JP4947486B2 - Glass for flat image display device, glass substrate using the same, and manufacturing method thereof - Google Patents

Description

  The present invention relates to a glass for flat image display devices, and more particularly to a glass suitable for a field emission display (hereinafter referred to as FED). The present invention also relates to a glass substrate for flat image display devices, and more particularly to a glass substrate suitable for FED. Furthermore, this invention relates to the manufacturing method of the glass substrate for flat image display apparatuses.

  The FED can use the technology cultivated in the cathode ray tube (CRT), and other flat image display devices such as a liquid crystal display (hereinafter referred to as LCD) and a plasma display (plasma display panel). This is expected as a next-generation flat image display device because power consumption can be reduced as compared with PDP).

  As shown in FIG. 1, the FED includes a front plate 8 having a phosphor 7 that emits light when irradiated with an electron beam, and a back plate 3 on which many elements 5 that emit electrons are formed. It has a structure hermetically sealed with a cured resin. The space inside the apparatus formed by the front plate 8 and the back plate 3 is kept in a vacuum state to enable electron irradiation. It is no exaggeration to say that the image characteristics of the FED depend on the electron emission source. In recent years, various electron emission devices have been proposed and developed. In these electron-emitting devices, when the strength of the electric field applied to the material is increased, the width of the energy barrier on the material surface gradually narrows according to the strength, and as a result, it becomes possible to break through the energy barrier. Is used. In this case, since the electric field follows Poisson's equation, if a portion where the electric field is concentrated is formed on the electron emitting member (emitter), electrons can be efficiently emitted with a relatively low extraction voltage. A surface conduction electron-emitting device is known as such an electron-emitting device.

In the surface conduction electron-emitting device, an energization process called forming may be performed in advance. According to Patent Document 1, forming is a process of locally destroying, deforming, or altering a conductive thin film formed on a substrate by sputtering or the like, and this process is brought into an electrically high resistance state. An electron emission portion is formed. Furthermore, there is a case where a process called activation process is performed on the element after forming. By performing the activation treatment, carbon or a carbon compound is deposited from at least an electron emission portion of the element from an organic substance present in the atmosphere, and better electron emission characteristics can be obtained. However, in recent years, higher performance has been demanded for flat image display devices such as a display. The image display device has a large screen, power saving, high definition, high image quality, space saving, low Costs are required. Therefore, in the electron-emitting device, a technique capable of maintaining the electron emission characteristic that is highly efficient and responds at high speed for a long time so that the flat image display device can stably provide a bright and clear display image is desired. Yes.
JP 7-235255 A

The glass substrate used for the FED is required to have the following characteristics.
(1) It has a thermal expansion coefficient compatible with the peripheral members so that the glass substrate does not crack in the heat treatment process. (2) The glass substrate is thermally contracted in the heat treatment process such as film formation and does not cause pattern displacement. (3) No internal defects that affect the quality of the FED, especially no bubble defects (4) Low density to reduce the overall weight of the FED (5) The flexure is small, that is, the specific Young's modulus is large so that the cassette can be easily put in and out of the FED manufacturing process. (6) The glass substrate is not easily broken by an impact such as film stress. The crack generation rate, which is an index of glass breakability, is low. However, conventional electron-emitting devices do not necessarily satisfy the requirements for stable electron-emitting characteristics. Is not obtained. Specifically, since a low-cost alkali glass is used for a conventional glass substrate to reduce the cost of a large display, sufficient element characteristics are not obtained. This is due to the problem that alkali glass has a relatively high dielectric constant and stray capacitance components are generated from the substrate. For this reason, when electrons are emitted at high speed, a charging current flows first due to the stray capacitance component, and stable electron emission cannot be obtained. In order to solve this problem, a method of forming a film having a low dielectric constant on the substrate surface can also be adopted. However, the number of film forming steps increases, which can be an obstacle to substantial cost reduction. Therefore, in order to fundamentally solve the above problem, (7) a glass having a low dielectric constant is desired.

  In addition, when forming an electron-emitting device, it is also required to increase the accuracy of sputtering. Since the concavo-convex shape of the film formed by sputtering is greatly affected by the concavo-convex shape on the surface of the glass substrate, a glass substrate with good surface smoothness is required. Although the surface smoothness of a glass substrate is determined by various factors, a glass substrate molding method and a processing method can be cited as factors having the greatest influence.

  As a method for forming a glass substrate, there are various methods such as an overflow down draw method (also referred to as a fusion method), a float method, a slot down draw method, and the like. Among them, the overflow downdraw method can obtain a glass substrate with high flatness without polishing the glass substrate, in other words, without a separate processing step. Therefore, it is considered that the overflow downdraw method is suitable as a method for forming a glass substrate for FED that requires excellent surface smoothness. However, the overflow down draw method has a higher viscosity at the time of glass molding than other molding methods, so if the devitrification resistance of the glass is poor, devitrification will occur during molding and glass molding. Can not be. Therefore, it can be said that it is desirable that the glass substrate for FED has (8) a glass composition that is not easily devitrified.

  However, conventional glass substrates for FED have no glass that satisfies all of the above required characteristics (1) to (8), and in particular, (7) glass having a low dielectric constant and (8) good devitrification resistance. It is difficult to obtain glass, and as a result, it is difficult to prevent the occurrence of stray capacitance components from the glass substrate and to ensure stable electron emission characteristics. Therefore, it is difficult to form a circuit pattern with high accuracy.

  Accordingly, the technical problem of the present invention is to obtain a glass that can satisfy the above required characteristics (1) to (6), (7) have a low dielectric constant, and (8) have good devitrification resistance. It is a technical problem to obtain a glass substrate using the same.

As a result of diligent efforts, the present inventor has made glass composition ranges of SiO ₂ 60 to 90%, Al ₂ O ₃ 3 to 10%, and B ₂ O ₃ 0.01 in terms of mol%. _{~10%, Li 2 O 0~4%} , Na 2 O 0~7%, K 2 O 0~8%, 0~3% MgO, CaO 0~4%, SrO 0~15%, BaO 0~15 % , The value of BaO / Al ₂ O ₃ in terms of mole fraction is restricted to 0.9 to 1.2 , and the average coefficient of thermal expansion at 30 to 380 ° C. is set to 50 to 90 × 10 ⁻⁷ / ° C. Thus, the inventors have found that the above problem can be solved by setting the dielectric constant at 25 ° C. and 1 MHz to less than 9, and propose as the present invention. In the present invention, “average thermal expansion coefficient at 30 to 380 ° C.” refers to a value measured using a dilatometer.

  By restricting the glass composition to the above range, a glass capable of satisfying the required characteristics (1) to (8) can be easily obtained. As a result, the glass for a flat image display device of the present invention does not impair the display characteristics of an image display device such as a display. Moreover, since the glass for flat image display devices of the present invention can satisfy the above required characteristics (1) to (8), the display device has a large screen, power saving, high definition, high image quality, and space saving. This can contribute to reduction in cost and cost.

By restricting the glass composition to the above range, a glass having good devitrification resistance can be obtained. In general, in the overflow down draw method, the devitrification resistance of the glass is required to be at least 1200 ° C. at a liquidus temperature and 10 ^4.5 dPa · s or more at a liquidus viscosity. Since the glass for the glass regulates the glass composition within the above range, it has good devitrification resistance, and achieves a liquidus temperature of 1200 ° C. or lower and a liquidus viscosity of 10 ^4.5 dPa · s or higher. Can do. Moreover, the glass for flat image display apparatuses of this invention has the viscosity characteristic suitable for the overflow down draw method by restrict | limiting the glass composition to said range. By adopting the overflow downdraw method, the surface quality of the glass substrate can be improved without providing a separate polishing step, and as a result, high-precision photolithography can be performed on the surface of the glass substrate. In addition, it is possible to form a circuit pattern with high accuracy and contribute to ensuring the reliability of the flat image display device (for example, reducing the probability of occurrence of disconnection or short circuit). The present invention does not exclude a molding method other than the overflow downdraw method. Even if it is a molding method other than the overflow downdraw method, the better the devitrification resistance of the glass in the glass production process, the more efficient the production of the glass substrate. Needless to say, it is effective.

Furthermore, since the glass for a flat image display device of the present invention regulates the average thermal expansion coefficient at 30 to 380 ° C. to 50 to 90 × 10 ⁻⁷ / ° C., the frit seal is satisfactorily performed, and the flat image display device It becomes possible to accurately prevent the glass substrate from being cracked by a heat treatment step such as film formation when manufacturing the substrate.

  The glass for flat image display device of the present invention regulates the dielectric constant at 25 ° C. and 1 MHz to less than 9, so that it does not form a low dielectric constant film on the glass substrate surface. Therefore, a stable electron emission characteristic can not be obtained and a stable electron emission characteristic can be secured. As a result, a bright and clear display image can be stably obtained in a flat image display device. It becomes possible to provide.

  In addition, the glass for a flat image display device of the present invention can maintain a high efficiency and high speed electron emission characteristic for a long time in an electron emission element, and as a result, stably provide a bright and clear display image. Is possible.

Secondly, glass for a flat image display apparatus of the present invention has a glass composition, SiO ₂ 60-89% by _{mol%, Al 2 O 3 4~8%} , B 2 O 3 1~5%, Li 2 O _{0~2%, Na 2 O 0~5%} , K 2 O 1~5%, 0~1% MgO, CaO 0~4%, SrO 2~13%, containing 3 to 10% BaO, the molar fraction The BaO / Al ₂ O ₃ value is 0.9 to 1.2 in terms of the rate, and the average thermal expansion coefficient at 30 to 380 ° C. is 60 to 80 × 10 ⁻⁷ / ° C., 25 ° C., and the dielectric constant at 1 MHz. Characterized by being less than 9.

Thirdly, the glass for a flat image display device of the present invention has a glass composition of SiO ₂ 68-73%, Al ₂ O ₃ 5-7%, B ₂ O ₃ 1.5-3%, ₂ O 0 to less than 0.5%, Na ₂ O 0 to 4%, K ₂ O 1.5 to 5%, MgO 0 to 0.5%, CaO 0 to 4%, SrO 6 to 10%, BaO 2 In the molar fraction of BaO / Al ₂ O ₃ of 0.9 to 1.2, and an average coefficient of thermal expansion at 30 to 380 ° C. of 65 to 75 × 10 ⁻⁷ / ° C. The dielectric constant at 25 ° C. and 1 MHz is 7.5 or less.

Fifth, the glass for a flat image display device of the present invention is characterized in that the Na ₂ O / K ₂ O value is 0 to 2 in terms of molar fraction.

Sixth, the glass for a flat image display device of the present invention is characterized in that the value of (Na ₂ O + K ₂ O) / (MgO + CaO + SrO + BaO) is 0 to 1 in terms of molar fraction.

Seventh, the glass for a flat image display device of the present invention is characterized in that the density is 3.0 g / cm ³ or less.

  Eighth, the glass for a flat image display device of the present invention is characterized by having a strain point of 590 ° C. or higher. In the present invention, “strain point” refers to a value measured by a method based on ASTM C336-71.

  Ninthly, the glass for flat image display devices of the present invention is characterized in that the liquidus temperature is 1200 ° C. or lower. In the present invention, the “liquid phase temperature” means that the glass is pulverized, passed through a standard sieve 30 mesh (500 μm), and the glass powder remaining at 50 mesh (300 μm) is placed in a platinum boat and placed in a temperature gradient furnace. The temperature at which crystals precipitate in the glass after being held for a period of time is measured.

Tenth, the glass for a flat image display device of the present invention is characterized by having a liquidus viscosity of 10 ^4.5 dPa · s or more. In the present invention, the “liquid phase viscosity” refers to a value obtained by measuring the viscosity of glass at the liquid phase temperature measured by the above method by a well-known platinum pulling method.

Eleventh, the glass for a flat image display device of the present invention is characterized by having a specific Young's modulus of 25 GPa / (g / cm ³ ) or more. In the present invention, the “specific Young's modulus” refers to a value obtained by dividing the Young's modulus obtained by the resonance method by the density.

  Twelfth, the glass for a flat image display device of the present invention is characterized in that the crack occurrence rate is 70% or less. In the present invention, the “crack occurrence rate” is the value obtained by optically polishing a square square pyramid-shaped Vickers indenter set to a load of 50 g in a constant temperature and humidity chamber maintained at a humidity of 30% and a temperature of 25 ° C. After performing the procedure of driving for 15 seconds and counting the number of cracks generated from the four corners of the indentation 15 seconds later (maximum 4 per indentation) 20 times for the same glass, (total crack count) (Number / 80) × 100 (%).

Thirteenth, the glass for a flat image display device of the present invention is characterized in that a temperature corresponding to a high temperature viscosity of 10 ^2.5 dPa · s is 1600 ° C. or lower. In the present invention, “temperature corresponding to high temperature viscosity of 10 ^2.5 dPa · s” refers to a value measured by a platinum ball pulling method.

  Fourteenth, the glass for a flat image display device of the present invention is characterized in that the flat image display device is an FED.

  15thly, the glass substrate for flat image display apparatuses of this invention is characterized by being comprised from the said glass for flat image display apparatuses.

  16thly, the manufacturing method of the glass substrate for flat image display devices of this invention is a manufacturing method of the said glass substrate for flat image display devices, Comprising: The shaping | molding method of a glass substrate is an overflow downdraw method Attached.

  The reason why the glass composition is limited to the above range will be described in detail below. In addition, the following% display points out mol% display, unless there is particular limitation.

SiO ₂ is a glass network former, and its content is 60 to 90%, preferably 63 to 80%, more preferably 65 to 75%, and still more preferably 68 to 73%. When the content of SiO ₂ exceeds 90%, it becomes difficult to melt and mold the glass, or the thermal expansion coefficient becomes too small to make it difficult to match the surrounding materials. On the other hand, when the content of SiO ₂ is less than 60%, the thermal expansion coefficient becomes too large, the thermal shock resistance of the glass is lowered, vitrification becomes difficult, and the dielectric constant tends to increase.

Al ₂ O ₃ is a component that increases the strain point and Young's modulus of glass, and its content is 3 to 10%, preferably 3 to 9%, more preferably 4 to 8%, and still more preferably 5 to 7%. It is. When the content of Al ₂ O ₃ is more than 10%, the devitrification resistance of the glass is deteriorated, the high-temperature viscosity is increased, and the meltability of the glass tends to be deteriorated. When the content of Al ₂ O ₃ is less than 3%, the thermal expansion coefficient increases, and the thermal shock resistance of the glass tends to decrease or the strain point of the glass tends to decrease. When manufacturing a flat image display device In the heat treatment step, the glass substrate is easily cracked, or is likely to be thermally deformed or contracted.

B ₂ O ₃ is a component that lowers the dielectric constant of glass and is an essential component. Further, B ₂ O ₃ improves the melting property of the glass is a component having an effect of suppressing devitrification, the content thereof is 0.01% to 10%, preferably 0.1 to 10% More preferably, it is 0.5-8%, More preferably, it is 1-5%, Most preferably, it is 1.5-3%. When the content of B ₂ O ₃ is more than 10%, the strain point tends to be lowered, and the glass substrate is cracked in the heat treatment process when the flat image display device is manufactured, and thermal deformation and thermal shrinkage occur. It tends to occur. On the other hand, when the content of B ₂ O ₃ exceeds 10%, the Young's modulus tends to decrease. On the other hand, when the content of B ₂ O ₃ is less than 0.01%, it is difficult to obtain the effect of reducing the dielectric constant.

Li ₂ O is a component that lowers the high-temperature viscosity and adjusts the thermal expansion coefficient, and its content is 0 to 4%, preferably 0 to 3%, more preferably 0 to 2%, still more preferably 0 to 0%. 1%, most preferably substantially free. When the content of Li ₂ O is more than 4%, the strain point is remarkably lowered, the thermal expansion coefficient is excessively increased, the density is increased, and the devitrification resistance tends to be deteriorated. Here, “substantially free of Li ₂ O” refers to a case where the content of Li ₂ O is 1000 ppm or less.

Na ₂ O is a component that lowers the high-temperature viscosity and adjusts the thermal expansion coefficient, and is a component that has an effect of increasing the Young's modulus among alkali metal oxides, and its content is preferably 0 to 7%, preferably Is 0 to 6%, more preferably 0 to 5%, still more preferably 0 to 4%. When the content of Na ₂ O is more than 7%, the strain point is lowered or the thermal expansion coefficient is too high. Further, from the viewpoint of accurately obtaining a glass having a high liquid phase viscosity, the content of Na ₂ O is preferably 0.5% or more, 1% or more, 1.5% or more, particularly 2% or more.

K ₂ O is a component that adjusts the coefficient of thermal expansion by lowering the high-temperature viscosity, and it is a component that makes it difficult to lower the viscosity near the liquidus temperature among alkali metal oxides, and makes it easy to obtain a glass with a high liquidus viscosity. The content is 0 to 8%, preferably 0.1 to 7%, more preferably 0.5 to 6%, still more preferably 1 to 5%, and most preferably 1.5 to 5%. When the content of K ₂ O is more than 8%, the strain point is lowered or the thermal expansion coefficient is too high. Further, from the viewpoint of obtaining a glass having a high liquid phase viscosity, the content of K ₂ O is preferably 0.1% or more, 0.5% or more, 1% or more, particularly 1.5% or more.

  MgO is a component that increases the strain point of the glass and at the same time lowers the high temperature viscosity, and its content is 0 to 3%, more preferably 0 to 1%, still more preferably 0 to 0.5%, most preferably. Is not substantially contained. When the content of MgO exceeds 3%, the density and the thermal expansion coefficient tend to be too high, and the devitrification resistance tends to deteriorate. From the viewpoint of increasing the strain point of the glass and at the same time reducing the high temperature viscosity, the above effect can be easily obtained if the MgO content is 0.1% or more, or 0.5% or more. It is necessary to limit the content thereof to such an extent that the devitrification resistance is not lowered. Here, “substantially free of MgO” refers to a case where the content of MgO is 1000 ppm or less.

  CaO is a component that lowers the high temperature viscosity without significantly reducing the strain point, and its content is 0 to 4%, more preferably 0 to 3.5%. When the content of CaO exceeds 4%, the density and the thermal expansion coefficient tend to be too high, and the devitrification resistance tends to deteriorate. From the viewpoint of accurately suppressing the deterioration of devitrification resistance, it is desirable that CaO is not substantially contained. Here, “substantially free of CaO” refers to a case where the content of CaO is 1000 ppm or less.

  SrO is a component that reduces the high temperature viscosity without deteriorating the devitrification resistance, without significantly reducing the strain point, and its content is 0 to 15%, preferably 2 to 13%, more preferably. It is 4 to 13%, more preferably 5 to 13%, and most preferably 6 to 10%. If the SrO content is more than 15%, the density and thermal expansion coefficient will be too high, or the balance of the glass composition will be lost, and the devitrification resistance will be deteriorated.

  BaO is a component that lowers the high temperature viscosity without significantly reducing the strain point in addition to not deteriorating the devitrification resistance, and its content is 0 to 15% (preferably 2 to 13%, 3 -10%, 4-10%, 5-9%). When the content of BaO is higher than 15%, the thermal expansion coefficient becomes too high, the density becomes high, or the balance of the glass composition is lost, and the devitrification resistance deteriorates conversely.

ZrO ₂ is a component that increases the strain point and Young's modulus, and its content is 0 to 8% (preferably 0.01 to 8%, 0.1 to 7%, 0.5 to 6%, 1 to 5%, 1-4%). If the ZrO ₂ content is more than 8%, the devitrification resistance may deteriorate, and the surface quality of the glass substrate such as average surface roughness and undulation may be adversely affected.

  The total amount of MgO + CaO + SrO + BaO is preferably 5 to 20%, more preferably 7 to 18%, still more preferably 8 to 14%. When the total amount of MgO + CaO + SrO + BaO exceeds 20%, the density and thermal expansion coefficient of the glass tend to increase and the devitrification resistance also tends to deteriorate. On the other hand, if the total amount of MgO + CaO + SrO + BaO is less than 5%, the meltability of the glass deteriorates or the thermal expansion coefficient becomes too small.

Further, 0.9 to 1.2 (preferably, 0.95 to 1.15) the value of the BaO / Al ₂ O ₃ in a molar fraction set to, without deteriorating the devitrification resistance of the glass, This is preferable because a high strain point can be achieved. When the molar fraction of BaO / Al ₂ O ₃ exceeds 2, the strain point is lowered and the density and the thermal expansion coefficient tend to be too high.

Furthermore, the effect of increasing the strain point while setting the molar fraction of BaO / Al ₂ O ₃ in the range of 0.9 to 1.2 and suppressing the deterioration of devitrification resistance is Na in terms of molar fraction. The value of ₂ O / K ₂ O is adjusted to a range of 0 to 2 (preferably 0 to 1.5, 0.3 to 1.4, 0.7 to 1.1, 0.8 to 0.9). By doing so, it becomes possible to enjoy more accurately. On the other hand, when the molar fraction of Na ₂ O / K ₂ O exceeds 2, the strain point is lowered or the balance of the glass composition is lost, and devitrification tends to occur. When the molar fraction of Na ₂ O / K ₂ O is small, the above effect due to adjustment of the molar fraction of Al ₂ O ₃ / BaO is somewhat difficult to obtain, so the molar fraction of Na ₂ O / K ₂ O More preferably, the rate is 0.3 or more.

From the viewpoint of reducing the glass crack generation rate, keeping the glass strain point high and not increasing the thermal expansion coefficient too much, the value of (Na ₂ O + K ₂ O) / (MgO + CaO + SrO + BaO) is set to 0 to 1 in terms of molar fraction. Is preferably set to 0.2 to 0.8, more preferably 0.3 to 0.8, and most preferably 0.5 to 0.8. preferable. If the value of (Na ₂ O + K ₂ O) / (MgO + CaO + SrO + BaO) in mass fraction is larger than 1, there is a possibility that the above effect cannot be enjoyed accurately.

In the glass for a flat image display device of the present invention, various components other than the above components can be added up to 10% within a range not impairing the properties of the glass. For example, ZnO, TiO ₂ , CeO ₂ , Y ₂ O ₃ , La ₂ O ₃ , and Nb ₂ O ₅ may be contained at 10% or less, respectively. Further, Fe ₂ O ₃ as a coloring _{agent, CoO, NiO, Cr 2 O} 3, Nd 2 O 5 and may each be contained below 2%. Further, As ₂ O ₃ as a fining _{agent, SO 3, Sb 2 O 3} , SnO 2, F, may be contained 0-3% in total of one or two or more selected from the group of Cl.

In the above composition range, it is naturally possible to select a preferred composition range by arbitrarily combining preferred ranges of the respective components, but among them, a more preferred composition range as a glass for a flat image display device is _{SiO 2 60~89%, Al 2 O} 3 4~8%, B 2 O 3 1~5%, Li 2 O 0~2%, Na 2 O 0~5%, K 2 O 1~5%, MgO 0~1%, CaO 0~4%, SrO 2~13%, containing 3 to 10% BaO, the value of BaO / Al ₂ O ₃ mole fraction is 0.9 to 1.2, and Glass having an average thermal expansion coefficient at 30 to 380 ° C. of 60 to 80 × 10 ⁻⁷ / ° C., 25 ° C., and a dielectric constant at 1 MHz of less than 9 is exemplified. If the composition range of the glass is regulated as described above, the devitrification resistance can be greatly improved, and a glass having a low dielectric constant can be obtained accurately.

As a further preferred embodiment of the glass for a flat image display _{apparatus, SiO 2 68~73%, Al 2} O 3 5~7%, B 2 O 3 1.5~3%, Li 2 O less than 0 to 0.5 percent, Contains Na ₂ O 0-4%, K ₂ O 1.5-5%, MgO 0-0.5%, CaO 0-4%, SrO 6-10%, BaO 2-8%, mole fraction The BaO / Al ₂ O ₃ value is 0.9 to 1.2, the average thermal expansion coefficient at 30 to 380 ° C. is 65 to 75 × 10 ⁻⁷ / ° C., 25 ° C., the dielectric constant at 1 MHz is 7 And glass having a thickness of 5 or less. If the composition range of the glass is restricted to the above, devitrification resistance can be remarkably improved, and a glass having a low dielectric constant can be obtained more accurately.

The flat image display glass of the present invention has an average coefficient of thermal expansion at 30 to 380 ° C. of 50 to 90 × 10 ⁻⁷ / ° C., preferably 55 to 85 × 10 ⁻⁷ / ° C., more preferably 60 to 80 × 10 ⁻⁷ / ° C. From the viewpoint of reliably frit-sealing and reliably preventing cracking of the glass substrate in a heat treatment step such as film formation when manufacturing a flat image display device, it is preferably less than 65 to 80 × 10 ⁻⁷ / ° C., 65 -75 * 10 < ^-7 > / degreeC is more preferable. When the average thermal expansion coefficient at 30 to 380 ° C. is smaller than 50 × 10 ⁻⁷ / ° C., the thermal expansion coefficient of the sealing glass for frit-sealing the front glass substrate and the rear glass substrate cannot be obtained, and the sealing step Later, problems such as cracks are likely to occur in the glass substrate. Moreover, when the average thermal expansion coefficient in 30-380 degreeC is larger than 90 * 10 < ^-7 > / degreeC, there exists a possibility that it may not match with the thermal expansion coefficient of the other peripheral member used for a flat image display apparatus.

  In the glass for a flat image display device of the present invention, the dielectric constant at 25 ° C. and 1 MHz is less than 9, preferably 8.5 or less, more preferably 8 or less, still more preferably 7.5 or less, and most preferably 7 or less. . If the dielectric constant of the glass is less than 9, even if a low dielectric constant film is not formed on the surface of the glass substrate, a charge current flows first due to the stray capacitance component, and stable electron emission cannot be obtained. Therefore, stable electron emission characteristics can be ensured, and as a result, a bright and clear display image can be stably provided in the flat image display device. Furthermore, since the dielectric constant of the glass substrate for a flat image display device of the present invention is less than 9, the amount of current required for light emission of the flat image display device can be reduced, and the power consumption of the flat image display device can be reduced. Can also contribute. However, if the dielectric constant of the glass is 9 or more, a stray capacitance component is generated from the glass substrate, which causes a charging current to flow, making it impossible to ensure stable electron emission characteristics, and high efficiency and high speed. It becomes impossible to maintain the electron emission characteristics in response to

In the planar image display device for glass of the present invention, the density is preferably at 3.0 g / cm ³ or less, more preferably 2.9 g / cm ³ or less. The lower the density of the glass, the lighter the glass can be, which can contribute to the weight reduction of the flat image display device. When the density is larger than 3.0 g / cm ³ , it is difficult to contribute to weight reduction of the flat image display device.

  In the glass for a flat image display device of the present invention, the strain point is preferably 590 ° C. or higher (preferably 600 ° C. or higher, 610 ° C. or higher, 620 ° C. or higher, 630 ° C. or higher). When the strain point is less than 590 ° C., thermal contraction of the glass substrate is likely to occur during a heat treatment step such as film formation when manufacturing a flat image display device, and patterning deviation of the gate electrode or the like is likely to occur.

  In the glass for a flat image display device of the present invention, the liquidus temperature is preferably 1200 ° C. or lower, more preferably 1100 ° C. or lower, still more preferably 1080 ° C. or lower, and most preferably 1050 ° C. or lower. In general, the overflow down draw method has a higher viscosity at the time of glass molding than other molding methods, so if the devitrification resistance of the glass is poor, devitrification will occur during molding and the glass substrate There is a risk that molding may become impossible. Specifically, if at least the liquidus temperature is higher than 1200 ° C., it is difficult to apply the overflow downdraw method. Therefore, if the liquidus temperature is higher than 1200 ° C., an unreasonable restriction is imposed on the method for forming the glass for a flat image display device, and there is a possibility that glass having a desired surface shape cannot be formed. The lower the liquidus temperature, the better the devitrification resistance of the glass.

In the glass for a flat image display device of the present invention, the liquid phase viscosity is preferably 10 ^4.5 dPa · s or more, more preferably 10 ^5.0 dPa · s or more, further preferably 10 ^5.5 dPa · s or more, and 10 ^5.8 dPa · s or more. Is most preferred. In general, the overflow down draw method has a higher viscosity at the time of glass molding than other molding methods, so if the devitrification resistance of the glass is poor, devitrification will occur during molding, and the glass substrate There is a possibility that it cannot be molded. Specifically, when the liquid phase viscosity is less than 10 ^4.5 dPa · s, it is difficult to apply the overflow downdraw method. Therefore, if the liquid phase viscosity is less than 10 ^4.5 dPa · s, an unreasonable restriction is imposed on the method for forming the glass for a flat image display device, and there is a possibility that a glass having a desired shape cannot be formed. Note that the higher the liquidus viscosity, the better the devitrification resistance of the glass.

In the planar image display device for glass of the present invention, specific Young's modulus is preferably 25GPa / g · cm ^-3 or more, more preferably 25.4GPa / g · cm ^-3 or more, 25.7GPa / g · cm ^-3 or more Is more preferable. If the specific Young's modulus is less than 25 GPa / g · cm ⁻³ , the glass substrates will bend and come into contact with each other during the FED manufacturing process, for example, when loading and unloading the cassette, and this will cause cracks in the glass. It becomes easy to do. In particular, in the case of a large and thin glass substrate, the tendency becomes remarkable.

  In the glass for a flat image display device of the present invention, the crack occurrence rate is preferably 70% or less, more preferably 60% or less, and further preferably 55% or less. If the crack generation rate is greater than 70%, the glass substrate may be broken by stress caused by the film formed on the glass substrate, or the glass substrate may be broken by other mechanical impacts.

In the glass for a flat image display device of the present invention, the temperature corresponding to the high temperature viscosity of 10 ^2.5 dPa · s is preferably 1650 ° C. or less, more preferably 1620 ° C. or less, and further preferably 1600 ° C. or less. The lower this temperature is, the faster the rising speed of bubbles present in the glass at the time of melting, so that it becomes easier to reduce bubbles and the bubble quality is improved. In addition, the lower the temperature, the more the durability of the furnace refractory is improved. As a result, it is possible to contribute to improving the durability of the melting furnace and the like. When the temperature corresponding to the high temperature viscosity of 10 ^2.5 dPa · s is higher than 1650 ° C., the rising speed of bubbles existing in the glass at the time of melting becomes slow, so that it becomes difficult to reduce the bubbles and the bubble quality deteriorates. In addition, when the temperature corresponding to the high temperature viscosity of 10 ^2.5 dPa · s is higher than 1650 ° C., the durability of the furnace refractory also decreases, and as a result, the durability of the melting furnace or the like decreases, and the manufacturing cost of the glass decreases. Invite soaring.

  In the glass for a flat image display device of the present invention, the flat image display device is preferably an FED. Since the glass for flat image display devices of the present invention satisfies the characteristics required for a glass substrate for FED, it can be suitably used for this application. In particular, the glass for a flat image display device of the present invention not only can reduce the dielectric constant, but can not only improve the surface quality of the glass substrate, but also satisfy the characteristics such as the thermal expansion coefficient at the same time. , It can be suitably used for this application. Therefore, the glass for a flat image display device of the present invention can suppress a situation in which a stray capacitance component is generated from the glass substrate, and can ensure stable electron emission characteristics. In addition, since the accuracy of sputtering can be increased when forming the electron-emitting device, it is possible to perform high-precision photolithography and form a circuit pattern with high accuracy. This can contribute to ensuring the reliability (for example, the probability of occurrence of disconnection or short-circuit can be reduced). As a result, the FED using the glass for a flat image display device of the present invention can stably provide a bright and clear display image.

  In the glass substrate for a flat image display device of the present invention, the average surface roughness (Ra) is preferably 10 mm or less, more preferably 7 mm or less, still more preferably 4 mm or less, and most preferably 2 mm or less. If the average surface roughness (Ra) is larger than 10 mm, it becomes difficult to perform accurate patterning of gate electrodes and the like in the manufacturing process of FED and the like, and as a result, the probability that the circuit electrodes are disconnected and shorted increases. It becomes difficult to ensure the reliability of the image display device. In the present invention, “average surface roughness (Ra)” refers to a value measured by a method based on SEMI D7-94 “Measurement Method of Surface Roughness of FPD Glass Substrate”.

  In the glass substrate for a flat image display device of the present invention, the undulation is preferably 0.1 μm or less, more preferably 0.05 μm or less, still more preferably less than 0.03 μm, and most preferably 0.01 μm or less. Furthermore, ideally, it is desirable that there is substantially no swell. In recent years, large screens and high definition of flat image display devices have been advanced. When the screen size of the flat image display device is increased, the video quality of the flat image display device may be impaired when the glass substrate has waviness. Therefore, if the swell is larger than 0.1 μm, it becomes difficult to satisfy the demand for a larger screen and higher definition of a recent flat image display device. If the waviness is larger than 0.1 μm, in the manufacturing process such as FED, the focus is not obtained at the time of exposure, and the patterning with high accuracy cannot be performed. As a result, the gate hole shape varies, and the desired cone shape is obtained. There is a risk of disappearing. In the electron-emitting device, electrons can be efficiently emitted at a low voltage at a portion where the electric field is concentrated. Therefore, when a desired conical shape cannot be obtained, the drive voltage is increased or electrons are not emitted. Such a problem may occur. In the present invention, “swell” is a value obtained by measuring WCA (filtered centerline swell) described in JIS B-0610 using a stylus type surface shape measuring device. Measured by a method based on STD D15-1296 “Measurement method of surface waviness of FPD glass substrate”, the cut-off at the time of measurement is 0.8 to 8 mm, and the length is 300 mm in the direction perpendicular to the drawing direction of the glass substrate. It was measured by the above.

  In the glass substrate for a flat image display device of the present invention, the difference between the maximum plate thickness and the minimum plate thickness is preferably 20 μm or less, and more preferably 10 μm or less. When the screen size of the flat image display device is increased, if the difference between the maximum thickness and the minimum thickness of the glass substrate is 20 μm or less, large distortion (streaks) is likely to occur on the screen, and as a result, the image is localized. And the image quality of the flat image display device deteriorates. Therefore, if the difference between the maximum thickness and the minimum thickness of the glass substrate is larger than 20 μm, it is not possible to satisfy the recent demand for larger screen and higher definition of flat image display devices. In addition, if the difference between the maximum thickness and the minimum thickness of the glass substrate is larger than 20 μm, the FED and other manufacturing processes are not focused during exposure, and high-precision patterning cannot be performed, resulting in variations in the gate hole shape. Therefore, there is a possibility that a desired cone shape cannot be obtained. In the electron-emitting device, electrons can be efficiently emitted at a low voltage at a portion where the electric field is concentrated. Therefore, when a desired conical shape cannot be obtained, the drive voltage is increased or electrons are not emitted. Such a problem may occur. Here, in the present invention, the “thickness difference between the maximum plate thickness and the minimum plate thickness” is obtained by scanning the laser from the plate thickness direction on any one side of the glass substrate using a laser type thickness measuring apparatus. Measures the maximum and minimum plate thicknesses of a substrate and indicates the value obtained by subtracting the minimum plate thickness from the maximum plate thickness value.

  In the glass substrate for a flat image display device of the present invention, the error with respect to the target plate thickness is preferably 10 μm or less, and more preferably 5 μm or less. If the error with respect to the target thickness of the glass substrate is larger than 10 μm, patterning of the gate electrode cannot be performed with high accuracy, and it becomes difficult to stably manufacture a high-quality flat image display device under a predetermined condition. There is a possibility that the manufacturing efficiency of the image display device is lowered. In the present invention, the “error with respect to the target plate thickness” is a value obtained by subtracting the minimum plate thickness obtained by the above method from the target plate thickness or a value obtained by subtracting the target plate thickness from the maximum plate thickness obtained by the above method. Point to the larger one.

In the glass substrate for a flat image display device of the present invention, the glass substrate tends to increase in size, but as the substrate area increases, the probability that devitrified substances appear in the substrate increases and the surface required for the glass substrate In addition to severe quality, it becomes difficult to form a glass substrate. Therefore, according to the alkali-free glass substrate of the present invention having good devitrification resistance and the like, the effects of the present invention can be enjoyed accurately, and there is a great merit particularly in producing a large glass substrate. . For example, the substrate area is 0.1 m ² or more (specifically, a size of 320 mm × 420 mm or more), particularly 0.5 m ² or more (specifically, a size of 630 mm × 830 mm or more), 1.0 m ² or more ( Specifically, a size of 950 mm × 1150 mm or more, further 2.3 m ² or more (specifically, a size of 1400 mm × 1700 mm or more), 3.5 m ² or more (specifically, 1750 mm × 2050 mm or more) The size becomes larger as the size increases to 4.8 m ² or more (specifically, the size of 2100 mm × 2300 mm or more).

  In the glass substrate for a flat image display device of the present invention, the flat image display device is preferably an FED. Since the glass substrate for flat image display devices of the present invention satisfies the characteristics required for a glass substrate for FED, it can be suitably used for this application. In particular, since the glass substrate for a flat image display device of the present invention can be formed by the overflow downdraw method, not only can the surface quality of the glass substrate be improved, but also the characteristics such as the thermal expansion coefficient are satisfied at the same time. Therefore, it can be suitably used for this application.

  The glass for a flat image display device of the present invention is prepared by putting a glass raw material prepared so as to have a desired glass composition into a continuous melting furnace, heating and melting the glass raw material, defoaming, and then supplying it to a molding device. It can be produced by forming molten glass into a plate shape and slowly cooling it.

  From the viewpoint of manufacturing a glass substrate with good surface quality, it is preferable to form a plate by an overflow down draw method. The reason for this is that, in the case of the overflow down draw method, the surface to be the surface of the glass substrate does not come into contact with the bowl-like refractory, and is molded in a free surface state. This is because it can be molded. Here, the overflow down draw method is to melt the molten glass from both sides of the heat-resistant bowl-like structure and draw the overflowed molten glass downward while joining at the lower end of the bowl-like structure. This is a method for producing a glass substrate. The structure and material of the bowl-shaped structure are not particularly limited as long as the dimensions and surface accuracy of the glass substrate are set to a desired state and can be used for a glass substrate for a flat image display device. Moreover, in order to perform the downward extending | stretching shaping | molding, you may apply force with what kind of method with respect to a glass substrate. For example, a method may be employed in which a heat-resistant roll having a sufficiently large width is rotated and stretched in contact with the glass substrate, or a plurality of pairs of heat-resistant rolls are only near the end face of the glass substrate. You may employ | adopt the method of making it contact and extending | stretching. Since the glass for a flat image display device of the present invention has excellent devitrification resistance and has a viscosity characteristic suitable for molding, molding by the overflow downdraw method can be performed with high accuracy.

  In addition to the overflow down draw method, various methods can be adopted as the method for producing a glass substrate for a flat image display device of the present invention. For example, various forming methods such as a float method, a slot down draw method, an overflow down draw method, a redraw method, and a roll out method can be employed. From the viewpoint of manufacturing a glass substrate at low cost, it is preferable to form the glass substrate by a float method. The reason is that in the case of the float process, it is easy to obtain a large plate glass at a relatively low cost.

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

In Tables 1 and 2, Sample No. 1 to 6, 12, and 13 show examples of the present invention . 7 to 11 and 14 show reference examples of the present invention . Reference numeral 15 denotes a comparative example of the present invention.

  Each sample was produced as follows.

  First, various glass raw materials were prepared so as to have the compositions shown in Tables 1 and 2. These raw materials were melted at 1580 ° C. for 5.5 hours using a platinum pot. Thereafter, the molten glass was poured out on a carbon plate, formed into a plate shape, and subjected to various evaluations.

  Each sample thus prepared was measured for average thermal expansion coefficient, dielectric constant, density, strain point, liquidus temperature, liquidus viscosity, high temperature viscosity, Young's modulus, specific Young's modulus, and crack generation rate. The results are shown in Tables 1 and 2.

  The thermal expansion coefficient is obtained by measuring an average thermal expansion coefficient at 30 to 380 ° C. using a dilatometer.

  The dielectric constant was measured by a method based on ASTM C336-71.

  The density was measured by the well-known Archimedes method.

  The strain point was measured by a method based on ASTM C336-71.

  The liquid phase temperature is measured by crushing glass, passing through a standard sieve 30 mesh (500 μm), putting the glass powder remaining on 50 mesh (300 μm) into a platinum boat, holding it in a temperature gradient furnace for 48 hours, The temperature at which precipitation occurs is measured. The liquid phase viscosity is obtained by measuring the viscosity of each glass at the liquid phase temperature by a well-known platinum pulling method.

A temperature corresponding to a high temperature viscosity of 10 ^2.5 dPa · s was measured by a well-known platinum ball pulling method.

  Young's modulus was measured by a resonance method. The specific Young's modulus is a value obtained by dividing the Young's modulus obtained by the resonance method by the density.

  The crack generation rate was set in a constant temperature and humidity chamber maintained at a humidity of 30% and a temperature of 25 ° C. The procedure for counting the number of cracks generated from the four corners of the indentation (up to 4 per indentation) was performed 20 times on the same glass, and then (total crack count / 80) × 100 (% ).

As apparent from Tables 1 and 2, Sample No. 1 to 14 have an average thermal expansion coefficient of 68 to 73 × 10 ⁻⁷ / ° C., a dielectric constant of 7.0 to 7.3, a density of 2.81 to 2.88 g / cm ³ , and a strain point of 591 to 657. , Liquid phase temperature of 980-1150 ° C., liquid phase viscosity of 10 ^4.6 to 10 ^6.2 dPa · s, high temperature viscosity corresponding to 10 ^2.5 dPa · s of 1489 to 1555 ° C., Young's modulus of 73 to 76 GPa, specific Young The rate is 25.5 to 26.7 GPa / (g / cm ³ ), the crack occurrence rate is 49 to 55%, and all the samples have an average thermal expansion coefficient of 50 to 90 × 10 ⁻⁷ / ° C., 25 ° C., The dielectric constant at 1 MHz is less than 9, the density is 3.0 g / cm ³ or less, the strain point is 590 ° C. or higher, the liquidus temperature is 1200 ° C. or lower, the liquid phase viscosity is 10 ^4.5 dPa · s or higher, and the high temperature viscosity is 10 ^2.5 dPa · s. The temperature corresponding to s is 1600 ° C. or lower, and the specific Young's modulus is 25 GPa (G / cm ³⁾ or more, and the cracking incidence was 70% or less.

  As apparent from Table 2, the sample No. No. 15 had a low strain point of 510 ° C. and poor heat resistance.

  The flat image display glass of the present invention can satisfy the above-mentioned characteristics (1) to (6) required for a glass substrate used for an FED, and (7) has a low dielectric constant, so that it is low on the surface of the glass substrate. Even if a film having a dielectric constant is not formed, the stray capacitance component does not cause a situation in which a charging current first flows and stable electron emission cannot be obtained. As a result, stable electron emission characteristics can be ensured. Furthermore, the glass for a flat image display device of the present invention (8) has good devitrification resistance, and can obtain a glass suitable for the overflow downdraw method or the like, thereby improving the surface quality of the glass substrate. It becomes possible. As a result, it becomes possible to perform photolithography with high accuracy on the surface of the glass substrate and to form a circuit pattern with high accuracy, and to ensure the reliability of the flat image display device (for example, occurrence of disconnection or short circuit). The probability can be reduced). Therefore, according to the glass for a flat image display device of the present invention, the electron-emitting device can maintain the electron emission characteristic that responds with high efficiency and high speed for a long time. As a result, the flat image display device is bright and clear. It is possible to provide a stable display image stably. Especially for television applications, the pixel size is designed according to the screen size, and especially for high-definition televisions, a high-definition pixel size is applied, so the efficiency of electron emission characteristics is ensured from the viewpoint of ensuring sufficient luminance. Therefore, it can be said that the glass for a flat image display device of the present invention is advantageous also in that respect.

  Although the present invention has been described in detail for the case where the flat image display device is an FED, the glass for the flat image display device of the present invention is naturally not limited to the FED application. For example, TFT-LCD, STN- It can be suitably used for various applications such as LCD, plasma assist liquid crystal display (PALC), PDP, electroluminescence display (EL) and the like.

It is a structure schematic explanatory drawing of FED.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Spacer 2 Gate line 3 Back plate 4 Emitter line 5 Electron emission element 6 Black matrix 7 Phosphor 8 Front plate

Claims (15)

A glass composition, SiO ₂ 60 to 90% by _{mol%, Al 2 O 3 3~10%} , B 2 O 3 0.01~10%, Li 2 O 0~4%, Na 2 O 0~7%, K ₂ O 0-8%, MgO 0-3%, CaO 0-4%, SrO 0-15%, BaO 0-15%,
The BaO / Al ₂ O ₃ value in terms of mole fraction is 0.9 to 1.2,
The glass for flat image display devices has an average thermal expansion coefficient at 30 to 380 ° C. of 50 to 90 × 10 ⁻⁷ / ° C., and a dielectric constant at 25 ° C. and 1 MHz of less than 9. A glass composition, SiO ₂ 60-89% by _{mol%, Al 2 O 3 4~8%} , B 2 O 3 1~5%, Li 2 O 0~2%, Na 2 O 0~5%, K 2 O 1-5%, MgO 0-1%, CaO 0-4%, SrO 2-13%, BaO 3-10%,
The BaO / Al ₂ O ₃ value in terms of mole fraction is 0.9 to 1.2,
2. The glass for a flat image display device according to claim 1, wherein an average coefficient of thermal expansion at 30 to 380 ° C. is 60 to 80 × 10 ⁻⁷ / ° C., a dielectric constant at 25 ° C. and 1 MHz is less than 9. . A glass composition, SiO ₂ 68 to 73% by _{mol%, Al 2 O 3 5~7%} , B 2 O 3 1.5~3%, Li 2 O less than 0~0.5%, Na ₂ O 0~ 4%, K ₂ O 1.5-4%, MgO 0-0.5%, CaO 0-4%, SrO 6-10%, BaO 2-8%,
The BaO / Al ₂ O ₃ value in terms of mole fraction is 0.9 to 1.2,
The planar image according to claim 1, wherein an average coefficient of thermal expansion at 30 to 380 ° C. is 65 to 75 × 10 ⁻⁷ / ° C., a dielectric constant at 25 ° C. and 1 MHz is 7.5 or less. Glass for display devices. The flat image display glass according to any one of claims 1 to 3 , wherein the Na ₂ O / K ₂ O value is 0 to 2 in terms of mole fraction. The mole fraction _{(Na 2 O + K 2 O} ) / (MgO + CaO + SrO + BaO) planar image display device for glass according to any one of claims 1 to 4, wherein the value of 0-1. Planar image display device for glass according to any one of claims 1 to 5, the density is equal to or is 3.0 g / cm ³ or less. The glass for flat image display devices according to any one of claims 1 to 6 , wherein a strain point is 590 ° C or higher. Planar image display device for glass according to any one of claims 1 to 7, wherein the liquidus temperature of 1200 ° C. or less. The liquid phase viscosity is 10 ^4.5 dPa · s or more, and the glass for a flat image display device according to any one of claims 1 to 8 . Specific Young's modulus 25GPa / (g / cm ³⁾ or more in the planar image display device for glass according to any one of claims 1 to 9, characterized in that. The flat image display glass according to any one of claims 1 to 10, wherein a crack occurrence rate is 70% or less. The glass for a flat image display device according to any one of claims 1 to 11 , wherein a temperature corresponding to a high temperature viscosity of 10 ^2.5 dPa · s is 1600 ° C or lower. The flat image display device glass according to any one of claims 1 to 12 , wherein the flat image display device is a field emission display. A glass substrate for a flat image display device, comprising the glass for a flat image display device according to any one of claims 1 to 13 . A method for producing a glass substrate for a flat image display device according to claim 14 ,
A method for producing a glass substrate for a flat image display device, wherein the glass substrate is formed by an overflow downdraw method.