JP5382609B2 - Glass substrate - Google Patents

Description

  The present invention relates to a glass substrate manufactured by a float process, and particularly to a glass substrate used in a flat panel display device such as a plasma display, a liquid crystal display, a field emission display, and an electroluminescence display.

  Conventionally, rectangular glass substrates have been widely used as display substrates used in flat panel display devices such as plasma displays, liquid crystal displays, field emission displays, and electroluminescence displays. Further, in order to prevent thermal deformation and thermal contraction of the substrate due to various heat treatments when manufacturing the display device, the glass substrate used for the display substrate includes, for example, 550 ° C. or higher as shown in Patent Documents 1 to 4. A glass having a strain point of 2 is used.

  In order to industrially produce such a glass substrate, generally, glass raw materials are prepared, the prepared glass raw materials are put into a glass melting furnace, melted and clarified, and then the glass melt is put into a molding apparatus. It can be obtained by feeding, forming into a plate shape by a method such as a slot down draw method, an overflow down draw method, a float method, a roll out method and the like.

In particular, when a large glass substrate is manufactured at a low cost and in a large amount, a float method is often used in which a glass melt is supplied onto a molten tin bath to form a desired plate thickness.
JP-A-8-290938 JP-A-8-290939 JP 2001-226138 A JP-A-2005-213132

  By the way, when manufacturing a glass substrate, a part of glass component evaporates from glass melt at high temperature, such as a glass melting process, a refining process, and a molding process. The glass component thus evaporated is cooled by a furnace inner wall surface such as a melting furnace or a molding furnace, and falls as an aggregate. In particular, in the case of a molding method in which the glass melt is drawn in the horizontal direction as in the float process, aggregates fall onto the glass melt formed into a plate shape in the molding process and become surface foreign matter. A glass substrate to which surface foreign matter is attached becomes a fatal problem in display applications that require high surface quality and cannot be used unless the surface foreign matter is removed.

  Polishing the glass substrate surface as a method for removing the surface foreign matter adhering to the glass substrate surface can be considered, but the problem of an increase in manufacturing cost arises. Further, in recent years, display devices have been improved in definition, and minute scratches on the glass surface due to polishing have been regarded as a problem.

  An object of the present invention is to provide a glass substrate having a high surface quality at a low cost, with little surface foreign matter, in a glass substrate manufactured by a float process.

As a result of various studies by the present inventors, by limiting the content of P ₂ O ₅ contained in the glass, evaporation of the glass component from the glass melt is suppressed, and generation of aggregates and fall of aggregates are performed. It has been found that a glass substrate having a high surface quality can be obtained without polishing, and adhesion of surface foreign matter to the glass substrate surface due to the above can be obtained, and the present invention has been proposed.

That is, the glass substrate of the present invention is a glass substrate manufactured by a float process, and is expressed in terms of mass percentage, SiO ₂ 50 to 75%, Al ₂ O _{3 3 to} 20%, B ₂ O ₃ 0 to 20%, MgO 0-15%, CaO 0-15%, SrO 0-15%, BaO 0-15%, RO (R represents Mg, Ca, Sr, Ba) 1-30%, ZnO 0-5%, Li ₂ O 0-5%, Na ₂ O 0-10%, K ₂ O 0-15%, R ′ ₂ O (R ′ represents Li, Na, K) 0-24%, ZrO ₂ 0-10% , P ₂ O ₅ 0.002 to 0.018% of composition is contained.

  Since the glass substrate of the present invention has a small amount of adhesion of surface foreign matter, a glass substrate having high surface quality can be obtained at low cost without polishing. Therefore, it is suitable as a glass substrate, particularly a glass substrate used in a flat panel display device.

In the glass substrate of the present invention, P ₂ O ₅ , which is a component that facilitates evaporation of the glass component from the glass melt, is limited to 0.018% by mass or less in a high-temperature process such as a glass melting process, a fining process, and a molding process. By doing so, evaporation of the glass component from the glass melt is suppressed. As a result, in a high-temperature process such as a glass melting process, a fining process, and a molding process, the generation of aggregates and the fall of aggregates can be suppressed, and the glass melt is drawn in a horizontal direction like the float process. Even if it exists, adhesion of the surface foreign material to the glass substrate surface by the fall of an aggregate can be suppressed, and even if it does not grind | polish, the glass substrate which has high surface quality can be obtained.

  In addition, since the glass substrate of the present invention has a strain point of glass of 560 ° C. or higher, it is possible to suppress the occurrence of thermal deformation and thermal shrinkage of the glass substrate in the heat process when manufacturing the display device. . The preferable range of the strain point is 570 ° C. or higher, more preferably 575 ° C. or higher.

Further, when the molten glass is formed into a plate shape, the temperature of the glass melt corresponding to a viscosity of 10 ⁴ dPa · s is set to 1200 in order to suppress the evaporation of the glass component and to form without burdening the forming apparatus. It is preferable to set it to below ℃. More preferably, it is 1180 degrees C or less, More preferably, it is 1170 degrees C or less.

In addition, in order to obtain a glass substrate excellent in thermal shock resistance that can be consistent with the thermal expansion coefficient of peripheral materials such as insulating paste, rib paste, and frit seal, and that is not easily broken even when quenched, 30 to 30 It is preferable to set the thermal expansion coefficient of the glass at 380 ° C. to 65 to 90 × 10 ⁻⁷ / ° C. More preferably, it is 75-87 * 10 < ^-7 > / degreeC.

A specific composition can be used as the glass substrate of the present invention, by mass _{percentage, SiO 2 50~75%, Al 2} O 3 3~20%, B 2 O 3 0~20%, MgO 0~15% , CaO 0-15%, SrO 0-15%, BaO 0-15%, RO (R represents Mg, Ca, Sr, Ba) 1-30%, ZnO 0-5%, Li ₂ O 0-5 %, Na ₂ O 0-10%, K ₂ O 0-15%, R ′ ₂ O (R ′ represents Li, Na, K) 0-24%, ZrO ₂ 0-10%, P ₂ O ₅ What is necessary is just to select suitably in the range which will be 0.002-0.018%. In this range, is capable of forming by a float ^process, 10 4 dPa · s 1200 ℃ the temperature of the glass melt corresponding to a viscosity of less than, 560 ° C. or more strain point, 60 to 90 × ^{10 -7} / It becomes easy to obtain a glass substrate having a thermal expansion coefficient of 0 ° C. and having a small amount of surface foreign matter and having a high surface quality.

  The reason why the ratio of each component is limited as described above in the glass substrate of the present invention will be described below.

SiO ₂ is a component that forms a network former of glass, and its content is 50 to 75%. When the content of SiO ₂ increases, the high-temperature viscosity of the glass increases, and it becomes difficult to melt and mold the glass. In addition, the coefficient of thermal expansion becomes too small, making it difficult to match the coefficient of thermal expansion of the surrounding material. On the other hand, when the content is reduced, the strain point of the glass is lowered, and the glass substrate is easily cracked or thermally deformed or contracted easily in the heat treatment step when manufacturing the display. In addition, the thermal expansion coefficient becomes too large, making it difficult to achieve consistency with the thermal expansion coefficient of the surrounding materials, and the thermal shock resistance tends to be reduced. A preferable range of SiO ₂ is 50 to 70%, and a more preferable range is 52 to 65%.

Al ₂ O ₃ is a component that increases the strain point of glass, and its content is 3 to 20%. When the content of Al ₂ O ₃ increases, the high temperature viscosity of the glass increases, and it becomes difficult to melt and mold the glass. In addition, the coefficient of thermal expansion becomes too small, making it difficult to match the coefficient of thermal expansion of the surrounding material. On the other hand, when the content is reduced, the strain point of the glass is lowered, and the glass substrate is easily cracked or thermally deformed or contracted easily in the heat treatment step when manufacturing the display. A preferable range of Al ₂ O ₃ is 3.5 to 15%, and a more preferable range is 4 to 11%. Incidentally, or higher strain point, if you want to lower the thermal expansion coefficient, it is preferable that the content of Al ₂ O ₃ to 4.5% or more.

B ₂ O ₃ is, to lower the viscosity of the glass or to enhance the meltability of the glass, the content thereof is 0-20%. When the content of B ₂ O ₃ is increased, the strain point of the glass is lowered, and the glass substrate is easily cracked or thermally deformed or contracted easily in the heat treatment step when manufacturing the display. A preferable range of B ₂ O ₃ is 0 to 12%, and a more preferable range is 0 to 4%.

  MgO is a component that lowers the high-temperature viscosity of the glass to increase the meltability and formability of the glass and increase the strain point of the glass, and its content is 0 to 15%. When the content of MgO increases, the glass tends to devitrify, and molding becomes difficult. The preferable range of MgO is 0 to 6%, and the more preferable range is 0 to 4%.

  CaO, like MgO, is a component that lowers the high-temperature viscosity of the glass to increase the meltability and formability of the glass and increase the strain point of the glass, and its content is 0 to 15%. Its content is 0-15%. When the content of CaO increases, the glass tends to devitrify, and molding becomes difficult. The preferable range of CaO is 0 to 8%, and the more preferable range is 0 to 7%.

  SrO is a component that lowers the high temperature viscosity of the glass and improves the meltability and formability of the glass, and its content is 0 to 15%. When the content of SrO increases, the glass tends to devitrify, and molding becomes difficult. A preferable range of SrO is 1 to 12%, and a more preferable range is 5 to 10%.

  BaO, like SrO, is a component that lowers the high-temperature viscosity of the glass and improves the meltability and moldability of the glass, and its content is 0 to 15%. When BaO increases, the glass tends to devitrify, and molding becomes difficult. The preferable range of BaO is 1 to 12%, and the more preferable range is 6 to 10%.

  In order to increase the strain point of the glass without devitrifying the glass and to reduce the high temperature viscosity of the glass and improve the meltability and formability, the total amount of MgO, CaO, SrO and BaO is used. A certain RO may be 1-30%. When the content of RO increases, the glass tends to devitrify, and molding becomes difficult. On the other hand, when the content of RO decreases, the high-temperature viscosity of the glass increases and melting and molding become difficult. A more preferable range of RO is 5 to 28%, and a further preferable range is 17 to 26%.

  ZnO is a component that lowers the high temperature viscosity of the glass and improves the meltability and formability of the glass, and its content is 0 to 5%. When the content of ZnO increases, the glass tends to devitrify, and molding becomes difficult. The preferable range of ZnO is 0 to 4%, and the more preferable range is 0 to 3%.

Li ₂ O is a component that lowers the high-temperature viscosity of the glass to increase the meltability and formability of the glass, and controls the thermal expansion coefficient of the glass, and its content is 0 to 5%. When the content of Li ₂ O is increased, the strain point of the glass is remarkably lowered, and the glass substrate is easily cracked or thermally deformed or contracted easily in the heat treatment process when manufacturing the display. In addition, the thermal expansion coefficient becomes too large, making it difficult to achieve consistency with the thermal expansion coefficient of the surrounding materials, and the thermal shock resistance tends to be reduced. A preferable range of Li ₂ O is 0 to 3%, and a more preferable range is 0 to 2%. When it is desired to increase the strain point or lower the thermal expansion coefficient, it is preferable not to contain Li ₂ O.

Na ₂ O is a component that lowers the high-temperature viscosity of the glass to increase the meltability and formability of the glass, and controls the thermal expansion coefficient of the glass, and its content is 0 to 10%. When the content of Na ₂ O is increased, the strain point of the glass is lowered, and the glass substrate is easily cracked or thermally deformed or contracted easily in the heat treatment process when manufacturing the display. In addition, the thermal expansion coefficient becomes too large, making it difficult to achieve consistency with the thermal expansion coefficient of the surrounding materials, and the thermal shock resistance tends to decrease. A preferable range of Na ₂ O is 1 to 9%, and a more preferable range is 1 to 8%. In addition, when it is desired to further increase the strain point or lower the thermal expansion coefficient without greatly reducing the moldability and meltability of the glass, the Na ₂ O content is preferably 6% or less.

K ₂ O, like Na ₂ O, is a component that lowers the high-temperature viscosity of the glass to increase the meltability and formability of the glass, and controls the thermal expansion coefficient of the glass, and its content is 0 to 15%. It is. When the content of K ₂ O is increased, the strain point of the glass is lowered, and the glass substrate is easily cracked or thermally deformed or contracted easily in the heat treatment process when manufacturing the display. In addition, the thermal expansion coefficient becomes too large, making it difficult to achieve consistency with the thermal expansion coefficient of the surrounding materials, and the thermal shock resistance tends to decrease. A preferable range of K ₂ O is 1 to 12%, and a more preferable range is 2 to 10%. In addition, when it is desired to further increase the strain point or lower the thermal expansion coefficient without greatly reducing the moldability and meltability of the glass, the content of K ₂ O is preferably 8% or less.

In order to improve the meltability without significantly reducing the strain point of the glass, R ′ ₂ O, which is the total amount of Li ₂ O, Na ₂ O and K ₂ O, is set to 0 to 24%. It is preferable. When the content of R ′ ₂ O is increased, the strain point of the glass is lowered, and the glass substrate is easily broken or thermally deformed or contracted in the heat treatment process when manufacturing the display. A more preferable range of R ′ ₂ O is 2.5 to 18%, and a more preferable range is 8 to 14%. In addition, when it is desired to improve the meltability and moldability of the glass, the content of R ′ ₂ O is preferably 3% or more.

ZrO ₂ is a component that increases the strain point of glass, and its content is 0 to 10%. When the ZrO ₂ content is increased, the density of the glass is remarkably increased, and devitrified materials due to ZrO ₂ tend to precipitate. A preferable range of ZrO ₂ is 0 to 8%, and a more preferable range is 0 to 6%. Incidentally, if it is desired to further increase the strain point, it is preferable that a content of ZrO ₂ to 0.5%.

P ₂ O ₅ is a component that is mixed as an impurity from a glass raw material or the like and facilitates evaporation of the glass component from the glass melt in a high-temperature process such as a glass melting process, a fining process, or a molding process. Its content is 0.002 to 0.018%. When the content of P ₂ O ₅ is increased, the glass component tends to evaporate from the glass melt in a high temperature process such as a glass melting process, a clarification process, and a molding process, and the surface on the glass substrate surface due to the falling of the aggregates It becomes impossible to suppress adhesion of foreign matter. On the other hand, when the content is reduced, a high-purity raw material and special equipment are required, and the manufacturing cost of the glass substrate is increased. A preferable range of P ₂ O ₅ is 0.003 to 0.012%, and a more preferable range is 0.004 to 0.009%. In order to reduce the content of P ₂ O ₅ in the glass at low cost, a natural raw material having a low content of P ₂ O ₅ may be used as an impurity.

In the present invention, in addition to the above components, for example, TiO ₂ is reduced to 5% to prevent ultraviolet coloring, and Y ₂ O ₃ , La ₂ O is used to improve the moldability by lowering the liquidus temperature. ₃ , Nb ₂ O _{3 up} to 3% each, Fe ₂ O ₃ , CoO, NiO, Cr ₂ O ₃ , Nd ₂ O _{3 up} to 2% each as colorants, SnO ₂ , SO ₃ , F, It is possible to add Cl or the like up to a total amount of 1%. As ₂ O ₃ and Sb ₂ O ₃ are fining agents. However, when forming by the float process, introduction is to be avoided because they are reduced in the float bath to become metallic foreign matter.

  Next, a method for producing the glass substrate of the present invention will be described.

First, select a small glass raw material of P ₂ O ₅ contained as an impurity, to formulate a glass raw material so that the above glass composition range. Subsequently, the prepared glass raw material is put into a continuous melting furnace, heated and melted, defoamed, supplied to a float bath, formed into a plate shape, and slowly cooled to obtain a glass substrate.

  Hereinafter, the glass substrate of this invention is demonstrated in detail based on an Example.

  Table 1 shows examples (samples Nos. 1 to 6) of the present invention, and Table 2 shows comparative examples (samples Nos. 7 to 9).

  Each sample in the table was prepared as follows.

  First, a glass raw material is prepared so as to have the glass composition in the table and melted in a continuous melting furnace. Subsequently, the glass was formed by a float method so that the thickness was 1.8 mm, and cut into a size of 2100 mm × 1000 mm to obtain a sample glass.

For each sample thus obtained, the strain point, the temperature of the glass melt corresponding to a viscosity of 10 ⁴ dPa · s, the thermal expansion coefficient, and the amount of surface foreign matter were measured. The results are shown in the table.

As can be seen from the table, the sample No. Each of the samples 1 to 6 has a surface foreign matter adhesion amount as small as 0.7 pieces / m ² or less, and has excellent surface quality without polishing, and has a problem as a glass substrate used in a flat panel display device. It was something that could be used. Further, the temperature of the glass melt corresponding to a viscosity of 10 ⁴ dPa · s was as low as 1160 ° C. or less, and molding was possible without imposing a burden on the molding apparatus. Furthermore, the strain point was as high as 565 ° C. or higher, and the thermal expansion coefficient was 83 to 85 × 10 ⁻⁷ / ° C., which had a thermal expansion coefficient that matched well with the surrounding materials.

On the other hand, sample No. which is a comparative example. 7 and no. In No. 8, the adhesion amount of the surface foreign matter was as large as 2.5 / m ² or more, and the surface quality was inferior. Sample No. For No. 9, the adhesion amount of the surface foreign matter was as small as 0.1 / m ² and the surface quality was excellent, but the raw material cost was high because the content of P ₂ O _{5 in} the glass was low.

  The strain point was measured based on ASTM C336-71. In addition, the higher the strain point, the more the thermal deformation and thermal shrinkage of the glass substrate in the thermal process when manufacturing the display device can be suppressed.

  Regarding the thermal expansion coefficient, a cylindrical sample having a diameter of 5.0 mm and a length of 20 mm was prepared, and the average thermal expansion coefficient at 30 to 380 ° C. was measured with a dilatometer.

The glass melt temperature corresponding to a glass viscosity of 10 ⁴ dPa · s was measured by a platinum ball pulling method. The temperature of the glass melt corresponding to 10 ⁴ dPa · s is a guideline for forming the glass into a plate shape, and the lower the temperature, the lower the glass component of the glass component when forming the molten glass into a plate shape. Evaporation can be suppressed, and molding can be performed without imposing a burden on the molding apparatus.

  Regarding the thermal expansion coefficient, a cylindrical sample having a diameter of 5.0 mm and a length of 20 mm was prepared, and the average thermal expansion coefficient at 30 to 380 ° C. was measured with a dilatometer.

The number of surface foreign matters was obtained by observing the surface of the glass substrate visually, counting the number of surface foreign matters, and converting the number per 1 m ² .

  The glass substrate of the present invention is not limited to the use of flat panel display devices such as a plasma display, a liquid crystal display, a field emission display, and an electroluminescence display. For example, the glass substrate is used as a glass substrate for solar cells or flat lamps. Is also possible.

Claims (4)

A glass substrate produced by a float process, by mass _{percentage, SiO 2 50~75%, Al 2} O 3 3~20%, B 2 O 3 0~20%, 0~15% MgO, CaO 0~ 15%, SrO 0-15%, BaO 0-15%, RO (R represents Mg, Ca, Sr, Ba) 1-30%, ZnO 0-5%, Li ₂ O 0-5%, Na _{2 O 0~10%, K 2 O 0~15} %, R '2 O (R' represents Li, Na, and _{K) 0~24%, ZrO 2 0~10} %, P 2 O 5 0.002~ A glass substrate containing a composition of 0.018%. By mass _{percentage, SiO 2 50~75%, Al 2} O 3 3~15%, 0~15% MgO, CaO 0~15%, SrO 0~15%, BaO 0~15%, RO (R is Mg, Ca, Sr, representing the _{Ba) 1~30%, 0~5% ZnO} , Li 2 O 0~5%, Na 2 O 1~10%, K 2 O 1~15%, R '2 O (R' ₂ represents Li, Na, and K). The composition contains 2.5 to 24%, ZrO ₂ 0 to 10%, and P ₂ O ₅ 0.002 to 0.018%. Glass substrate.   The glass substrate according to claim 1, wherein the glass substrate is used as a glass substrate for a flat panel display device.   It uses as a glass substrate for plasma display apparatuses, The glass substrate in any one of Claims 1-3 characterized by the above-mentioned.