Laminated glass

The present invention relates to laminated glass, and particularly to laminated glass suitable for mobile phones, digital cameras, PDAs (personal digital assistants), touch panel displays, and the like.

Devices such as mobile phones, digital cameras, PDAs, and touch panel displays are becoming more and more popular.

Glass plates for these applications are required to have characteristics such as thinness, light weight, and high strength. Currently, as a glass plate for these purposes, a tempered glass plate having a compressive stress layer on its surface is used (see Patent Document 1 and Non-Patent Document 1). The tempered glass plate is attached to the liquid crystal panel mainly via the touch panel.

<p><patcit num="1"><text>Japanese Unexamined Patent Publication No. 2006-83045</text></patcit></p>

<p><nplcit num="1"><text>Tetsuro Izumitani et al., "New Glass and Its Physical Properties", First Edition, Keiei System Research Institute, Inc., August 20, 1984, p.451-498</text></nplcit></p>

<p> The larger the compressive stress value of the compressive stress layer or the thicker the compressive stress layer, the higher the mechanical strength of the tempered glass plate.</p><p> However, a tensile stress corresponding to the magnitude of the compressive stress is generated inside the tempered glass plate, and the tensile stress may damage the tempered glass plate. Such internal tensile stress increases as the compressive stress value of the compressive stress layer increases, as the thickness of the compressive stress layer increases, or as the thickness of the tempered glass plate decreases.</p><p> The internal tensile stress can be calculated by the following formula.</p><p> [Internal tensile stress] = ([Compressive stress value of compressive stress layer] x [Thickness of compressive stress layer]) / ([Plate thickness]-[Thickness of compressive stress layer] x 2) When it is difficult to measure the internal tensile stress with a surface stress meter such as laminated glass, it can be calculated using the following formula 1 and the Senarmon method by observing with a polarizing microscope from the cross-sectional direction of the tempered glass plate. it can.</p><p><maths num="1"><img file="JP2011136895A_D0001.tif" /></maths></p><p> σ: compressive stress value (MPa), λ: light source wavelength, R: optical elastic constant ((nm / cm) / (kg / cm)²)), t: Optical path length (cm, sample thickness), θ: Angle of rotation When the high-strength tempered glass plate is thinned, the tempered glass plate may self-destruct due to the internal tensile stress. If such a tempered glass plate is incorporated into a housing such as a mobile phone as a cover glass, the tempered glass plate may scatter if the tempered glass plate is self-destructed.</p><p> In order to prevent scattering due to self-destruction, a resin film is proposed on the surface of a tempered glass plate, but the resin film is easily scratched on the surface, and is particularly suitable for devices such as touch panel displays as a protective member. After a period of use, the appearance is impaired and the visibility of the display is reduced.</p><p> On the other hand, if the tempered glass plate is exposed to the outer surface side and the touch panel (or liquid crystal panel) and the tempered glass plate are laminated with a resin film, the shatterproof effect and the scratch prevention effect can be enjoyed to some extent. However, in such a configuration, a touch panel (or liquid crystal panel) that has already been completed is bonded, so once a bonding failure occurs, even a good touch panel (or liquid crystal panel) becomes a defective product, and the device The manufacturing cost will rise.</p><p> Therefore, in the present invention, despite being thin and having high mechanical strength, the glass pieces are unlikely to scatter even if they are self-destructed due to internal tensile stress, and the visibility of the display or the like is unlikely to be deteriorated by long-term use. The technical issue is to create a protective member such as a touch panel display.</p>

<p> As a result of diligent studies, the present inventor has found that the above technical problems can be solved by using laminated glass in which a tempered glass plate and a thin unreinforced glass plate are laminated, and proposes the present invention. is there. That is, the laminated glass of the present invention is a laminated glass provided with a tempered glass plate having a compressive stress layer on its surface and an unreinforced glass plate having no compressive stress layer on its surface, and the thickness of the tempered glass plate is 2.0. It is characterized in that it is mm or less and the thickness of the untempered glass plate is 500 μm or less. The number of tempered glass plates and unreinforced glass plates is not particularly limited, but considering the total thickness of the laminated glass, one tempered glass plate and one unreinforced glass plate, or one tempered glass plate and not yet. A combination of two tempered glass plates is preferred.</p><p> By laminating an unreinforced glass plate with a plate thickness of 500 μm or less to a tempered glass plate with a plate thickness of 2.0 mm or less, it is possible to increase the mechanical strength of the laminated glass while reducing the plate thickness of the entire laminated glass. Further, by laminating the unreinforced glass plate to the tempered glass plate, it is possible to prevent the glass pieces from scattering even when the tempered glass plate is self-destructed due to the internal tensile stress. Further, since the surface of the untempered glass plate is not easily scratched, it is possible to prevent a situation in which the visibility of the display or the like is deteriorated by long-term use.</p><p> Secondly, the laminated glass of the present invention is characterized in that the surface roughness (Ra) of the tempered glass plate is 10 Å or less, and the surface roughness (Ra) of the untempered glass plate is 10 Å or less. Here, "surface roughness (Ra)" refers to a value measured by a method conforming to JIS B 0601: 2001.</p><p> Thirdly, the laminated glass of the present invention is characterized in that a tempered glass plate and an untempered glass plate are bonded with a resin.</p><p> Fourth, the laminated glass of the present invention is characterized in that the external dimensions of the unreinforced glass plate are equal to or smaller than the external dimensions of the tempered glass plate. In this way, it becomes easy to prevent the untempered glass plate from being damaged.</p><p> Fifth, in the laminated glass of the present invention, the difference in the coefficient of thermal expansion between the tempered glass plate and the untempered glass plate is 50 × 10.^-7It is characterized by being less than / ° C. Here, the "coefficient of thermal expansion" refers to an average value in a temperature range of 30 to 380 ° C, and can be measured with, for example, a dilatometer.</p><p> Sixth, the laminated glass of the present invention is characterized in that the compressive stress value of the compressive stress layer of the tempered glass plate is 50 MPa or more and the thickness of the compressive stress layer is 20 μm or more. Here, the "compressive stress value of the compressive stress layer" and the "thickness of the compressive stress layer" are calculated from the number of interference fringes observed by a surface stress meter (for example, FSM-6000 manufactured by Toshiba Corporation) and their intervals. be able to.</p><p> Seventh, in the laminated glass of the present invention, the tempered glass plate has a glass composition of SiO by mass.₂ 45-75%, Al₂O₃ 1-25%, Li₂O 0-9%, Na₂O 0 ~ 20%, K₂Containing O 0-8%, substantially As₂O₃Such contains F, the PbO characterized that no. Here, "substantially As₂O₃"Does not contain" means As in the glass composition₂O₃Refers to the case where the content of is 0.1% or less. Further, "substantially free of F" refers to a case where the content of F in the glass composition is 0.05% or less. Further, "substantially free of PbO" refers to a case where the content of PbO in the glass composition is 0.1% or less.</p><p> Eighth, the laminated glass of the present invention is characterized in that the tempered glass plate is formed by a down draw method (preferably an overflow down draw method). Here, the "overflow down draw method" is also called a fusion method, in which molten glass is overflowed from both sides of a heat-resistant gutter-shaped structure, and the overflowed molten glass is merged at the lower end of the gutter-shaped structure. However, it is a method of manufacturing a glass plate by stretching and molding downward.</p><p> Ninth, the laminated glass of the present invention has a tempered glass plate having a liquidus viscosity of 10.^4.0It is characterized by being dPa · s or more. Here, the "liquid phase viscosity" refers to a value obtained by measuring the viscosity of glass at the liquid phase temperature by the platinum ball pulling method. The "liquid phase temperature" is the temperature gradient in a temperature gradient furnace for 24 hours by putting the glass powder that has passed through a standard sieve of 30 mesh (screen opening 500 μm) and remains in 50 mesh (screen opening 300 μm) into a platinum boat. Refers to the lowest temperature at which crystals precipitate after holding (primary phase precipitation temperature).</p><p> Tenth, the laminated glass of the present invention is characterized in that the Young's modulus of the tempered glass plate is 67 GPa or more. Here, "Young's modulus" refers to a value measured by the resonance method.</p><p> Eleventh, the laminated glass of the present invention is characterized in that the internal tensile stress of the tempered glass plate is 20 MPa or more. When the internal tensile stress of the tempered glass plate is 20 MPa or more, it becomes necessary to attach the unreinforced glass plate to the tempered glass plate in order to prevent the glass pieces from scattering due to the self-destruction of the tempered glass plate.</p><p> Twelve, the laminated glass of the present invention is characterized in that an untempered glass plate is formed by a downdraw method (preferably an overflow downdraw method).</p><p> Thirteenth, the laminated glass of the present invention is characterized in that the thickness of the untempered glass plate is 200 μm or less.</p><p> Fourteenth, the laminated glass of the present invention is characterized in that it is used for a display.</p><p> Fifteenth, the laminated glass of the present invention is characterized in that it is used as a protective member for a touch panel display.</p>

The laminated glass of the present invention has a tempered glass plate having a thickness of 2.0 mm or less and an untempered glass plate having a thickness of 500 μm or less.

The thickness of the tempered glass plate according to the present invention is 2.0 mm or less, preferably 1.0 mm or less, 0.8 mm or less, 0.7 mm or less, 0.5 mm or less, 0.4 mm or less, and particularly preferably 0.3 mm or less. The smaller the thickness of the tempered glass plate, the thinner and lighter the laminated glass can be. However, if the thickness of the tempered glass plate is less than 0.1 mm, there is a high possibility that the tempered glass plate will self-destruct during the tempering process, the manufacturing yield of the tempered glass plate will decrease, and the mechanical strength of the laminated glass will be secured. It becomes difficult to do. Therefore, the thickness of the tempered glass plate is preferably 0.1 mm or more, particularly 0.2 mm or more.

The thickness of the untempered glass plate according to the present invention is 500 μm or less, preferably 400 μm or less, 300 μm or less, 200 μm or less, 100 μm or less, and particularly preferably 50 μm or less. The smaller the thickness of the untempered glass plate, the thinner and lighter the laminated glass can be. However, when the thickness of the untempered glass plate is 10 μm or less, it becomes difficult to secure the mechanical strength of the laminated glass. When the thickness of the untempered glass plate is 10 μm or less, the untempered glass plate is placed on the device side and adhered to the housing, liquid crystal panel, touch panel, etc. on the untempered glass plate side via double-sided tape or the like. In the case of, the untempered glass plate is easily broken.

In the laminated glass of the present invention, the ratio of (thickness of untempered glass plate) / (thickness of tempered glass) is 0.01 to 1, 0.03 to 1, 0.06 to 1, 0.08 to 1, 0.1 to 1, 0.15 to 1. , 0.2 to 0.9, particularly preferably 0.3 to 0.8. In this way, it becomes easy to increase the mechanical strength of the laminated glass. If the ratio of (thickness of untempered glass plate) / (thickness of tempered glass) is larger than 1, there is a high possibility that the tempered glass plate will self-destruct and the glass pieces will scatter. On the other hand, if the ratio of (thickness of untempered glass plate) / (thickness of tempered glass) is less than 0.01, the possibility of damage to the untempered glass plate increases.

The thickness of the laminated glass of the present invention is preferably 2.0 mm or less, 1.5 mm or less, 1.3 mm or less, 1 mm or less, 0.9 mm or less, 0.7 mm or less, and particularly preferably 0.5 mm or less. The smaller the thickness of the laminated glass, the thinner and lighter the laminated glass can be.

The surface roughness (Ra) of the tempered glass plate according to the present invention is preferably 10 Å or less, 8 Å or less, 6 Å or less, and particularly preferably 4 Å or less. Further, the surface roughness (Ra) of the untempered glass plate according to the present invention is also preferably 10 Å or less, 8 Å or less, 6 Å or less, and particularly preferably 4 Å or less. If the surface roughness (Ra) of the tempered glass plate and / or the unreinforced glass plate is larger than 10 Å, air may be entrained during laminating, resulting in a defect or a decrease in the mechanical strength of the laminated glass.

In the laminated glass of the present invention, it is preferable that the tempered glass plate and the untempered glass plate are bonded with a resin. As the resin, ultraviolet curable resin, heat curable resin and the like are suitable in terms of workability. For example, methacrylic resin (PMA), polyvinylidene chloride (PVC), polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS) , Polyethylene terephthalate (PBT), Cellulose acetate (CA), Dialyl phthalate resin (DAP), Uria resin (UP), Polyvinyl butyral (PVB), Polyvinyl formal (PVF), Polyvinyl alcohol (PVAL), Vinyl acetate resin (PVAc) ), Ionomer (IO), Polymethylpentene (TPX), Polyethylene (PE), Ethylene Vinyl Acetate Copolymer (EVA), Melamine Resin (MF), Unsaturated Polyester (UP), Vinylidene Chloride (PVDC), Polysulphon Perfluoro resin such as (PSF), polyvinylidene chloride (PVDF), methacrylic-styrene copolymer resin (MS), polyarate (PAR), polyallyl sulphon (PASF), polybutadiene (BR), polyether sulphon (PESF), Polyether ether ketone (PEEK), polycarbonate (PC), etc. can be used.

In the laminated glass of the present invention, the value of [(maximum external dimension of tempered glass plate)-(maximum external dimension of untempered glass plate)] is 1.0 mm or less, 0.5 mm or less, 0.3 mm or less, 0.1 mm or less, 0.08 mm. Hereinafter, 0.05 mm or less, 0.03 mm or less, particularly 0.01 mm or less is preferable. If the value of [(Maximum external dimension of tempered glass plate)-(Maximum external dimension of untempered glass plate)] is larger than 0.5 mm, the appearance of laminated glass is likely to be spoiled. On the other hand, when the value of [(maximum external dimension of tempered glass plate)-(maximum external dimension of untempered glass plate)] becomes negative, the unreinforced glass plate is easily damaged.

In the laminated glass of the present invention, the difference in the coefficient of thermal expansion between the tempered glass plate and the untempered glass plate is 50 × 10.^-7Below / ° C, 30 × 10^-7Below / ° C, 10 × 10^-7Below / ° C, 5 × 10^-7Below / ° C, 3 × 10^-7Below / ° C, 1 × 10^-7Below / ° C, especially 0.5 × 10^-7It is preferably less than / ° C. The smaller the difference in the coefficient of thermal expansion, the less likely it is that warpage or the like will occur even when the tempered glass plate and the unreinforced glass plate are bonded with a thermosetting resin or the like.

The tempered glass plate according to the present invention has a compressive stress layer on its surface. Methods for forming a compressive stress layer on the surface include a physical strengthening method, a chemical strengthening method, and a laminating method. The tempered glass plate according to the present invention preferably has a compressive stress layer formed by a chemical strengthening method. The chemical strengthening method is a method of introducing alkaline ions having a large ionic radius into the surface of a glass plate by ion exchange at a temperature below the strain point of the glass. The conditions for ion exchange are not particularly limited, and may be determined in consideration of the viscosity characteristics of the glass and the like. Especially KNO₃K in molten salt₂O in the glass plate Li₂O, Na₂By ion exchange with O, a compressive stress layer can be efficiently formed on the surface of the glass plate. If the compressive stress layer is formed by the chemical strengthening method, the compressive stress layer can be formed satisfactorily even if the thickness of the glass plate is small, and a desired mechanical strength can be obtained.

The tempered glass plate according to the present invention has a compressive stress layer on its surface. The compressive stress value of the compressive stress layer is preferably 50 MPa or more, 100 MPa or more, 200 MPa or more, 300 MPa or more, 400 MPa or more, 500 MPa or more, 600 MPa or more, 700 MPa or more, and particularly 800 MPa or more. The larger the compressive stress value, the higher the mechanical strength of the tempered glass plate, and as a result, the higher the mechanical strength of the laminated glass. The thickness of the compressive stress layer is preferably 20 μm or more, 25 μm or more, 30 μm or more, 35 μm or more, 40 μm or more, 45 μm or more, 50 μm or more, and particularly 55 μm or more. If the thickness of the compressive stress layer is too small, fractures originating from polishing marks, handling scratches, etc. formed on the tempered glass plate are likely to occur. On the other hand, if the thickness of the compressive stress layer is too large, the internal tensile stress of the tempered glass plate becomes too high, and the tempered glass plate tends to self-destruct. Therefore, the thickness of the compressive stress layer is preferably 200 μm or less, 150 μm or less, 120 μm or less, and particularly preferably 100 μm or less. As a method of forming a compressive stress layer on the surface, KNO at 350 to 500 ° C₃A method of immersing in molten salt for 2 to 24 hours is preferable.

The reason for limiting the glass composition range as described above in the tempered glass plate according to the present invention will be described below. In addition, the following% display indicates mass% unless otherwise specified.

SiO₂Is a component forming a network, and its content is 45 to 75%, preferably 50 to 75%, more preferably 52 to 65%, still more preferably 52 to 63%. SiO₂When the content of the above is large, the meltability and moldability are lowered, and the coefficient of thermal expansion becomes too low, so that it becomes difficult to match the coefficient of thermal expansion of the peripheral material. On the other hand, SiO₂When the content of is low, the coefficient of thermal expansion becomes too high, and the thermal shock resistance tends to decrease. Also, SiO₂When the content of is small, it becomes difficult to vitrify and the devitrification resistance tends to decrease.

Al₂O₃Is a component that enhances heat resistance, ion exchange performance, and Young's modulus, and its content is 1 to 25%. Al₂O₃When the content of the above is large, devitrified crystals are likely to be deposited on the glass, or the coefficient of thermal expansion becomes too low, and it becomes difficult to match the coefficient of thermal expansion of the peripheral material. Also, Al₂O₃When the content of is high, the high-temperature viscosity is high and the meltability may be lowered. On the other hand, Al₂O₃If the content of the ion exchange is low, the ion exchange performance may not be sufficiently exhibited. From the above point of view, Al₂O₃Suitable upper limit range is 20% or less, 17% or less, 16.5% or less, 16% or less, especially 15% or less, and suitable lower limit range is 1.5% or more, 3% or more, 5% or more, 10% or more, Especially 12% or more.

Li₂O is an ion exchange component, a component that lowers high-temperature viscosity, enhances meltability and moldability, and further enhances Young's modulus. Li₂The O content is 0 to 9%, preferably 0 to 3.5%, more preferably 0 to 1%, and even more preferably 0 to 0.1%. Li₂When the O content is high, the glass is easily devitrified and the liquidus viscosity is lowered. In addition, the coefficient of thermal expansion becomes too high, the thermal shock resistance is lowered, and the coefficient of thermal expansion of peripheral materials is lowered. It becomes difficult to match with. Also, Li₂If the O content is large, the strain point may be lowered too much, and the heat resistance may be lowered, or conversely, the ion exchange performance may be lowered.

Na₂O is an ion exchange component, and is a component that lowers high-temperature viscosity, enhances meltability and moldability, and enhances devitrification resistance. Na₂The content of O is 0 to 20%, preferably 8 to 20%, more preferably 10 to 18%, still more preferably 11 to 16%, and most preferably 11 to 15%. Na₂If the O content is high, the coefficient of thermal expansion becomes too high, the thermal shock resistance is lowered, and it becomes difficult to match the coefficient of thermal expansion of the surrounding materials. Also, Na₂If the O content is large, the strain point may be lowered too much, and the heat resistance may be lowered, or conversely, the ion exchange performance may be lowered. In addition, Na₂If the O content is too high, the component balance of the glass composition is impaired, and conversely, the devitrification resistance tends to decrease.

K₂O is a component having a large effect of promoting ion exchange, particularly an effect of deeply forming a compressive stress layer among alkali metal oxides. Also, K₂O is a component that lowers the high-temperature viscosity, enhances meltability and moldability, and lowers the crack occurrence rate. In addition, K₂O is also a component that enhances devitrification resistance. K₂The O content is 0 to 8%, preferably 0.5 to 8%, more preferably 1 to 8%, still more preferably 2 to 8%, and particularly preferably 3 to 7%. K₂If the O content is high, the coefficient of thermal expansion becomes too high, the thermal shock resistance is lowered, and it becomes difficult to match the coefficient of thermal expansion of the surrounding materials. Also, K₂If the O content is too high, the component balance of the glass composition is impaired, and conversely, the devitrification resistance tends to decrease.

In the tempered glass plate according to the present invention, after the compressive stress layer is formed by ion exchange treatment, a part of the compressive stress layer in the thickness direction is removed to reduce the internal tensile stress and prevent the situation from the end face to fracture. Therefore, it is preferable not to remove the compressive stress layer on the end face. In order to perform such processing accurately, it is preferable to increase the compressive stress value and the thickness of the compressive stress layer, and the mass ratio (Al).₂O₃+ K₂O) / Na₂It is preferable to regulate the value of O to 0.1 to 6.5, 0.1 to 5, 0.2 to 3, 0.2 to 2.5, 0.4 to 2, 0.7 to 1.7, and particularly 1.0 to 1.5. Mass ratio (Al₂O₃+ K₂O) / Na₂When the value of O is smaller than 0.1, it becomes difficult to sufficiently increase the compressive stress value and the thickness of the compressive stress layer. On the other hand, mass ratio (Al₂O₃+ K₂O) / Na₂When the value of O is larger than 6.5, the devitrification resistance tends to decrease, and Na₂The O content is insufficient and the compressive stress value tends to decrease.

Li₂O + Na₂O + K₂O (Li₂O, Na₂OK₂If the content of (the total amount of O) is too large, the glass tends to be devitrified, and the coefficient of thermal expansion becomes too high, resulting in a decrease in thermal shock resistance, or a tempered glass plate and an unreinforced glass plate. Warpage due to the difference in thermal expansion is likely to occur during bonding. Also, Li₂O + Na₂O + K₂If the O content is too large, the strain point may be lowered too much, and the compressive stress value of the compressive stress layer may be lowered too much. Therefore, Li₂O + Na₂O + K₂The O content is preferably 30% or less, 22% or less, and particularly preferably 20% or less. Meanwhile, Li₂O + Na₂O + K₂If the O content is too small, the ion exchange performance and meltability tend to deteriorate. Therefore, Li₂O + Na₂O + K₂The O content is preferably 5% or more, 10% or more, 13% or more, 15% or more, and particularly preferably 17% or more.

As₂O₃, F is a component having a clarifying effect, but it is preferable that it is not substantially contained because it may have an adverse effect on the environment. Further, since PbO is an environmentally hazardous substance, it is preferable that it is not substantially contained.

In addition to the above components, the following components can be added.

B₂O₃Is a component that lowers the liquidus temperature, high temperature viscosity and density, and its content is preferably 0 to 7%, 0 to 5%, 0 to 3%, and particularly preferably 0 to 1%. B₂O₃When the content of the above is large, the surface is burnt due to ion exchange, the water resistance is lowered, the low temperature viscosity is lowered too much, and the compressive stress value of the compressive stress layer is likely to be lowered.

TiO₂Is a component that enhances the ion exchange performance and enhances the mechanical strength of the glass plate, but if the content is too large, the glass tends to be devitrified or easily colored. Therefore, TiO₂The content of is preferably 0 to 10%, 0 to 5%, 0 to 1%, particularly 0 to 0.5%, and it is desirable that the content is substantially not contained. Here, "substantially TiO₂"Does not contain" means TiO in the glass composition₂Refers to the case where the content of is 0.1% or less.

If an appropriate amount of ZnO is added to the glass system according to the present invention, the compressive stress value of the compressive stress layer tends to increase. In addition, ZnO is a component that lowers high-temperature viscosity and increases Young's modulus. However, when the ZnO content is high, the density and the coefficient of thermal expansion become too high, and the devitrification resistance tends to decrease. Therefore, the ZnO content is preferably 0 to 15%, 0 to 10%, 0 to 2%, 0 to 0.5%, and particularly preferably 0 to 0.1%.

MgO + CaO + SrO + BaO (total amount of MgO, CaO, SrO, BaO) is a component that can be added for various purposes. However, when the content of MgO + CaO + SrO + BaO increases, the density and coefficient of thermal expansion increase, the devitrification resistance decreases, and the ion exchange performance tends to decrease. Therefore, the content of MgO + CaO + SrO + BaO is preferably 0 to 16%, 0 to 10%, and particularly preferably 0 to 6%.

MgO is a component that lowers high-temperature viscosity, enhances meltability and moldability, and enhances strain point and Young's modulus. In addition, MgO is a component that has a relatively large effect of enhancing ion exchange performance among alkaline earth metal oxides. However, when the MgO content is high, the density, the coefficient of thermal expansion and the crack occurrence rate are high, and the glass is easily devitrified. Therefore, the MgO content is preferably 10% or less, 9% or less, 6% or less, 4% or less, and particularly preferably 3% or less.

CaO is a component that lowers high-temperature viscosity, enhances meltability and moldability, and enhances strain points and Young's modulus. However, when the CaO content is high, the density, the coefficient of thermal expansion and the crack occurrence rate are high, and the glass is easily devitrified. Therefore, the content is preferably 10% or less, 8% or less, 5% or less, and particularly preferably 3% or less.

SrO is a component that lowers high-temperature viscosity, enhances meltability and moldability, and enhances strain point and Young's modulus. However, when the SrO content is high, the density, the coefficient of thermal expansion and the crack generation rate are high, the glass is liable to be devitrified, and the ion exchange performance is liable to be deteriorated. Therefore, the content of SrO is preferably 10% or less, 8% or less, 5% or less, 3% or less, 1% or less, 0.8% or less, particularly 0.5% or less, and it is desirable that the SrO content is substantially not contained. Here, "substantially free of SrO" refers to a case where the content of SrO in the glass composition is 0.2% or less.

BaO is a component that lowers high-temperature viscosity, enhances meltability and moldability, and enhances strain point and Young's modulus. However, when the BaO content is high, the density, the coefficient of thermal expansion and the crack generation rate are high, the glass is liable to be devitrified, and the ion exchange performance is liable to be deteriorated. In addition, since the raw material compound of BaO is an environmentally hazardous substance, it is desirable to refrain from using it as much as possible from an environmental point of view. Therefore, the BaO content is preferably 3% or less, 2.5% or less, 2% or less, 1% or less, 0.8% or less, particularly 0.5% or less, and it is desirable that the BaO content is substantially not contained. Here, "substantially free of BaO" refers to a case where the content of BaO in the glass composition is 0.1% or less.

ZrO₂Is a component that enhances strain point, Young's modulus, and ion exchange performance, and is a component that lowers high-temperature viscosity. But ZrO₂When the content of is high, the devitrification resistance may be extremely lowered. Therefore, ZrO₂The content of is preferably 0 to 10%, 0 to 9%, 2 to 9%, 3 to 9%, 3 to 8%, 3.5 to 7%, 3.5 to 6%, and particularly preferably 3.5 to 5.5%.

P₂O₅Is a component that enhances the ion exchange performance, and is particularly effective in forming a deep compressive stress layer. But P₂O₅When the content of the glass increases, the glass tends to be phase-separated and the water resistance tends to decrease. Therefore, P₂O₅The content of 5% or less, 4% or less, 3% or less, 2% or less, 1% or less, particularly 0.5% or less is preferable.

MgO + CaO + SrO + BaO Li₂O + Na₂O + K₂When the value divided by O becomes large, the density becomes too high and the devitrification resistance tends to decrease. Therefore, the mass ratio (MgO + CaO + SrO + BaO) / (Li₂O + Na₂O + K₂The value of O) is preferably 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, and particularly preferably 0.1 or less.

SO as a fining agent₃, Cl, CeO₂, Sb₂O₃, SnO₂It is preferable to add 0 to 3% of one or more selected from the group of. As₂O₃, F has a clarification effect, but as described above, it may have an adverse effect on the environment, so it is preferable that F is not substantially contained. Also, Sb₂O₃Is As₂O₃Although its toxicity is low, it may be preferable to reduce the amount of addition, and it may be preferable that it is not substantially contained. Here, "substantially Sb₂O₃"Does not contain" means Sb in the glass composition₂O₃Refers to the case where the content of is 0.1% or less. Considering the environmental load and clarification effect, SnO as a clarifying agent₂Is preferable, and the content thereof is preferably 0.01 to 3%, particularly preferably 0.05 to 1%. Also, Sb₂O₃And SO₃Is a fining agent suitable for applications requiring high transmittance because it has a large effect of suppressing a decrease in transmittance, and its content is preferably 0.001 to 5% in total.

Nb₂O₅And La₂O₃Rare earth oxides such as are components that increase Young's modulus. However, the rare earth oxide is a component whose raw material cost is high and whose devitrification resistance tends to decrease when it is contained in a large amount. Therefore, the content of the rare earth oxide is preferably 3% or less, 2% or less, 1% or less, particularly 0.5% or less, and it is desirable that the rare earth oxide is not substantially contained. Here, "substantially free of rare earth oxides" refers to a case where the content of rare earth oxides in the glass composition is 0.1% or less.

The transition metal oxides such as Co, Ni, and Cu are coloring components and components that reduce the transmittance of the glass plate. In particular, in the case of display applications, if the content of the transition metal oxide is large, the visibility of the display may be impaired. Therefore, it is desirable to adjust the amount of raw materials and cullet used so that the content of the transition metal oxide is 0.5% or less, 0.1% or less, particularly 0.05% or less.

It is naturally possible to form a suitable glass composition range by appropriately combining the suitable content ranges of the above components, but among them, the more suitable glass composition range is (1) SiO₂ 45-75%, Al₂O₃ 1-25%, Li₂O 0-9%, Na₂O 7 ~ 20%, K₂Containing O 0-8%, substantially As₂O₃, F, PbO free, (2) SiO₂ 45-75%, Al₂O₃ 3-25%, Li₂O 0 ~ 3.5%, Na₂O 7 ~ 20%, K₂Contains 0-7% O, mass ratio (Al₂O₃+ K₂O) / Na₂The value of O is 0.1 to 3, and it is practically As₂O₃, F, PbO free, (3) SiO₂ 45-70%, Al₂O₃ 10 ~ 20%, Li₂O 0 ~ 3%, Na₂O 7 ~ 20%, K₂Contains 0-7% O, mass ratio (Al₂O₃+ K₂O) / Na₂The value of O is 0.5 to 2, and it is practically As₂O₃, F, PbO free, (4) SiO₂ 45-65%, Al₂O₃ 10 ~ 20%, Li₂O 0 ~ 3%, Na₂O 7 ~ 16%, K₂O 0 ~ 7%, MgO + CaO + SrO + BaO 0 ~ 10%, mass ratio (Al₂O₃+ K₂O) / Na₂The value of O is 0.3 to 1.8, and it is practically As₂O₃, F, PbO free, (5) SiO₂ 45-65%, Al₂O₃ 11 ~ 20%, Li₂O 0 ~ 3%, Na₂O 7 ~ 16%, K₂O 0 ~ 7%, MgO 0 ~ 3%, MgO + CaO + SrO + BaO 0 ~ 9%, mass ratio (Al₂O₃+ K₂O) / Na₂The value of O is 1 to 1.5, and it is practically As₂O₃, F, PbO free, (6) SiO₂ 50 ~ 63%, Al₂O₃ 11-18%, Li₂O 0 ~ 2%, Na₂O 8 ~ 15.5%, K₂O 0 ~ 6%, MgO 0 ~ 3%, MgO + CaO + SrO + BaO 0 ~ 8%, mass ratio (Al₂O₃+ K₂O) / Na₂The value of O is 1 to 1.5, and it is practically As₂O₃, F, PbO free, (7) SiO₂ 50 ~ 63%, Al₂O₃ 11 ~ 16%, Li₂O 0 ~ 1%, Na₂O 8 ~ 15%, K₂O 0.1 ~ 5%, MgO 0 ~ 2.5%, MgO + CaO + SrO + BaO 0 ~ 6%, mass ratio (Al₂O₃+ K₂O) / Na₂The value of O is 1 to 1.5, and it is practically As₂O₃, F, does not contain PbO. As described above, if the glass composition range is regulated, it is possible to significantly improve the devitrification resistance, easily secure the viscosity characteristics suitable for molding by the overflow downdraw method, and significantly improve the ion exchange performance. ..

The tempered glass plate according to the present invention preferably has the following characteristics.

In the tempered glass plate according to the present invention, the liquidus temperature is preferably 1200 ° C or lower, 1100 ° C or lower, 1050 ° C or lower, 1000 ° C or lower, 930 ° C or lower, 900 ° C or lower, particularly 880 ° C or lower. .. The lower the liquidus temperature, the more difficult it is for the glass to devitrify during molding by the overflow downdraw method or the like.

In the tempered glass plate according to the present invention, the liquidus viscosity is 10.^4.0dPa s or more, 10^4.3dPa s or more, 10^4.5dPa s or more, 10^5.0dPa s or more, 10^5.5dPa s or more, 10^5.7dPa s or more, 10^5.9dPa · s and above, especially 10^6.0dPa · s or more is preferable. The higher the liquidus viscosity, the more difficult it is for the glass to devitrify during molding by the overflow downdraw method or the like.

In the tempered glass plate according to the present invention, the density is 2.8 g / cm.³Below, 2.7g / cm³Below, 2.6g / cm³Below, 2.57g / cm³Below, 2.55g / cm³Below, 2.5g / cm³Below, 2.45 g / cm³Below, especially 2.4g / cm³The following is preferable. The lower the density, the lighter the weight of the laminated glass. The "density" can be measured by a well-known Archimedes method or the like.

In the tempered glass plate according to the present invention, the coefficient of thermal expansion is 30 to 110 × 10.^-7/ ° C, 70 ~ 105 × 10^-7/ ° C, 75 ~ 100 × 10^-7/ ° C, 80 ~ 100 × 10^-7/ ° C, especially 80 ~ 90 × 10^-7/ ° C is preferred. If the coefficient of thermal expansion is regulated within the above range, it becomes easy to match the coefficient of thermal expansion of a member such as a metal or an organic adhesive, and peeling of a member such as a metal or an organic adhesive can be prevented.

In the tempered glass plate according to the present invention, 10^2.5The temperature at dPa · s is preferably 1700 ° C or lower, 1600 ° C or lower, 1560 ° C or lower, 1500 ° C or lower, 1450 ° C or lower, 1420 ° C or lower, and particularly preferably 1400 ° C or lower. Ten^2.5The lower the temperature at dPa · s, the smaller the load on the glass manufacturing equipment such as the melting kiln, and the higher the foam quality. In addition, 10^2.5The lower the temperature at dPa · s, the lower the temperature at which the glass can be melted. In addition, 10^2.5The temperature at dPa · s corresponds to the melting temperature. Therefore, 10^2.5The lower the temperature at dPa · s, the cheaper the tempered glass plate can be manufactured. Here, "10^2.5"Temperature at dPa · s" refers to the value measured by the platinum ball pulling method.

In the tempered glass plate according to the present invention, the Young's modulus is preferably 67 GPa or more, 68 GPa or more, 70 GPa or more, 71 GPa or more, and particularly 73 GPa or more. The higher the Young's modulus, the more difficult it is for the tempered glass plate to bend. Therefore, when the display is pressed with a pen or the like in a device such as a touch panel display, it becomes difficult to press the liquid crystal element or the like inside the device, resulting in display failure of the display. It becomes difficult. On the other hand, if the Young's modulus is too high, when the tempered glass plate is pressed by a pen or the like and deformed, the stress generated by the deformation tends to increase, and this tendency becomes remarkable especially when the plate thickness is small. Therefore, Young's modulus is preferably 100 GPa or less, 95 GPa or less, 90 GPa or less, 85 GPa or less, 80 GPa or less, and particularly 78 GPa or less. The "Young's modulus" can be measured by a resonance method or the like.

In the tempered glass plate according to the present invention, the Young's modulus is 27 GPa / (g / cm).³) Above, 28GPa / (g / cm³) Above, 29GPa / (g / cm³) Above, especially 30GPa / (g / cm³) The above is preferable. The higher the specific young ratio, the more difficult it is for the glass plate to bend due to its own weight. Therefore, when storing the tempered glass plate in a cassette or the like in the manufacturing process, it becomes possible to narrow the clearance between the tempered glass plates and store the glass plate. As a result, the productivity of the tempered glass plate is improved.

The tempered glass plate according to the present invention is preferably formed by an overflow down draw method. By doing so, it is possible to produce a glass plate that is unpolished and has good surface quality. The reason is that in the case of the overflow down draw method, the surface of the glass plate that should be the surface does not come into contact with the gutter-shaped refractory and is formed in a free surface state. The structure and material of the gutter-shaped structure are not particularly limited as long as they can achieve desired dimensions and surface quality. Further, the method of applying a force to the glass plate in order to perform downward stretching molding is not particularly limited as long as it can achieve desired dimensions and surface quality. For example, a method of rotating and stretching a heat-resistant roll having a sufficiently large width in contact with the glass plate may be adopted, or a plurality of pairs of heat-resistant rolls may be stretched only in the vicinity of the end face of the glass plate. You may adopt the method of stretching by contacting with. The lower the liquidus temperature and the higher the liquidus viscosity, the easier it is to mold the glass plate by the overflow downdraw method. In addition, the liquidus temperature is 1300 ° C or less, and the liquidus viscosity is 10.^4.0If it is dPa · s or more, it can be molded by the overflow down draw method.

In addition to the overflow down draw method, the tempered glass plate according to the present invention can be formed by, for example, a float method, a slot down method, a redraw method, a rollout method, a press method, or the like.

In the laminated glass of the present invention, various materials can be used as the untempered glass plate. For example, silicate glass, borosilicate glass, non-alkali glass and the like can be used. Here, "alkali-free glass" refers to glass having an alkali metal oxide content of 1000 ppm (mass) or less, preferably 500 ppm (mass) or less in the glass composition.

In the laminated glass of the present invention, it is preferable to use glass having the same composition as the tempered glass plate (glass before tempering treatment) as the untempered glass plate. In this way, the glass characteristics (coefficient of thermal expansion, etc.) of the tempered glass plate and the untempered glass plate can be easily matched, and the manufacturing cost of the laminated glass can be reduced.

The untempered glass plate according to the present invention is preferably formed by an overflow down draw method. By doing so, it is possible to produce a glass plate having a small plate thickness, unpolished, and good surface quality. In addition to the overflow down draw method, the untempered glass plate according to the present invention can also be formed by, for example, a float method, a slot down method, a redraw method, a rollout method, a press method, or the like.

The laminated glass of the present invention is preferably used for a display, and more preferably for a touch panel display. Touch panel displays are installed in mobile phones, digital cameras, PDAs, etc. For touch panel displays for mobile applications, there are strong demands for weight reduction, thinning, and high strength. Although the laminated glass of the present invention is thin and has high mechanical strength, it is suitable for this application because glass pieces are hard to scatter even if it is self-destructed by internal tensile stress. Further, the laminated glass of the present invention is also suitable as a cover glass for protecting a liquid crystal display or the like mounted on a mobile phone, a digital camera or the like.

Hereinafter, the present invention will be described based on examples.

Tables 1 to 3 show tempered glass plates (Sample Nos. 1 to 17) according to the present invention.

<tables num="1"><img file="JP2011136895A_D0002.tif" /></tables>

<tables num="2"><img file="JP2011136895A_D0003.tif" /></tables>

<tables num="3"><img file="JP2011136895A_D0004.tif" /></tables>

Each sample was prepared as follows. First, glass raw materials were prepared so as to have the glass composition shown in the table, and melted at 1600 ° C. for 8 hours using a platinum pot. Then, the molten glass was poured onto a carbon plate and formed into a plate shape. Various characteristics of the obtained glass plate were evaluated.

Density is a value measured by the well-known Archimedes method.

The strain point Ps and the slow cooling point Ta are values measured based on the method of ASTM C336.

The softening point Ts is a value measured based on the method of ASTM C338.

10^4.0dPa s, 10^3.0dPa s, 10^2.5The temperature at dPa · s is a value measured by the platinum ball pulling method.

The coefficient of thermal expansion α is a value obtained by measuring the average coefficient of thermal expansion at 30 to 380 ° C. using a dilatometer.

The liquidus temperature passes through a standard mesh of 30 mesh (opening of sieves 500 μm), and the glass powder remaining on 50 mesh (opening of sieve 300 μm) is placed in a platinum boat and held in a temperature gradient furnace for 24 hours to obtain crystals. It is a value obtained by measuring the temperature of precipitation.

The liquidus viscosity is a value obtained by measuring the viscosity of glass at the liquidus temperature by the platinum ball pulling method.

Young's modulus is a value measured by the resonance method.

As is clear from Tables 1 to 3, samples No. 1 to 17 have a density of 2.8 g / cm.³Below, 10^2.5The temperature at dPa · s is 1650 ° C or less, and the coefficient of thermal expansion is 44 to 100 × 10.^-7/ ° C, liquidus viscosity is 10^3.7The Young's modulus was 67 GPa or higher and dPa · s or higher. Although the glass composition of the surface layer is microscopically different before and after the ion exchange treatment, the glass composition is not substantially different as a whole. Therefore, characteristic values such as density, viscosity, and Young's modulus do not substantially differ depending on the presence or absence of ion exchange.

Subsequently, after optically polishing both sides of each sample, an ion exchange treatment was performed. Ion exchange treatment is KNO at 410 ° C₃KNO in molten salt for 4 hours or 440 ° C₃This was done by immersing in molten salt for 6 hours. Finally, after cleaning the surface of each sample, using a surface stress meter (FSM-6000 manufactured by Toshiba Corporation), the compressive stress value and depth of the compressive stress layer (from the number of observed interference fringes and their intervals) ( Thickness) was calculated. In the measurement, the refractive index was 1.52 and the photoelastic constant was 28 [(nm / cm) / MPa]. As a result, the compressive stress values of the compressive stress layers of Samples Nos. 1 to 16 were 300 MPa or more and the depth was 5 μm or more.

In the case of manufacturing a tempered glass plate on an industrial scale, it is desirable to perform ion exchange treatment with both sides unpolished after molding the glass plate by an overflow down draw method or the like.

<tables num="4"><img file="JP2011136895A_D0005.tif" /></tables>

In addition, the glass raw material prepared so as to have the glass composition of sample No. 9 shown in Table 2 is put into a continuous melting furnace, and this glass raw material is heated and melted at 1500 to 1600 ° C, clarified, and then overflowed down. Molding was performed by the draw method to prepare a glass plate (Ra = 2Å) having a thickness of 40 mm × 80 mm × 0.5 mm. Next, KNO this glass plate₃It was immersed in molten salt and subjected to ion exchange treatment at 440 ° C for 6 hours to prepare a tempered glass plate. In addition, the glass raw material prepared so as to have the glass composition of sample No. 9 shown in Table 2 was put into a continuous melting furnace, and this glass raw material was heated and melted at 1500 to 1600 ° C, clarified, and then overflowed down. Molding was performed by the draw method to prepare an untempered glass plate (Ra = 2Å) having a thickness of 39.99 mm × 79.99 mm × 0.05 mm. Finally, the tempered glass plate and the untempered glass plate were bonded with an ultraviolet curable resin to prepare a laminated glass. In addition, laminated glass was prepared in the same manner for Samples Nos. 7, 8 and 10 to 16 (tempered glass plate).

In addition, the glass raw material prepared so as to have the glass composition of sample No. 9 shown in Table 2 is put into a continuous melting furnace, and this glass raw material is heated and melted at 1500 to 1600 ° C, clarified, and then overflowed down. Molding was performed by the draw method to prepare a glass plate (Ra = 2Å) having a thickness of 40 mm × 80 mm × 0.5 mm. Next, KNO this glass plate₃It was immersed in molten salt and subjected to ion exchange treatment at 440 ° C for 6 hours to prepare a tempered glass plate. Further, as an untempered glass plate, a glass raw material prepared so as to have the glass composition of sample No. 18 shown in Table 4 was put into a continuous melting furnace, and this glass raw material was heated and melted at 1500 to 1600 ° C. After clarification, molding was performed by the overflow down draw method to prepare an untempered glass plate (non-tempered glass, Ra = 2 Å) having a thickness of 39.99 mm × 79.99 mm × 50 μm. Finally, the tempered glass plate and the untempered glass plate were bonded with an ultraviolet curable resin to prepare a laminated glass. The glass characteristics of Sample No. 18 were measured by the above method. In addition, laminated glass was prepared in the same manner for Samples Nos. 7, 8 and 10 to 16 (tempered glass plate).

In addition, the glass raw material prepared so as to have the glass composition of sample No. 9 shown in Table 2 is put into a continuous melting furnace, and this glass raw material is heated and melted at 1500 to 1600 ° C, clarified, and then overflowed down. Molding was performed by the draw method to prepare a glass plate (Ra = 2Å) having a thickness of 40 mm × 80 mm × 0.7 mm. Next, KNO this glass plate₃It was immersed in molten salt and subjected to ion exchange treatment at 440 ° C for 6 hours to prepare a tempered glass plate. In addition, the glass raw material prepared so as to have the glass composition of sample No. 19 shown in Table 2 is put into a continuous melting furnace, and this glass raw material is heated and melted at 1500 to 1600 ° C, clarified, and then overflowed down. Molding was performed by the draw method to prepare an untempered glass plate (Ra = 2Å) having a thickness of 39.99 mm × 79.99 mm × 0.2 mm. Finally, the tempered glass plate and the untempered glass plate were bonded with an ultraviolet curable resin to prepare a laminated glass. In addition, laminated glass was prepared in the same manner for Samples Nos. 7, 8 and 10 to 16 (tempered glass plate).

In addition, the glass raw material prepared so as to have the glass composition of sample No. 9 shown in Table 2 is put into a continuous melting furnace, and this glass raw material is heated and melted at 1500 to 1600 ° C, clarified, and then overflowed down. Molding was performed by the draw method to prepare a glass plate (Ra = 2Å) having a thickness of 40 mm × 80 mm × 0.7 mm. Next, KNO this glass plate₃It was immersed in molten salt and subjected to ion exchange treatment at 440 ° C for 6 hours to prepare a tempered glass plate. Further, as an untempered glass plate, a glass raw material prepared so as to have the glass composition of sample No. 18 shown in Table 4 was put into a continuous melting furnace, and this glass raw material was heated and melted at 1500 to 1600 ° C. After clarification, molding was performed by the overflow down draw method to prepare an untempered glass plate (non-tempered glass, Ra = 2 Å) having a thickness of 39.99 mm × 79.99 mm × 145 μm. Finally, the tempered glass plate and the untempered glass plate were bonded with an ultraviolet curable resin to prepare a laminated glass. The glass characteristics of Sample No. 18 were measured by the above method. In addition, laminated glass was prepared in the same manner for Samples Nos. 7, 8 and 10 to 16 (tempered glass plate).

The glass raw material prepared so as to have the glass composition of sample No. 9 shown in Table 2 is put into a continuous melting furnace, and this glass raw material is heated and melted at 1500 to 1600 ° C. A glass plate (Ra = 2Å) with a thickness of 40 mm × 80 mm × 0.7 mm was produced. Next, KNO this glass plate₃It was immersed in molten salt and subjected to ion exchange treatment at 440 ° C for 6 hours to prepare a tempered glass plate. Further, as an untempered glass plate, a glass raw material prepared so as to have the glass composition of sample No. 19 shown in Table 4 was put into a continuous melting furnace, and this glass raw material was heated and melted at 1500 to 1600 ° C. After clarification, molding was performed by the overflow down draw method to prepare an untempered glass plate (non-tempered glass plate, Ra = 2 Å) having a thickness of 39.99 mm × 79.99 mm × 200 μm. Finally, the tempered glass plate and the untempered glass plate were bonded with an ultraviolet curable resin to prepare a laminated glass. The glass characteristics of Sample No. 19 were measured by the above method. In addition, laminated glass was prepared in the same manner for Samples Nos. 7, 8 and 10 to 16 (tempered glass plate).

Tables 5 to 7 show the laminated glass of the present invention (samples B to E, G to J, L to O). In addition, samples A, F, and K are only tempered glass plates, and unreinforced glass plates are not bonded to each other.

<tables num="5"><img file="JP2011136895A_D0006.tif" /></tables>

<tables num="6"><img file="JP2011136895A_D0007.tif" /></tables>

<tables num="7"><img file="JP2011136895A_D0008.tif" /></tables>

Each sample was prepared as follows. The glass raw material prepared so as to have the glass composition of sample No. 9 shown in Table 2 is put into a continuous melting furnace, and this glass raw material is heated and melted at 1500 to 1600 ° C. A glass plate having the dimensions shown in the table was prepared. Next, KNO this glass plate₃It was immersed in molten salt and subjected to ion exchange treatment at 440 ° C for 6 hours to prepare a tempered glass plate. Further, as an untempered glass plate, glass raw materials prepared so as to have the glass compositions of Samples Nos. 18 and 19 shown in Table 4 are put into a continuous melting furnace, and the glass raw materials are heated and melted at 1500 to 1600 ° C. After clarification, molding was performed by the overflow down draw method to prepare an untempered glass plate having the dimensions shown in the table. Finally, the tempered glass plate and the untempered glass plate were bonded with an ultraviolet curable resin to prepare a laminated glass. For samples C, E, H, J, M, and O, the external dimensions of the unreinforced glass plate are slightly smaller than the external dimensions of the tempered glass plate, and the four peripheral ends of the unreinforced glass plate are the outer circumference of the tempered glass plate. The bonding was done so that it would not come out of the side surface.

A four-point bending test was performed on the samples A to E. First, samples A to E were placed on two cylindrical rods (R = 2.0 mm) separated by 50 mm. Next, samples A to E were pressurized from above using a cylindrical rod (R = 2.0 mm). Specific conditions are: Weight gauge: Shimadzu strength tester, Weighting speed: 5 mm / min, Upper push width: 25 mm, Lower receiving width: 50 mm, Push position: Center, Push side: Long side, sample B to E were arranged with the untempered glass plate facing up. As a result of the four-point bending test, there was no significant difference in the fracture strength of samples A to E. In addition, sample A was destroyed to 50 pieces (size of about 5 mm square or less) and the small pieces were scattered in various directions, but samples B to E were not destroyed by the small pieces and did not scatter at all. ..

A ring-on-ring test was performed on samples F to J. First, samples F to J were placed on a ring-shaped jig having a diameter of 25 mm. Next, samples F to J were pressurized from above using a jig having a diameter of 12.5 mm. The specific conditions were a weight meter: Shimadzu strength tester, weighting speed: 0.5 mm / min, pushing position: center, and samples G to J were placed with the untempered glass plate facing up. As a result of the ring-on-ring test, there was no significant difference in the fracture strength of samples F to J. In addition, sample F was destroyed to 50 pieces (size of about 5 mm square or less) and the small pieces were scattered in various directions, but samples G to J were not destroyed by the small pieces and did not scatter at all. ..

A hardball drop test was performed on samples K to O. A hard ball with a mass of 38.5 g was freely dropped onto the sample. The height was started from 50 cm, and the drop height was gradually increased until it cracked. Further, the outer peripheral portion 3 mm of the glass plate was received by an acrylic jig, and the samples L to O were arranged with the untempered glass plate facing upward. As a result of the hardball drop test, sample K was destroyed by free fall from a height of about 180 cm to more than 50 pieces (size of about 5 mm square or less), and the small pieces were scattered in various directions. On the other hand, the samples L to O did not crack even when dropped freely from a height of 300 cm.

The laminated glass of the present invention is suitable as a protective plate for a mobile phone, a digital camera, a touch panel display such as a PDA, or a cover glass. In addition to these applications, the laminated glass of the present invention can be used for applications requiring high mechanical strength, such as window glass, magnetic disk substrates, cover glass for solar cells, cover glass for solid-state image sensors, and tableware. Expected to be applied.