JP2015086080A - Physically-strengthened glass, and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide high-strength, white and physically-strengthened glass.SOLUTION: The high-strength, white and physically-strengthened glass is: white glass of which the whole light reflectance is 10% or higher when the wavelength of the light is set within 400-800 nm; silicate-based white glass which has a temperature difference (T-T) of 150°C or higher in a thermal expansion curve thereof, in the case that the temperature as Tis defined when the instantaneous thermal expansion coefficient thereof becomes zero and the temperature as Tis defined when the instantaneous thermal expansion coefficient thereof becomes 1.2 times that of the average thermal expansion coefficient thereof at 50°C to 350°C, and which contains ZrOand PO; or binodal phase-separated glass having 40-3,000 nm spherical particle diameter as the average diameter.

Description

  The present invention relates to a white glass for physical strengthening having high reflectance and high strength, a method for producing white physical strengthened glass, and white physical strengthened glass.

  Conventionally, white glass has been obtained by forming a white coating film on the front surface, back surface, or both surfaces. In particular, in order to obtain a high-strength white glass, it has been obtained by forming a white coating film on a chemically strengthened or physically strengthened transparent glass.

  In the tempered glass in which the white coating film is formed on the transparent glass, there is a problem that the cost is increased because the extra step is included. In addition, there is a problem that the reflectance or the design property of the portion where the coating film is bald is lowered when scratches are attached.

  Therefore, an object of the present invention is to provide a method for producing physically strengthened glass and a physically strengthened glass that are white and have a surface subjected to compressive stress by rapidly cooling the glass from near the softening point temperature.

1. Measured by heating a white glass having a total light reflectance of 10% or more in the entire wavelength range from 400 nm to 800 nm at a rate of 5 ° C./min to a temperature at which it is softened by the method described in JIS R 3103-3: 2001. in the thermal expansion curve, rapid thermal expansion coefficient and temperature T _s becomes zero, the instantaneous thermal expansion coefficient and a temperature of the T _1.2 as the 1.2 times the average thermal expansion coefficient of 350 ° C. from 50 ° C. Sometimes, white glass for physical strengthening is provided in which Τ _s −Τ _1.2 is 150 ° C. or higher.
2. 2. The white glass for physical strengthening as described in 1 above, wherein the white glass is a phase separation glass.
3. 3. The phase-separated glass according to 2 above, wherein a white glass for physical strengthening in a binodal state in which one separated phase has an independent spherical shape and is dispersed in a matrix of the other separated phase.
4). The white glass for physical strengthening as described in 3 above, wherein the average diameter of the separated phase is 40 to 3000 nm.
5. Provided is a method for producing a physically tempered glass including a step of rapidly cooling a white glass having a total light reflectance of 10% or more in a wavelength range of 400 nm to 800 nm.
6). The manufacturing method of the physical strengthened glass including the process of quenching the white glass for physical strengthening in any one of said 1-4 is provided.
7). A white physical tempered glass obtained by the method for producing a physical tempered glass according to 5 or 6 is provided.
8). 8. The white physical tempered glass as described in 7 above, which has a compressive stress on the surface.
9. The white physical tempered glass according to 7 or 8 above, which has a compressive stress layer on the surface.
10. The white physical tempered glass according to any one of 7 to 9 above, wherein the 10.3 point bending strength is 120 MPa or more.
11. The white physical tempered glass according to any one of 7 to 10 above, wherein the glass has a thickness of 1 to 10 mm.

  According to the present invention, a high-strength white physical strengthening glass can be obtained.

  In addition, according to the production method of the present invention, white physical tempered glass having a compressive stress layer in the surface layer and enhanced resistance to scratches can be produced by quenching white glass to physically strengthen the glass. it can.

  According to the method for producing physically strengthened glass of the present invention, white glass having sufficient strength can be obtained.

  When a coating film is formed on a transparent glass and whitened, if the coating film is chipped and peeled off, the transparent glass is exposed, scratches are conspicuous, and the reflectance decreases. On the other hand, according to the present invention, by physically strengthening the white glass, scratches and chips on the glass surface are less likely to occur, and even if scratches or chips occur, the new surface is white glass, The scratches are not noticeable and the reflection performance can be maintained.

A white glass used in the present invention, the temperature at which the rapid thermal expansion coefficient and temperature T _s becomes zero, the instantaneous thermal expansion coefficient becomes 1.2 times the average thermal expansion coefficient of 350 ° C. from 50 ° C. the when the T _1.2, by using the physical reinforcing white glass T _{s-tau 1.2} is 0.99 ° C. or higher, it is easy to physically strengthened, high-strength white physically strengthened glass is obtained.

  Furthermore, according to the present invention, it is possible to use white tempered glass having excellent design and high strength as an interior material or exterior material of a building, an in-vehicle interior material, a casing of an electronic device or a home appliance. .

  Hereinafter, preferred embodiments of the white physical tempered glass of the present invention will be described.

  Examples of the white glass in the present invention include phase separation glass and crystallized glass.

  Moreover, it is a manufacturing method of physically strengthened glass including the process of rapidly cooling white glass.

  The glass production method is not particularly limited. For example, a suitable amount of various raw materials are prepared, heated to about 1400 to 1700 ° C. and melted, and then homogenized by defoaming, stirring, etc., and a well-known float method, downdraw method, press It is formed into a plate or the like by casting or a roll-out method, or cast to form a block.

  A phase-separated glass or crystallized glass can be obtained by heat-treating the glass formed into a plate shape or a block shape.

  In the present invention, after the glass is melted, homogenized, molded, and slowly cooled, the glass is phase-separated by heat treatment for melting, homogenizing, molding, annealing, or shape processing without any special heat treatment. Phase glass or crystallized crystallized glass is also included. In this case, the step of whitening the glass is included in the steps of melting, molding and the like.

As the raw material used in the present invention, oxides, composite oxides, carbonates, hydroxides, and hydrates thereof can be used as appropriate. Examples of the oxide include cinnabar (silicon dioxide), magnesium oxide, aluminum oxide, lanthanum oxide, zirconia (ZrO ₂ ), titanium oxide, and boron oxide.

Examples of the composite oxide include dolomite [CaMg (CO ₃ ) ₂ ], zircon (ZrSiO ₄ ), borax [Na ₂ B ₄ O ₅ (OH) ₄ .8H ₂ O], sodium metaphosphate (NaPO ₃ ), and the like. Is mentioned.

Examples of the carbonate include sodium carbonate, soda ash and potassium carbonate, and barium carbonate. Examples of the hydroxide include magnesium hydroxide and aluminum hydroxide. Examples of the hydrate include boric acid (H ₃ BO ₃ ) and phosphoric acid (H ₃ PO ₄ ).

Examples of these raw materials include natural raw materials, purified raw materials, and particle size adjusting raw materials. Examples of the material for adjusting the oxidation / reduction state (redox) of glass include materials containing organic or inorganic carbon such as coke or sucrose, raw materials containing hydrogen such as ammonium chloride, and SnO _2. Examples thereof include raw materials that generate oxygen when dissolved.

  As for the particle size of each raw material, each raw material having an appropriate particle size can be used as appropriate. By adjusting the dissolution rate of each raw material according to the gas generated during melting, the amount of moisture in the glass, the redox state, and the raw material particle size, quality improvement such as residual foam, foreign matter, agglomerates, substrate homogeneity, etc., fine adjustment of color It can be used as appropriate.

As a clarifying agent in melting the glass, SO ₃ , chloride or fluoride, SnO ₂ , CeO ₂ , Sb ₂ O ₃ , As ₂ O _{3 and the} like may be appropriately contained.

  The white glass of the present invention is preferably a phase separation glass or a crystallized glass.

  The phase separation glass can be obtained by phase separation of the glass. The phase separation means that a single-phase glass is divided into two or more glass phases. Examples of the method for phase separation of glass include a method for heat-treating glass.

  As a condition for heat treatment for phase separation of glass, a temperature 50 to 400 ° C. higher than the glass transition point is typically preferable. A temperature higher by 100 ° C to 300 ° C is more preferable. The time for heat-treating the glass is preferably 0.5 to 64 hours, and more preferably 1 to 32 hours. From the viewpoint of mass productivity, it is preferably 24 hours or less, and more preferably within 12 hours. In the phase separation step of phase separation of the glass before the molding step of molding the glass, it is preferable to hold the glass at a temperature not higher than the phase separation start temperature and not lower than 1100 ° C.

  Whether or not the glass is phase-separated can be determined by SEM (scanning electron microscope). When the glass is phase-separated, it can be observed that it is divided into two or more phases when observed with an SEM.

  Examples of the state of the phase-separated glass include a binodal state and a spinodal state. The binodal state is a phase separation by a nucleation-growth mechanism and is generally spherical. The spinodal state is a state in which the phase separation is intertwined with each other in three dimensions with some degree of regularity.

  A preferable composition range of the phase strengthening glass for physical strengthening will be described. In the present specification, the content of the glass component will be described using a molar percentage display unless otherwise specified.

The SiO ₂ content is preferably 45 to 75%. SiO ₂ is a basic component that forms a network structure of white glass. By setting it to 45% or more, excellent mechanical strength and weather resistance are exhibited. More preferably, it is 50% or more, more preferably 55% or more, and particularly preferably 57% or more. On the other hand, it can prevent that the melting temperature of glass becomes high by setting it as 75% or less. More preferably, it is 70% or less, More preferably, it is 65% or less.

It is preferable to contain 0 to 10% of Al ₂ O ₃ . In addition, for example, the content of Al ₂ O ₃ is preferably 0 to 15%. Al ₂ O ₃ may or may not be contained, but when it is contained, the content is preferably 10% or less. Is the meaning. Al ₂ O ₃ has an effect of improving the stability of the glass or improving the strength, and when it is contained, it is preferably contained at 1% or more. By containing 1% or more, a sufficient effect can be obtained. More preferably, it is 2% or more, and further preferably 3% or more. By making it 10% or less, it is possible to prevent the acid resistance from being lowered. More preferably, it is 8% or less, More preferably, it is 7% or less.

The total amount of alkali components (Li ₂ O, Na ₂ O, K ₂ O) is preferably 5 to 25%. The alkali component is a component that improves the solubility of the glass, and can increase the expansion coefficient and increase the strength of the glass by physical strengthening. When it contains, it is preferable that it is 5% or more. By containing 5% or more, a sufficient content effect can be obtained. Preferably it is 8% or more, More preferably, it is 10% or more. Moreover, it can prevent that the weather resistance of glass falls by setting it as 25% or less. More preferably, it is 20% or less, More preferably, it is 15% or less.

It preferably contains Na ₂ O. By containing Na ₂ O, the expansion coefficient can be increased and the strength of the glass can be increased by physical strengthening. The Na ₂ O content in the glass is preferably 5% or more. If it is less than 5%, it becomes difficult to form a large surface compressive stress layer by physical strengthening. Preferably it is 7% or more, More preferably, it is 9% or more. When Na ₂ O exceeds 17%, the weather resistance decreases. Preferably it is 15% or less, More preferably, it is 13% or less.

  It is preferable to contain alkaline earth components (MgO, CaO, SrO, BaO) in a total amount of 5 to 25%. The alkaline earth component is a component that improves the solubility of the glass, and when it is contained, it is 5% or more. By containing 5% or more, a sufficient content effect can be obtained. Preferably it is 7% or more, More preferably, it is 9% or more, More preferably, it is 10% or more. Moreover, it can prevent that the weather resistance of glass falls by setting it as 25% or less. More preferably, it is 20% or less, More preferably, it is 16% or less.

  BaO is not essential, but it may be preferably contained up to 15% in order to whiten and obtain a high reflectance. If it exceeds 15%, devitrification tends to occur.

  Further, in order to obtain white color and high reflectance, the content of CaO + BaO is preferably 2% or more and 16% or less, more preferably 12% or less, and further preferably 10% or less. preferable.

The content of B ₂ O ₃ is preferably 0 to 7%. When it contains, it is preferable to contain 0.5% or more. By containing 0.5% or more, the viscosity of the glass can be lowered. Moreover, it can suppress that the crystal | crystallization which is not intended in glass melt | dissolves and a shaping | molding process. Preferably it is 1% or more, More preferably, it is 2% or more. Moreover, volatilization in a melt | dissolution process can be reduced by setting it as 7% or less. Preferably it is 5% or less, More preferably, it is 4% or less.

The content of P ₂ O ₅ is preferably 0.5 to 8%. P ₂ O ₅ is effective to promote phase separation, it is preferable to contain 0.5% or more. More preferably, it is 1% or more, More preferably, it is 2% or more. By making it 8% or less, volatilization can be reduced. Preferably it is 6% or less, More preferably, it is 5% or less.

ZrO ₂ is not essential, but may contain up to 3% because of the effect of improving the weather resistance and solubility of the glass. If it exceeds 3%, the glass may be easily damaged. Preferably it is 2% or less, More preferably, it is 1% or less.

  In order to increase the surface compressive stress in the physically strengthened layer having a surface compressive stress by quenching the phase-separated glass, the phase-separated glass subjected to the rapid cooling process is preferably in a binodal state. In particular, it is preferable that a dispersed phase of other components rich in alkali is present in the silica-rich matrix.

  However, it does not actively exclude spinodal ones.

  Crystallized glass can be obtained by heat-treating homogeneous glass. Typically, crystal nuclei are generated at a temperature 50 ° C. to 400 ° C. higher than the glass transition point, and crystals are grown at a temperature 100 ° C. to 500 ° C. higher than the glass transition point. The generation and growth of nuclei may be separate processes or may be performed simultaneously.

Examples of the crystallized glass include β-quartz solid solution, β-spodumene solid solution, lithium disilicate, enstatite, and crystallized glass having nepheline as the main crystal, and milky white glass having CaF ₂ and NaF as the main crystal. .

  Co, Mn, Fe, Ni, Cu, Cr, V, Bi, Er, Τm, Nd, Sm, Sn, Ce, Pr, Eu, Ag or Au are added to the white glass of the present invention as coloring components. Also good. When added, it is 5% or less in terms of mol% based on oxide. Fe containing 0.5% or less as an impurity in the raw material may be contained as uncolored glass.

  In the wavelength range of 400 nm to 800 nm of the white glass for physical strengthening, the total light reflectance is preferably 10% or more. When the total light reflectance is 10% or more, it is possible to give design properties or to improve the illumination effect by reflecting light. More preferably, it is 20% or more, more preferably 30% or more, particularly preferably 50% or more, and most preferably 70% or more.

  In order to whiten, in the phase-separated glass, the average size of one phase or the average particle size of the dispersed phase in the phase-separated glass is preferably 40 to 3000 nm, more preferably 60 to 2000 nm, 100 More preferably, it is -1000 nm.

  In order to whiten the crystallized glass, the average particle diameter of the crystal is preferably 40 to 3000 nm, more preferably 60 to 2000 nm, and still more preferably 100 to 1000 nm.

  The average particle diameter can be measured by SEM observation. Here, the average size of one phase in the phase separation state is the average of the widths of the phases intertwined with each other in the spinodal state, and when one phase is spherical in the binodal state When the diameter of one phase is elliptical, it is the average value of the major axis and the minor axis. The average particle size of the dispersed phase is the average size in the binodal state. In the crystallized glass, the diameter is in the case of a sphere, and the average value of the major axis and the minor axis in the case where one phase is an elliptical sphere or a polygon.

  For whitening, it is preferable that the difference in refractive index between the dispersed phase particles in the phase-separated glass and the surrounding matrix is large. In crystallized glass, it is preferable that the crystal and the glass matrix have a large refractive index.

  Further, the volume ratio of the dispersed phase particles in the phase-separated glass or the crystal ratio in the crystal glass is preferably 5% or more, more preferably 10% or more, and more preferably 20% or more. Further preferred. Here, the volume ratio of the particles of the dispersed phase can be estimated from the ratio of the dispersed particles by calculating the ratio of the dispersed particles distributed on the glass surface from the SEM observation photograph.

  Phase separation may be accompanied by crystallization. Crystallization may contribute to whitening. Therefore, the composite phase of phase separation + crystal phase is not particularly excluded. However, those which are crystallized to such an extent that the strength decreases, the start temperature for rapid cooling increases, and the rapid cooling performance (compressive stress, stress layer thickness) decreases are not preferable. Preferably, the volume of crystal phase particles / (volume of dispersed phase particles + volume of crystal particles) in the phase-separated glass is 50% or less. Preferably it is 20% or less. More preferably, it is 10% or less. More preferably, it is 1% or less. More preferably, 0% is preferable.

Physical reinforcing white glass, the thermal expansion curve, a temperature at which the rapid thermal expansion coefficient is zero and T _s, the temperature at which the rapid thermal expansion coefficient is 1.2 times the average thermal expansion coefficient of 350 ° C. from 50 ° C. when a T _1.2, I am preferred T _{s-tau 1.2} is 0.99 ° C. or higher. When Τ _s −Τ _1.2 is 150 ° C. or higher, a strong compressive stress can be applied when physically strengthened by rapid cooling. Preferably it is 160 degreeC or more, More preferably, it is 170 degreeC or more. Further, Τ _s −Τ _1.2 is preferably 400 ° C. or lower. By being 400 ° C. or lower, it is possible to prevent self-destruction due to distortion due to stress surface distribution. Self-destruction is a phenomenon in which glass naturally breaks.

In the production method of the present invention, the white glass is quenched and physically strengthened to have high strength. Physical strengthening is a method of increasing the strength of glass by forming a compressive stress layer on the glass surface by quenching from a temperature near the softening point. The viscosity of the glass and the temperature near the softening point refers to a temperature of ^{10 7 ~10 11 d · Pa ·} s. By setting it to 10 ⁷ d · Pa · s or more, physical strengthening can be performed while suppressing deformation of the glass. Preferably it is ^107.5 d * Pa * s or more, More preferably, it is ^108.0 d * Pa * s or more. By setting it to 10 ¹¹ d · Pa · s or less, strong compressive stress due to physical strengthening can be applied. It is preferably 10 ¹⁰ d · Pa · s or less, more preferably 10 ^9.5 d · Pa · s or less.

  The physical strengthening method is not particularly limited as long as it can be rapidly cooled, and examples thereof include a method of blowing air.

  The white physical tempered glass (hereinafter also referred to as the physical tempered glass of the present invention) obtained by the production method of the present invention, the phase-separated glass of the present invention that has been quenched and the white glass having a compression stress layer on the surface of the present invention, The surface is provided with a compressive stress layer by rapid cooling. The surface compressive stress is preferably 20 MPa or more, more preferably 40 MPa or more, and further preferably 60 MPa or more. The surface compressive stress can be measured by utilizing birefringence as long as it has optical transparency.

  The depth of the surface compressive stress layer generated by physical strengthening is preferably 100 μm or more. By setting the thickness to 100 μm, it is possible to suppress breakage of the glass due to scratches attached during use. Preferably it is 150 micrometers or more, More preferably, it is 200 micrometers or more.

  The three-point bending strength is preferably 120 MPa or more. By being 120 MPa or more, the glass can be prevented from being damaged due to deformation or the like when the object collides with the glass. Preferably it is 140 MPa or more, More preferably, it is 160 MPa or more, Most preferably, it is 180 MPa or more. The three-point bending strength is 500 MPa or less. By setting the pressure to 500 MPa or less, it is possible to prevent the glass from being explosively broken when it breaks. Preferably it is 400 MPa or less, More preferably, it is 350 MPa or less.

  The thickness of the glass is preferably 1 to 10 mm. By setting the thickness to 1 mm or more, a strong compressive stress and / or a deep surface compressive stress layer can be applied. Preferably it is 2 mm or more, More preferably, it is 3 mm or more. Moreover, it can prevent that weight becomes too heavy by setting it as 10 mm or less. Preferably it is 8 mm or less, More preferably, it is 6 mm or less, More preferably, it is 5 mm or less.

  It is also possible to apply surface compressive stress due to a difference in thermal expansion by thinly coating the surface with a glass having a smaller thermal expansion coefficient than the white glass and the physically strengthened glass of the present invention. If clear glass is used, the effect of improving the aesthetics due to the reflection of the front and back surfaces of the coated glass can be obtained.

  The white glass and physical tempered glass of the present invention having high strength and aesthetics can be used for portable electronic devices, information terminals, home appliances, and furniture. Moreover, it can also be used for interior materials and exterior materials of structures such as vehicle interior materials and exterior materials, building materials, tunnels, and tunnels. In addition, it is not limited to these for illustration.

  The white glass and the physically tempered glass of the present invention may be formed not only in a flat plate shape but also in a concave shape or a convex shape. In this case, you may press-form in the state which reheated and melt | dissolved the glass shape | molded in the flat plate or the block. Moreover, you may shape | mold into a desired shape by what is called a direct press method which flows out and press-molds a molten glass directly on a press die. Moreover, you may shape | mold at the time of the heating for physical reinforcement | strengthening. Moreover, you may carry out cutting etc. after shaping | molding.

  The white glass and the physically tempered glass of the present invention may be laminated with a resin or the like in order to prevent them from being broken and scattered when a vehicle or the like collides, or a laminated glass using a resin or the like as an intermediate layer between glass and glass. It is good. In this case, the glass on the back surface may be white glass, other colored glass, or transparent glass.

  In order to make the white glass of the present invention easy to handle or to prevent strength reduction due to cracks or the like, the edge may be polished.

  The size of the white glass of the present invention preferably has a short side or short diameter of 5 mm or more, more preferably 10 mm or more, still more preferably 30 mm or more, and particularly preferably 50 mm or more. By setting it to 5 mm or more, sufficient strength can be imparted by rapid cooling. The length of the long side or major axis is preferably 3000 mm or less, more preferably 2000 mm or less, and still more preferably 1000 mm or less. It can handle easily by setting it as 3000 mm or less.

[Measuring method]
(A) Total light reflectance As for the total light reflectance of glass, the total light reflectance of wavelength 400-800 nm was acquired using the glass of 1 mm thickness or 3 mm thickness by which the upper and lower surfaces were mirror-finished.
(B) Bending point (Τ _s ), linear thermal expansion coefficient (α), and _{ｎ n}
Based on JIS R 3103-3: 2001, a cylindrical sample having a diameter of 5 mm and a length of 20 mm was prepared, and the temperature rising rate was 5 ° C./min using a thermal dilatometer (manufactured by Bruker AXS, ΤMA4000SA). measured under a load of 10g, it was asked to Τ _s. Further, JIS R 1618: Based on 2002, measured T _s of the measurement as well as thermal dilatometer (Bruker AXS, Inc., TauMA4000SA) at a heating rate of 5 ° C. / min using a, 50 to 350 ° C. The average linear expansion coefficient α and the instantaneous thermal expansion coefficient every 5 seconds were determined. Further, the same measurement data, rapid thermal expansion coefficient of every 5 seconds was determined temperature T _n at which becomes n times the α mean coefficient of thermal expansion of 350 ° C. from 50 ° C..
(C) Three-point bending strength The three-point bending strength was measured with a model 8561 dynamic test apparatus manufactured by Instron. The sample shape was 50 × 10 × 5 mm, and the measurement was performed at room temperature under conditions of a crosshead speed of 0.5 mm / min and a support span of 30 mm. After physically strengthening the glass plate whose both surfaces were mirror-polished with cerium oxide, the bending strength (unit: MPa) was measured.
(D) Viscosity measurement The viscosity of glass is 10 ¹³ to 10 ⁹ dPa by a penetration method using a range viscosity measuring device (WRVM-313) manufactured by Opto Corporation using a sample having a diameter of 10 mm and a thickness of 5 mm. The viscosity of s was measured, and the viscosity of 10 ⁹ to 10 ⁵ dPa · s was measured by the parallel plate method.

[Examples 1 to 6]
(1) Glass melting The raw materials were melted at the melting temperature shown in Table 1 for 2 hours so as to have the compositions shown in Tables 1 and 2, cast into molds and allowed to cool. Although it was a transparent melt at the melting temperature, phase separation occurred while it was poured into a mold and allowed to cool, and became white. Then, after hold | maintaining for 1 hour at the slow cooling temperature shown in Table 1, it cooled gradually to room temperature at 1 degree-C / min, and obtained white plate-shaped glass by grinding | polishing. A mass of sodium sulfate corresponding to 0.1 to 0.4% of the mass was added to the composition shown in Table 1. SEM confirmed that the glass was phase separated.

(2) Total light reflectivity measurement The total light reflectivity was measured using the sample of 1 mm thickness or 3 mm thickness by which the upper and lower surfaces of the glass after slow cooling were mirror-finished. Table 2 shows the total light reflectance at wavelengths of 400 nm, 600 nm, and 800 nm and the minimum value of the total light reflectance at 400 to 800 nm. In Example 2, the glass after being rapidly cooled from a temperature at which the viscosity of the glass becomes 10 ⁹ dPa · s was processed to a thickness of 1 mm, and the total light reflectance was measured. Table 2 shows the total light reflectance at wavelengths of 400 nm, 600 nm, and 800 nm. Table 2 shows the minimum value of the total light reflectance at wavelengths of 400 to 800 nm.
(3) Measurement of Τ _s , α, Τ _n The glass after slow cooling was processed into a cylindrical sample having a diameter of 5 mm and a length of 20 mm, and Τ _s , α, and Τ _n were measured. The results are shown in Tables 3 and 4.
(4) Viscosity measurement The glass after slow cooling was processed into φ10 mm and a thickness of 5 mm, and the viscosity was measured.
(5) Rapid cooling treatment For the sample of Example 2, the sample shape was 50 × 10 × 5 mm, held in the electric furnace for 5 minutes at the rapid cooling start temperature shown in Tables 3 and 4, and then taken out of the electric furnace and into the atmosphere It was physically strengthened by allowing it to cool in the air and quenching it. Tables 3 and 4 also show the viscosity of the sample at the quenching start temperature.
(6) Three-point bending measurement Three-point bending strength was measured for the sample before the rapid cooling treatment and after the rapid cooling treatment of (5). Three measurements were performed for each condition, and an average value was calculated. The results are shown in Tables 3 and 4.

[Example 7]
(1) Glass melting After the raw materials were melted at the melting temperature shown in Table 1 for 2 hours so as to have the composition shown in Table 2, the temperature in the furnace was lowered to 1360 ° C. at a rate of 25 ° C./min. After maintaining the temperature for 30 minutes, it was poured into a mold and allowed to cool to form. When removed at 1360 ° C., the melt was already white. After maintaining at the slow cooling temperature shown in Table 1 for 1 hour, it was gradually cooled to room temperature at 1 ° C./min and polished to obtain a white plate glass. A mass of sodium sulfate corresponding to 0.1 to 0.4% of the mass was added to the composition shown in Table 2. SEM confirmed that the glass was phase separated.
(2) Total light reflectance measurement It carried out similarly to Examples 1-6. Moreover, the glass after carrying out the rapid cooling process from the temperature from which the viscosity of glass becomes 10 < ⁹ > dPa * s was processed into 1 mm thickness, and the total light reflectance was measured. The results are shown in Table 4.
(3) Measurement of Τ _s , α, Τ _{n The} measurement was performed in the same manner as in Examples 1-6. The results are shown in Table 4.
(4) Viscosity measurement It carried out similarly to Examples 1-6.
(5) Rapid cooling process It carried out similarly to Examples 1-6. The results are shown in Table 4.
(6) Three-point bending measurement It carried out similarly to Examples 1-6. The results are shown in Table 4.

[Example 8]
(1) Glass melting and crystallization treatment The raw materials were melted at the melting temperature shown in Table 3 for 2 hours so as to have the composition shown in Table 1, then poured into a mold and allowed to cool to form. The melt was transparent and was transparent after molding. After maintaining at the slow cooling temperature shown in Table 1 for 1 hour, it was gradually cooled to room temperature at 1 ° C./min. Then, for crystallization treatment, the temperature was raised to 950 ° C. at a rate of 10 ° C./min, held at 950 ° C. for 1 hour, and then lowered at a rate of 5 ° C./min. Crystallization occurred and white glass was formed. By polishing, a white plate-like glass was obtained. A mass of sodium sulfate corresponding to 0.1% of the mass was added to the composition shown in Table 3. X-ray diffraction measurements confirmed that enstatite and rutile crystals were precipitated.
(2) Total light reflectance measurement It carried out similarly to Examples 1-6 except using the glass after crystallization. Moreover, the glass after carrying out the rapid cooling process from the temperature from which the viscosity of glass becomes 10 < ⁹ > dPa * s was processed into 1 mm thickness, and the total light reflectance was measured. The results are shown in Table 4.
(3) Measurement of Τ _s , α, Τ _{n The} measurement was performed in the same manner as in Examples 1 to 6 except that glass after crystallization was used. The results are shown in Table 4.
(4) Viscosity measurement It carried out like Examples 1-6 except using the glass after crystallization.
(5) Quenching treatment This was carried out in the same manner as in Examples 1 to 6 except that the glass after crystallization was used. The results are shown in Table 4.
(6) Three-point bending measurement This was performed in the same manner as in Examples 1 to 6 except that the glass after crystallization was used. The results are shown in Table 4.

[Comparative Example 1]
(1) Glass melting The raw material was melted at the melting temperature shown in Table 1 for 2 hours so as to have the composition shown in Table 2, and then poured into a mold and allowed to cool to form. The melt was transparent and was transparent after molding. After maintaining at the slow cooling temperature shown in Table 1 for 1 hour, the glass was gradually cooled to room temperature at 1 ° C./min and polished to obtain a transparent plate glass. A mass of sodium sulfate corresponding to 0.1% of the mass was added to the composition shown in Table 2.
(2) Total light reflectance measurement It carried out similarly to Examples 1-6. The results are shown in Table 4.
(3) Measurement of Τ _s , α, Τ _{n The} measurement was performed in the same manner as in Examples 1-6. The results are shown in Table 4.
(4) Viscosity measurement It carried out similarly to Examples 1-6.
(5) Rapid cooling process It carried out similarly to Examples 1-6. The results are shown in Table 4.
(6) Three-point bending measurement It carried out similarly to Examples 1-6. The results are shown in Table 4.

[Comparative Examples 2 and 3]
(1) Glass melting and phase separation treatment The raw materials were melted at the melting temperature shown in Table 1 for 2 hours so as to have the composition shown in Table 2, then poured into a mold and allowed to cool to form. The melt was transparent and was transparent after molding. After maintaining at the slow cooling temperature shown in Table 1 for 1 hour, it was gradually cooled to room temperature at 1 ° C./min. Thereafter, for phase separation treatment, the temperature was raised to 900 ° C. at a rate of 10 ° C./min, held at 900 ° C. for 4 hours, and then lowered at a rate of 5 ° C./min. Phase separation occurred and white glass was formed. By polishing, a white plate-like glass was obtained. A mass of sodium sulfate corresponding to 0.1% of the mass was added to the composition shown in Table 2. SEM confirmed that the glass was phase separated.
(2) Performed in the same manner as in Examples 1 to 6 except that the glass after the phase separation treatment for total light reflectance measurement was used. The results are shown in Table 4.
(3) It was carried out in the same manner as in Examples 1 to 6 except that the glass after the phase separation treatment with Τ _s , α and _{ｎ n} was used. The results are shown in Table 4.
(4) Performed in the same manner as in Examples 1 to 6 except that the glass after the rapid cooling and phase separation treatment was used. The results are shown in Table 4.

Examples 1-8 are excellent in shielding properties because the total light reflectance is as high as 10% or more, and it was found that Examples 2, 7, and 8 having a large value of Τ _s -Τ _n have high bending strength. . On the other hand, in Comparative Example 1, since the total light reflectance is low, there is no shielding property, and since the value of _{ｓ s} −Τ _n is small, the bending strength is lower than those in Examples 1-8. It was. In Comparative Examples 2 and 3, since the value of _{ｓ s} −Τ _n is small, the bending strength is considered to be lower than those in Examples 1-8.
In Examples 2, 7, and 8, the total light reflectance before and after the quenching treatment was hardly changed. Therefore, it was found that stable whiteness can be obtained even when the quenching treatment is performed.

Claims (11)

In white glass total light reflectance is 10% or more in the range of 800nm wavelength 400 nm, the temperature at which the rapid thermal expansion coefficient becomes zero in the thermal expansion curve and T _s, the instantaneous thermal expansion coefficient of 350 ° C. from 50 ° C. A white glass for physical strengthening in which Τ _{s- １．２ 1.2} is 150 ° C or higher when a temperature that is 1.2 times the average thermal expansion coefficient is Τ _1.2 . (The thermal expansion curve is measured by heating at a rate of 5 ° C./min up to the softening temperature by the method described in JIS R 3103-3: 2001.)   The white glass for physical strengthening according to claim 1, wherein the white glass is a phase separation glass.   The white glass for physical strengthening according to claim 2, which is a binodal phase-separated glass.   The white glass for physical strengthening according to claim 3, which is a phase-separated glass having a spherical particle diameter of 40 to 3000 nm in average diameter.   A method for producing physically tempered glass, comprising a step of rapidly cooling white glass having a total light reflectance of 10% or more in a wavelength range of 400 nm to 800 nm.   The manufacturing method of the physical strengthened glass including the process of rapidly cooling the white glass for physical strengthening in any one of Claims 1-4.   The white physical tempered glass obtained by the manufacturing method of the physical tempered glass of Claim 5 or 6.   The white physical tempered glass according to claim 7, wherein the surface has compressive stress.   The white physical tempered glass according to claim 7 or 8, which has a compressive stress layer on a surface thereof.   The white physical tempered glass according to claim 7, which has a three-point bending strength of 120 MPa or more.   The white physical tempered glass according to claim 7, wherein the glass has a thickness of 1 to 10 mm.