JP2007308329A - Glass for flat image display device, glass substrate using the same, and method for manufacturing the glass substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a glass substrate for a flat image display device, which has good surface quality, by obtaining glass high in devitrification resistance and suitable for an overflow-down-draw method. <P>SOLUTION: In the glass for a flat image display device, the composition of the glass is regulated within a range of 45-70 mass% SiO<SB>2</SB>, 3-20% mass% Al<SB>2</SB>O<SB>3</SB>, 0-10% mass% B<SB>2</SB>O<SB>3</SB>, 0-10 mass% MgO, 0-10 mass% CaO, 0-17 mass% SrO, 0-17 mass% BaO, 0-10 mass% Na<SB>2</SB>O, 0-10 mass% K<SB>2</SB>O, and 0.01-8 mass% ZrO<SB>2</SB>, and the coefficient of thermal expansion within a temperature range of 30 to 380°C is set to be 50-90×10<SP>-7</SP>/°C. <P>COPYRIGHT: (C)2008,JPO&INPIT

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 surface of the material is gradually narrowed according to the strength. As a result, it is possible to break through the energy barrier and use the phenomenon that electrons are emitted from the material. 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 Spindt-type emitter is widely known as such a general field emission type electron-emitting device.

  In the manufacturing process of the Spindt-type emitter, the insulating layer and the gate electrode are sequentially formed on the insulating substrate on which the conductive layer is formed by a sputtering method, a vacuum evaporation method, or the like. Subsequently, the insulating layer and part of the gate electrode are etched using a photolithography method and a reactive ion etching method (RIE) so that a circular hole (gate hole) is opened until the conductive layer is exposed. . Next, a release layer is formed only on the top and side surfaces of the gate electrode by oblique deposition. Subsequently, a metal material for an emitter is deposited on the conductive layer by normal anisotropic deposition from the perpendicular direction. At this time, as the deposition progresses, the opening diameter of the gate hole is narrowed, and at the same time, a conical emitter is formed on the conductive layer in a self-aligning manner. Deposition is performed until the gate hole is finally closed. Finally, the peeling layer is peeled off by etching, and the gate electrode is patterned as necessary. As a result, a field electron emission device including a Spindt-type emitter is obtained. That is, various films and emitters such as a transparent electrode and an insulating film are formed on the surface of a glass substrate used for FED, and various circuits and patterns are formed by photolithography etching (photoetching).

The glass substrate used for the FED is required to have the following characteristics.
(1) Have 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 does not shrink due to heat shrinkage in the heat treatment process such as film formation. (3) No internal defects that affect the image quality of the FED, especially no bubble defects (4) Low density to reduce the overall weight of the FED By the way, in recent years, in order to produce an FED with high electron emission efficiency, it is required to further improve the accuracy of photolithography. In order to improve the accuracy of photolithography, it is necessary to collect light passing through the mask more. However, if light is collected more, the depth of focus becomes shallower. Therefore, if the flatness of the glass substrate is poor, the focal point is not obtained during exposure, and high-precision patterning cannot be performed. As a result, the gate hole shape varies, so that a desired conical shape may not be obtained. As described above, the electron-emitting device can efficiently emit electrons at a low voltage in a portion where the electric field is concentrated. However, when a desired conical shape cannot be obtained, the drive voltage becomes high. Or there may be a problem that electrons are not emitted.

  Under such circumstances, in addition to the above required characteristics (1) to (4), the glass substrate for FED is required to have (5) excellent surface shape of the glass substrate, that is, excellent flatness of the glass substrate. Is done. The flatness of the glass substrate is determined by various factors, and the most influential factor is a glass substrate forming method and a processing method.

  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 an excellent surface shape.

  On the other hand, the overflow downdraw 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 is desirable that the glass substrate for FED has (6) a glass composition that is not easily devitrified.

  However, conventional FED glass substrates do not satisfy all of the above required characteristics (1) to (6), and in particular, it is difficult to obtain a glass having good devitrification resistance. The method could not be adopted and was manufactured by a molding method such as a float method. As a result, it was difficult to obtain a glass substrate with good surface quality as a glass substrate for FED.

  Therefore, the present invention can satisfy the above required characteristics (1) to (4), has good devitrification resistance, and has a surface quality by obtaining a glass suitable for the overflow down draw method or the like. It is a technical problem to obtain a good glass substrate.

The present inventors, as a result of extensive studies, the glass for a flat image display apparatus, the composition range of the glass, SiO ₂ 45 to 70% by _{mass%, Al 2 O 3 3~20%} , B 2 O 3 0~10 %, 0~10% MgO, CaO 0~10 %, SrO 0~17%, BaO 0~17%, Na 2 O 0~10%, K 2 O 0~10%, ZrO 2 0.01~8% It is found that the above problem can be solved by setting the thermal expansion coefficient at 30 to 380 ° C. to 50 to 90 × 10 ⁻⁷ / ° C., and is proposed as the present invention. In addition, in this invention, "The thermal expansion coefficient in 30-380 degreeC" points out the value which measured the average thermal expansion coefficient in 30-380 degreeC using the dilatometer.

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 specifically required to be at least a liquid phase temperature of 1200 ° C. or lower and a liquid phase viscosity of 10 ^4.5 dPa · s or higher. Since the glass for flat image display apparatus regulates the glass within the above-mentioned range, it has good devitrification resistance, a liquidus temperature of 1200 ° C. or less, and a liquidus viscosity of 10 ^4.5 dPa · s or more. Can be achieved. 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. 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 down draw 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.

Further, the present inventor has found that in order to improve the surface quality of the glass substrate, it is sufficient to reduce the melting and separation of the glass during melting. That is, it has been clarified that a slight difference in thermal expansion coefficient due to the composition difference generates a portion having a different volume shrinkage rate during glass molding, and that portion is a cause of worsening the surface roughness and waviness of the glass substrate. Further, as the main component to produce a composition difference of the glass has a high contribution of ZrO _2, it was also discovered that it is possible to reduce striae by subtracting the components. On the other hand, ZrO ₂ is found to be a necessary component for increasing the strain point and ensuring the viscosity necessary for performing the overflow downdraw method, and does not cause glass striae and is sufficient. In order to ensure the strain point and the liquid phase viscosity, it has been found that the content of ZrO ₂ may be regulated to an appropriate amount. Therefore, the glass for a flat image display device of the present invention can suppress the difference in the composition of the glass by restricting the ZrO ₂ content to a range of 0.01 to 8% as the glass composition, and the viscosity characteristic of the glass. As a result, it is possible to give the glass advantageous properties for ensuring the surface quality of the glass substrate.

Furthermore, the glass for a flat image display device of the present invention can perform frit sealing satisfactorily by regulating the thermal expansion coefficient at 30 to 380 ° C. to 50 to 90 × 10 ⁻⁷ / ° C. It is possible to accurately prevent the glass substrate from cracking in a heat treatment step such as film formation when manufacturing the display device.

Secondly, the planar image display device for glass of the present invention, a glass composition, SiO ₂ 50-60% by _{mass%, Al 2 O 3 5~10%} , B 2 O 3 0~5%, MgO 0~ 5%, CaO 0~5%, SrO 5~12.5%, BaO 9~14%, Na 2 O 0~5%, K 2 O 3~6%, containing ZrO ₂ 1 to 4%, and It is characterized by a coefficient of thermal expansion at 30 to 380 ° C. of 65 to 80 × 10 ⁻⁷ / ° C.

Third, the glass for a flat image display device of the present invention has a glass composition of SiO ₂ 55 to 58%, Al ₂ O ₃ 7 to 9.5%, B ₂ O ₃ 0 to 2%, MgO as a glass composition. 0 to 3%, CaO 0 to 1%, SrO 7 to 10.5%, BaO 11.5 to 14%, Na ₂ O 1 to 5%, K ₂ O 3 to 6%, ZrO _{2 2.5 to 4} And a thermal expansion coefficient at 30 to 380 ° C. is 65 to 75 × 10 ⁻⁷ / ° C.

Fourthly, the glass for a flat image display device of the present invention is characterized in that, in the glass composition, the value of Al ₂ O ₃ / BaO is 0.1 to _{2 in} terms of molar fraction.

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

Sixth, the glass for a flat image display device of the present invention is characterized by having a liquidus temperature of 1200 ° C. or lower and / or a liquidus viscosity of 10 ^4.5 dPa · s or higher. In the present invention, the “liquid phase viscosity” is obtained by crushing glass, passing through a standard sieve 30 mesh (500 μm), and putting the glass powder remaining on 50 mesh (300 μm) into a platinum boat, and putting it in a temperature gradient furnace. The temperature at which the crystals are deposited is measured by keeping the time. 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.

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 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 1650 ° 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.

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

  Eleventh, the glass substrate for a flat image display device of the present invention is characterized by being composed of the glass for a flat image display device.

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

  13thly, the manufacturing method of the glass substrate for flat image display apparatuses of this invention is a manufacturing method of the said glass substrate for flat image display apparatuses, Comprising: The shaping | molding method of a glass substrate is an overflow downdraw method Attached.

  The flat image display glass of the present invention can satisfy the above required characteristics (1) to (4), has good devitrification resistance, and can obtain a glass suitable for an overflow down draw method or the like. By being able to do so, it becomes possible to improve the surface quality of the glass substrate. As a result, high-precision photolithography can be performed on the surface of the glass substrate, and the electron emission characteristics of the electron source can be stably maintained. Furthermore, since the glass substrate for a flat image display device of the present invention can perform photolithography with high accuracy, it becomes possible to form a circuit pattern with high accuracy and ensure the reliability of the flat image display device (for example, This can contribute to reducing the probability of occurrence of disconnection and short circuit.

  The reason why the composition range is limited as described above will be described in detail below. In addition, the following% display points out the mass% except the case where there is especially limitation.

SiO ₂ is a glass network former, and its content is 45 to 70%, preferably 48 to 65%, more preferably 50 to 60%, still more preferably 52 to 58%, most preferably 55 to 58%. %. When the content of SiO ₂ exceeds 70%, 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 45%, the thermal expansion coefficient becomes too large, and the thermal shock resistance of the glass tends to decrease, or vitrification tends to be difficult.

Al ₂ O ₃ is a component that increases the strain point and Young's modulus of glass, and its content is 3 to 20%, preferably 5 to 18%, more preferably 6 to 15%, and still more preferably 7 to 13%. It is. When the content of Al ₂ O ₃ is more than 20%, 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. In addition, from the viewpoint of improving the devitrification resistance of the glass, if the content of Al ₂ O ₃ is suppressed to 11% or less, further 10% or less, particularly 9.5% or less, the above effect can be enjoyed more accurately. Can do.

B ₂ O ₃ is a component having an effect of improving the meltability of glass and suppressing devitrification related to ZrO ₂ , and its content is 0 to 10%, preferably 0.1 to 8%. More preferably, it is 0.5 to 5%. When the content of B ₂ O ₃ is more than 10%, the strain point and Young's modulus tend to decrease, and the glass substrate is cracked in the heat treatment step when manufacturing the flat image display device, Heat shrinkage tends to occur. Further, from the viewpoint of increasing the strain point and Young's modulus of the glass, if the content of B ₂ O ₃ is reduced to 3% or less (preferably 2.5% or less, 2% or less), the above effects can be obtained more accurately. You can enjoy it.

  MgO is a component that increases the strain point of glass, and its content is 0 to 10%, more preferably 0 to 8%, still more preferably 0 to 5%, and most preferably 0 to 3%. When the content of MgO exceeds 10%, the thermal expansion coefficient tends to be too high, the density becomes high, or the devitrification resistance tends to deteriorate.

  CaO is a component that lowers the high-temperature viscosity without significantly reducing the strain point, and its content is 0 to 10%, more preferably 0 to 8%, still more preferably 0 to 5%, and most preferably 0. ~ 1%. When the content of CaO exceeds 10%, the thermal expansion coefficient tends to be too high, the density becomes high, and the devitrification resistance tends to deteriorate.

  SrO is a component that lowers the high temperature viscosity without deteriorating devitrification resistance, and its content is 0 to 17%, preferably 2 to 15%, more preferably 5 to 13%, and still more preferably 7 ~ 13%. If the SrO content exceeds 17%, the thermal expansion coefficient and density become too high, or the balance of the glass composition is lacking and the devitrification resistance deteriorates. Further, from the viewpoint of improving the devitrification resistance of the glass, when the SrO content is 11% or less, and further 10.5% or less, the above-described effect can be enjoyed more accurately.

  BaO is a component that lowers the high temperature viscosity without deteriorating devitrification resistance, and its content is 0 to 17% (preferably 2 to 17%, 5 to 16%, 7 to 15%, 9 to 14). %, 11.5-14%). When the content of BaO is higher than 17%, the thermal expansion coefficient becomes too high, the density becomes high, the balance of the glass composition is lost, and the devitrification resistance deteriorates conversely.

  The total amount of MgO + CaO + SrO + BaO is preferably 15 to 28%, more preferably 17 to 26%, and still more preferably 19 to 24%. When the total amount of MgO + CaO + SrO + BaO exceeds 28%, 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 15%, the meltability of the glass deteriorates or the thermal expansion coefficient becomes too small.

  SrO and BaO have a liquid phase viscosity suitable for molding by the overflow down draw method because the viscosity in the vicinity of the liquid phase temperature does not decrease much even when introduced into the glass composition as compared with other alkaline earth metal oxides. In order to obtain it, it is desirable to make it contain actively. Furthermore, from the viewpoint of improving the devitrification resistance and chemical durability of the glass, the value of (MgO + CaO) / (SrO + BaO) is 0 to 0.2 (preferably 0 to 0.1, 0 to 0) in terms of mass fraction. .05) is effective. In particular, from the above viewpoint, the value of SrO / BaO is 0.4 to 1.2 (preferably 0.4 to 1.2, 0.5 to 1.1, 0.6 to 1.0 by mass fraction). , 0.6 to 0.9, 0.6 to 0.8) is effective. If it is out of the set value range, the assumed effect cannot be fully enjoyed.

Na ₂ O is a component that reduces the high temperature viscosity and adjusts the coefficient of thermal expansion, and its content is 0 to 10%, preferably 0.1 to 8%, more preferably 0.5 to 6%, More preferably, it is 1 to 5%. When the content of Na ₂ O exceeds 10%, the strain point decreases or the thermal expansion coefficient becomes too high.

K ₂ O is a component that decreases the high-temperature viscosity and adjusts the thermal expansion coefficient, and its content is 0 to 10%, preferably 0.1 to 8%, and more preferably 0.5 to 6%. When the content of K ₂ O is more than 10%, the strain point is lowered or the thermal expansion coefficient is too high. In particular, it is desirable to contain K ₂ O in an amount of 1% or more (preferably 2% or more, preferably 3% or more) in order to enjoy the effect of reducing the high temperature viscosity and the effect of adjusting the thermal expansion coefficient.

ZrO ₂ is a component that increases the strain point and Young's modulus, and is an essential component in the present invention. The content of ZrO ₂ is 0.01 to 8% (preferably 0.1 to 8%, 0.5 to 7%, 1 to 6%, 2 to 5%, 2.5 to 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. When the content of ZrO ₂ is less than 0.01%, the strain point is lowered and it is difficult to ensure the viscosity characteristics necessary for molding by the overflow down draw method.

Moreover, the value of Al ₂ O ₃ / BaO is 0.1 to 2 (preferably 0.3 to ₂ , 0.5 to 1.5, 0.7 to 1.3, 0.8 to 0.8 by mole fraction). 1.1) is preferable because a high strain point can be achieved without deteriorating the devitrification resistance of the glass. When the molar fraction of Al ₂ O ₃ / BaO exceeds 2, devitrification resistance tends to deteriorate. When the molar fraction of Al ₂ O ₃ / BaO is smaller than 0.1, the devitrification resistance of the glass deteriorates and the strain point tends to decrease.

Furthermore, the effect of increasing the strain point while suppressing the devitrification resistance by setting the molar fraction of Al ₂ O ₃ / BaO in the range of 0.1 to ₂ is Na ₂ O / K. The value of ₂ O is adjusted to a range of 0 to 2 (preferably 0.3 to 1.5, 0.5 to 1.3, 0.7 to 1.1, 0.8 to 0.9). Thus, it can be enjoyed more accurately. 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. On the other hand, if 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 is likely to occur.

From the viewpoint of keeping the strain point of the glass high and not increasing the thermal expansion coefficient too much, it is preferable to set the value of (Na ₂ O + K ₂ O) / (MgO + CaO + SrO + BaO) to 0 to 0.5 in terms of mass fraction. More preferably, it is set to 0.1 to 0.4, and more preferably 0.2 to 0.4. If the value of (Na ₂ O + K ₂ O) / (MgO + CaO + SrO + BaO) in terms of mass fraction is greater than 0.5, the above effects may not be enjoyed accurately.

In the glass 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 the glass for a flat image display device is _{SiO 2 50~60%, Al 2 O} 3 5~10%, B 2 O 3 0~5%, 0~5% MgO, CaO 0~5%, SrO 5~12.5%, BaO 9~14% , Na ₂ O 0 to 5%, K ₂ O 3 to 6%, ZrO ₂ 1 to 4%, and a glass having a coefficient of thermal expansion at 30 to 380 ° C. of 65 to 80 × 10 ⁻⁷ / ° C. Can be mentioned. By restricting the glass composition range to the above, the devitrification resistance can be greatly improved, and the viscosity characteristics necessary for molding by the overflow downdraw method can be ensured accurately.

As a further preferred embodiment of the glass for a flat image display _{apparatus, SiO 2 55~58%, Al 2} O 3 7~9.5%, B 2 O 3 0~2%, 0~3% MgO, CaO 0~1% And SrO 7 to 10.5%, BaO 11.5 to 14%, Na ₂ O 1 to 5%, K ₂ O 3 to 6%, ZrO _{2 2.5 to 4} %, and 30 to 380 ° C. Glass having a coefficient of thermal expansion of 65 to 75 × 10 ⁻⁷ / ° C. is mentioned. When the composition range of the glass is regulated as described above, the devitrification resistance can be remarkably improved, and the viscosity characteristics necessary for forming by the overflow down draw method can be more accurately ensured.

The glass for a flat image display device of the present invention has a thermal expansion coefficient 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. A thermal expansion coefficient smaller than 50 × 10 ^-7 / ℃ at 30 to 380 ° C., no is consistent with the thermal expansion coefficient of the sealing glass to a frit sealing the front glass substrate and a rear glass substrate, after the sealing step Problems such as cracks are likely to occur in the glass substrate. Further, if the thermal expansion coefficient at 30 to 380 ° C. is larger than 90 × 10 ⁻⁷ / ° C., there is a possibility that the thermal expansion coefficient of other peripheral members used in the flat image display device cannot be matched.

  In the glass for a flat image display device of the present invention, the liquidus temperature is preferably 1200 ° C. or lower, more preferably 1080 ° C. or lower, still more preferably 1050 ° C. or lower, and most preferably 1000 ° 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 possibility that it cannot be molded. 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. Moreover, generally, the improvement of the characteristics of glass is achieved by lowering some characteristics, and tends to be in a so-called trade-off relationship with other characteristics. Here, considering the balance for satisfying various properties required for the glass, such as viscosity, density, and coefficient of thermal expansion, it is a guideline that the liquidus temperature of the glass is designed to be 850 ° C. or higher.

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 it 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 glass having a desired shape cannot be formed. Note that the higher the liquidus viscosity, the better the devitrification resistance of the glass. Here, considering the balance for satisfying various properties required for the glass, such as viscosity, density, and coefficient of thermal expansion, it is a guideline that the liquid phase viscosity of the glass is designed to be 10 ^6.5 dPa · s or less.

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 is likely to occur.

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. There is a risk of a surge.

  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 by the FED, it can be suitably used for this application. In particular, since the glass for flat image display devices of the present invention can employ 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. , It can be suitably used for this application.

  The glass for a flat image display device of the present invention is preferably used as a glass substrate. The glass for a flat image display device of the present invention can employ various molding methods, but in any case, since the glass has excellent devitrification resistance, it can be molded into a glass substrate satisfactorily. The present invention can be applied to a flat image display device.

  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 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, when the difference between the maximum thickness and the minimum thickness of the glass substrate is larger than 20 μm, a part where the distance (gap) between the front plate and the back plate is locally different is generated. In such a case, in a flat image display device such as an FED, the acceleration voltage applied between the front plate and the back plate varies, or the speed of electrons that collide with the phosphor changes, and the flat image display device There is a risk of adversely affecting the luminance characteristics. In addition, when the difference between the maximum thickness and the minimum thickness of the glass substrate is larger than 20 μm, in the manufacturing process such as FED, since the focus is not achieved at the time of exposure, high-precision patterning cannot be performed, and as a result, the gate hole shape varies. Therefore, there is a possibility that a desired cone shape cannot be obtained. As described above, the electron-emitting device can efficiently emit electrons at a low voltage in a portion where the electric field is concentrated. However, if a desired conical shape cannot be obtained, the drive voltage becomes high. Or a problem that electrons are not emitted occurs. Therefore, if the difference between the maximum thickness and the minimum thickness of the glass substrate is larger than 20 μm, it becomes difficult to satisfy the demand for higher definition of the flat image display device. 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. The value obtained by subtracting the value of the minimum thickness from the value of the maximum thickness after measuring the maximum thickness and the minimum thickness of the 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 recent demand for larger screens and higher definition of flat image display devices. 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 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 and the like cannot be performed with high accuracy, and it becomes difficult to stably manufacture a high-quality flat image display device under predetermined conditions. . In the present invention, the “error with respect to the target plate thickness” refers to the larger one of the absolute values obtained by subtracting the maximum plate thickness or the minimum plate thickness obtained by the above method from the target plate thickness.

In the glass substrate for a flat image display apparatus of the present invention, the ratio (a value obtained by dividing the Young's modulus by the density) Young's modulus is preferably 25GPa / g · cm ^-3 or more, 26GPa / g · cm ^-3 or more, and 26 More preferably, it is 5 GPa / g · cm ⁻³ or more. If the specific Young's modulus is 25 GPa / g · cm ⁻³ or more, a large and thin glass substrate, specifically, the glass substrate has a vertical dimension of 500 mm or more, a horizontal dimension of 600 mm or more, and a thickness of 0.7 mm or less. Even if it exists, it can suppress to the deflection amount of the grade which does not produce a problem. As the Young's modulus, a value measured by a known resonance method is used.

  In the glass substrate for a flat image display device of the present invention, the size of the substrate glass is preferably 32 inches or more, more preferably 36 inches or more, and still more preferably 40 inches or more. As the size of the substrate glass increases, the surface quality required for the substrate glass becomes stricter, and the formation of the substrate glass becomes more difficult, so that the effects of the present invention can be enjoyed accurately.

  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 by the 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, 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 to 5, Sample No. 1-24 show the Example of this invention, Sample No. Reference numeral 25 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 to 5. 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.

  For each sample thus prepared, density, thermal expansion coefficient, strain point, liquidus temperature, liquidus viscosity, and high temperature viscosity were measured. In addition, Example No. The Young's modulus was measured about the samples of 21-24. The results are shown in Tables 1-5.

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

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

  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 was measured by the well-known platinum pulling method for the viscosity of each glass at the liquid phase temperature.

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.

As is apparent from Tables 1 to 5, sample No. 1 to 24 have a density of 2.83 to 2.89 g / cm ³ , a thermal expansion coefficient of 67 to 78 × 10 ⁻⁷ / ° C., a strain point of 605 to 660 ° C., a liquidus temperature of 950 to 1200 ° C., a liquid phase viscosity 10 ^4.5 to 10 ^6.4, temperature corresponding to the viscosity ^of 10 ^2.5 dPa · s is the 1510-1,650 ° C., all samples density 3.0 g / cm ³ or less, the thermal expansion coefficient 50 to 90 × A temperature corresponding to a temperature of 10 ⁻⁷ / ° C., a strain point of 590 ° C. or higher, a liquidus temperature of 1200 ° C. or lower, a liquidus viscosity of 10 ^4.5 dPa · s or higher, and a high temperature viscosity of 10 ^2.5 dPa · s is 1650. It was below ℃.

  As is apparent from Table 5, sample No. No. 25 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 (4) required for a glass substrate used in an FED, has good devitrification resistance, and has an overflow downdraw method or the like. It is possible to improve the surface quality of the glass substrate. As a result, high-precision photolithography can be performed on the surface of the glass substrate, and the electron emission characteristics of the electron source can be stably maintained. Furthermore, since the glass substrate for a flat image display device of the present invention can perform photolithography with high accuracy, it becomes possible to form a circuit pattern with high accuracy and ensure the reliability of the flat image display device (for example, This can contribute to reducing the probability of occurrence of disconnection and short circuit.

  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 (13)

A glass composition, SiO ₂ 45 to 70% by _{mass%, Al 2 O 3 3~20%} , B 2 O 3 0~10%, 0~10% MgO, CaO 0~10%, SrO 0~17%, BaO 0 to 17%, Na ₂ O 0 to 10%, K ₂ O 0 to 10%, ZrO ₂ 0.01 to 8%, and the thermal expansion coefficient at 30 to 380 ° C. is 50 to 90 × 10 ^{− 7} / ° C. Glass for flat image display devices. A glass composition, SiO ₂ 50-60% by _{mass%, Al 2 O 3 5~10%} , B 2 O 3 0~5%, 0~5% MgO, CaO 0~5%, SrO 5~12.5 %, BaO 9-14%, Na ₂ O 0-5%, K ₂ O 3-6%, ZrO ₂ 1-4%, and the coefficient of thermal expansion at 30-380 ° C. is 65-80 × 10 ^{− The} glass for a flat image display device according to claim 1, wherein the glass is ⁷ / ° C. A glass composition, SiO ₂ 55 to 58% by _{mass%, Al 2 O 3 7~10%} , B 2 O 3 0~2%, 0~3% MgO, CaO 0~1%, SrO 7~10.5 %, BaO 11.5 to 14%, Na ₂ O 1 to 5%, K ₂ O 3 to 6%, ZrO _{2 2.5 to 4} %, and the coefficient of thermal expansion at 30 to 380 ° C. is 65 to 65%. The glass for a flat image display device according to claim 1, wherein the glass for a flat image display device is 75 × 10 ⁻⁷ / ° C. The flat image display glass according to claim 1, wherein the Al ₂ O ₃ / BaO value is 0.1 to _{2 in} terms of molar fraction. The glass for a flat image display device according to claim 1, wherein the Na ₂ O / K ₂ O value is 0 to 2 in terms of mole fraction. The glass for flat image display devices according to claim 1, wherein the liquidus temperature is 1200 ° C. or less and / or the liquidus viscosity is 10 ^4.5 dPa · s or more. The glass for a flat image display device according to claim 1, wherein the density is 3.0 g / cm ³ or less.   The glass for a flat image display device according to any one of claims 1 to 7, wherein a strain point is 590 ° C or more. 9. The glass for a flat image display device according to claim 1, wherein a temperature corresponding to a high temperature viscosity of 10 ^2.5 dPa · s is 1650 ° C. or lower.   The flat image display device according to claim 1, wherein the flat image display device is a field emission display.   A glass substrate for a flat image display device, comprising the flat image display device glass according to any one of claims 1 to 10.   The flat image display device according to claim 11, wherein the flat image display device is a field emission display. A method for producing a glass substrate for a flat image display device according to claim 11 or 12,
A method for producing a glass substrate for a flat image display device, wherein the glass substrate is formed by an overflow downdraw method.

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