JP7183108B2 - glass - Google Patents

Description

The present invention relates to glass, and specifically to mobile phones, digital cameras, PDAs (portable terminals), solar cells, chip size packages (CSP), charge-coupled devices (CCD), and same-magnification proximity solid-state imaging devices (CIS). cover glass, particularly glass suitable for the cover glass of a touch panel display.

Devices such as mobile phones, digital cameras, PDAs, etc. tend to become more popular. For these applications, tempered glass subjected to ion exchange treatment is used as a cover glass for touch panel displays (see Patent Document 1 and Non-Patent Document 1).

Conventionally, tempered glass has been produced by cutting a glass plate into a predetermined shape in advance and then performing an ion exchange treatment, that is, so-called “cutting before tempering”. After processing, a film such as a touch sensor is formed and cut into a predetermined size, that is, so-called "cutting after strengthening" is under consideration. Cutting after strengthening dramatically improves device manufacturing efficiency.

JP-A-2006-83045

Tetsuro Izumiya et al., "New Glass and Its Physical Properties", First Edition, Management System Research Institute, August 20, 1984, p. 451-498

By the way, the cover glass is required to (1) be resistant to scratches and (2) have high drop impact strength. A conventional cover glass is tempered glass having a compressive stress layer on its surface by ion exchange treatment in order to satisfy the above characteristics (1) and (2).

However, the ion exchange treatment increases the production cost of the cover glass.

In addition, when cutting after strengthening, the compressive stress layer existing on the surface becomes a barrier, so the tempered glass is easily broken during cutting. Strength tends to decrease. Furthermore, when a film such as a touch sensor is formed on the surface of the tempered glass, the in-plane strength of the tempered glass tends to decrease.

Furthermore, in recent years, the use of cover glass for large-sized televisions has also been studied, and tempered glass is used for the cover glass. However, conventional tempered glass cannot be said to be sufficiently lightweight and does not contribute to weight reduction of large-sized devices.

The present invention has been made in view of the above circumstances, and its technical object is to create a glass that is resistant to scratches, has high drop impact strength, and is lightweight even without ion exchange treatment. .

As a result of repeating various experiments, the inventors of the present invention have found that the above technical problems can be solved by restricting the glass composition range to a predetermined range, and propose the present invention. That is, the glass of the present invention has, as a glass composition, SiO ₂ 50 to 70%, Al ₂ O ₃ 0 to 20%, B ₂ O ₃ 15 to 30%, Li ₂ O + Na ₂ O + K ₂ O 0 to 0. 3%, and MgO+CaO+SrO+BaO 0-12%. Here, " _Li2O + _Na2O + _K2O " refers to the total amount of _Li2O , _Na2O and _K2O . "MgO+CaO+SrO+BaO" refers to the total amount of MgO, CaO, SrO and BaO.

The glass of the present invention contains 15% by mass or more of B ₂ O ₃ in the glass composition. In this way, scratch resistance and crack resistance can be improved. Furthermore, since the Young's modulus is lowered, drop impact resistance can be enhanced. Furthermore, in the glass of the present invention, the content of Li ₂ O + Na ₂ O + K ₂ O in the glass composition is regulated to 3% by mass or less, and the content of MgO + CaO + SrO + BaO is regulated to 12% by mass or less, preferably 8% by mass or less. By doing so, the density is easily lowered, and as a result, the weight of the cover glass is easily reduced.

Further, the glass of the present invention has a composition of SiO ₂ 58 to 70%, Al ₂ O ₃ 7 to 20%, B ₂ O ₃ 18 to 30%, and Li ₂ O + Na ₂ O + K ₂ O 0 to 1 in mass %. %, and MgO+CaO+SrO+BaO 0-10%.

Further, the glass of the present invention has a glass composition of 50 to 70% SiO ₂ , 0 to 15% Al ₂ O ₃ , 15 to 30% B ₂ O ₃ , and 0 to 3 Li ₂ O+Na ₂ O+K ₂ O in mass %. %, MgO+CaO+SrO+BaO 0-8%.

In the glass of the present invention, B ₂ O ₃ -(MgO+CaO+SrO+BaO) is preferably 5% by mass or more. Here, “B ₂ O ₃ −(MgO+CaO+SrO+BaO)” refers to the value obtained by subtracting the total content of MgO, CaO, SrO and BaO from the content of B ₂ O ₃ .

For example, in the case of a glass film having a thickness of 200 μm or less, it is required to be lightweight and to be bent with a small radius of curvature so as to be advantageous when wound into a roll. Therefore, by adopting the above structure, it becomes easy to obtain a glass having a low density and a low Young's modulus, which is suitable as a film-like glass material.

Further, the glass of the present invention preferably has a mass ratio of (SrO+BaO)/(MgO+CaO) of 1 or less. Here, "(SrO+BaO)/(MgO+CaO)" refers to a value obtained by dividing the total content of SrO and BaO by the total content of MgO and CaO.

By adopting the above structure, it becomes easy to obtain a low-density glass, and it is suitable as a film-like glass material.

In addition, the glass of the present invention has a B ₂ O ₃ content greater than an Al ₂ O ₃ content on a mass basis (that is, B ₂ O ₃ —Al ₂ O ₃ is greater than 0% by mass). is preferred.

By adopting the above structure, it becomes easy to obtain a glass with a low Young's modulus, and it is suitable as a film-like glass material.

Further, the glass of the present invention preferably has a liquidus viscosity of 10 ^5.0 dPa·s or more. Here, the "liquidus viscosity" refers to a value obtained by measuring the viscosity of the glass at the liquidus temperature by the platinum ball pull-up method. The "liquidus temperature" is measured by passing through a 30-mesh (500 µm) standard sieve, placing the glass powder remaining on the 50-mesh (300 µm) in a platinum boat, holding it in a temperature gradient furnace for 24 hours, and measuring the temperature at which crystals precipitate. Refers to the measured value.

Further, the glass of the present invention has a density of 2.40 g/cm ³ or less (especially 2.30 g/cm ³ or less), a thermal expansion coefficient of 25 to 40×10 ^-7 /°C in a temperature range of 30 to 380°C, a strain It is characterized by having a point of 610° C. or less and a Young's modulus of 66 GPa or less (especially 65 GPa or less). Here, "density" can be measured by the well-known Archimedes method. "Thermal expansion coefficient in the temperature range of 30 to 380°C" refers to the average value measured with a dilatometer. "Strain point" refers to a value measured according to the method of ASTM C336. "Young's modulus" refers to a value measured by the well-known resonance method.

Moreover, the glass of the present invention is preferably formed by an overflow down-draw method. Here, in the "overflow down-draw method", molten glass is overflowed from both sides of a heat-resistant gutter-shaped structure, and the overflowed molten glass is drawn downward while joining at the lower end of the gutter-shaped structure. It is a method of producing a glass plate.

Moreover, it is preferable to use the glass of this invention for a cover glass.

Further, the glass of the present invention is preferably not ion-exchanged. In this way, the manufacturing cost of the cover glass can be reduced.

By the way, when the glass of the present invention is used as a cover glass or the like, contamination due to adhesion of fingerprints or the like tends to become a problem. In such a case, it is preferable that photocatalyst particles are supported on the glass surface.

With such a configuration, dirt such as fingerprints adhering to the surface can be decomposed and removed by the action of the photocatalyst particles.

Further, a glass containing a large amount of B ₂ O ₃ has a strong tendency of phase separation, and there are cases where phase separation occurs on the surface without special heat treatment. By subjecting such glass to acid treatment, the surface portion becomes porous, making it possible to easily obtain glass having a large specific surface area.

Further, the glass of the present invention preferably has a porous surface. Here, "having a porous surface" means that only the surface is porous, in other words, the entire particle is not porous. The term "porous" means a state in which numerous pores are present, but the pores do not necessarily communicate with each other.

By adopting the above configuration, many photocatalyst particles can be supported on the glass surface, and many organic substances can be adsorbed on the photocatalyst surface, so that the photocatalytic function can be greatly improved.

In the glass of the present invention, the photocatalyst particles are preferably titanium oxide particles.

By adopting the above structure, when irradiated with light including ultraviolet light such as sunlight, organic substances such as dirt and bacteria are quickly decomposed, and excellent antifouling, antibacterial, and antifungal effects can be obtained.

The cover glass of the present invention is characterized by having a porous glass surface and supporting photocatalyst particles.

Since the cover glass having the above structure can decompose and remove stains such as fingerprints adhering to the surface by the action of the photocatalyst particles, it is easy to maintain a clean state.

In the method for producing the glass of the present invention, the glass composition is SiO ₂ 50 to 70%, Al ₂ O ₃ 0 to 20%, B ₂ O ₃ 15 to 30%, Li ₂ O + Na ₂ O + K ₂ O 0 in mass %. It is characterized by melting and shaping a raw material batch prepared to a glass containing ˜3% MgO+CaO+SrO+BaO 0-12%. More preferably, in mass %, SiO ₂ 58-70%, Al 2 O ₃ 7-20 _% , B ₂ O ₃ 18-30%, Li ₂ O+Na ₂ O+K ₂ O 0-1%, MgO+CaO+SrO+BaO 0-10 SiO ₂ 50 to 70%, Al 2 O ₃ 0 to 15%, B ₂ O ₃ 15 to 30%, Li ₂ O + Na ₂ O + K ₂ O 0 to 3% _, MgO + CaO + SrO + BaO 0 to It is preferred to prepare the raw batch to give a glass containing 8%.

Further, in the production method of the present invention, it is preferable that the glass surface is further coated with a solution containing a photocatalyst component and then heat-treated to support photocatalyst particles on the glass surface.

By adopting the above configuration, the photocatalyst particles can be easily supported on the glass surface.

Further, in the manufacturing method of the present invention, it is preferable to apply a solution containing a photocatalyst component after acid-treating the glass surface.

By adopting the above structure, the surface of the glass serving as the base material becomes porous and the specific surface area can be increased, so that a large amount of photocatalyst particles can be supported.

Further, in the production method of the present invention, it is preferable to use a solution in which titanium oxide particles are dispersed as the solution containing the photocatalyst component.

By adopting the above configuration, the titanium oxide particles capable of quickly decomposing organic matters such as dirt and bacteria can be easily applied to the glass surface.

The reason why the content of each component in the glass of the present invention is limited as described above will be described below. In addition, the following % display points out the mass % unless there is particular notice.

The content of SiO ₂ is preferably 50-70%, 53-70%, 55-70%, 58-70%, 60-70%, 62-69%, especially 62-67%. If the _SiO2 content is too low, the density tends to increase. On the other hand, if the content of SiO ₂ is too high, the high-temperature viscosity increases, the meltability decreases, and defects such as devitrified crystals (cristobalite) tend to occur in the glass.

Al ₂ O ₃ is an optional component, but if its content is too small, the scratch resistance, crack resistance, and heat resistance tend to deteriorate. In addition, the transmittance tends to decrease due to phase separation. Therefore, the preferable lower limit of Al ₂ O ₃ is 0% or more, 1% or more, 2% or more, 3% or more, 4% or more, 5% or more, 6% or more, 7% or more, 8% or more, especially 9 % or more. On the other hand, Al ₂ O ₃ has the function of increasing the Young's modulus, but if the content is too large, the Young's modulus becomes too high and the impact strength tends to decrease. Moreover, when making it into film-like glass, it becomes difficult to make a curvature radius small. Furthermore, if the content of Al ₂ O ₃ is too high, the liquidus temperature becomes high and the devitrification resistance tends to decrease. Therefore, the preferred upper limit range of Al ₂ O ₃ is 20% or less, 19% or less, 18% or less, 17% or less, 15% or less, 13% or less, 12% or less, particularly 11% or less.

B ₂ O ₃ is a component that enhances scratch resistance and crack resistance, and is a component that lowers Young's modulus. It is also a component that lowers the density. It is also a component that reduces dielectric loss and vibration loss. Furthermore, it is a component that facilitates the induction of phase separation. If the glass is phase-separated, it becomes easier to modify the glass surface into a porous state by acid treatment, and it becomes possible to support photocatalyst particles and obtain a high degree of photocatalytic activity. The content of B ₂ O ₃ is preferably 15-30%. If the content of B ₂ O ₃ is too small, the scratch resistance and crack resistance tend to decrease, and the Young's modulus tends to increase, resulting in a decrease in impact resistance. Moreover, when making it into film-like glass, it becomes difficult to make a curvature radius small. Furthermore, the action as a flux becomes insufficient, the high-temperature viscosity increases, and the foam quality tends to deteriorate. Furthermore, it becomes difficult to achieve low density. Therefore, the preferred lower limit range of B ₂ O ₃ is 15% or more, 18% or more, 20% or more, 20% or more, 22% or more, 24% or more, especially 25% or more. On the other hand, if the content of B ₂ O ₃ is too large, the heat resistance and chemical durability tend to deteriorate, and the transmittance tends to decrease due to phase separation. Therefore, the preferable upper limit range of B ₂ O ₃ is 30% or less, 28% or less, and 27% or less.

B ₂ O ₃ —Al ₂ O ₃ is more than 0%, 1% or more, 2% or more, 3% or more, 4% or more, 5% or more, 6% or more, 7% or more, 8% or more, 9% or more , in particular greater than or equal to 10%. The larger this value, the easier it is for the Young's modulus to decrease, making it easier to increase the drop impact strength. Moreover, when it is made into film-like glass, it becomes easy to make curvature radius small. “B ₂ O ₃ —Al ₂ O ₃ ” is obtained by subtracting the content of Al ₂ O ₃ from the content of B ₂ O ₃ .

Alkali metal oxide is a component that enhances meltability and moldability. Impact resistance is lowered, and it becomes difficult to match the coefficient of thermal expansion of surrounding materials. Alkali metal oxides reduce photocatalytic activity when photocatalyst particles are supported on the surface. Therefore, the content of Li ₂ O+Na ₂ O+K ₂ O is preferably 0-3%, 0-2%, 0-1%, 0-0.5%, 0-0.2%, 0-0.1 %, especially from 0 to less than 0.1%. The respective contents of Li ₂ O, Na ₂ O and K ₂ O are preferably 0-3%, 0-2%, 0-1%, 0-0.5%, 0-0.2%, 0 ~0.1%, especially between 0 and less than 0.1%. In addition, when the content of the alkali metal oxide is small, an alkali barrier film such as a SiO ₂ film becomes unnecessary.

Alkaline earth metal oxide is a component that lowers the liquidus temperature to make it difficult for crystal foreign matter to occur in the glass, and is a component that enhances meltability and formability. The content of MgO+CaO+SrO+BaO is preferably 0-12%, 0-10%, 0-8%, 0-7%, 1-7%, 2-7%, 3-9%, especially 3-6% . If the content of MgO+CaO+SrO+BaO is too small, the function as a flux cannot be sufficiently exhibited, and in addition to the deterioration of the meltability, the resistance to devitrification tends to deteriorate. On the other hand, if the content of MgO + CaO + SrO + BaO is too large, the density increases, making it difficult to reduce the weight of the glass, and in addition, the coefficient of thermal expansion becomes unreasonably high, and the thermal shock resistance tends to decrease. Further, the phase separation of the glass deteriorates. Furthermore, the Young's modulus increases, and it becomes difficult to reduce the radius of curvature in the case of film-like glass.

If the mass ratio (MgO+CaO+SrO+BaO)/Al ₂ O ₃ is too small, the devitrification resistance is lowered, making it difficult to form a glass sheet by the overflow downdraw method. On the other hand, if the mass ratio (MgO+CaO+SrO+BaO)/Al ₂ O ₃ is too large, the density and thermal expansion coefficient may unduly increase. Therefore, the mass ratio (MgO+CaO+SrO+BaO)/Al ₂ O ₃ is preferably 0.1-1.2, 0.2-1.2, 0.3-1.2, 0.4-1.1, especially 0 0.5 to 1.0. Note that "(MgO+CaO+SrO+ _BaO )/ _Al2O3 " refers to a value obtained by dividing the content of MgO+CaO+SrO+BaO _by the content of _Al2O3 .

The mass ratio (SrO+BaO)/B ₂ O ₃ is preferably 0.1 or less, 0.05 or less, 0.03 or less, particularly 0.02 or less. By doing so, it becomes easier to improve scratch resistance and crack resistance. "SrO+BaO" is the total amount of SrO and BaO. Also, "(SrO+BaO) _{/ B2O3} " indicates a value _obtained by dividing the content of SrO+BaO by the content of _B2O3 .

Also, the mass ratio B ₂ O ₃ /(SrO+BaO) is preferably 10 or more, 20 or more, 30 or more, 40 or more, particularly 50 or more. By doing so, it becomes easier to improve scratch resistance and crack resistance. In addition, " _B2O3 /(SrO ₊ BaO)" refers to the value obtained by dividing the content of SrO+BaO by the content of _{B2O3 .}

B ₂ O ₃ −(MgO+CaO+SrO+BaO) is preferably 5% or more, 6% or more, 7% or more, 8% or more, 9% or more, 10% or more, 11% or more, especially 12% or more. By doing so, the density is easily lowered, so that the weight of the device can be easily reduced. Also, Young's modulus becomes small.

MgO is a component that lowers high-temperature viscosity and enhances meltability without lowering the strain point, and is the component most effective in lowering density among alkaline earth metal oxides. Furthermore, it is a component that enhances crack resistance. It is also a component that facilitates the induction of phase separation. If the glass is phase-separated, it becomes easier to modify the glass surface into a porous state by acid treatment, and it becomes possible to support photocatalyst particles and obtain a high degree of photocatalytic activity. The content of MgO is preferably 0-12%, 0-10%, 0-8%, 0.1-6%, 0.5-3%, especially 1-2%. However, if the content of MgO is too high, the liquidus temperature rises and the devitrification resistance tends to decrease. Moreover, the glass tends to undergo phase separation, and the transparency tends to decrease.

CaO is a component that lowers the high-temperature viscosity without lowering the strain point to remarkably enhance the meltability, and is also a component that has a large effect of enhancing the devitrification resistance in the glass composition system of the present invention. Therefore, the preferable lower limit range of CaO is 0% or more, 0.1% or more, 1% or more, 2% or more, 3% or more, particularly 4% or more. On the other hand, if the content of CaO is too high, the coefficient of thermal expansion and density will unduly increase, or the balance of components in the glass composition will be impaired, and the resistance to devitrification will rather deteriorate. Therefore, the preferable upper limit range of CaO is 12% or less, 10% or less, 8% or less, 7% or less, 6% or less, and particularly 5% or less.

SrO is a component that lowers high-temperature viscosity and improves meltability without lowering the strain point. Therefore, the content of SrO is preferably 0-3%, 0-2%, 0-1.5%, 0-1%, 0-0.5%, especially 0-0.1%.

BaO is a component that lowers high-temperature viscosity and improves meltability without lowering the strain point. Therefore, the content of BaO is preferably 0-3%, 0-2%, 0-1.5%, 0-1%, 0-0.5%, especially 0-0.1%.

The mass ratio (SrO+BaO)/(MgO+CaO) is preferably 1 or less, 0.8 or less, 0.5 or less, especially 0.3 or less. If the mass ratio (SrO+BaO)/(MgO+CaO) is too large, the density of the glass will be too high.

In addition to the above components, the following components may be introduced into the glass composition.

ZnO is a component that enhances the meltability, but when contained in a large amount in the glass composition, the glass tends to devitrify and the density tends to increase. The content of ZnO is therefore preferably 0-5%, 0-3%, 0-0.5%, 0-0.3%, especially 0-0.1%.

_ZrO2 is a component that increases Young's modulus. The content of ZrO ₂ is preferably 0-5%, 0-3%, 0-0.5%, 0-0.2%, especially 0-0.02%. If the content of ZrO ₂ is too high, the liquidus temperature rises and devitrification crystals of zircon tend to precipitate.

TiO ₂ is a component that lowers high-temperature viscosity and enhances meltability, and is also a component that suppresses solarization. . Thus, the content of TiO ₂ is preferably 0-5%, 0-3%, 0-1%, 0-0.1%, especially 0-0.02%.

P ₂ O ₅ is a component that enhances devitrification resistance, but if it is contained in a large amount in the glass composition, the glass tends to undergo phase separation and become milky, and there is a possibility that the water resistance may be significantly lowered. The content of P ₂ O ₅ is therefore preferably 0-5%, 0-1%, 0-0.5%, especially 0-0.1%.

SnO ₂ is a component that has a good clarification action in a high temperature range and also a component that lowers the high temperature viscosity. The SnO ₂ content is preferably 0-1%, 0.01-0.5%, 0.05-0.3%, especially 0.1-0.3%. When the SnO ₂ content is too high, devitrified crystals of SnO ₂ tend to precipitate in the glass.

As described above, _the glass of the present _invention preferably contains SnO ₂ as a fining agent. etc.) may be added up to 1%.

As ₂ O ₃ , Sb ₂ O ₃ , F, and Cl also act effectively as refining agents, and the glass of the present invention does not exclude the inclusion of these components, but from an environmental point of view, these components are Each content is preferably less than 0.1%, particularly less than 0.05%.

The glass of the present invention preferably has the following properties.

The density is preferably 2.40 g/cm ³ or less, 2.35 g/cm ³ or less, particularly 2.30 g/cm ³ or less. If the density is too high, it becomes difficult to reduce the weight of the glass.

The coefficient of thermal expansion in the temperature range from 30 to 380°C is preferably from 25 to 40 x 10 ^-7 /°C, from 30 to 38 x 10 ^-7 /°C, especially from 32 to 36 x 10 ^-7 /°C. If the coefficient of thermal expansion is too low, it will be difficult to match the coefficient of thermal expansion with that of various peripheral materials, and the glass sheet will tend to warp. On the other hand, if the coefficient of thermal expansion is too high, the thermal shock resistance tends to decrease.

The strain point is preferably 610° C. or lower, 600° C. or lower, 590° C. or lower, 580° C. or lower, particularly 570° C. or lower. If the viscosity of the glass, particularly the strain point, is low, when an object that has fallen from a high altitude collides with the glass, the deformation of the glass facilitates the relaxation of the impact stress and the impact of the drop.

The temperature at 10 ^2.5 dPa·s is preferably 1650°C or less, 1620°C or less, 1600°C or less, especially 1580°C or less. The bubble quality affects not only the glass yield but also the touch sensor yield. Therefore, it is important to lower the high-temperature viscosity and improve the foam quality. Here, "temperature at 10 ^2.5 dPa·s" is a value measured by the platinum ball pull-up method.

Young's modulus is preferably 66 GPa or less, 65 GPa or less, 63 GPa or less, 61 GPa or less, particularly 60 GPa or less. Reducing the Young's modulus can reduce the stress generated per constant amount of deformation. Also, when an object that has fallen from a high altitude collides with the glass, the glass is likely to be elastically deformed, so that the impact of the drop can be easily mitigated. As a result, it is suitable for applications in which the amount of deformation of the glass is limited to a small range, particularly for cover glass. In the case of forming a glass film, the lower the Young's modulus, the smaller the radius of curvature of the film.

The liquidus temperature is preferably 1180° C. or lower, 1150° C. or lower, 1130° C. or lower, 1110° C. or lower, 1090° C. or lower, particularly 1070° C. or lower. The liquidus viscosity is preferably 10 ^5.0 dPa·s or more, 10 ^5.2 dPa·s or more, 10 ^5.3 dPa·s or more, 10 ^5.5 dPa·s or more, particularly 10 ^5.7 dPa·s or more. s or more. In this way, devitrification crystals are less likely to occur during molding, so that the glass sheet can be easily molded by an overflow down-draw method or the like, and the surface quality of the glass sheet can be easily improved.

The scratch resistance is preferably 5N or higher, 7N or higher, 10N or higher, 12N or higher, 15N or higher. If the scratch resistance is low, it becomes difficult for scratches accompanied by cracks to enter the glass. Here, "scratch resistance" means that when the glass surface is scratched with a Knoop indenter at a speed of 0.4 mm / s, a crack with a width of more than twice the scratch is scratched in a direction perpendicular to the scratching direction. Refers to a load that occurs over 15% of the total length. The scratch test is performed using a Bruker tribology tester UMT-2 in a constant temperature and humidity chamber maintained at a humidity of 30% and a temperature of 25%.

The crack resistance is preferably 200 gf or more, 500 gf or more, 700 gf or more, 900 gf or more, 1200 gf or more, 1500 gf or more, 2000 gf or more, 2500 gf or more, 3000 gf or more, particularly 35000 gf or more. If the crack resistance is low, the glass will be easily scratched. Here, "crack resistance" refers to a load at which the crack generation rate is 50%. Moreover, the "crack incidence rate" refers to a value measured as follows. First, in a constant temperature and humidity chamber maintained at a humidity of 30% and a temperature of 25°C, a Vickers indenter set to a predetermined load is driven into the glass surface (optical polished surface) for 15 seconds, and after 15 seconds, the indentations are generated from the four corners. Count the number of cracks (up to 4 per indentation). After indenting the indenter 50 times in this manner and obtaining the total number of cracks, the total number of cracks/200×100(%) is used.

The dielectric loss tangent at a frequency of 1 MHz is preferably 0.01 or less, 0.05 or less, particularly 0.001 or less.

The internal friction is preferably 0.01 or less, 0.002 or less, 0.001 or less, especially 0.0008 or less.

The glass of the present invention is prepared by putting a glass batch prepared to have a predetermined glass composition into a continuous glass melting furnace, heating and melting the glass batch, refining the resulting molten glass, and then supplying it to a molding apparatus. After that, it can be produced by molding into a flat plate shape or the like.

The glass of the present invention is preferably formed by the overflow downdraw method. In this way, an unpolished glass plate with good surface quality can be obtained. In the case of the overflow down-draw method, the surface to be the surface of the glass sheet does not come into contact with the gutter-shaped refractory and is molded in the state of a free surface, so that the surface quality of the glass sheet can be improved. Since the glass of the present invention has excellent devitrification resistance and viscosity characteristics suitable for molding, it can be efficiently molded into a glass sheet by the overflow down-draw method.

The glass of the present invention can employ various molding methods other than the overflow downdraw method. For example, molding methods such as a slot-down method, a float method, and a roll-out method can be adopted.

The glass of the present invention preferably has a flat plate shape, that is, is a glass plate, and has a plate thickness of 0.6 mm or less, 0.5 mm or less, or 0.4 mm or less, particularly preferably 0.05 to 0.3 mm. If it is flat plate shape, it will be easy to apply to a cover glass. Further, the smaller the plate thickness, the easier it is to reduce the weight of the glass plate, and the easier it is to reduce the weight of the device.

Moreover, the glass of the present invention is preferably in the form of a film. In this case, the plate thickness is preferably 200 μm or less, 100 μm or less, 50 μm or less, particularly 30 μm or less.

The glass of the present invention preferably has various functional films on its surface. As a functional film, for example, a transparent conductive film for imparting conductivity, an antireflection film for reducing reflectance, and an antiglare function are imparted to improve visibility and improve writing comfort with a touch pen or the like. An anti-glare film for preventing adhesion of fingerprints and an antifouling film for imparting water repellency and oil repellency are preferable. The transparent conductive film functions as an electrode for the touch sensor, and is preferably formed on the surface to be the display device side, for example. As the transparent conductive film, for example, tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), or the like is used. In particular, ITO is preferable because of its low electric resistance. ITO can be formed, for example, by a sputtering method. Moreover, FTO and ATO can be formed by a CVD (Chemical Vapor Deposition) method. An antireflection coating is formed on the surface to be the viewer side. Moreover, when there is a gap between the touch panel and the cover glass, it is preferable to form an antireflection film on the surface that should be the back side of the cover glass (the side opposite to the display device side). The antireflection film is preferably a dielectric multilayer film in which, for example, low refractive index layers with a relatively low refractive index and high refractive index layers with a relatively high refractive index are alternately laminated. The antireflection film can be formed by, for example, a sputtering method, a CVD method, or the like. When used as a cover glass, the anti-glare film is formed on the surface to be the viewer side. The antiglare film preferably has an uneven structure. The uneven structure may be an island-shaped structure that partially covers the surface of the glass. Moreover, it is preferable that the concave-convex structure does not have regularity. Thereby, the anti-glare function can be enhanced. The anti-glare film can be formed, for example, by applying a translucent material such as SiO ₂ by a spray method and drying it. When used as a cover glass, the antifouling film is formed on the surface to be the viewer side. The antifouling film preferably contains a fluoropolymer containing silicon in the main chain. As the fluorine-containing polymer, a polymer having --O--Si--O-- units in the main chain and water-repellent functional groups containing fluorine in the side chains is preferable. A fluoropolymer can be synthesized, for example, by dehydration condensation of silanol. When forming an antireflection film and an antifouling film, it is preferable to form an antifouling film on the antireflection film. Furthermore, when forming an anti-glare film, it is preferable to first form an anti-glare film and then form an antireflection film and/or an antifouling film thereon.

The glass or cover glass of the present invention preferably has photocatalyst particles supported on its surface. Particles made of various materials can be used as the photocatalyst particles. For example, titanium oxide particles, tungsten oxide particles, and the like can be used. Anatase-type titanium oxide particles are particularly preferred. The reason why anatase-type titanium oxide is preferable is that it has higher reactivity as a photocatalyst than rutile-type or brookite-type titanium oxide. The average particle size of the photocatalyst particles is preferably 1 nm or more, 2 nm or more, particularly 3 nm or more, and is preferably 200 nm, 100 nm or less, 50 nm or less, 30 nm or less, 20 nm or less, particularly 10 nm or less.

In addition to the ultraviolet-light-responsive photocatalysts described above, visible-light-responsive photocatalysts such as nitrogen-doped titanium oxide particles, copper oxide-doped titanium oxide particles, and copper oxide-doped tungsten oxide particles may also be used. If this type of photocatalyst is used, the effect of the photocatalyst can be obtained even in an indoor environment. Moreover, when used in an outdoor environment, there is an advantage that more light energy can be used than the ultraviolet light responsive type.

In order to support a large amount of photocatalyst particles on the surface, it is desirable that the glass surface be porous. As a method of making the surface porous, a method of acid-treating the glass surface can be employed. That is, the glass composition according to the present invention has a property of being easily phase-separated, and in many cases, the surface is phase-separated. Therefore, when the surface is treated with an acid, the phase containing a large amount of boric acid and having a low acid resistance is eluted, and the phase containing a large amount of silicon and having a high acid resistance remains on the surface. As a result, the glass surface becomes porous and the specific surface area is significantly increased. Since the inside of the glass is difficult to undergo phase separation, only the surface of the glass becomes porous even after the acid treatment. The thickness (depth) of the porous surface (porous layer) is preferably 10 μm or less. If the thickness of the porous surface is too thin, the effect of increasing the specific surface area is reduced. If the thickness of the surface is too thick, organic substances and the like will be deposited inside and the function as a photocatalyst will be lowered.

Next, a method for supporting photocatalyst particles on the above-described glass will be described.

First, a glass having the above composition is prepared. It is important that the glass to be prepared has phase separation. The size of the phase-separated particles contained in the glass is preferably 1 nm or more, 2 nm or more, 3 nm or more, 5 nm or more, particularly 10 nm or more, and preferably 100 nm or less, 80 nm or less, particularly 60 nm or less. Such glasses can be made using the overflow downdraw method. The characteristics such as the composition and characteristics of the glass are as described above, and the description is omitted here.

As a pretreatment, it is preferable to acid-treat the surface of the glass. By acid-treating the surface in advance, the surface of the glass can be modified to be porous and the specific surface area can be increased. As a method of acid treatment, for example, a method of immersing the glass in an acid solution can be adopted. Alternatively, the acid solution may be sprayed onto the glass. Acids that can be used include, for example, hydrochloric acid, nitric acid, and sulfuric acid.

Next, the surface of the glass is coated with a solution containing photocatalyst particles. The application method is not limited. For example, a method of dispersing photocatalyst particles and immersing glass in a solution can be employed. Alternatively, a solution containing photocatalyst particles may be sprayed onto the glass surface.

The glass is then heat treated. The heat treatment can fix the photocatalyst particles on the glass surface. The heating temperature is preferably 250° C. or higher, 410° C. or higher, particularly 420° C. or higher. The higher the heating temperature, the more strongly the photocatalyst particles can be fixed to the glass surface. If the heating temperature is too high, the glass may be softened to clog the pores and reduce the surface area. Therefore, the heating temperature is preferably 650° C. or lower.

Thus, a glass having a photocatalyst carried on its surface can be obtained.

Preferred embodiments of the glass of the present invention are illustrated below.
(1) Glass composition, in mass %, SiO ₂ 55-70%, Al 2 O ₃ 3-15%, B ₂ O ₃ 18-30%, Li ₂ O + Na ₂ O + K ₂ O 0-1% _, MgO + CaO + SrO + BaO 0 Glass containing ~7%.
(2) The glass composition, in mass %, is SiO ₂ 55-70%, Al ₂ O ₃ 3-12%, B ₂ O ₃ 20-30%, Li ₂ O + Na ₂ O + K ₂ O 0-0.5%, Glass containing 0 to 6% of MgO+CaO+SrO+BaO, having a density of 2.28 g/cm ³ or less, a strain point of 610° C. or less, and a Young's modulus of 66 GPa or less.
(3) Glass composition, in mass %, SiO ₂ 58-70%, Al 2 O ₃ 7-20%, B ₂ O ₃ 18-30%, Li ₂ O + Na ₂ O + K ₂ O 0-1%, _MgO + CaO + SrO + BaO 0 A glass containing ~6% and having a Young's modulus of 63 GPa or less.
(4) Glass having a density of 2.40 g/cm ³ or less, a thermal expansion coefficient of 36×10 ⁻⁷ /° C. or less in a temperature range of 30 to 380° C., a strain point of 610° C. or less, and a Young's modulus of 63 GPa or less. .
(5) It has a density of 2.30 g/cm ³ or less, a thermal expansion coefficient of 25 to 36×10 ^-7 /°C in a temperature range of 30 to 380°C, a strain point of 610°C or less, and a Young's modulus of 63 GPa or less. glass.
(6) It has a density of 2.30 g/cm ³ or less, a thermal expansion coefficient of 25 to 40×10 ^-7 /°C in a temperature range of 30 to 380°C, a strain point of 610°C or less, and a Young's modulus of 65 GPa or less. glass.

The present invention will be described in detail below based on examples. It should be noted that the following examples are merely illustrative. The present invention is by no means limited to the following examples.

Tables 1-6 show examples of the invention (Sample Nos. 1-42). In addition, [not yet] in the table indicates that the measurement has not been performed.

Sample no. 1-42 were produced. First, a glass raw material prepared so as to have the glass composition shown in the table was placed in a platinum crucible, melted at 1600° C. for 24 hours, poured onto a carbon plate, and formed into a flat plate. Next, density ρ, coefficient of thermal expansion α, strain point Ps, annealing point Ta, softening point Ts, temperature at 10 ⁴ dPa·s, temperature at 10 ³ dPa·s, 10 ^2. The temperature at ⁵ dPa·s, Young's modulus E, liquidus temperature TL, liquidus viscosity logηTL, scratch resistance and crack resistance were evaluated. Although SnO ₂ was used as the clarifier in this example, clarifiers other than SnO ₂ may be used. Further, if the melting conditions and the batch are adjusted so that bubbles can be easily removed, the clarifier may not be used.

The density ρ is a value measured by the well-known Archimedes method.

The coefficient of thermal expansion α is a value measured with a dilatometer and is an average value in the temperature range of 30 to 380°C.

The strain point Ps, annealing point Ta and softening point Ts are values measured according to the methods of ASTM C336 and C338.

The temperature at 10 ^4.0 dPa·s, the temperature at 10 ^3.0 dPa·s, and the temperature at 10 ^2.5 dPa·s are values measured by the platinum ball pull-up method.

Young's modulus E is a value measured by a resonance method. The higher the Young's modulus, the higher the specific Young's modulus (Young's modulus/density).

The liquidus temperature TL passes through a standard sieve of 30 mesh (500 μm),
μm) is placed in a platinum boat, held in a temperature gradient furnace for 24 hours, and the temperature at which crystals precipitate is measured.

The liquidus viscosity logηTL is a value obtained by measuring the viscosity of the glass at the liquidus temperature TL by the platinum ball pull-up method.

Scratch resistance is measured by scratching the glass surface with a Knoop indenter at a speed of 0.4 mm / s. A load generated over a length of 15% or more of the total length was measured, and the case where the load was 10 N or more was evaluated as "O", and the case where the load was less than 10 N was evaluated as "X". The scratch test was performed using a Bruker tribology tester UMT-2 in a constant temperature and humidity chamber maintained at a humidity of 30% and a temperature of 25%.

Crack resistance was evaluated as "○" when the load at which the crack generation rate was 50% was 1000 gf or more, and as "X" when it was less than 1000 gf. The crack generation rate was measured as follows. First, in a constant temperature and humidity chamber maintained at a humidity of 30% and a temperature of 25°C, a Vickers indenter set to a predetermined load is driven into the glass surface (optical polished surface) for 15 seconds, and after 15 seconds, the indentations are generated from the four corners. Count the number of cracks (up to 4 per indentation). After indenting the indenter 50 times in this way and determining the total number of cracks, it was determined by the formula: total number of cracks/200×100(%).

The dielectric loss tangent at a frequency of 1 MHz was measured at 1 MHz and 25° C. by a known parallel plate capacitor method.

Internal friction was measured using the known half width method.

Sample No. listed in Table 1. After melting the materials of 4 and 5 in a test melting furnace to obtain molten glass, a glass plate having a thickness of 0.3 mm was formed by an overflow down-draw method. As a result, the warpage of the glass plate was 0.075% or less, the waviness (WCA) was 0.15 μm or less (cutoff fh: 0.8 mm, fl: 8 mm), and the surface roughness (Ry) was 20 Å or less (cutoff λc : 9 μm). At the time of molding, the surface of the glass plate can be controlled by appropriately adjusting the speed of the pulling roller, the speed of the cooling roller, the temperature distribution of the heating device, the temperature of the molten glass, the flow rate of the molten glass, the plate drawing speed, the rotation speed of the stirring stirrer, etc. Adjusted the quality. "Warp" is a value measured by placing a glass plate on an optical surface plate and using a clearance gauge described in JIS B-7524. "Waviness" is a value obtained by measuring WCA (filtered centerline waviness) described in JIS B-0610 using a stylus-type surface profile measuring device. Measurement Method of Surface Waviness of Glass Substrate". "Average surface roughness (Ry)" is a value measured by a method based on SEMI D7-94 "Method for measuring surface roughness of FPD glass substrate".

No. 1 created in Example 2. A glass sample was prepared by processing the glass of No. 5 into a size of 100 mm x 100 mm x 0.3 mm. This glass sample was immersed in 80° C.-5 wt % HCl for 10 minutes to modify the surface into a porous state. Subsequently, the acid-treated glass sample was immersed in an ethanol aqueous solution for 10 minutes for washing.

Next, the glass sample was immersed for 5 minutes in a solution in which 2 wt % of titanium oxide (anatase) particles having an average particle size of 5 nm were dispersed in a 2-propanol solution to adhere the titanium particles to the surface of the glass sample.

After that, the glass sample was placed in an annealer maintained at 500° C., heat-treated for 2 hours, and taken out to obtain a glass sample having titanium oxide particles supported on its surface. By irradiating the sample thus obtained with ultraviolet rays, fingerprints and organic matter can be decomposed by the photocatalytic function of the titanium oxide particles.

Sample No. described in Table 3. After melting the material No. 19 in a test melting furnace to obtain molten glass, a glass film having a thickness of 100 μm was formed by an overflow down-draw method. This film-like glass could be wound into a roll having a radius of curvature of 60 mm.

The glass of the present invention is suitable as a cover glass, but it can also be used as a substrate for flat displays such as liquid crystal displays and organic EL displays, as a substrate for image sensors such as CSP, CCD and CIS, and as a substrate for touch sensors. preferred. In addition, when photocatalyst particles are supported on the surface, the antifouling function can be permanently maintained, so it can be used as architectural glass, for example, in addition to the above applications.

Claims (10)

The plate thickness is 0.6 mm or less, and the glass composition is SiO ₂ 50 to 70%, Al ₂ O ₃ 0 to 11%, B ₂ O ₃ 20 to 30%, and Li ₂ O + Na ₂ O + K ₂ O in mass%. 0-1%, MgO+CaO+SrO+BaO 2-10%, CaO 0-5.5%, SrO 0-3%, BaO 0-3%, ZnO 0-5%, and B ₂ O ₃ -Al ₂ O ₃ A glass plate having a content of 9% by mass or more. 2. The glass plate according to claim 1, wherein the glass composition contains 7 to 11% by mass of Al ₂ O ₃ . 3. The glass plate according to claim 1, wherein the glass composition contains 3 to 8% by mass of MgO+CaO+SrO+BaO. 4. The glass plate according to claim 1, wherein B ₂ O ₃ −(MgO+CaO+SrO+BaO) is 12 mass % or more. 5. The glass plate according to claim 1, wherein (SrO+BaO)/(MgO+CaO) is 1 or less in mass ratio. It has a density of 2.40 g/cm ³ or less, a thermal expansion coefficient of 25 to 40×10 ⁻⁷ /° C. in a temperature range of 30 to 380° C., a strain point of 610° C. or less, and a Young's modulus of 66 GPa or less. The glass plate according to any one of claims 1 to 5. 7. The glass plate according to any one of claims 1 to 6, which has a liquidus viscosity of 10 ^5.0 dPa·s or more. 8. The glass plate according to any one of claims 1 to 7, which is formed by an overflow down-draw method. 9. The glass plate according to any one of claims 1 to 8, which is used as a cover glass. 10. The glass plate according to any one of claims 1 to 9, which is not subjected to ion exchange treatment.