since it is generally used widely and a high intensity light source can be obtained, a CO ₂ laser, a YAG laser, or an excimer laser is preferable.

In CO ₂ lasers, light rays with an oscillation wavelength of 10600 nm are most common. The light ray of this wavelength range becomes 90% or more with respect to the glass ribbon of almost all glass compositions, regardless of the thickness of a glass ribbon.

In the excimer laser, light rays having oscillation wavelengths of 157, 193, 248, 308, and 351 nm are common. If it is this wavelength range, although water absorption will change according to the thickness of a glass ribbon, water absorption will be 30% or more with respect to the glass ribbon of the said thickness of almost all glass compositions.

On the other hand, in the YAG laser, 355 nm and 266 nm light which are its harmonics can be used except the 1064 nm light which is a fundamental wavelength. Similarly with respect to the YVO ₄ laser, the absorbance becomes 30% or more by using harmonic light rays.

However, depending on the relationship between the oscillation wavelength and the composition of the glass ribbon, the absorptance with respect to the glass ribbon is low and may be less than 30%. Therefore, it is necessary to select the oscillation wavelength of a laser beam suitably according to the composition of a glass ribbon so that the absorption rate with respect to a glass ribbon may be 30% or more.

The intensity of the laser light source used in the method of the present invention may be appropriately selected depending 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 form, etc.), and the like. However, in order to exert the intended effect by irradiation of a laser beam, it is preferable that the intensity of a light source is higher.

However, when an extremely high intensity light source is used, there is a fear that deterioration or evaporation of the glass may occur, a raised shape may occur on the surface of the glass ribbon, or local residual stress or birefringence may occur within the glass ribbon.

For this reason, it is preferable to use the laser light source whose average power is 0.1-100W, More preferably, it is 0.5-50W, It is further more preferable that it is 1-30W. In addition, the suitable range of the intensity | strength of a light source changes also with kinds of the laser light source to be used. For example, in the case of a CO ₂ laser, since the absorption is high for almost all glass ribbons of glass composition, it is preferable to use a laser light source having an average power of 0.1 to 50 W, more preferably 0.5 to 30 W, 1 More preferably, it is 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, the absorptivity to the glass ribbon is lowered. Therefore, it is preferable to use a laser light source having an average output of 1 to 100 W, More preferably, it is 2-50W, It is still more preferable that it is 5-30W.

The oscillation form of the laser light source is not particularly limited, either, continuous oscillation light (CW light) or pulse oscillation light may be used. In addition, when using the laser light source of continuous light, in order to prevent the temperature of the site | part which irradiated the laser beam of the glass ribbon to raise excessively, for example, after irradiating for 0.1 second, for example, laser is irradiated by stopping irradiation of 0.05 second etc. You may irradiate light rays intermittently.

Irradiation time of a laser beam can also be suitably selected according to a position with a bubble, a magnitude | size, the glass composition of a glass ribbon, etc.

Generally, although the shape of the laser beam in an irradiation site | part, for example, a glass ribbon surface (irradiation surface), is circular, you may irradiate the laser beam of the cross-sectional shape which fitted the bubble which made the substantially oval shape. For example, you may irradiate a laser beam using an elliptical lens so that the shape of the laser beam in an irradiation site | part may become an ellipse shape. In addition, you may scan a laser beam using optical systems, such as a dichroic mirror, so that the shape of the laser beam in an irradiation site may form an ellipse shape. In addition, you may irradiate a some laser beam so that the whole shape in an irradiation site may form an ellipse shape.

Also in these cases, the largest axis | shaft D of the laser beam in the surface of the glass ribbon 10, and the center axis of the shape which projected the central axis and the bubble of the laser beam in the glass ribbon surface in the normal direction of a glass ribbon surface It is preferable to irradiate a laser beam so that the distance E may satisfy the above formulas (1) to (3). Here, the maximum diameter D and the distance E of the laser beam correspond to the maximum diameter of the laser beam forming the ellipse shape, and the central axis of the laser beam forming the ellipse shape and the central axis of the shape in which the bubbles are projected in the normal direction of the glass ribbon surface. Interpret as distance

In the method of this invention, it is preferable to determine the order which detects the bubble in a glass ribbon, and to irradiate a laser beam to the bubble detected in the said order. It is preferable to detect the bubbles present in the glass ribbon in the order of detecting the bubbles, determine whether the laser beam irradiation is necessary from the size or position of the detected bubbles, and irradiate the laser beam toward the bubbles determined to be necessary. . As a method of detecting the size and position of the bubbles present in the glass ribbon, for example, a method of directly observing with a camera or a laser beam for inspection is irradiated to the glass ribbon, and scattered light from the bubbles present in the glass ribbon is transferred to the camera. The method of detection is mentioned. In addition, there is also a method of simultaneously measuring the location and velocity of the particles called the PIV method, which can be suitably used for the detection of bubbles present in the glass ribbon.

<Examples>

Hereinafter, the present invention will be further described with reference to Examples.

A glass plate having bubbles present therein was prepared. The glass plate was a glass substrate for liquid crystal displays of 3 cm x 3 cm (brand name AN100, the product made by Asahi Glass Co., Ltd., strain point 670 degreeC, softening point 950 degreeC), and thickness was 0.7 mm. The foam in this glass plate was substantially elliptical and the maximum diameter was 400 micrometers. Put a glass plate in a heating furnace, and then the temperature of the glass sheet by 800 ℃, were investigated under the following conditions from the CO ₂ laser light source toward the bubble in the glass plate.

Beam form: Continuous oscillation light (CW light)

Maximum diameter of the light beam on the glass plate surface: 1.4 mm

Average power: 5 W

Survey time: 10 seconds

The maximum diameter of the bubble after irradiation is reduced to about 200 µm from the original 400 µm. In addition, when visually confirming the vicinity and the periphery of the irradiation area on a glass plate, the change of the shape of a glass plate surface, the change of a refractive index, etc. cannot be confirmed.

Similarly, a glass of foam having a maximum diameter of 300 µm is prepared (glass same as above except for the maximum diameter of the foam), and a laser having a maximum diameter of 0.5 mm of light is irradiated (a laser irradiation condition similar to the above except for the maximum diameter of the light beam). ). The maximum diameter of the foam is reduced to about 300 to 150 µm originally. In addition, even if the vicinity and the periphery of the irradiation area on a glass plate are visually confirmed, the shape change, the refractive index change, etc. of the glass plate surface are not confirmed.

Although this invention was detailed also demonstrated with reference to the specific embodiment, it is clear for those skilled in the art that various changes and correction can be added without deviating from the mind and range of this invention.

This application is based on the JP Patent application 2007-290652 of an application on November 8, 2007, The content is taken in here as a reference.

As mentioned above, although the advantage of the case of manufacturing the glass plate for display substrates, especially the glass plate for flat panel display substrates, and the glass plate for photomasks about the method of this invention was demonstrated, the glass plate of uses other than these, for example, a house, Even when a glass plate used for a window of a building such as a building or a glass plate used for a window of a transport institution such as an automobile, a railroad, an aircraft, a ship, or the like is reduced, it is preferable to reduce the bubbles present in the glass plate because it improves visibility and appearance. Do.

1: Foam
10: glass plate (glass ribbon)

Claims (15)

The glass plate containing foam is heated to a temperature at which the glass has a viscosity of 10 ⁷ to 10 ^14.5 dPa · s, and under the heating temperature, a laser beam having a wavelength at which an absorption rate to the glass plate is 30% or more is obtained from the glass plate. A method for producing a glass plate, characterized in that the foam is reduced or disappeared by irradiation with the foam inside. The method for producing a glass plate according to claim 1, wherein the temperature at which the glass has a viscosity of 10 ⁷ to 10 ^14.5 dPa · s is higher than or equal to the strain point of the glass and lower than or equal to the softening point. The manufacturing method of the glass plate of Claim 1 or 2 in which the largest diameter D of the said laser beam in the surface of the said glass plate satisfy | fills a following formula.
d ₂ ≤D≤4d ₁
(Wherein, d ₁ and d ₂ represents a maximum diameter and a minimum diameter in the shape respectively projected onto the foam in the direction of the normal of the surface of the glass plate.) The manufacturing method of the glass plate of Claim 1 or 2 whose maximum diameter of the bubble which exists in the said glass plate after irradiation of the said laser beam is less than 350 micrometers. It is a manufacturing method of the glass plate including the shaping | molding process which shape | molds a molten glass with a glass ribbon, the cooling process which cools a glass ribbon, and the cutting process which cuts the cooled glass ribbon and makes it into a glass plate,
In a temperature range in which the glass 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 to the glass ribbon is 30% or more to reduce or reduce the bubbles. The manufacturing method of the glass plate provided with the process of disappearing. 6. The method of claim 5, wherein the production of the viscosity of the glass 10 ⁷ to 10 ^14.5 dPa · s in the temperature region of the glass plate while at least the distortion point of the glass of the glass ribbon, the temperature range of the softening point or less. The manufacturing method of the glass plate of Claim 5 or 6 in which the largest diameter D of the said laser beam in the surface of the said glass ribbon satisfy | fills the following formula.
d ₂ ≤D≤4d ₁
(Wherein d ₁ and d ₂ respectively represent the maximum and minimum diameters in the 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 in which the largest diameter D of the said laser beam in the surface of the said glass ribbon satisfy | fills the following formula.
d ₁ ≤D≤2d ₁
(Wherein, d ₁ represents the maximum diameter of the shape by projecting the bubbles in the normal direction of the glass ribbon surface.) The distance E between the central axis of the laser beam on the glass ribbon surface and the central axis of the shape in which the bubble is projected in the normal direction of the glass ribbon surface satisfies the following equation. Method for producing a glass plate.
0≤E≤d _2/2
(Wherein, d ₂ denotes the minimum diameter of the shape by projecting the bubbles in the normal direction of the glass ribbon surface. Further, the central axis of the shape in any of the orthogonal axis through any point in the shape , The axis where the cross-sectional secondary moments are all zero.) The manufacturing method of the glass plate of Claim 5 or 6 whose wavelength of the said laser beam is 10-360 nm or 2700-10600 nm. The manufacturing method of the glass plate of Claim 5 or 6 whose thickness of the glass ribbon of the said laser beam irradiation position is 0.05-25 mm. The manufacturing method of the glass plate of Claim 5 or 6 which has a procedure which detects the bubble in a glass ribbon, and irradiates a laser beam to the bubble detected by the said order. The manufacturing method of the glass plate of Claim 5 or 6 whose maximum diameter of the bubble in the said glass ribbon is less than 350 micrometers after irradiation of the said laser beam. The method for producing a glass plate according to claim 5 or 6, wherein after irradiation of the laser beam, there is substantially no foam having a maximum diameter of 80 µm or more within a range of 10 µm in depth from the surface of the glass ribbon. The method for producing a glass plate according to claim 5 or 6, 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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