JP5950248B2 - Display device manufacturing method - Google Patents

Description

  The present invention relates to a tempered glass, and more particularly to a tempered glass suitable for a cover glass used for a display device such as a mobile phone, a digital camera, and a PDA (mobile terminal). The present invention also relates to a display device, and more particularly to a display device such as a mobile phone, a digital camera, and a PDA (mobile terminal).

  Display devices such as mobile phones, digital cameras, PDAs, touch panel displays, large televisions, etc., are becoming increasingly popular.

  Conventionally, in these applications, a resin plate made of acrylic or the like has been used as a protective member for protecting the display. However, since the Young's modulus is low, the resin plate is easily bent when the display surface of the display is pressed with a pen or a human finger. For this reason, the resin plate may come into contact with the internal display and display defects may occur. In addition, the resin plate has a problem that the surface is easily scratched and visibility is easily lowered. A method for solving these problems is to use a glass plate as a protective member. The glass plate for this application has (1) high mechanical strength, (2) low density and light weight, (3) low cost and a large amount of supply, (4) excellent foam quality, 5) It has a high light transmittance in the visible range, and (6) it has a high Young's modulus so that it is difficult to bend when the surface is pushed with a pen or a finger. In particular, when the requirement of (1) is not satisfied, tempered glass tempered by ion exchange treatment has been conventionally used since the use as a protective member is not sufficient (see Patent Documents 1 and 2 and Non-Patent Document 1). ).

  Conventionally, tempered glass has been produced by so-called “pre-strengthening cutting”, in which tempered glass is scribed and cut in advance after being scribed into a predetermined shape. After the replacement process, scribe cutting to a predetermined size, so-called “cutting after reinforcement” has been studied. When cutting after tempering, the production efficiency of tempered glass and various devices is dramatically improved.

JP 2006-83045 A JP 2011-88763 A

Tetsuro Izumiya et al., “New Glass and its Properties”, first edition, Management System Laboratory, Inc., August 20, 1984, p. 451-498

  When cutting after strengthening, the cut surface is a newly generated surface and is not subjected to strengthening processing. In this case, minute cracks (crack sources) are inevitably generated on the cut surface. For this reason, it was thought that the tempered glass cut after the tempering has lower mechanical strength, particularly the end face strength, than the tempered glass cut before the tempering.

  Until now, physical processing such as chamfering and fire polishing, and etching treatment have been performed on this cut surface to remove microcracks present on the cut surface (especially the edge region where the surface intersects the cut surface). The method of increasing the end face strength has been adopted.

  However, even if physical processing or etching treatment is performed on the cut surface, the desired end face strength cannot be obtained, and there is still room for improvement.

  The present invention has been made in view of the above circumstances, and a technical problem thereof is to devise a tempered glass having a high end face strength despite being scribe-cut after the tempering treatment.

  As a result of intensive studies, the inventor surprisingly can solve the above technical problem by not intentionally performing post-processing such as chamfering on the cut surface of the tempered glass cut after tempering. It is discovered and proposed as the present invention. That is, the tempered glass of the present invention is a tempered glass having a compressive stress layer on the surface thereof, which is scribed by cutting after the tempering treatment, and all or part of the cut surface is not physically processed or etched. Features.

  According to the inventor's investigation, when scribe cutting is performed after the strengthening treatment, a certain compressive stress is also generated on the cut surface due to the influence of the compressive stress layer on the surface. In particular, the smaller the thickness of the tempered glass, the greater the compressive stress generated on the cut surface. When physical processing or etching treatment is performed on the cut surface of such tempered glass, the compressive stress generated on the cut surface disappears, and the end surface strength of tempered glass is lower than when physical processing or etching processing is not performed. Decreases. Therefore, in the present invention, the end face strength of the tempered glass is improved by using the cut surface without any physical processing or etching treatment and using it as it is. In this case, the cut surface of the tempered glass is in a state in which the minute cracks are not removed, but the progress of the minute cracks is suppressed by the compressive stress generated on the cut surface.

  Moreover, since the tempered glass of the present invention is scribe-cut after the tempering process, and all or a part of the cut surface is not physically processed or etched, the manufacturing cost can be greatly reduced.

  Secondly, it is preferable that the tempered glass of the present invention is formed by forming a scribe line on the surface of the tempered glass and then dividing along the scribe line. If it does in this way, it will become difficult to advance the crack which is not intended at the time of cutting. To break the tempered glass along the scribe line, it is important that the tempered glass is not self-destructed during the formation of the scribe line. Self-destruction is a phenomenon in which tempered glass is spontaneously destroyed when it receives damage deeper than the stress depth due to the effects of compressive stress existing on the surface of tempered glass and tensile stress existing inside. If self-breaking of the tempered glass starts during the formation of the scribe line, it becomes difficult to perform desired cutting. For this reason, it is preferable to regulate the depth of the scribe line within 10 times, within 5 times, particularly within 3 times the stress depth. In forming the scribe line, it is preferable to use a diamond wheel tip or the like from the viewpoint of workability.

  Third, the tempered glass of the present invention preferably has a thickness of 1.0 mm or less. The smaller the thickness, the more easily the compressive stress is generated on the cut surface due to the influence of the compressive stress layer on the surface, and the mechanical strength of the cut surface is less likely to be lowered without physical processing or etching treatment on the cut surface. Become.

Fourth, in the tempered glass of the present invention, the tempered glass has a glass composition of mass%, SiO ₂ 40 to 71%, Al ₂ O ₃ 7 to 23%, Li ₂ O 0 to 1%, Na ₂ O. _7-20%, preferably contains K 2 O 0~15%. If it does in this way, it will become easy to make ion exchange performance and devitrification resistance compatible at a high level.

  Fifth, it is preferable that the tempered glass of the present invention has a compressive stress value of the compressive stress layer of 400 MPa or more and a stress depth of 15 μm or more. If it does in this way, it will become easy to ensure desired mechanical strength. Here, “compressive stress value of compressive stress layer” and “stress depth” are interference fringes observed when an evaluation sample is observed using a surface stress meter (for example, FSM-6000 manufactured by Orihara Seisakusho). The value calculated from the number of and the interval.

  Sixth, it is preferable that the tempered glass of the present invention has an unpolished surface. If it does in this way, while improving the productivity of tempered glass, it will become easy to raise the mechanical strength of the surface.

  Seventhly, it is preferable that the tempered glass of the present invention is formed by an overflow downdraw method or a float method. Forming by the overflow down draw method makes it easy to produce a glass plate that is unpolished and has a good surface quality, and makes it easy to produce a thin glass plate. As a result, it is easy to increase the mechanical strength of the surface of tempered glass. Become. Here, the “overflow down draw method” is a method in which molten glass overflows from both sides of a heat-resistant bowl-shaped structure, and the overflowed molten glass is stretched downward while joining at the lower end of the bowl-shaped structure. This is a method of forming a glass plate. Moreover, if it shape | molds by the float glass process, a large sized glass plate can be produced efficiently.

  Eighth, the display device of the present invention is a display device including a cover glass that protects the display unit, and the cover glass is the tempered glass described above.

  Ninthly, in the display device of the present invention, it is preferable that the surface of the tempered glass on the side where the scribe line is formed is the outside (for example, in the case of a touch panel display, the side pressed by a finger, a pen, or the like). The surface on the side where the scribe line is formed has more initial scratches than the surface on the side where the scribe line is not formed. For this reason, if the surface on the side where the scribe line is formed is on the outside, when the surface is pressed with a pen or a finger, tensile stress is hardly generated on the surface on which the scribe line is formed, resulting in strengthening It becomes easy to prevent breakage of glass and the like.

  Tenth, in the display device of the present invention, it is preferable that a transparent conductive film (for example, ITO) is formed on the surface of the tempered glass on which the scribe line is not formed. If it does in this way, it will become easy to arrange | position the surface of the tempered glass of the side in which the scribe line is formed outside. Moreover, it becomes easy to prevent the situation where the transparent conductive film or the like is contaminated by glass powder or the like when the scribe line is formed.

  Eleventhly, in the display device of the present invention, it is preferable that the tempered glass warps outwardly. In this way, when the surface is pressed with a pen or a finger, a compressive stress is generated on the outer surface of the tempered glass, and as a result, breakage of the tempered glass due to the outer surface state of the tempered glass is prevented. It becomes easy.

  12thly, it is preferable that the display device of this invention is further equipped with a housing | casing, and all or one part of this housing | casing is not contacting the cut surface of tempered glass.

  Thirteenthly, in the display device of the present invention, it is preferable that the tempered glass and the housing are fixed with resin.

  Fourteenth, in the display device of the present invention, it is preferable that the cut surface of the tempered glass is not exposed to the outside.

Sample No. shown in the column of Example. It is data which shows the result of the 1 and 2 four-point bending tests.

  The tempered glass of the present invention has a compressive stress layer on its surface. As a method for forming a compressive stress layer on the surface, there are a physical strengthening method and a chemical strengthening method. The tempered glass of the present invention is preferably made by a chemical tempering method.

  The chemical strengthening method is a method of introducing alkali ions having a large ion radius to the glass surface by ion exchange treatment at a temperature below the strain point of the glass. If the compressive stress layer is formed by the chemical strengthening method, even if the glass thickness is small, the compressive stress layer can be properly formed. The tempered glass does not break easily like the physical tempering method.

  The ion exchange solution, ion exchange temperature, and ion exchange time may be determined in consideration of the viscosity characteristics of the glass. In particular, when the Na component in the strengthening glass is ion exchanged with K ions in the potassium nitrate solution, a compressive stress layer can be efficiently formed on the glass surface.

  The tempered glass of the present invention is scribe-cut after the tempering treatment. When scribing the tempered glass, it is preferable that the depth of the scribe scratch is larger than the stress thickness and the internal tensile stress value is 40 MPa or less. Moreover, it is preferable to start scribing from the area | region 5 mm or more away from the edge of tempered glass, and it is preferable to complete | finish scribing in the area | region 5 mm or more away from the edge of tempered glass. If it does in this way, it will become difficult to generate the unintended crack at the time of scribing, and it will become easy to perform scribing cutting after reinforcement appropriately. Here, the internal tensile stress value is a value calculated by the following equation.

  Internal tensile stress value = (compressive stress value × stress depth) / (thickness−stress depth × 2)

  In the tempered glass of the present invention, all or part of the cut surface is not physically processed or etched. In the tempered glass of the present invention, it is preferable that the whole or part of the edge region where the surface and the cut surface intersect is not physically processed or etched. Here, the physical processing refers to chamfering processing (polishing processing), fire polishing, and the like. When physical processing or etching is not performed on the entire cut surface, the manufacturing cost of the tempered glass can be significantly reduced. In addition, about the corner | angular part of the surface direction of tempered glass, in order to raise mechanical strength, you may chamfer or R chamfer.

  In the tempered glass of the present invention, the thickness is preferably 1.0 mm or less, 0.8 mm or less, 0.7 mm or less, 0.6 mm or less, particularly 0.5 mm or less. In this way, compressive stress is likely to be generated on the cut surface due to the influence of the compressive stress layer on the surface, and the mechanical strength of the cut surface is unlikely to decrease even if physical processing or etching treatment is not performed on the cut surface. . On the other hand, if the thickness is too small, it becomes difficult to obtain a desired mechanical strength. Therefore, the thickness is preferably 0.1 mm or more.

Tempered glass of the present invention has a glass composition, in _{mass%, SiO 2 40~71%, Al} 2 O 3 7~23%, Li 2 O 0~1%, Na 2 O 7~20%, K 2 O It is preferable to contain 0 to 15%. The reason for limiting the content range of each component as described above will be described below. In addition, in description of the containing range of each component,% display points out the mass% unless there is particular notice.

SiO ₂ is a component that forms a network of glass. The content of SiO ₂ is preferably 40 to 71%, 40 to 70%, 40 to 63%, 45 to 63%, 50 to 59%, particularly 55 to 58.5%. When the content of SiO ₂ is too large, the meltability and moldability are lowered, the thermal expansion coefficient is too low, and it is difficult to match the peripheral material and the thermal expansion coefficient. On the other hand, when the content of SiO ₂ is too small, it becomes difficult to vitrify, the thermal expansion coefficient becomes high, and the thermal shock resistance tends to be lowered.

Al ₂ O ₃ is a component that enhances ion exchange performance. Al ₂ O ₃ also has the effect of increasing the strain point and Young's modulus. When the content of Al ₂ O ₃ is too large, devitrification crystal glass becomes easy to precipitate, it is difficult to forming by the overflow down-draw method. If the content of Al ₂ O ₃ is too large, the thermal expansion coefficient becomes too low, or become peripheral material and thermal expansion coefficient hardly consistent, becomes difficult to melt the higher the viscosity at high temperature. On the other hand, when the content of Al ₂ O ₃ is too small, a possibility arises which can not exhibit a sufficient ion exchange performance. From the above viewpoint, the preferable upper limit range of Al ₂ O ₃ is 23% or less, 21% or less, 20% or less, 19% or less, 18% or less, 17% or less, particularly 16.5% or less. The preferable lower limit range of ₂ O ₃ is 7% or more, 7.5% or more, 8.5% or more, 9% or more, 10% or more, 11% or more, particularly 12% or more.

Li ₂ O is an ion exchange component and a component that lowers the high-temperature viscosity and improves the meltability and moldability. Li ₂ O is a component that increases the Young's modulus. Furthermore, Li ₂ O has a high effect of increasing the compressive stress value among alkali metal oxides. However, when the content of Li 2 _O is too large, and decreases the liquidus viscosity, it tends glass devitrified. Further, when the content of Li 2 _O is too large, the thermal expansion coefficient becomes too high, or the thermal shock resistance decreases, the peripheral material and the coefficient of thermal expansion is hardly consistent. Furthermore, the low-temperature viscosity is too low, and stress relaxation is likely to occur, and the compressive stress value may be lowered. Therefore, the content of Li ₂ O is preferably 0 to 1%, 0 to 0.5%, and 0 to 0.1%, and is substantially not contained, that is, suppressed to less than 0.01%. desirable.

Na ₂ O is an ion exchange component and a component that lowers the high-temperature viscosity and improves the meltability and moldability. Na ₂ O is also a component that improves devitrification resistance. The content of Na ₂ O is preferably 7 to 20%, 10 to 20%, 10 to 19%, 12 to 19%, 12 to 17%, 13 to 17%, particularly 14 to 17%. When the content of Na 2 _O is too large, the thermal expansion coefficient becomes too high, or the thermal shock resistance decreases, the peripheral material and the coefficient of thermal expansion is hardly consistent. Further, when the content of Na 2 _O is too large, or the strain point excessively lowers, they lack the balance of the glass composition, rather devitrification resistance tends to decrease. On the other hand, if a small amount of Na 2 _O, lowered the melting property, become too coefficient of thermal expansion is low, the ion exchange performance tends to decrease.

K ₂ O has an effect of promoting ion exchange, and has a high effect of increasing the stress depth among alkali metal oxides. K ₂ O is a component that lowers the high-temperature viscosity and improves the meltability and moldability. Furthermore, K ₂ O is also a component that improves devitrification resistance. The content of K ₂ O is preferably 0 to 15%. When the content of K 2 _O is too large, the thermal expansion coefficient becomes high, or the thermal shock resistance is lowered, the peripheral material and the coefficient of thermal expansion is hardly consistent. Furthermore, there is a tendency that the strain point is excessively lowered, the balance of the glass composition is lacking, and the devitrification resistance is lowered. Therefore, the preferable upper limit range of K ₂ O is 12% or less, 10% or less, 8% or less, particularly 6% or less.

If the total amount of the alkali metal oxide R ₂ O (R is one or more selected from Li, Na, K) is too large, the glass tends to be devitrified, and the thermal expansion coefficient becomes too high. The thermal shock resistance is lowered, and the thermal expansion coefficient is difficult to match with the surrounding materials. Further, there is a case where the total content of alkali metal oxides R _{2 O} is too large, too lowered strain point, not obtain a high compression stress value. Furthermore, the viscosity in the vicinity of the liquidus temperature may decrease, and it may be difficult to ensure a high liquidus viscosity. Therefore, the total amount of R ₂ O is preferably 22% or less, 20% or less, and particularly 19% or less. On the other hand, if the total amount of R ₂ O is too small, the ion exchange performance and meltability may decrease. Therefore, the total amount of R ₂ O is preferably 8% or more, 10% or more, 13% or more, particularly 15% or more.

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

  For example, alkaline earth metal oxide R′O (R ′ is one or more selected from Mg, Ca, Sr, and Ba) is a component that can be added for various purposes. However, when the amount of the alkaline earth metal oxide R′O increases, the density and thermal expansion coefficient increase and the devitrification resistance decreases, and the ion exchange performance tends to decrease. Therefore, the total amount of the alkaline earth metal oxide R′O is preferably 0 to 9.9%, 0 to 8%, 0 to 6%, particularly 0 to 5%.

  MgO is a component that increases the meltability and moldability by lowering the viscosity at high temperature, and increases the strain point and Young's modulus. Among alkaline earth metal oxides, MgO has a high effect of improving ion exchange performance. However, when the content of MgO increases, the density and thermal expansion coefficient increase, and the glass tends to devitrify. The content of MgO is preferably 0 to 9%, in particular 1 to 8%.

  CaO is a component that lowers the high-temperature viscosity to increase meltability and moldability, and increases the strain point and Young's modulus. Among alkaline earth metal oxides, CaO is highly effective in increasing ion exchange performance. The content of CaO is preferably 0 to 6%. However, when the content of CaO is increased, the density and thermal expansion coefficient may be increased, the glass may be easily devitrified, and the ion exchange performance may be decreased. Therefore, the content of CaO is preferably 0 to 4%, 0 to 3%, 0 to 2%, 0 to 1%, particularly 0 to 0.1%.

  SrO and BaO are components that lower the high-temperature viscosity, improve the meltability and moldability, and increase the strain point and Young's modulus, and their contents are each preferably 0 to 3%. When the content of SrO or BaO increases, the ion exchange performance decreases, the density and thermal expansion coefficient increase, and the glass tends to devitrify. The content of SrO is preferably 2% or less, 1.5% or less, 1% or less, 0.5% or less, 0.2% or less, particularly 0.1% or less. Further, the content of BaO is preferably 2.5% or less, 2% or less, 1% or less, 0.8% or less, 0.5% or less, 0.2% or less, particularly 0.1% or less. .

ZrO ₂ has the effect of significantly increasing the ion exchange performance, increasing the Young's modulus and strain point, and reducing the high temperature viscosity. Furthermore, since it has the effect of increasing the viscosity in the vicinity of the liquid phase viscosity, the ion exchange performance and the liquid phase viscosity can be simultaneously increased by containing a predetermined amount. However, if the content of ZrO ₂ is too large, the devitrification resistance may be extremely lowered. Therefore, the content of ZrO ₂ is preferably 0 to 10%, 0.001 to 10%, 0.1 to 9%, 0.5 to 7%, 0.8 to 5%, 1 to 5%, 2 .5-5%.

B ₂ O ₃ has the effect of reducing the liquidus temperature, the high temperature viscosity, and the density, and also has the effect of increasing the ion exchange performance, particularly the compressive stress value. However, when the content of B ₂ O ₃ is too large, or scorch is generated on the surface by ion exchange treatment, or water resistance is lowered, the liquidus viscosity may be decreased. Further, when the content of B ₂ O ₃ is too large, stress depth tends to decrease. Therefore, the content of B ₂ O ₃ is preferably 0 to 6%, 0 to 3%, 0 to 1%, 0 to 0.5%, particularly 0 to 0.1%.

TiO ₂ has an effect of improving the ion exchange performance and an effect of reducing the high temperature viscosity. However, when the content of TiO ₂ is too large, or glass is colored, or reduced devitrification, density increases. In particular, when used as a cover glass for a display, when the content of TiO ₂ increases, the transmittance tends to change when the melting atmosphere or the raw material is changed. Therefore, in the process of bonding the tempered glass to the device using light such as an ultraviolet curable resin, the ultraviolet irradiation conditions are likely to fluctuate, making stable production difficult. Therefore, the content of TiO ₂ is preferably 10% or less, 8% or less, 6% or less, 5% or less, 4% or less, 2% or less, 0.7% or less, 0.5% or less, 0.1% % Or less, particularly 0.01% or less.

P ₂ O ₅ is a component that enhances ion exchange performance, and is particularly a component that has a high effect of increasing the stress thickness. However, when the content of P ₂ O ₅ is increased, the glass is phase-separated and the water resistance and devitrification resistance are liable to be lowered. Therefore, the content of P ₂ O ₅ is preferably 5% or less, 4% or less, 3% or less, and particularly 2% or less.

As a fining _{agent, As 2 O 3, Sb 2} O 3, CeO 2, F, SO 3, is selected from the group of Cl were one or two or more may be contained from 0.001 to 3%. However, As ₂ O ₃ and Sb ₂ O ₃ are preferably used as much as possible in consideration of the environment, and it is desirable to limit their contents to less than 0.1%, and further less than 0.01%. Further, CeO ₂ is a component that lowers the transmittance, so that the content is desirably limited to less than 0.1%, and more preferably less than 0.01%. Further, since F may cause a decrease in compressive stress value due to a decrease in low-temperature viscosity, the content is preferably limited to less than 0.1%, particularly less than 0.01%. Accordingly, preferred fining agents are SO ₃ and Cl, and one or both of SO ₃ and Cl is 0 to 3%, 0.001 to 1%, 0.01 to 0.5%, and even more preferably 0.00. It is preferable to add 05 to 0.4%.

Rare earth oxides such as Nb ₂ O ₅ and La ₂ O ₃ are components that increase the Young's modulus. However, the cost of the raw material itself is high, and if it is contained in a large amount, the devitrification resistance is lowered. Therefore, the content thereof is preferably 3% or less, 2% or less, 1% or less, 0.5% or less, particularly 0.1% or less.

Transition metal oxides such as CoO ₃ and NiO may strongly color the glass and reduce the transmittance of the tempered glass. In particular, when used for touch panel display applications, if the content of the transition metal oxide is large, the visibility of the touch panel display is impaired. Therefore, it is desirable to adjust the amount of the raw material or 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.

As described above, the tempered glass of the present invention has a compressive stress layer on the surface. The compressive stress value of the compressive stress layer is preferably 300 MPa or more, 400 MPa or more, 500 MPa or more, and particularly 600 MPa or more. The greater the compressive stress value, the higher the mechanical strength of the tempered glass. On the other hand, when the compressive stress value is too large, it becomes difficult to scribe-cut the tempered glass. Therefore, the compressive stress value of the compressive stress layer is preferably 1500 MPa or less, 1200 MPa or less, 1000 MPa or less, and particularly 900 MPa or less. If the content of Al ₂ O ₃ , TiO ₂ , ZrO ₂ , MgO, ZnO in the glass composition is increased or the content of SrO, BaO is decreased, the compressive stress value tends to increase. Further, if the ion exchange time is shortened or the temperature of the ion exchange solution is lowered, the compressive stress value tends to increase.

The stress depth is preferably 10 μm or more, 15 μm or more, 20 μm or more, particularly 25 μm or more. As the stress depth increases, even if the tempered glass is deeply scratched, the tempered glass becomes difficult to break and the variation in mechanical strength becomes smaller. On the other hand, when the stress depth is too large, it becomes difficult to scribe-cut the tempered glass. The stress depth is preferably 100 μm or less, less than 80 μm, 60 μm or less, particularly less than 50 μm. In addition, if the content of K ₂ O or P ₂ O _{5 in} the glass composition is increased or the content of SrO or BaO is decreased, the stress depth tends to increase. Moreover, if the ion exchange time is lengthened or the temperature of the ion exchange solution is increased, the stress depth tends to increase.

The tempered glass of the present invention, the density is 2.6 g / cm ³ or less, particularly preferably 2.55 g / cm ³ or less. The lower the density, the lighter the tempered glass. In addition, the content of SiO ₂ , B ₂ O ₃ , P ₂ O _{5 in} the glass composition is increased, or the content of alkali metal oxide, alkaline earth metal oxide, ZnO, ZrO ₂ , TiO ₂ is decreased. As a result, the density tends to decrease.

In the tempered glass of the present invention, the thermal expansion coefficient is preferably 80 × 10 ^{−7 to} 120 × 10 ⁻⁷ / ° C., 85 × 10 ^{−7 to} 110 × 10 ⁻⁷ / ° C., 90 × 10 ^{−7 to} 110 ×. 10 ⁻⁷ / ° C., particularly 90 × 10 ^{−7 to} 105 × 10 ⁻⁷ / ° C. If the thermal expansion coefficient is regulated within the above range, it becomes easy to match the thermal expansion coefficient of a member such as a metal or an organic adhesive, and it becomes easy to prevent peeling of a member such as a metal or an organic adhesive. Here, the “thermal expansion coefficient” refers to a value obtained by measuring an average thermal expansion coefficient in a temperature range of 30 to 380 ° C. using a dilatometer. If the content of alkali metal oxides and alkaline earth metal oxides in the glass composition is increased, the coefficient of thermal expansion tends to increase, and conversely the content of alkali metal oxides and alkaline earth metal oxides is reduced. If it decreases, the thermal expansion coefficient tends to decrease.

In the tempered glass of the present invention, the strain point is preferably 500 ° C. or higher, 520 ° C. or higher, 530 ° C. or higher, particularly 550 ° C. or higher. The higher the strain point, the better the heat resistance. When heat-treating tempered glass, the compressive stress layer is less likely to disappear. Furthermore, it becomes easy to form a high-quality film in patterning of a touch panel sensor or the like. If the content of alkaline earth metal oxide, Al ₂ O ₃ , ZrO ₂ , P ₂ O _{5 in} the glass composition is increased or the content of alkali metal oxide is reduced, the strain point becomes higher. easy.

In the tempered glass of the present invention, the temperature at 10 ^4.0 dPa · s is preferably 1280 ° C. or lower, 1230 ° C. or lower, 1200 ° C. or lower, 1180 ° C. or lower, particularly 1160 ° C. or lower. Here, “temperature at 10 ^4.0 dPa · s” refers to a value measured by a platinum ball pulling method. The lower the temperature at 10 ^4.0 dPa · s, the less the burden on the forming equipment, the longer the life of the forming equipment, and as a result, the manufacturing cost of tempered glass is likely to be reduced. If the content of alkali metal oxide, alkaline earth metal oxide, ZnO, B ₂ O ₃ , TiO ₂ is increased, or the content of SiO ₂ , Al ₂ O ₃ is decreased, 10 ^4.0 The temperature at dPa · s tends to decrease.

In the tempered glass of the present invention, the temperature at 10 ^2.5 dPa · s is preferably 1620 ° C. or lower, 1550 ° C. or lower, 1530 ° C. or lower, 1500 ° C. or lower, particularly 1450 ° C. or lower. Here, “temperature at 10 ^2.5 dPa · s” refers to a value measured by a platinum ball pulling method. The lower the temperature at 10 ^2.5 dPa · s, the lower the temperature melting becomes possible, and the burden on glass production equipment such as a melting kiln is reduced, and the bubble quality is easily improved. Therefore, the lower the temperature at 10 ^2.5 dPa · s, the easier it is to reduce the manufacturing cost of tempered glass. The temperature at 10 ^2.5 dPa · s corresponds to the melting temperature. Also, if the content of alkali metal oxide, alkaline earth metal oxide, ZnO, B ₂ O ₃ , TiO _{2 in} the glass composition is increased or the content of SiO ₂ , Al ₂ O ₃ is reduced, The temperature at 10 ^2.5 dPa · s tends to decrease.

In the tempered glass of the present invention, the liquidus temperature is preferably 1200 ° C. or lower, 1150 ° C. or lower, 1100 ° C. or lower, 1050 ° C. or lower, 1000 ° C. or lower, 950 ° C. or lower, 900 ° C. or lower, particularly 880 ° C. or lower. Here, the “liquid phase temperature” is obtained by passing the glass powder that passes through a standard sieve 30 mesh (a sieve opening of 500 μm) and remains in 50 mesh (a sieve opening of 300 μm) into a platinum boat and puts it in a temperature gradient furnace for 24 hours. It refers to the temperature at which crystals precipitate after being held. In addition, devitrification resistance and a moldability improve, so that liquidus temperature is low. Also, increase the content of Na ₂ O, K ₂ O, B ₂ O _{3 in} the glass composition or reduce the content of Al ₂ O ₃ , Li ₂ O, MgO, ZnO, TiO ₂ , ZrO _2. In this case, the liquidus temperature tends to decrease.

In the tempered glass of the present invention, the liquid phase viscosity is preferably 10 ^4.0 dPa · s or more, 10 ^4.4 dPa · s or more, 10 ^4.8 dPa · s or more, 10 ^5.0 dPa · s or more, 10 ^5.4 dPa · s or more, 10 ^5.6 dPa · s or more, 10 ^6.0 dPa · s or more, 10 ^6.2 dPa · s or more, particularly 10 ^6.3 dPa · s or more. Here, “liquid phase viscosity” refers to a value obtained by measuring the viscosity at the liquid phase temperature by a platinum ball pulling method. In addition, devitrification resistance and a moldability improve, so that liquid phase viscosity is high. Also, if the content of Na ₂ O, K ₂ O in the glass composition is increased or the content of Al ₂ O ₃ , Li ₂ O, MgO, ZnO, TiO ₂ , ZrO ₂ is reduced, the liquidus viscosity Tends to be high.

  The tempered glass of the present invention preferably has an unpolished surface, particularly preferably both surfaces are unpolished, and the average surface roughness (Ra) of the unpolished surface is preferably 10 mm or less, more preferably Is 5 mm or less, more preferably 4 mm or less, still more preferably 3 mm or less, and most preferably 2 mm or less. The average surface roughness (Ra) may be measured by a method based on SEMI D7-97 “Measurement method of surface roughness of FPD glass substrate”. Although the theoretical strength of glass is inherently very high, it often breaks even at stresses much lower than the theoretical strength. This is because a small defect called Griffith flow occurs on the glass surface in a post-molding process such as a polishing process. Therefore, if the surface of the tempered glass is unpolished, the mechanical strength of the original tempered glass is maintained and the tempered glass is difficult to break. In addition, if the surface is unpolished during scribe cutting after the tempering treatment, it is difficult to cause undue cracks, breakage, and the like during scribe cutting. Furthermore, if the surface of the tempered glass is unpolished, the polishing step can be omitted, so that the manufacturing cost of the tempered glass can be reduced. In order to obtain an unpolished surface, glass may be formed by an overflow down draw method.

  The tempered glass of the present invention is preferably molded by an overflow downdraw method. If it does in this way, it will become easy to shape | mold the glass plate which is unpolished and has favorable surface quality, As a result, it will become easy to raise the mechanical strength of the surface of tempered glass. The reason for this is that, in the case of the overflow downdraw method, the surface to be the surface does not come into contact with the bowl-like refractory and is molded in a free surface state. Furthermore, if it is an overflow downdraw method, the glass plate of thickness 0.5mm or less can be shape | molded appropriately. The structure and material of the bowl-shaped structure are not particularly limited as long as desired dimensions and surface quality can be realized. In addition, the method of applying a force to the glass in order to perform the downward stretch molding is not particularly limited as long as desired dimensions and surface quality can be realized. For example, a method may be adopted in which a heat-resistant roll having a sufficiently large width is rotated and stretched in contact with glass, or a plurality of pairs of heat-resistant rolls are contacted only near the end face of the glass. It is also possible to adopt a method of stretching by stretching.

  The tempered glass of the present invention can be formed by a slot down draw method, a float method, a roll out method, a redraw method, or the like in addition to the overflow down draw method.

  The display device of the present invention is a display device including a cover glass that protects a display unit, and the cover glass is the tempered glass described above. The display device of the present invention has an effect that can be enjoyed by the tempered glass of the present invention.

  In the display device of the present invention, the surface of the tempered glass on the side where the scribe line is formed is preferably outside. The surface on the side where the scribe line is formed has more initial scratches than the surface on the side where the scribe line is not formed. For this reason, if the surface on the side where the scribe line is formed is on the outside, when the surface is pressed with a pen or a finger, tensile stress is hardly generated on the surface on which the scribe line is formed, resulting in strengthening It becomes easy to prevent breakage of glass and the like.

  When the tempered glass is formed by the float process, a scribe line is formed on the surface of the tin bath side (so-called bottom surface) at the time of molding, and the surface on which the scribe line is formed is outside the display device. It is preferable to arrange. If it does in this way, destruction of tempered glass etc. can be prevented effectively. According to the investigation by the present inventors, it has been found that the surface on the tin bath side has higher mechanical strength than the other surface.

  In the display device of the present invention, it is preferable that a transparent conductive film is formed on the surface of the tempered glass on the side where no scribe line is formed. If it does in this way, it will become easy to arrange | position the surface of the tempered glass of the side in which the scribe line is formed outside. Moreover, it becomes easy to prevent the situation where the transparent conductive film or the like is contaminated by glass powder or the like when the scribe line is formed. As a method for forming the transparent conductive film, a known method such as a CVD method or a sputtering method can be used.

  In the display device of the present invention, it is preferable that the tempered glass is warped outwardly. In this way, when pressing the outer surface of the tempered glass with a pen or a finger, a compressive stress is generated on the outer surface, and as a result, it becomes easy to prevent breakage of the tempered glass caused by the outer surface. . Here, as a method of making the tempered glass warped in a convex shape, a method in which the composition state of the surface layer on the front surface and the back surface is changed, a method of ion exchange treatment, and a glass is bent by a roller or the like at the time of molding. And a method of applying a pressing force from the direction of the cut surface of the tempered glass. In addition, when glass is shape | molded by the float glass process, the composition state of the surface layer of a front surface and a back surface will change easily.

  It is preferable that the display device of the present invention further includes a housing, and all or a part of the housing is not in contact with the cut surface of the tempered glass. If it does in this way, it will become easy to prevent the situation where the cut surface of a case and tempered glass contact and the micro crack which exists in a cut surface advances.

  In the display device of the present invention, the tempered glass and the housing are preferably fixed with resin. If it does in this way, tempered glass can be fixed to a case, protecting the cut surface of tempered glass. In addition, a well-known thing can be used as resin.

  In the display device of the present invention, it is preferable that the cut surface of the tempered glass is not exposed to the outside. If it does in this way, it will become easy to prevent the situation where an impact is added to the cut surface of tempered glass and the micro crack which exists in a cut surface advances. In addition, if tempered glass is housed in the housing and the gap between the housing and the cut surface of the tempered glass is closed with a resin or the like if necessary, the cut surface of the tempered glass may not be exposed to the outside. it can.

  Hereinafter, based on an Example, this invention is demonstrated in detail. The following examples are merely illustrative. The present invention is not limited to the following examples.

  Table 1 shows an example (sample No. 1) and a comparative example (sample No. 2) of the present invention.

Sample no. 1 was produced. First, a tempered glass having a size of 150 mm × 180 mm × 0.7 mm thickness was prepared. This tempered glass has a glass composition of 5% by mass of SiO ₂ 57.4%, Al ₂ O ₃ 13%, B ₂ O ₃ 2%, MgO 2%, CaO 2%, Li ₂ O 0.1%. , Na ₂ O 14.5%, K ₂ O 5%, ZrO ₂ 4%. This glass for strengthening is formed by the overflow downdraw method, and the surface is unpolished.

  Ion exchange treatment was performed by immersing the glass for strengthening in a potassium nitrate solution at 400 ° C. for 80 minutes to obtain tempered glass. Next, the obtained tempered glass was moved to a bath maintained at 380 ° C. and subjected to heat treatment for 105 minutes. After the heat treatment, the tempered glass was taken out in a room temperature environment. Subsequently, after the obtained tempered glass was washed, the compressive stress value and the stress depth were calculated from the number of interference fringes observed using a surface stress meter (FSM-6000 manufactured by Orihara Seisakusho Co., Ltd.) and the interval therebetween. . In the calculation, the refractive index of the sample was 1.53, and the optical elastic constant was 28 [(nm / cm) / MPa]. As a result, the compressive stress value was 600 MPa, and the stress depth was 25 μm.

  Furthermore, the obtained tempered glass was scribe-cut to obtain a tempered glass having dimensions of 40 mm × 80 mm × 0.7 mm. At the time of scribe cutting, a scribe line was formed on the surface of the tempered glass at a speed of 50 mm / second using a diamond wheel tip. Then, a pressing force was applied along the scribe line so that a tensile stress was applied, and the product was divided into a predetermined shape.

  Sample No. after scribe cutting For No. 1, a four-point bending test was performed. The conditions of the four-point bending test were as follows: upper support rod span: 25 mm, lower support rod span: 50 mm, upper support rod lowering speed: 5 mm / min. The surface on which the scribe line was formed was brought into contact with the upper support bar. The results are shown in Table 1 and FIG.

  Next, sample No. In the same manner as in No. 1, sample no. 2 was produced. Sample No. In No. 2, the cut surface is chamfered, and only the sample No. 2 is chamfered. 1 and different. Sample No. A chamfered surface (chamfer dimension of 0.1 mm in the plate thickness direction) is formed on the cut surface 2 by mirror surface grinding.

  Sample No. after scribe cutting For No. 2, a four-point bending test was performed. The conditions of the four-point bending test were as follows: upper support rod span: 25 mm, lower support rod span: 50 mm, upper support rod lowering speed: 5 mm / min. The surface on which the scribe line was formed was brought into contact with the upper support bar. The results are shown in Table 1 and FIG.

  As apparent from Table 1 and FIG. In No. 1, since the chamfering process was not performed on the cut surface, the end surface strength was high and the variation was small. On the other hand, sample No. In No. 2, since the cut surface was chamfered, the end surface strength was low and the variation was large.

  Sample No. after scribe cutting according to [Example 1] When a four-point bending test was conducted with the surface on which the scribe line was not formed in contact with the upper support rod, the surface on which the scribe line was formed was brought into contact with the upper support rod. The end face strength was 10% or more lower than the average. The conditions of the four-point bending test were as follows: upper support rod span: 25 mm, lower support rod span: 50 mm, upper support rod descending speed: 5 mm / min.

  The tempered glass of the present invention is suitable for a cover glass of a display device such as a mobile phone, a digital camera, or a PDA. In addition to these uses, the tempered glass of the present invention is used for applications requiring high mechanical strength, such as window glass, magnetic disk substrates, flat panel display substrates, cover glass for solid-state image sensors, tableware, etc. Application to can be expected.

Claims (10)

A method for manufacturing a display device including a cover glass for protecting a display unit,
As the cover glass , using a tempered glass having a compressive stress layer on the surface,
The tempered glass is scribed along the scribe line after the tempering treatment, and all or part of the cut surface is not physically processed,
A method of manufacturing a display device , characterized in that the surface of the tempered glass on the side on which the scribe line is formed is disposed outside the display device. Tempered glass, as a glass composition, in _{mass%, SiO 2 40~71%, Al} 2 O 3 7~23%, Li 2 O 0~1%, Na 2 O 7~20%, K 2 O 0~15 % . The method for manufacturing a display device according to claim 1 , comprising : The method for manufacturing a display device according to claim 1, wherein the tempered glass is formed by an overflow downdraw method or a float method. The method for manufacturing a display device according to claim 1, wherein the surface of the tempered glass is not polished. The method for manufacturing a display device according to claim 1, wherein the compressive stress value of the compressive stress layer of the tempered glass is 400 MPa or more and the stress depth is 15 μm or more. Method of manufacturing a display device according to any one of claims 1 to 5, characterized in that the scribe line is a transparent conductive film on the surface of the tempered glass on the side not formed are formed. The method for manufacturing a display device according to any one of claims 1 to 6 , wherein the tempered glass is warped convexly outward. Comprising a display device further housing, all or a portion of the housing is, in the display device according to any one of claims 1 to 7, characterized in that not in contact with the cut surface of the tempered glass Manufacturing method . The method for manufacturing a display device according to any one of claims 1 to 8 , wherein the tempered glass and the housing are fixed by a resin. The method for manufacturing a display device according to any one of claims 1 to 9 , wherein a cut surface of the tempered glass is not exposed to the outside.