JPWO2014163130A1 - Glass substrate and slow cooling method thereof - Google Patents

Abstract

Thermal contraction when the glass substrate 1 has a thickness of 0.5 mm or less and a side of 300 mm or more, and is heated from room temperature at 5 ° C./min, held at 500 ° C. for 1 hour, and then cooled at 5 ° C./min. The absolute value of the rate is 10 ppm or less, and the number of surface defects 2 is 100 / m 2 or less.

Description

  The present invention relates to a slow cooling technique for a glass substrate.

  In recent years, with the advent of smartphones and tablet-type terminals, flat panel displays (hereinafter referred to as FPD) have become thinner and lighter, and higher definition has been advanced.

  As a substrate for FPD, a glass substrate is widely used, and in response to the demands for reducing the thickness and weight, the reduction of the thickness of the glass substrate is promoted.

  As a method for forming a glass substrate, a down draw method typified by an overflow down draw method is widely used because the smoothness of the glass substrate to be formed is excellent.

  In the downdraw method, the current situation is that the glass substrate is made thinner by increasing the glass drawing speed.

  However, in the case of the downdraw method, since the long glass that is the base of the glass substrate is moved downward while passing through the slow cooling zone, if the drawing speed is increased, the residence time in the slow cooling zone is shortened. Solidifies in a rapidly cooled state. As a result, when such a glass substrate is used for FPD, there is a problem that the thermal shrinkage of the glass substrate increases during the heat treatment included in the manufacturing process.

  Specifically, in the FPD manufacturing process, when a thin film electric circuit is formed on the surface of the glass substrate, the glass substrate is subjected to heat treatment at a high temperature. At this time, if the thermal contraction of the glass substrate is large, the circuit pattern formed on the surface of the glass substrate may be deviated from the design, which may cause a serious trouble that the desired electrical performance cannot be maintained.

  In addition, with the increasing definition of FPD, the circuit pattern of a thin film electric circuit formed on a glass substrate is also miniaturized. For this reason, there is a high possibility that surface defects such as minute foreign substances will adversely affect the formation of thin film electric circuits.

  Therefore, in Patent Document 1, (1) before the manufacturing process of the FPD, the molded glass substrate is put into a slow cooling furnace and slowly cooled again, and (2) a plurality of heat-resistant glass ceramics are placed in the slow cooling furnace. It is disclosed that a dust-proof wall made of a (crystallized glass) plate is provided to prevent fine foreign substances or the like generated from a refractory or a heating element from adhering to a glass substrate.

JP-A-5-330835

  However, when a plurality of refractory glass ceramic plates are arranged to form a dust-proof wall as in Patent Document 1, the glass ceramic plates cannot be fixed together by welding, so that a joint between the plates is inevitably formed. Since minute foreign matters generated from the refractory or the heating element can enter through the joint, it is impossible to reliably prevent the fine foreign matters from adhering to the surface of the glass substrate.

  In particular, when a metal heater is used as the heating element, the oxidized metal powder may enter through the seam of the dust-proof wall, and a surface defect made of metal foreign matter may be formed on the surface of the glass substrate. And since the surface defect of such a metal foreign material has conductivity, a short circuit or the like occurs in the thin film electric circuit formed on the glass substrate, causing a fatal trouble in electrical characteristics compared to the surface defect of a non-metal foreign material. Easy to invite.

  Although it is conceivable that the seam of the refractory glass ceramic plate is closed with a refractory material, a minute foreign matter is generated from the closed refractory material, which may contaminate the surface of the glass substrate, which is not practical.

  In the same document, the glass substrate is slowly cooled while being moved by a transfer conveyor made of heat-resistant steel in a slow cooling furnace, but metal foreign matter can also be generated from the transfer conveyor. Therefore, the surface defect of a metal foreign material can be formed in a glass substrate similarly to the case where a metal heater is used.

  Here, the minute foreign matter or the like adhering to the surface of the glass substrate in the slow cooling step is baked on the surface of the glass substrate by heat treatment at the time of slow cooling, and it becomes difficult to remove even by subsequent cleaning. Therefore, there is a high possibility that these minute foreign matters remain as surface defects of the glass substrate in various processes such as the FPD assembly process.

  Therefore, in the glass substrate manufactured by the slow cooling method of patent document 1, it becomes difficult to respond | correspond to the glass substrate of a high performance display use. That is, glass substrates for high performance displays are required to be (1) thin, (2) small thermal shrinkage in the FPD manufacturing process, and (3) few surface defects. In the glass substrate manufactured by the slow cooling method disclosed in 1), it becomes extremely difficult to satisfy all these three requirements.

  In view of the above circumstances, an object of the present invention is to provide a glass substrate that can be used for high-definition display without problems.

The glass substrate according to the present invention created to solve the above problems is a glass substrate having a thickness of 0.5 mm or less and a side of 300 mm or more, and is heated to 500 ° C. after being heated from room temperature at 5 ° C./min. And the absolute value of the thermal shrinkage rate when the temperature is lowered at 5 ° C./min is 10 ppm or less, and the number of surface defects is 200 pieces / m ² or less. The surface defects include minute foreign matters such as glass powder and metal powder, and minute scratches.

  According to such a configuration, both the thermal contraction rate and the number of surface defects are managed in an appropriate range. Therefore, even when used as a glass substrate for a high-definition display, good electrical characteristics can be realized without causing thermal shrinkage and surface defects of the glass substrate during the heat treatment included in the manufacturing process. In other words, a conventional method such as the slow cooling method disclosed in Patent Document 1 cannot provide a glass substrate that can simultaneously achieve the thermal shrinkage rate and the number of surface defects.

Here, the heat shrinkage rate is a value measured by the following method (hereinafter the same). That is, as shown in FIG. 5A, first, a 160 mm × 30 mm strip-shaped sample G is prepared as a glass substrate sample. The markings M are formed at positions 20 to 40 mm away from the edge using # 1000 water-resistant abrasive paper on each of both ends in the long side direction of the strip-shaped sample G. After that, as shown in FIG. 5B, the strip-shaped sample G on which the marking M is formed is folded in two along the direction orthogonal to the marking M to produce sample pieces Ga and Gb. And after heat-processing only one sample piece Gb on predetermined conditions, as shown to FIG. 5C, in the state which arranged in parallel the sample piece Ga which has not heat-processed, and the sample piece Gb which heat-processed, The amount of displacement (ΔL ₁ , ΔL ₂ ) of the marking M on the sample pieces Ga and Gb is read with a laser microscope, and the thermal contraction rate is calculated by the following equation. Note that l ₀ in the equation is the distance between the initial markings M.
Thermal contraction rate = [{ΔL ₁ (μm) + ΔL ₂ (μm)} × 10 ³ ] / l ₀ (mm) (ppm)

  The number of surface defects is a value obtained by measuring the number of defects on the glass substrate using a surface inspection apparatus (model number: GI-7200) manufactured by Hitachi High-Technology Co., Ltd., and dividing the number of defects by the area of the glass substrate. (Hereinafter the same).

Said structure WHEREIN: It is preferable that the number of the metal foreign material contained in the said surface defect is 10 piece / m < ² > or less.

In the above configuration, the number of surface defects is preferably 150 pieces / m ² or less, and more preferably 100 pieces / m ² or less. The lower limit of the number of surface defects is, for example, 1 / m ² or more. If it is attempted to reduce the number of surface defects to less than 1 / m ^2, it is necessary to manage the manufacturing conditions excessively strictly, which may deteriorate the manufacturing efficiency of the glass substrate.

  A glass substrate having the above-described configuration is suitable as a substrate for forming a thin film electric circuit.

  The glass substrate slow cooling method according to the present invention, which was created to solve the above-mentioned problems, is provided in a slow cooling space provided inside a glass chamber made of integrated glass in a multistage manner in the vertical direction. In addition, a glass shelf having an accommodating portion is disposed, and a laminated body in which a glass substrate is stacked on a supporting glass is accommodated in each of the accommodating portions, and then, the slow cooling space from the outside of the glass chamber. And the glass substrate is slowly cooled.

According to such a configuration, the glass substrate is slowly cooled in the slowly cooling space in the glass chamber made of integrated glass. That is, since the integrated glass has no seam, the inner surface of the glass chamber forming the slow cooling space is continuous without a gap. As a result, fine foreign matter including metallic foreign matter does not enter from the outside through the glass chamber into the slow cooling space from the outside of the glass chamber. Also, in the slow cooling space of the glass chamber, a glass plate supported by a supporting glass is arranged in the glass shelf housing, but since these members are all glass, metal foreign matter is generated in the slow cooling space. There is nothing to do. Therefore, in this state, if the glass substrate is gradually cooled by heating the annealing space from the outside of the glass chamber, the glass substrate with small thermal shrinkage and few surface defects, that is, the absolute value of the thermal shrinkage rate already described is obtained. A glass substrate having 10 ppm or less and the number of surface defects of 100 / m ² or less can be produced. Here, since it accommodates in the state of the laminated body which laminated | stacked the glass substrate on support glass in the accommodating part of a glass shelf, the bending by the dead weight of the glass substrate at the time of slow cooling can be suppressed. As a result, the generation | occurrence | production of the damage | wound by the contact between glass substrates and the curvature of the glass substrate after slow cooling can be reduced as much as possible. Further, since the entire surface of the glass substrate is supported by the supporting glass, the in-plane temperature distribution of the glass substrate can be easily made uniform.

  Said structure WHEREIN: It is preferable that the inorganic thin film is formed in the upper surface of the said support body.

  In this way, since the glass substrate is stacked on the supporting glass through the inorganic thin film, the supporting substrate and the glass substrate are not bonded even after the completion of slow cooling, and the glass substrate is easily peeled off from the supporting body. Can be taken out.

  Said structure WHEREIN: It is preferable that the said glass chamber is formed with quartz glass.

  That is, quartz glass has a high infrared transmittance, so that the glass substrate can be efficiently heat-treated. In addition, since quartz glass has high workability, it can be expected to reduce the manufacturing cost of the glass chamber.

  Said structure WHEREIN: It is preferable that the said accommodating part supports the said support glass from the downward direction with the some protrusion disperse | distributed and arrange | positioned.

  In this way, even when the glass substrate is increased in size, the substantially entire surface of the supporting glass can be stably supported by the protrusions. Therefore, it is possible to reliably prevent the glass substrate from being bent during the slow cooling.

  Said structure WHEREIN: It is preferable to heat the said glass substrate at the temperature lower than a strain point.

  When the glass substrate is heated at a temperature higher than the strain point and gradually cooled, a large shape change occurs in the glass substrate in the slow cooling step, and there is a possibility that the problem becomes greater than a decrease in the thermal shrinkage rate. Therefore, in the slow cooling of the glass substrate, it is preferable to heat the glass substrate at a temperature lower than the strain point as described above.

Said structure WHEREIN: It is preferable that the difference of the linear thermal expansion coefficient in 30-380 degreeC of the contact part with the said support glass of the said accommodating part and the said support glass is 40 * 10 < ^-7 > / degrees C or less.

  In this way, during the slow cooling, rubbing due to the difference in thermal expansion is less likely to occur between the housing portion and the support glass, so that the generation of glass powder can be reduced.

  As described above, according to the present invention, the thermal contraction and surface defects of the glass substrate can be made as small as possible, so that it is possible to provide a glass substrate that can cope with high-definition display applications without problems.

It is a perspective view which shows the glass substrate which concerns on embodiment of this invention. It is sectional drawing which shows the slow cooling apparatus used for manufacture of the glass substrate of this embodiment. It is a perspective view for demonstrating the support form of the glass substrate in the slow cooling apparatus shown in FIG. It is sectional drawing for demonstrating the support form of the glass substrate in the slow cooling apparatus shown in FIG. It is a top view for demonstrating the measurement procedure of the thermal contraction rate of a glass substrate. It is a top view for demonstrating the measurement procedure of the thermal contraction rate of a glass substrate. It is a top view for demonstrating the measurement procedure of the thermal contraction rate of a glass substrate.

  The present invention will be described with reference to the accompanying drawings.

  As shown in FIG. 1, a glass substrate 1 according to an embodiment of the present invention has a rectangular shape with one side of 300 mm or more (for example, 730 mm × 920 mm), and is used as an FPD substrate that realizes a high-definition image. That is, a thin film electric circuit is formed on the surface of the glass substrate 1.

  The thickness of the glass substrate 1 is 500 μm or less, preferably 300 μm or less, more preferably 200 μm or less, and most preferably 100 μm or less. In addition, when the intensity | strength of the glass substrate 1 is considered, it is preferable that the thickness of the glass substrate 1 is 5 micrometers or more.

  The absolute value of the thermal contraction rate of the glass substrate 1 is 10 ppm or less, preferably 8 ppm or less, more preferably 6 ppm or less. Thus, the glass substrate 1 is not greatly deformed due to thermal contraction in FPD manufacturing-related processing, particularly in the step of forming a thin film electric circuit on the glass substrate 1.

As shown in FIG. 1 in which a part of the surface of the glass substrate 1 is enlarged (X region in the drawing), the number of surface defects 2 on the glass substrate 1 is 200 pieces / m ² or less, preferably 150 pieces / m. ² or less, more preferably 100 pieces / m ² or less. Further, in this embodiment, the number of metal foreign matters contained in the surface defect 2 is restricted to 10 pieces / m ² or less. That is, since the number of metal foreign objects is suppressed in this way, the total number of surface defects 2 is reduced as a result. As a result, even when the glass substrate 1 is used as an FPD substrate, troubles such as disconnection or short-circuiting of the thin film electric circuit are less likely to occur due to the surface defect 2 of the glass substrate 1. Therefore, the synergistic effect with the management of the heat shrinkage rate as described above can appropriately form the circuit pattern of the thin film electric circuit on the glass substrate 1 and maintain the electrical characteristics of the FPD favorably.

  Here, the size of the surface defect 2 is preferably 1 μm or less. This is because if the size of the surface defect exceeds 1 μm, it may be difficult to satisfy the required characteristics as a glass substrate for FPD regardless of the number of surface defects.

  The strain point of the glass substrate 1 is 600 ° C. or higher, preferably 650 ° C. or higher. When the strain point of the glass substrate 1 is within the above numerical range, the thermal shrinkage rate of the glass substrate 1 can be reduced.

  The average surface roughness Ra of the glass substrate 1 is preferably 2.0 nm or less, more preferably 1.0 nm or less, still more preferably 0.5 nm or less, and 0.2 nm or less. Is preferred. Here, the average surface roughness Ra is a value measured by a method based on SEMI D7-94 “Measurement method of surface roughness of FPD glass substrate” (hereinafter the same).

  As the glass substrate 1, various glasses such as silicate glass, silica glass, and borosilicate glass can be used. In the present embodiment, alkali-free glass is used. When alkali-free glass is used, aged deterioration of the glass substrate 1 can be reduced as much as possible. Here, the alkali-free glass means a glass that does not substantially contain an alkali component (alkali metal oxide). Specifically, it means a glass having an alkali component content of 1000 ppm or less. The content of the alkali component is preferably 500 ppm or less, and more preferably 300 ppm or less.

The glass substrate 1 has a glass composition of mass%, SiO ₂ 40-80%, Al ₂ O ₃ 10-30%, B ₂ O ₃ 0-20%, MgO 0-20%, CaO 0-20%, It is preferable to contain SrO 0-20% and BaO 0-20%. Thereby, the strain point of the glass substrate 1 becomes high and it becomes easy to ensure the optimal liquid phase viscosity at the time of shaping | molding. Furthermore, various characteristics (for example, chemical resistance, specific Young's modulus, meltability, etc.) required for a glass substrate for FPD can be satisfactorily satisfied.

  Next, the manufacturing method of the glass substrate 1 comprised as mentioned above is demonstrated.

  The manufacturing method of the glass substrate 1 is divided roughly into the formation process which shape | molds the glass substrate 1 from a molten glass using the overflow downdraw method, and the slow cooling process which anneals the shape | molded glass substrate 1 again. Since a well-known method can be employed for the forming process, the following description will focus on the slow cooling process. In addition, you may provide the washing | cleaning process of the glass substrate 1 between a shaping | molding process and a slow cooling process, or after a slow cooling process.

  As shown in FIG. 2, the slow cooling device 3 used in the slow cooling process includes a glass chamber 4, a glass shelf 5 disposed inside the glass chamber 4, a lifting platform 6 on which the glass shelf 5 is placed, A furnace wall 7 surrounding the periphery of the glass chamber 4 and a heater 8 for heating the glass chamber 4 from the outside are provided. The slow cooling device 3 is disposed in a clean room.

  The glass chamber 4 has a covered cylindrical shape formed by integrally molding quartz glass, and has a slow cooling space S therein. That is, the glass chamber 4 defines the slow cooling space S by a continuous continuous surface.

  The glass shelf 5 is made of quartz glass and has a plurality of accommodating portions 9 provided in a multistage shape in the vertical direction. Each accommodating portion 9 is provided with a detachable shelf board 10, and a laminated body formed by stacking the support glass 11 and the glass substrate 1 is accommodated on the shelf board 10. In this embodiment, the shelf board 10 is also formed of quartz glass.

  The mounting portion 12 of the lifting platform 6 is made of quartz glass and closes the lower opening of the glass chamber 4 at the raised position. On the other hand, by lowering the lifting platform 6 to a lowering position outside the figure, the stacked body is loaded and unloaded on the glass shelf 5 on the mounting portion 12.

  The furnace wall 7 is made of a refractory material, and a plurality of heaters 8 are attached to the side inner wall surface and the upper inner wall surface of the furnace wall 7. The heater 8 is not particularly limited, but in this embodiment, a metal heating element (for example, a nichrome heating element) is used.

  In addition, you may provide the cooling means (blower etc.) which cools the glass chamber 4 from the outside separately. Thereby, the atmosphere of the slow cooling space S once heated by the heater 8 can be efficiently cooled.

  As shown in FIG. 3, an inorganic thin film 13 is formed on the upper surface of the support glass 11, and the glass substrate 1 is stacked on the support glass 11 through the inorganic thin film 13. Thereby, the surface of the glass substrate 1 and the surface of the support glass 11 do not contact directly. Therefore, the glass substrate 1 does not adhere to the support glass 11 by heating during the slow cooling, and the glass substrate 1 can be easily peeled from the support glass 11 after the slow cooling. The inorganic thin film 13 may be omitted.

The support glass 11 is made of silicate glass, silica glass, borosilicate glass, alkali-free glass, or the like, similar to the glass substrate 1. However, as the supporting glass 11, it is preferable to use a glass having a difference in linear thermal expansion coefficient at 30 to 380 ° C. with respect to the glass substrate 1 within 5 × 10 ⁻⁷ / ° C. Thereby, it becomes difficult to produce the friction accompanying a thermal expansion difference between the glass substrate 1 and the support glass 11 by the heat processing at the time of slow cooling. Therefore, scratches are hardly formed on the glass substrate 1 and can contribute to the reduction of the surface defects 2. From such a viewpoint, it is most preferable that the supporting glass 11 and the glass substrate 1 use glasses having the same composition.

  The thickness of the supporting glass 11 is preferably the same as the thickness of the glass substrate 1 or larger than the thickness of the glass substrate 1. Specifically, the thickness of the support glass 11 is preferably 0.2 mm or more, more preferably 0.3 mm or more, and further preferably 0.5 mm or more. When the laminated body of the supporting glass 11 and the glass substrate 1 is supported by a plurality of protrusions as described later, the thickness of the supporting glass 11 is 1.0 mm or more from the viewpoint of preventing the glass substrate 1 and the like from being bent. It is preferable that In addition, since the increase in thickness causes an increase in weight and an increase in heat capacity necessary for heating, and the heating efficiency of the glass substrate 1 decreases as the heat capacity increases, the thickness of the support glass 11 is 2.0 mm or less. It is preferable that

  The size of the support glass 11 is preferably the same as the size of the glass substrate 1 or larger than the size of the glass substrate 1. Thereby, since the end surface of the glass substrate 1 does not protrude to the outer side of the support glass 11, the situation where the end surface of the glass substrate 1 collides with another member and is damaged can be reduced.

  The surface roughness Ra of the inorganic thin film 13 formed on the support glass 11 is preferably 5.0 nm or less, more preferably 4.0 nm or less, and even more preferably 3.0 nm or less. Most preferably, it is 2.5 nm or less. That is, if the surface roughness Ra of the glass substrate 1 and the surface roughness Ra of the inorganic thin film 13 are each 5.0 nm or less, the adhesion due to the surface state without interposing an adhesive or the like between them. Works. Thereby, since the glass substrate 1 does not easily fall off from the support glass 11, handling becomes easy. In this case, the glass substrate 1 and the inorganic thin film 13 are not completely fixed by the adhesive, but are only in close contact due to the surface state of both, so that the glass substrate 1 is supported after the slow cooling. The glass 11 can be easily peeled off. The surface roughness Ra of the inorganic thin film 13 is preferably 0.5 nm or more, and more preferably 1.0 nm or more. This is because the glass substrate 1 can be easily peeled from the support glass 11 even when heat treatment is performed at a high temperature of 500 ° C. or higher. In addition, it is not necessary to make the adhesive force resulting from both surface states act between the glass substrate 1 and the inorganic thin film 13. FIG.

Inorganic thin film 13, ITO, Ti, Si, Au , Ag, Al, Cr, Cu, Mg, Ti, SiO, SiO 2, Al 2 O 3, MgO, Y 2 O 3, L 2 O 3, Pr 6 O ₁₁ , Sc ₂ O ₃ , WO ₃ , HfO ₂ , In ₂ O ₃ , ZrO ₂ , Nd ₂ O ₃ , Ta ₂ O ₅ , CeO, Nb ₂ O ₅ , TiO, TiO ₂ , Ti ₃ O ₅ , NiO, It is preferably formed of one or more selected from ZnO. In particular, the inorganic thin film 13 is preferably formed of an oxide such as ITO. In the case of an oxide thin film, since it is thermally stable, the same support glass 11 can be repeatedly used for a slow cooling process.

  The thickness of the inorganic thin film 13 is preferably 5 nm or more and 500 nm or less, more preferably 5 nm or more and 400 nm or less, and most preferably 5 nm or more and 300 nm or less. If the thickness of the inorganic thin film 13 is less than 5 nm, the glass substrate 1 may be difficult to peel off.

  In this embodiment, the shelf plate 10 of the glass shelf 5 is configured by a lattice-shaped frame body, and a plurality of pin-shaped protrusions 14 are provided on the upper surface thereof. As shown in FIG. 4, the plurality of protrusions 14 support the supporting glass 11, that is, the laminated body of the supporting glass 11 and the glass substrate 1 from below. In this embodiment, the tip of the protrusion 14 is a flat portion 15 at the center and a chamfered portion 16 with the corners cut off. That is, the laminated body is supported in a state of being in surface contact with the flat portion 15 of the plurality of protrusions 14 in a narrow range. In addition, the front-end | tip part of the processus | protrusion 14 may be comprised by a curved surface, and you may make it support a laminated body by point contact.

Here, the difference in coefficient of linear thermal expansion at 30 to 380 ° C. between the support glass 11 and the shelf board 10 is preferably 40 × 10 ⁻⁷ / ° C. or less. Thereby, since it becomes difficult to generate | occur | produce rubbing between the support glass 11 and the processus | protrusion 14 at the time of the heat processing of a slow cooling process, generation | occurrence | production of the glass powder which causes the surface defect of the glass substrate 1 can be reduced as much as possible.

  Next, the slow cooling process using the slow cooling apparatus comprised as mentioned above is demonstrated.

  First, as shown in FIG. 2, the glass shelf 5 is disposed in the slow cooling space provided in the glass chamber 4, and is supported on each of the shelf boards 10 provided in the housing portion 9 of the glass shelf 5. The laminated body which laminates | stacks the glass substrate 1 on the glass 11 is accommodated. And after that, the slow cooling space S is heated by the heater 8 from the outside of the glass chamber 4, and each glass substrate 1 accommodated in each accommodating part 9 is annealed.

  According to this, since the glass chamber 4 partitions and forms the slow cooling space S by a continuous continuous surface, minute foreign matters including metallic foreign matters from the outside into the slow cooling space S from the outside of the glass chamber 4. Intrusion can be prevented.

  Moreover, although the glass substrate 1 supported by the support glass 11 is arrange | positioned at the shelf 10 of the glass shelf 5 in the slow cooling space S, since these members are all glass, it is metal in the slow cooling space S. No foreign matter is generated.

Therefore, in this state, if the slow cooling space S is heated from the outside of the glass chamber 4 by the heater 8 and the glass substrate 1 in the slow cooling space S is gradually cooled, the glass substrate 1 with small thermal shrinkage and few surface defects. That is, it is possible to manufacture the glass substrate 1 having the absolute value of the heat shrinkage ratio already described of 10 ppm or less and the number of surface defects of 200 pieces / m ² or less.

  Here, since it accommodates in the accommodating part 9 of the glass shelf 5 in the state of the laminated body which laminated | stacked the glass substrate 1 on the support glass 11, the bending by the dead weight of the glass substrate 1 at the time of slow cooling is suppressed. Can do. As a result, generation | occurrence | production of the damage | wound by the contact between glass substrates 1 and the curvature of the glass substrate 1 after slow cooling can be reduced as much as possible. Further, since the entire surface of the glass substrate 1 is supported by the support glass 11, the in-plane temperature distribution of the glass substrate 1 can be easily made uniform.

  In addition, this invention is not limited to the said embodiment, It can implement with a various form. For example, in the above embodiment, the case where the glass chamber 4 and the glass shelf 5 are formed of quartz glass has been described. However, these members are formed of crystallized glass (for example, Neoceram manufactured by Nippon Electric Glass Co., Ltd.). May be. Even in this case, it is important that the glass chamber 4 is formed by integrally molding the crystallized glass without any gap.

  Moreover, in the said embodiment, although the case where the laminated body of the glass substrate 1 and the support glass 11 was supported by the protrusion 14 of the shelf board 10 was demonstrated, when the size of the glass substrate 1 is small, the shelf board 10 is attached. It may be omitted and only the both ends of the supporting glass 11 may be supported by the glass shelf 5.

  Moreover, although the said embodiment demonstrated the case where the mounting base 12 of the raising / lowering stand 6 in which the glass shelf 5 was mounted was raised / lowered as a method of accommodating the glass substrate 1 in the slow cooling space S in the glass chamber 4, You may make it raise / lower the glass chamber 4 with respect to the mounting part of the glass shelf 5. FIG.

  In the case where the glass chamber 4 is formed of quartz glass as in the above embodiment, the integral molding includes the case where the joint portions are seamlessly integrated by welding.

  Examples 1 to 6 of the present invention are shown in Table 1, and Comparative Examples 1 to 4 are shown in Table 2. In Examples 1 to 6, each glass substrate having the glass composition shown in Table 1 was subjected to heat treatment (slow cooling) using the slow cooling apparatus provided with the quartz chamber already described, and then the thermal shrinkage rate and surface quality were determined. evaluated. On the other hand, in Comparative Examples 1 to 3, the glass substrate having the corresponding glass composition shown in Table 2 was evaluated for thermal shrinkage and surface quality without performing heat treatment (slow cooling after molding). Moreover, in Comparative Example 4, the glass substrate having the corresponding glass composition shown in Table 2 was subjected to heat treatment (slow cooling) with a temperature profile similar to that of the example using a slow cooling device equipped with a metal chamber. The heat shrinkage rate and the surface quality were evaluated.

  Here, the slow cooling of the glass substrate is a temperature in which the glass substrate is heated from room temperature to 550 ° C. at 10 ° C./min, held at 550 ° C. for 1 hour, and then cooled from 550 ° C. to room temperature at 3 ° C./min. Made in profile. In addition, the heat shrinkage rate was maintained at 500 ° C. for 1 hour after heating the glass substrate slowly cooled under the above conditions or a glass substrate not slowly cooled from room temperature to 500 ° C. at 5 ° C./min. The temperature profile was 5 ° C./min. That is, in Examples 1 to 6 and Comparative Example 4, the heat shrinkage rate was measured by heating again the glass substrate on which the slow cooling after forming was performed.

  Further, the evaluation of the surface quality (the number of surface defects and metallic foreign objects) was prepared for 20 glass substrate samples for each example and each comparative example, and the lower limit and upper limit of the measurement results of these 20 samples. It was defined as a range using.

According to Table 2, Comparative Examples 1 to 3 in which heat treatment was not performed after molding had a large value in which the thermal shrinkage rate significantly exceeded 10 ppm. Further, in Comparative Example 4 in which heat treatment was performed using a metal chamber, the thermal shrinkage rate was suppressed to 10 ppm, but the surface defects were extremely high at 400 pieces / m ² or more, and it was fatal as a glass substrate for FPD. There are very many metal foreign objects that can be defects of 30 to 100 / m ² . Therefore, it turns out that the glass substrate of Comparative Examples 1-4 is incompatible as a glass substrate for high-definition FPD.

On the other hand, according to Table 1, in all of Examples 1 to 6, the heat shrinkage rate is 10 ppm or less and the surface defects are less than 70 / m ² (the number of metal foreign matters is less than 2 / m ² ). It can be confirmed that it is suppressed, and it can be seen that it is also suitable as a glass substrate for high-definition FPD.

DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Surface defect 3 Slow cooling apparatus 4 Glass chamber 5 Glass shelf 6 Elevator 7 Furnace wall 8 Heater 9 Accommodating part 10 Shelf plate 11 Support glass 12 Placement part 13 Inorganic thin film 14 Protrusion

Claims (11)

A glass substrate having a thickness of 0.5 mm or less and a side of 300 mm or more,
When the temperature is raised from room temperature at 5 ° C./min, held at 500 ° C. for 1 hour, and the temperature is lowered at 5 ° C./min, the absolute value of thermal shrinkage is 10 ppm or less, and the number of surface defects is 200 / M ² or less, a glass substrate. ^2. The glass substrate according to claim 1, wherein the number of metal foreign substances contained in the surface defect is 10 / m ² or less. 3. The glass substrate according to claim 1, wherein the number of surface defects is 150 / m ² or less. The number of the said surface defects is 100 pieces / m < ² > or less, The glass substrate of any one of Claims 1-3 characterized by the above-mentioned.   It is a board | substrate for forming a thin film electrical circuit, The glass substrate of any one of Claims 1-4 characterized by the above-mentioned. In the slow cooling space provided inside the glass chamber made of integrated glass, a glass shelf having a storage section provided in a multi-stage shape in the vertical direction is arranged,
In each of the accommodating portions, a laminated body formed by stacking a glass substrate on a supporting glass is accommodated,
Thereafter, the glass substrate is gradually cooled by heating the slow cooling space from the outside of the glass chamber to slowly cool the glass substrate.   The method for slowly cooling a glass substrate according to claim 6, wherein an inorganic thin film is formed on the upper surface of the supporting glass.   The method for slowly cooling a glass substrate according to claim 6 or 7, wherein the glass chamber is made of quartz glass.   The method for gradually cooling a glass substrate according to any one of claims 6 to 8, wherein the housing portion supports the support glass from below with a plurality of protrusions arranged in a dispersed manner.   The method for gradually cooling a glass substrate according to any one of claims 6 to 9, wherein the glass substrate is heated at a temperature lower than a strain point. The difference of the linear thermal expansion coefficient in 30-380 degreeC with the contact part with the said support glass of the said accommodating part, and the said support glass is 40 * 10 < ^-7 > / degrees C or less, It is characterized by the above-mentioned. The method for slowly cooling a glass substrate according to any one of 10.

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