JP2010248031A - Manufacture method for near-sheet glass, press molding apparatus, manufacture method for substrate for information recording medium, manufacture method for information recording medium, and manufacture method for optical part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacture method for a near-sheet glass using a direct press method, which gives little warpage and excels in productivity, and can dispense with a new another step after the unloading step to correct the warpage. <P>SOLUTION: The manufacture method for a near-sheet glass comprises a formation step of pressing a molten glass to make a near-sheet glass, and a soaking/cooling step of cooling and soaking the near-sheet glass, wherein in a process of a part of the soaking/cooling step, an upper surface cooling rate regulating member is arranged so as to be in contact with or in close vicinity to the upper surface of the near-sheet glass on a lower mold, and the upper surface cooling rate regulating member is supported by a support fixed directly or indirectly on a floor surface. There are also provided a press molding apparatus using the manufacture method, a manufacture method for a substrate for an information recording medium, a manufacture method for an information recording medium, and a manufacture method for an optical part. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a substantially plate-like glass, a press molding apparatus, a method for producing a substrate for an information recording medium, a method for producing an information recording medium, and a method for producing an optical component.

  There is known a method for obtaining a substantially thin glass plate which is relatively thin and has no bending by a method of directly press-molding molten glass using a pair of molds composed of an upper mold and a lower mold (so-called direct press method). Various techniques have been proposed for such a direct press method.

  For example, a technique has been proposed in which a lower mold surface having a long contact time with molten glass and an upper mold surface disposed to face the lower mold are heated to predetermined different temperatures (see Patent Document 1). According to this technology, symmetric heat removal is achieved during press molding for a limited time in the direct press method, and the temperature of the molding surface and the glass raw material are almost all below the softening point of the glass. It can be balanced.

  In addition, when the inside of the glass is in a temperature state higher than the glass transition temperature, after the press mold is finished by separating the upper mold from the glass, the inside of the substantially plate-like glass is lower than the glass transition temperature than the temperature at the time of press molding. A technique for applying a press for correcting warpage while the temperature is still high has been proposed (see Patent Document 2).

  Also, after taking out the substantially plate-like glass from the mold after press molding, when the glass temperature is below the yield point and exceeds the strain point, pressure is applied to the main surface of the substantially plate-like glass, or There has been proposed a technique for correcting warping by applying pressure and annealing (see Patent Document 3).

Japanese Patent Laid-Open No. 5-105458

Japanese Patent Laid-Open No. 10-236831

JP 2004-107098 A

  In the direct press system, generally plate-like glass obtained by press-molding molten glass generally moves with the rotation of the rotary table while being placed on the lower mold. Next, when the lower mold on which the substantially plate-like glass is placed reaches a predetermined position, only the substantially plate-like glass is taken out from the lower mold by a method such as adsorption by a take-out device installed beside the rotary table. And the taken out substantially plate-shaped glass is generally transferred to the slow cooling apparatus of the next process.

  From the end of press forming until the substantially plate-shaped glass is removed from the lower mold, the lower surface and the upper surface of the substantially plate-shaped glass are placed under extremely different cooling conditions. That is, the lower surface side has a relatively large heat capacity, and heat exchange is performed by heat conduction in a state of surface contact with a lower mold made of metal (such as cast iron) having high heat conductivity. On the other hand, heat exchange is performed on the upper surface side by radiation into air at approximately room temperature and heat transfer by convection. Moreover, in the stage immediately after press molding performed in a short time, the temperature of the substantially sheet glass is maintained in a temperature range in which plastic deformation is possible. In such a state that it is easily deformed, the substantially glass sheet exposed to different cooling conditions on the upper surface and lower surface can maintain the shape during pressing in the process of solidifying and heat shrinking by cooling inside. It becomes difficult. In particular, when the shape of a substantially plate-like glass is close to a thin plate shape that maintains its shape, the stress generated by the difference in cooling rate between the upper and lower surfaces is less likely to remain as internal stress and is easily released as deformation (warp, swell). Become. Here, the lower surface side of the substantially plate-like glass that is in surface contact with the lower mold having a large heat capacity and excellent thermal conductivity can realize cooling with a small temperature difference on the entire surface as being almost integral with the lower mold. On the other hand, the upper surface side of the substantially plate-like glass after the upper mold is detached is basically exposed to the atmosphere side. Therefore, the thinner the substantially plate-like glass is, the more easily the influence on the upper surface side of the substantially plate-like glass is sensitive to fluctuations in the outside air, including the air flow, and it is difficult to achieve uniform cooling.

  In the technique shown in Patent Document 1, the glass plate in the molten state starts from contacting the lower mold until the press is completed by the upper mold and the lower mold. This eliminates the influence caused by the relatively longer contact time of the lower mold than the mold. That is, during pressing, the lower die and the upper die are maintained at different temperatures, and the heat of the substantially plate glass is removed symmetrically around the center surface of the substantially plate glass during pressing. Thus, the warpage of the substantially plate-like glass is prevented from occurring. And in order to implement | achieve this, it is necessary to remove sufficient heat | fever from substantially plate-like glass, For this reason, in the technique shown by patent document 1, press time is made longer. However, the longer press time leads to a decrease in the number of productions of substantially plate-like glass per hour, thereby reducing productivity.

  Patent Document 1 describes that, during pressing, “pressing is carried out for a sufficient time until the temperature of the mold surface and the glass sheet are all less than the softening point of the glass sheet and almost reached equilibrium”. However, even if the temperature is below the softening point, if the temperature is around the yield point, the upper and lower surfaces of the substantially plate-like glass are exposed to non-uniform cooling conditions and warpage occurs again. In consideration of this point, in order to reliably suppress the warpage, the press must be continued until the glass is cooled to a temperature below the glass transition point (more preferably below the strain point). In this case, since the pressing time is further increased, the number of productions of substantially plate-like glass per hour is further reduced.

  In the technique disclosed in Patent Document 2, when the temperature of the substantially plate-like glass after pressing is lower than that during pressing and within a range higher than the glass transition point, pressing for warping correction is performed. For this reason, the flatness of the substantially plate-like glass is improved by the contact between the substantially plate-like glass and the upper mold. For this reason, after the press for a short time of normal, compared with the case where no forced cooling operation is applied to the upper surface side of the substantially plate-like glass, the technique described in Patent Document 2 obtains a certain degree of warpage improvement effect. Can do.

  However, as in the press, the time during which heat exchange is possible due to the contact between the substantially plate-like glass and the upper die is limited in the warp correction press. Therefore, the substantially plate-like glass after undergoing the warp correction press is cooled at substantially different speeds on the upper and lower surfaces of the substantially plate-like glass during the period until the temperature falls below the glass transition point. . Therefore, it is difficult to avoid warping of the substantially plate glass again within this period. Therefore, although the technique described in Patent Document 2 can obtain a certain degree of warpage improvement effect as described above, it is fundamentally difficult to suppress the occurrence of warpage that occurs again after the warp correction press.

  In the technique shown in Patent Document 3, in order to improve the flatness of the substantially plate-like glass in addition to the normally-cooled (annealing) step after the take-out step of taking out the substantially plate-like glass from the mold (lower die). Further, the method further includes a step of correcting the warp by applying pressure to the main surface of the substantially plate-like glass. However, the implementation of the process of correcting such warpage increases the production cost. In addition to this, if an attempt is made to correct the warp by forcibly applying heat during annealing on a substantially plate-like glass that has been cooled to near the strain point in a state where the warp has occurred, the excess length accompanying the deformation is: When trying to flatten substantially plate-like glass, it may not be removed as a small swell.

  The present invention has been made in view of the above circumstances, and in the case of manufacturing a substantially plate-like glass by the direct press method, the warp of the obtained substantially plate-like glass is extremely small, and is excellent in productivity and warping. It is an object of the present invention to provide a method for producing a substantially plate-like glass that does not require a new separate process after the take-out process for correction. Furthermore, the present invention provides a press molding apparatus for producing a substantially plate-like glass using the method for producing a substantially plate-like glass, and a method for producing a substrate for an information recording medium using the method for producing the substantially plate-like glass, It is an object to provide an information recording medium manufacturing method and an optical component manufacturing method.

  The above-mentioned subject is achieved by the following present invention. That is, in the method for producing a substantially plate-like glass according to the present invention, the molten glass supplied on the lower mold press surface is the upper mold press surface and the upper mold disposed opposite to the lower mold press surface. After the upper mold is separated from the upper surface of the glass formed into a substantially flat plate, the substantially flat plate-like glass is cooled and soaked. And at least a part of the entire process in which the soaking / cooling process is performed, and is in contact with or close to the upper surface of the substantially plate-like glass positioned on the lower die press surface. As described above, the upper surface cooling rate adjusting member is arranged, and the upper surface cooling rate adjusting member is supported by a support portion fixed directly or indirectly to the floor surface.

  In one embodiment of the method for producing substantially plate-like glass of the present invention, it is preferable that the temperature of the upper surface cooling rate adjusting member is controlled by at least one temperature control means selected from a heating means and a cooling means.

  In another embodiment of the method for producing the substantially plate-like glass of the present invention, the curvature of the surface of the upper surface cooling rate adjusting member that contacts the upper surface of the substantially plate-like glass is the same as the curvature of the upper surface of the substantially plate-like glass. It is preferable that

  In another embodiment of the method for producing a substantially plate-like glass of the present invention, a glass supply step of cutting the molten glass continuously flowing out from the nozzle every predetermined volume and supplying the molten glass onto the lower press surface, After passing through, it is preferable that a shaping | molding process and a soaking | uniform-heating / cooling process are implemented in this order, and the extraction process which takes out the substantially plate-shaped glass on the press surface of a lower mold | type after that from a lower mold | type is implemented after that.

  In another embodiment of the method for producing a substantially plate-like glass of the present invention, the lower mold moves while alternately repeating movement and stop in the circulation direction, and the glass supply step is performed at any one stop position. One or more stops located downstream in the circulation direction from the stop position where the molding process is performed, with the molding process being performed at the stop position located downstream in the circulation direction with reference to the stop position where the glass supply process is performed It is preferable that the soaking / cooling step is performed between the position and the stop position where the extraction step is performed.

  The press molding apparatus of the present invention includes one upper mold having a press surface for press-molding a predetermined volume of molten glass and a plurality of lower molds, and a main shaft serving as a rotation center, and the plurality of lower molds are equally spaced. And a circular rotary table that repeats rotation and stop in one direction for each rotation angle obtained by dividing 360 degrees by the number of lower molds, and a nozzle connected to a molten glass supply source. Glass supply means for cutting the molten glass flowing out at a predetermined capacity and supplying it to the lower die press surface that stops at any one stop position of the rotary table, and any one stop position as a reference The molten glass positioned on the lower die press surface is pressed against the lower die press surface that stops at the stop position on the downstream side of the rotary table in the rotational direction and is arranged to be opposed to the lower die press surface. Molded almost into a plate The upper die having a pressing surface and the lower die pressing surface at a stop position sandwiching one or more stop positions on the downstream side in the rotation direction of the rotary table with reference to the stop position where the upper die is arranged A take-out means for taking out the substantially plate-like glass located on the upper side from the lower mold, and extending from the main shaft located on the upper surface side of the rotary table to the outer peripheral side of the rotary table, and at the tip thereof in the vicinity of the lower mold press surface, And a support portion provided with an upper surface cooling rate adjusting member that is movable with respect to the lower die press surface and between the spindle side, and rotates after passing through a stop position where the upper die is disposed. In a section where the lower mold moves along the downstream side in the rotational direction of the table until it reaches the stop position where the take-out means is arranged, it is positioned on the lower mold press surface in at least a part of the section. A roughly plate-shaped moth Top cooling rate adjusting member so as to contact with or close to the upper surface of the scan is being arranged.

  One embodiment of the press molding apparatus of the present invention preferably includes at least one temperature control means selected from heating means and cooling means for controlling the temperature of the upper surface cooling rate adjusting member.

  The information recording medium substrate manufacturing method of the present invention is for an information recording medium through at least a grinding / polishing step of grinding / polishing the main surface of the substantially plate-like glass produced by the method of producing a substantially plate-like glass of the invention. A substrate is manufactured.

  The information recording medium manufacturing method of the present invention includes at least an information recording layer forming step of forming an information recording layer on the main surface of the information recording medium substrate manufactured by the information recording medium substrate manufacturing method of the present invention. A recording medium is produced.

  The method for producing an optical component of the present invention is to produce an optical component through at least a grinding / polishing step of grinding / polishing the main surface of the substantially plate-like glass produced by the method for producing a substantially plate-like glass of the present invention. It is characterized by.

  As described above, according to the present invention, in the case of manufacturing a substantially plate-like glass by the direct press method, the warp of the obtained substantially plate-like glass is extremely small, and the productivity is excellent, and the warp is corrected. Thus, it is possible to provide a method for producing a substantially plate-like glass which does not require a new separate step after the extraction step. Furthermore, according to the present invention, a press molding apparatus for producing a substantially plate-like glass by using the method for producing a substantially plate-like glass, and a substrate for an information recording medium using the method for producing the substantially plate-like glass. A method, an information recording medium manufacturing method, and an optical component manufacturing method can be provided.

It is a schematic cross section which shows an example of the cross-section of the press molding apparatus of this embodiment. It is an upper surface schematic diagram which shows an example of the rotary table which comprises the press molding apparatus of this embodiment.

-Manufacturing method of substantially plate glass-
The method for producing a substantially plate-like glass according to the present embodiment is such that the molten glass supplied on the lower mold press surface is an upper mold press surface arranged opposite to the lower mold press surface and the lower mold press surface. A step of forming a substantially flat plate by pressing with a surface, and a soaking / cooling step that cools and soaks the substantially flat glass after separating the upper mold from the upper surface of the glass formed into a substantially flat plate. An upper surface so as to be in contact with or close to the upper surface of the substantially plate-like glass positioned on the lower die press surface in at least a part of the entire process in which the soaking / cooling step is performed. The cooling rate adjusting member is disposed, and the upper surface cooling rate adjusting member is supported by a support portion fixed directly or indirectly to the floor surface.

  That is, in the manufacturing method of the substantially plate-like glass of the present embodiment, at least a part of the whole process in which the soaking / cooling process is performed (hereinafter, this part of the process is referred to as “cover state by the upper surface cooling rate adjusting member The solid member having a larger heat capacity and higher thermal conductivity than air is applied not only to the lower mold on the lower surface side of the substantially glass plate but also to the upper surface side (that is, the upper surface cooling rate adjustment). Member) will be arranged. For this reason, the whole substantially plate-like glass is in a state of being substantially encapsulated by a solid member having a larger heat capacity and higher thermal conductivity than air. In such a state, the difference in cooling conditions between the upper surface side and the lower surface side of the substantially plate-like glass is extremely small as compared with the case where the upper surface side is directly exposed to air convection. Therefore, when substantially plate-shaped glass is cooled, maintaining the state mentioned above, the cooling rate difference for every micro part on both surfaces of substantially plate-shaped glass will be suppressed. Therefore, although the temperature of the substantially plate-like glass immediately after pressing is maintained in a temperature range where deformation is easy, the occurrence of warpage of the substantially plate-like glass and the residual stress inside the substantially plate-like glass is suppressed.

  As a result, the entire plate glass is cooled and solidified while maintaining a state in which there is almost no warp or residual stress immediately after pressing, and solidification proceeds, so that the warp of the finally obtained plate glass is extremely small. Is easy. In addition to this, since it is not necessary to lengthen the press time as in the technique described in Patent Document 1, it is excellent in productivity, and after the extraction process as in the technique described in Patent Document 3. Furthermore, it is not necessary to perform a new process for correcting the warp.

  In order to suppress the amount of warpage to a smaller extent, the longer the period during which the cover state by the upper surface cooling rate adjusting member is maintained during the soaking / cooling step, the more preferable, specifically, the upper surface cooling rate adjusting member At the end of the period during which the cover state is maintained, the temperature of the substantially plate-like glass is preferably below the yield point of the glass, more preferably below the glass transition point, particularly below the strain point. Most preferred. In particular, even if the upper surface cooling rate adjusting member is removed from the upper surface of the substantially plate-like glass after the temperature becomes lower than the strain point, and there is a large imbalance in the cooling conditions between the upper surface side and the lower surface side, at this stage There is no room for new strain in the substantially plate-like glass. Therefore, in this case, the amount of warpage can be further suppressed. In addition, the cover state by the upper surface cooling rate adjusting member is maintained in order to reliably prevent the warpage from starting when the upper surface and the lower surface of the substantially plate-like glass immediately after pressing are exposed to different cooling conditions. The start of the period is preferably closer to the start time of the soaking / cooling step, and is preferably substantially the same as the start time. In addition, if the start of the period during which the cover state by the upper surface cooling rate adjusting member is maintained is delayed from the start of the soaking / cooling process, at least the substantially glass sheet is used at the start so that warpage can be reliably suppressed. It is particularly preferable that the temperature of the glass be higher than the glass transition point.

  The temperature of the upper surface cooling rate adjusting member when the upper surface cooling rate adjusting member is disposed on the upper surface of the substantially plate-like glass is preferably close to the temperature of the lower mold surface at this time, specifically Is preferably within ± 50 ° C., more preferably within ± 10 ° C. with respect to the temperature of the lower mold surface. Thereby, the environment which wraps the whole outer periphery of the substantially plate-like glass in the state which is easy to deform | transform immediately after a press with the object which has substantially the same surface temperature is realizable. For this reason, the cooling conditions on the upper surface side and the lower surface side of the substantially plate-like glass can be made approximate or substantially the same.

  In order to suppress warpage, an upper surface cooling rate adjusting member that is not supported by any support portion may be simply disposed on the upper surface of the substantially plate-like glass. However, with such a configuration, the upper surface cooling rate adjusting member is not supported by the support member, and a positional shift may occur when the upper surface cooling rate adjusting member is disposed on the upper surface of the substantially plate-like glass. In such a case, the cooling condition of a part of the upper surface of the substantially plate-like glass is greatly different from other parts, and as a result, there is a risk of causing warpage. In particular, in order to ensure productivity, it is necessary to arrange the upper surface cooling rate adjusting member on the upper surface of the substantially plate-like glass in a shorter time, but in this case, the positional deviation is more likely to occur. In addition to this, the upper surface cooling rate adjusting member cannot be well arranged on the substantially plate-like glass upper surface, and is easily dropped.

  In addition, when mass-producing substantially plate-like glass, usually, a plurality of lower molds are circulated while repeatedly moving and stopping on the circulation line by arranging a plurality of lower molds on the periphery of the rotary table, etc. Each step is performed. In consideration of manufacturing the substantially plate-like glass by such a process, it is necessary to arrange the upper surface cooling rate adjusting member on the upper surface of the substantially plate-like glass while the lower mold is temporarily stopped. However, if the stop time of the lower mold is shortened in order to increase the production efficiency, the above-described misalignment and dropout are likely to occur.

  However, in the manufacturing method of the substantially plate-like glass of the present embodiment, the upper surface cooling rate adjusting member is supported by a support portion fixed directly or indirectly to the floor surface. For this reason, it is possible to easily prevent displacement and dropout. Therefore, productivity can be further improved in this sense. Here, the “floor surface” is a surface that does not vibrate or shake to the extent that it affects the positioning accuracy when the top surface cooling rate adjustment member is placed, as long as the ground is stable and there is no earthquake. For example, in the case of a building such as a factory, an iron plate floor surface or a concrete floor surface provided on a structure formed of a steel frame or the like can be used. In addition, “(the support part) is directly or indirectly fixed to the floor surface” is not only when the support part is directly fixed to the floor surface, but is also substantially fixed to the floor surface and the floor surface. The case where the support part is being fixed to the rigid member which does not vibrate or shake like the same. As the rigid member, for example, in the case of the rotary table described above, a columnar main shaft that constitutes the rotation center axis thereof may be mentioned. In addition, when using a rotary table, although a support part may be arrange | positioned on the floor surface located in the outer peripheral side of a rotary table, it is more preferable to attach a support part to a main axis | shaft.

  The “support portion” is not particularly limited as long as it is a member that can support the upper surface cooling rate adjusting member at its tip and has rigidity, and examples thereof include a metal rod-like member. In order to dispose the upper surface cooling rate adjusting member on the upper surface of the substantially plate-shaped glass or to separate the upper surface cooling rate adjusting member from the upper surface of the substantially plate-shaped glass after that, (1) A movable part is provided on the floor side (the rigid member side when indirectly fixed), (2) a movable part is provided in the middle of the support part, or (3) it is movable on the tip side of the support part. Can be provided. However, from the viewpoint that it is easy to ensure higher positioning accuracy, the embodiment shown in the above (2) or (3) is preferable, and the embodiment shown in the above (3) is particularly preferable.

  Thus, in the manufacturing method of the substantially plate glass of this embodiment, the upper surface cooling rate adjusting member is supported by the support portion. For this reason, the arrangement of the upper surface cooling rate adjusting member on the upper surface of the substantially plate-like glass is arranged so that the upper surface of the upper glass plate and the upper surface cooling rate adjusting member are in contact with each other, but not in contact with each other. You may arrange in. In addition, the said "proximity" means that the clearance gap between a substantially plate-shaped glass upper surface and the lower surface side of an upper surface cooling rate adjustment member is 5 mm or less, and 1 mm or less is more preferable. When the gap is too large, the cooling conditions between the upper surface and the lower surface of the substantially plate-like glass greatly deviate due to air convection, and as a result, it becomes difficult to suppress warpage. However, by setting the gap to 5 mm or less, it is possible to suppress the deviation of the cooling condition between the upper surface and the lower surface of the substantially plate-like glass and to reliably suppress the warpage. In addition, when the upper surface cooling rate adjusting member is disposed close to the upper surface of the substantially glass sheet, the upper surface cooling rate adjusting member can be more reliably prevented from being damaged by the upper surface cooling rate adjusting member than when the upper surface cooling rate adjusting member is disposed in contact. can do.

  The shape of the substantially plate glass produced by the method for producing the substantially plate glass of the present embodiment is not particularly limited, and can be appropriately selected according to the purpose. For example, in the case of a substrate for an information recording medium such as a magnetic recording medium, a thin disc shape having the same thickness as a whole, or a thick portion partially in the central portion and / or outer peripheral portion in the diameter direction in the disc shape In the case of an optical component such as a lens, a shape in which the cross-sectional shape in the diametrical direction is convex or concave may be used. Thus, although the shape of the substantially plate-like glass can be selected as appropriate, generally, the maximum thickness is in the range of 1 mm to 5 mm, the maximum outer diameter is in the range of 15 mm to 150 mm, and the ratio of the maximum thickness to the maximum outer diameter is It is preferable to be within the range of 0.01 to 0.1.

  In addition, as described above, the thinner the plate-like glass in the high-temperature state immediately after pressing, the smaller the strength for maintaining the shape. For this reason, in such a substantially plate-like glass, if the cooling conditions of the upper and lower surfaces immediately after pressing are greatly different, such as when contacting the air and when contacting the lower mold, the amount of warpage tends to become very large. Such a problem is particularly remarkable in a substantially plate-like glass in which the ratio (Tmin / D) of the thickness Tmin of the thinnest portion to the diameter D is 0.1 or less. Therefore, the method for producing a substantially plate-like glass of the present embodiment is preferably used for producing a substantially plate-like glass having a ratio of the thickness Tmin of the thinnest portion to the diameter D (Tmin / D) of 0.1 or less. More preferably, it is used for producing a substantially plate-like glass having a Tmin / D of 0.02 or less, and more preferably, it is used for producing a substantially plate-like glass having a Tmin / D of 0.015 or less. In addition, although it does not specifically limit about the minimum of Tmin / D, It is preferable to set it as 0.005 or more practically.

  In addition, although it does not specifically limit as a use of the substantially plate glass manufactured with the manufacturing method of the substantially plate glass of this embodiment, For example, substantially plate shape used for preparation of substrates for information recording media, such as a magnetic recording medium Examples thereof include glass and substantially plate-like glass for optical components. Typical sizes of the substantially plate-like glass used for the production of the information recording medium substrate have a thickness of 0.7 mm to 2 mm and a diameter of 2.5 cm to 15 cm. And Tmin / D is 0.1 or less.

  Next, the upper surface cooling rate adjusting member will be described. The upper surface cooling rate adjusting member used in the method for producing a substantially plate-like glass according to the present embodiment is substantially the same as that immediately after press forming in at least a part of the soaking / cooling step performed following the forming step. It is used to significantly suppress the difference in cooling conditions between the upper and lower surfaces of the sheet glass compared to when the upper surface is exposed to air (except when the upper surface cooling rate adjusting member is disposed close to the glass). . There are no particular limitations on the characteristics of the upper surface cooling rate adjusting member, such as the shape and constituent materials, as long as such an object can be achieved. However, specifically, it is preferable to have the following characteristics.

  First, the shape of the surface (opposite surface) facing the upper surface of the substantially plate-like glass of the upper surface cooling rate adjusting member is particularly preferably at least substantially the same size as the upper surface of the substantially plate-like glass to be produced. The shape may be larger than that. Thereby, the whole upper surface of substantially plate-shaped glass can be covered with an upper surface cooling rate adjustment member, and the dispersion | variation in the cooling conditions of the whole substantially plate-shaped glass upper surface can be suppressed. As a result, warpage and deformation caused by in-plane cooling unevenness can be suppressed. The temperature of the upper surface cooling rate adjusting member is preferably controllable by a temperature control means using a heating means such as a heater, an air cooling method such as a heat sink, or a water cooling method using cooling water. Thereby, the deviation of the cooling conditions between the upper surface side and the lower surface side of the substantially plate-like glass can be controlled to be smaller. For this reason, it is easier to suppress warpage.

  Moreover, it is preferable that the curvature of the surface which contacts a substantially disk-shaped glass of an upper surface cooling rate adjustment member and the curvature of the upper surface of a substantially disk-shaped glass are the same. In this case, the entire upper surface of the substantially disk-shaped glass is substantially in contact with the substantially disk-shaped glass, or the entire upper surface of the approximately disk-shaped glass and the surface of the upper surface cooling rate adjusting member that is in contact with the substantially disk-shaped glass. The same gap spacing is maintained at virtually any position on the entire surface. For this reason, uniform cooling with little variation can be realized on the entire upper surface of the substantially disk-shaped glass. In this case, warpage and deformation due to in-plane cooling unevenness can be suppressed.

  The upper surface cooling rate adjusting member is preferably approximated to the lower mold in terms of heat capacity, surface area, thermal conductivity characteristics, and surface emissivity characteristics. Thereby, the deviation of the cooling conditions between the upper and lower surfaces of the substantially plate-like glass can be more easily suppressed. Here, the emissivity characteristic of the surface is the emissivity of the object surface when blackbody radiation is 1.0. If the emissivity is high (close to 1.0), more heat can be radiated per unit area and unit time. In addition, “approximate to the lower mold in terms of heat capacity, surface area, thermal conductivity characteristics, and surface emissivity characteristics” means within ± 20% of the lower mold, and ± 10% Is preferably within ± 5%, more preferably within ± 5%, and even more preferably within ± 1%.

  Next, the whole process of the manufacturing method of the substantially plate glass of this embodiment is demonstrated. In the manufacturing method of the substantially plate-like glass of the present embodiment, the molten glass continuously flowing out from the nozzle is cut for each predetermined volume, and after passing through the glass supply step for supplying the molten glass onto the press surface of the lower die, the above-described method is performed. The molding process and the soaking / cooling process are performed in this order. Thereafter, a step of taking out the substantially plate-like glass on the press surface of the lower die from the lower die is performed. In addition to these four steps, other steps may be performed as necessary. For example, before carrying out the glass supply step, a solid lubricant powder application step for applying a heat-resistant solid lubricant powder such as BN powder onto the press surface of the lower die, or a lower die preheating step for preheating the lower die Etc. can be implemented.

  In order to ensure mass productivity, it is preferable to move the lower mold while alternately repeating movement and stop in the circulation direction when performing each step. As a method of circulating the lower mold on a predetermined circulation line while alternately moving and stopping, a plurality of lower molds are arranged at regular intervals along the periphery of the rotatable circular table. The method using the rotary table is a representative example, but is not limited thereto. When the lower mold is circulated and moved in the circulation direction, for example, the lower mold is moved while alternately repeating movement and stop in the circulation direction, and the glass supply process is performed at any one of the stop positions. One or more stop positions positioned downstream in the circulation direction from the stop position where the molding process is performed at the stop position positioned downstream in the circulation direction with reference to the stop position where the supply process is performed Then, the soaking / cooling process is performed until the stop position where the extraction process is performed.

  That is, a predetermined process such as a glass supply process is performed on the basis of the stop position of the lower mold. The position where the lower mold stops is fixed at the same position on the circulation line. Therefore, when 12 lower molds are arranged on the circulation line, there are 12 lower mold stop positions. Here, assuming that numbers 1 to 12 are sequentially attached to the lower mold stop position along the circulation direction of the lower mold, for example, the glass supply process is performed at the first lower mold stop position, The molding process is performed at the second lower mold stop position, the soaking and cooling process is performed while the lower mold passes through the third to eighth lower mold stop positions, and the mold is taken out at the ninth lower mold stop position. Embodiment in which the lower mold preheating process is performed while the lower mold passes through the 10th to 12th lower mold stop positions, and the solid lubricant powder application process is performed at the 12th lower mold stop position. It can be.

  In addition, when the soaking / cooling step is performed in the process where the lower die passes through the a-th to b-th lower die stop positions, the timing for arranging the upper surface cooling rate adjusting member on the upper surface of the substantially plate-like glass is as follows. The upper surface cooling rate adjusting member disposed on the upper surface of the substantially plate-like glass can be selected from the cases where the lower die is stopped at any of the a-th to b-1 lower die stop positions. The timing of separating from the upper surface can be selected from the case where the lower die is stopped at any one of the (a + 1) th to b-th lower die stop positions. Note that a means an integer within a range of 3 or more and the total number of lower molds arranged on the circulation line minus 2 or less when the glass supply process is performed at the first lower mold stop position. , B means an integer in the range of less than the total number of molds −1 that is greater than a and arranged on the circulation line.

  Here, from the viewpoint of reducing the amount of warpage, the timing for arranging the upper surface cooling rate adjusting member on the upper surface of the substantially plate-like glass is preferably as the lower die stop position number is smaller, and the soaking / cooling process is started. After that, the earliest lower mold stop position is most preferred. Further, the timing for separating the upper surface cooling rate adjusting member from the upper surface of the substantially plate-like glass is preferably the lower mold stop position where the temperature of the substantially plate-like glass is lower than the yield point of the glass, and lower than the glass transition point. The lower mold stop position is more preferable, and it is particularly preferable that the lower mold stop position be equal to or lower than the strain point. Therefore, in consideration of this point, the timing at which the upper surface cooling rate adjusting member is separated from the upper surface of the substantially plate-like glass is usually set to the lower mold stop position when the soaking / cooling process is completed. .

  In the molding process, the temperatures of the upper and lower press surfaces are adjusted to a temperature suitable for molding the molten glass into a substantially plate shape. This temperature is appropriately determined depending on the glass type, the thickness, the size of the glass plate, and the like. In addition, after the soaking / cooling step, it is particularly preferable that the extraction step is usually performed at a stage where the temperature of the substantially plate-like glass is equal to or lower than the yield point of the glass. And it is suitable for the substantially plate-shaped glass taken out from the lower mold | type to arrange | position in a slow cooling furnace and to cool slowly.

  The glass composition of the substantially plate-like glass produced by the method for producing the substantially plate-like glass of the present embodiment can be appropriately selected according to the use of the substantially plate-like glass. For example, when a substantially plate-like glass is used for producing a substrate for an information recording medium, aluminosilicate glass, soda lime glass, soda aluminosilicate glass, aluminoborosilicate glass, borosilicate glass, quartz glass, chain silicate glass, etc. Can be mentioned. These glasses may be crystallized glass base materials that crystallize by heat treatment. Suitable glass compositions are exemplified below.

(1) Glass composition 1
In weight percentages, SiO ₂ is from 60 to 87%, Li ₂ O is 5 to 20%, Na ₂ O is 0 to 5%, K ₂ O is 0%, Na ₂ O and K ₂ O is in total 0.5-10%, MgO 0.5-7.5%, CaO 0-9.5%, SrO 0-15%, BaO 0-13%, ZnO 0-13%, B ₂ 0-3% for O ₃ , 0-10% for Al ₂ O ₃ , 0.5-8% for P ₂ O ₅ , 0-5% for TiO ₂ , 0-3% for ZrO ₂ , 0 for SnO ₂ ~ 3%, As ₂ O ₃ and Sb ₂ O ₃ in total 0 to 2%, containing one or more metal element fluorides of the above metal oxide as a total amount of 0 to 5%, optionally As coloring components, V ₂ O ₅ , CuO, MnO ₂ , Cr ₂ O ₃ , CoO, MoO ₃ , NiO, Fe ₂ O ₃ , TeO ₂ , CeO ₂ , Pr ₂ O ₃ , Nd ₂ O ₃ , Er ₂ O few were selected from the _third group of Glass composition containing Kutomo one of 0-5%. Glass made of this glass composition can be crystallized by heat treatment, and lithium disilicate as the main crystal, and in some cases α-cristobalite, α-quartz, lithium monosilicate, β-spodumene, etc. are precipitated in the glass matrix. . In this case, it is preferable to control the crystal grain size to 3.0 μm or less.

(2) Glass composition 2
In terms of% by weight, SiO ₂ is 45 to 75%, CaO is 4 to 30%, Na ₂ O is 2 to 15%, K ₂ O is 0 to 20%, Al ₂ O ₃ is 0 to 7%, MgO is 0 to 2%, ZnO is 0 to 2%, SnO ₂ is 0~2%, Sb ₂ O ₃ is 0~1%, B ₂ O ₃ is 0~6%, ZrO ₂ is 0 to 12%, Li ₂ O is 0 to 3%, fluoride of one or more metal elements of the above metal oxide is contained in a total amount of 3 to 12%, and in some cases, Cr ₂ O ₃ , Co ₃ O _4, etc. as coloring components Glass composition to contain. The glass having this glass composition can be crystallized by heat treatment, and canasite or potassium fluoro-richitelite is precipitated in the glass matrix as the main crystal. In this case, it is preferable to control the crystal grain size to 1.0 μm or less.

(3) Glass composition 3
In terms of% by weight, SiO ₂ is 62-80%, Al ₂ O ₃ is 4-18%, ZrO ₂ is 0-15%, Li ₂ O is 1-12%, and Na ₂ O is 1-13%. Glass. In weight percent, 62-75% of SiO _2, 5 to 15% of Al ₂ O _3, 4 to 10% of Li ₂ O, 4 to 12% of Na ₂ O, and 5.5 to 15% of ZrO ₂ And a weight ratio of Na ₂ O / ZrO ₂ is 0.5 to 2.0, and a weight ratio of Al ₂ O ₃ / ZrO ₂ is 0.4 to 2.5. In addition, you may perform the chemical strengthening process using ion exchange with respect to the glass which consists of this glass composition.

  In addition, when a substantially plate-like glass is used for production of an optical component, a phosphate glass, a lanthanum borate glass, a silicate glass, or a fluorophosphate having a desired optical property value such as a refractive index. Glass etc. are mentioned. Suitable glass compositions are exemplified below.

  Next, a specific example of the shape of the substantially plate glass will be described. The shape of the substantially plate-like glass can be appropriately selected depending on the application. In addition, when producing the substrate for information recording media using substantially plate-like glass, it is preferable that the shape of substantially plate-like glass has the shape and dimension shown below.

(1) When producing a glass substrate for an information recording medium substrate having a diameter of 1 inch The dimensions of a glass substrate of this size are an outer diameter: 27.4 mm, a thickness: 0.381 mm, and a center hole inner diameter: 7.0 mm. For this reason, the dimension of the substantially plate-like glass suitable for producing a glass substrate of this size by processing the substantially plate-like glass is an outer diameter: 27.4 to 30 mm, and the portion to be processed into the glass substrate. The thickness is 0.8 to 1.0 mm (a uniform thickness is preferable in the diameter direction), and the thickness of the portion where the center hole is opened is 0.8 to 1.0 mm. Moreover, when providing a thick part in a center part, it is suitable that the diameter of a center thick part shall be 4-6 mm. When producing a substantially plate-like glass adopting such dimensions, when the molten glass is pressed, the molten glass can be stretched smoothly in the outer diameter direction to be thinned. Moreover, when manufacturing a glass substrate by post-processing substantially plate glass, 0.05-0.4 mm can be ensured as a grinding | polishing and grinding allowance.

(2) When producing a glass substrate for an information recording medium substrate having a diameter of 2.5 inches The dimensions of the glass substrate of this size are as follows: outer diameter: 65.0 mm, thickness: 0.635 mm, center hole inner diameter: 20.0 mm is there. For this reason, the dimensions of the substantially plate-like glass suitable for producing a glass substrate of this size by processing the substantially plate-like glass are the outer diameter: 65 to 68 mm, the thickness of the portion to be processed into the glass substrate. The thickness is 0.7 to 1.0 mm (a uniform thickness is preferable in the diameter direction), and the thickness of the portion where the center hole is formed is 1.1 to 1.5 mm. Moreover, when providing a thick part in a center part, it is suitable that the diameter of a center thick part shall be 16-19 mm. When producing a substantially plate-like glass adopting such dimensions, when the molten glass is pressed, the molten glass can be stretched smoothly in the outer diameter direction to be thinned. Moreover, when manufacturing a glass substrate by post-processing substantially plate glass, 0.05-0.4 mm can be ensured as a grinding | polishing and grinding allowance.

(3) When producing a glass substrate for an information recording medium substrate having a diameter of 3.5 inches The dimensions of this size glass substrate are as follows: outer diameter: 95.0 mm, thickness: 1.0 mm, center hole inner diameter: 25.0 mm is there. For this reason, the dimensions of the substantially plate-like glass suitable for producing a glass substrate of this size by processing the substantially plate-like glass are the outer diameter: 95 to 98 mm, the thickness of the portion to be processed into the glass substrate. The thickness is 1.05 to 1.4 mm (a uniform thickness is preferable in the diameter direction), and the thickness of the portion where the center hole is opened is 1.5 to 2.1 mm. Moreover, when providing a thick part in a center part, it is suitable that the diameter of a center thick part shall be 21-24 mm. When producing a substantially plate-like glass adopting such dimensions, when the molten glass is pressed, the molten glass can be stretched smoothly in the outer diameter direction to be thinned. Moreover, when manufacturing a glass substrate by post-processing substantially plate glass, 0.05-0.4 mm can be ensured as a grinding | polishing and grinding allowance.

-Press molding equipment-
The press molding apparatus using the method for producing a substantially plate-like glass of the present embodiment is not particularly limited as long as it has a configuration capable of implementing the method for producing a substantially plate-like glass of the present embodiment, but the constitution shown below It is particularly preferred that the device has That is, the press molding apparatus of the present embodiment includes one upper mold and a plurality of lower molds having a press surface for press-molding a predetermined volume of molten glass, and a plurality of lower molds. Are arranged at the peripheral edge at equal intervals, and connected to a molten glass supply source and a circular rotary table that repeats rotation and stop in one direction for each rotation angle obtained by dividing 360 degrees by the number of lower molds. Glass supply means for cutting the molten glass continuously flowing out from the nozzle at a predetermined capacity and supplying it on the press surface of the lower die that stops at any one stop position of the rotary table, and any one stop position As a reference, a molten glass located on the lower die press surface is arranged opposite to the lower die press surface that stops at the stop position downstream in the rotation direction of the rotary table and is movable in the vertical direction. Press An upper die having a press surface to be formed into a substantially plate shape, and a stop position located on the downstream side in the rotation direction of the rotary table with one or more stop positions sandwiched with reference to the stop position where the upper die is arranged A take-out means for taking out the substantially plate-like glass located on the lower die press surface from the lower die, and a main die located on the upper surface side of the rotary table, extending from the outer periphery side of the rotary table, to the tip of the lower die press It is preferable to include at least a surface portion and a support portion that is provided so as to be movable between the upper side of the lower die press surface and the main shaft side and includes an upper surface cooling rate adjusting member.

  And in the press molding apparatus of this embodiment, after passing through the stop position where the upper mold is arranged, along the downstream side in the rotation direction of the rotary table, until the stop position where the take-out means is arranged is reached. In the section in which the lower mold moves, the upper surface cooling rate adjusting member is arranged so as to be in contact with or close to the upper surface of the substantially plate-like glass located on the lower mold press surface in at least a part of the section.

  Note that the press molding apparatus of the present embodiment controls the temperature of the upper surface cooling rate adjusting member in addition to the upper die, the lower die, the rotary table, the glass supply unit, the takeout unit, the support unit, and the upper surface cooling rate adjusting member. Preferably, at least one temperature control means selected from a heating means and a cooling means is provided. These temperature control means are usually provided also in the upper mold and the lower mold. The heating means includes, for example, an upper surface cooling rate adjusting member, a nichrome heater that heats an object to be heated such as an upper mold and a lower mold by resistance heating, a coil made of a conductor that is heated by induction heating, and heat exchange with a high-temperature gas. And a structure that functions as a heat exchanger that heats by heating (for example, a hollow portion through which gas flows). In addition, as a cooling means, a structure that functions as a heat exchanger that cools by heat exchange with a cooling medium such as water or air at a temperature sufficiently lower than the object to be cooled or near room temperature (for example, a hollow portion through which the cooling medium flows) And a hollow part for spraying and vaporizing a liquid).

  Further, if necessary, solid lubricant powder spraying means may be provided in order to adhere a heat-resistant solid lubricant powder such as BN onto the press surface of the lower die. The number of lower molds arranged on the rotary table is the four steps that are required to be carried out at the minimum in order to produce a substantially plate-like glass, the glass supply step, the forming step, the soaking / cooling step, and the takeout. In principle, at least four are sufficient to correspond to the process. However, in consideration of securing the cooling period of the substantially plate-shaped glass from press molding to removal and securing the remaining heat time of the lower mold press surface before press molding, the number of lower molds is practically 6 or more. About 30 or less are preferable.

  The material of the lower mold, the upper mold, and the upper surface cooling rate adjusting member is preferably a material that has heat resistance and high thermal conductivity. Examples of such materials include graphite, tungsten alloys, nitrides, carbides, refractory metals, and the like, and cast iron is particularly preferable from the viewpoint of being inexpensive and easy to process and having sufficient strength and durability.

  Next, an example of the press molding apparatus of this embodiment is demonstrated using drawing. FIG. 1 is a schematic cross-sectional view showing an example of a cross-sectional structure of the press molding apparatus according to the present embodiment, and specifically shows a cross-sectional view when the press molding apparatus is cut in the diameter direction of the rotary table. Is. The main part of the press molding apparatus 1 shown in FIG. 1 includes a base part 10 installed on the floor 2, a rotary table 12 arranged on the base part 10, and a rotation center axis of the rotary table 12 (in the figure). And a main shaft 14 which is provided on the upper surface side of the rotary table 12 so as to extend right along the dotted line indicated by the reference numeral A) and the floor surface side is supported by the base portion 10. The rotary table 12 can rotate integrally with the main shaft 14, and the main shaft 14 is repeatedly rotated and stopped at predetermined angles in one direction along the rotation center axis by a driving means (not shown). Can do. Here, a lower mold 16 is disposed on the upper surface side of the turntable 12 and on the peripheral edge thereof. Further, one end is fixed to the main shaft 14, and a support portion 18 is provided so as to extend from the rotation center axis A to the outer peripheral side.

  The support portion 18 includes a support portion main body 20 fixed to the main shaft 14, a movable arm support portion 22 provided on the opposite side of the support portion main body 20 to the main shaft 14, and a movable arm support portion. 22 is provided on the side opposite to the side fixed to the support body 20 (hereinafter sometimes referred to as “tip portion”), and the lower die 16 side and the support portion body 20 side start from the tip portion. The movable arm 24 is configured to reciprocate so as to draw an arc (a double-headed arrow R1 in the figure). A substantially disc-shaped upper surface cooling rate adjusting member 26 is provided at the tip of the movable arm 24 (on the side opposite to the side where the operating arm support portion 22 of the movable arm 24 is provided). In addition, although illustration is abbreviate | omitted about the means to reciprocate the movable arm 24 to the double arrow R1 direction, a hydraulic cylinder etc. can be utilized, for example.

  Here, as the movable arm 24 moves, the upper surface cooling rate adjusting member 26 is disposed in contact with or close to the upper surface of a substantially plate-like glass (not shown in the drawing) disposed on the pressing surface of the lower die 16. The first state (the solid line portion in the figure) or the second state in which the upper and lower surfaces of the upper surface cooling rate adjusting member 26 are substantially parallel to the rotation center axis A apart from the press surface of the lower die 16 ( The dotted line portion in the figure) can be taken. And at the time of manufacturing substantially plate-shaped glass, after the lower mold passes through the stop position where the upper mold is arranged, it reaches the stop position where the take-out means is arranged along the downstream side in the rotation direction of the rotary table. In the section in which the lower mold moves between the upper surface cooling speed adjustment member 26 in the at least part of the section, the upper surface cooling rate adjusting member 26 is in the first state. In other than the left section, the upper surface cooling rate adjusting member 26 is in the second state.

-Specific examples of manufacturing substantially plate-like glass-
Next, a specific example of manufacturing a substantially plate-like glass using the glass molding apparatus of the present embodiment will be described in more detail with reference to the drawings. FIG. 2 is a top schematic view showing an example of a rotary table constituting the press molding apparatus of the present embodiment. In FIG. 2, the description of other members other than the rotary table 12 and the lower mold 16 is omitted. The circular rotary table 12 shown in FIG. 2 has twelve lower molds 16 arranged at equal intervals along its peripheral edge. And when manufacturing substantially plate-shaped glass, it rotates to the arrow R direction (clockwise direction), repeating rotation and a stop every 30 degrees alternately. In FIG. 2, a line indicated by a one-dot chain line means a stop position of the lower mold 16. There are 12 stop positions corresponding to the number of lower molds. In FIG. 2, numbers P1 to P12 are given to the respective stop positions along the direction of the arrow R2. Therefore, in the press molding apparatus 1 shown in FIG. 1, when the rotary table shown in FIG. 2 is used, the twelve supports provided with the upper surface cooling rate adjusting member 26 at the tip so as to correspond to the position and number of the lower mold 16 are used. Will have a part.

  Here, when manufacturing substantially plate-shaped glass using the turntable 12 shown in FIG. 2, each process can be implemented at each stop position P1-P12 as shown in the following Table 1, for example. That is, in the example shown in Table 1, after the glass supply process is performed at the stop position P1, the molding process is performed at the stop position P2 adjacent to the stop position P1, and then the lower mold that has finished the molding process is stopped. While moving from position P3 to P9 while alternately repeating rotation and stop, a soaking / cooling step is performed in which the entire substantially plate-like glass in a high-temperature state immediately after pressing is cooled while being soaked. At this time, the upper surface cooling rate adjusting member 26 is disposed on the upper surface of the substantially plate-like glass at the stop position P3 and rotates in this state together with the rotary table 12, and at the stop position P8, the upper surface from the upper surface of the substantially plate-like glass. The cooling rate adjusting member 26 is separated.

  Next, when the lower die 16 moves to the stop position P9, the substantially plate-like glass located on the press surface of the lower die 16 is taken out. The substantially plate-like glass taken out from the lower mold 16 is then placed in a slow cooling furnace and gradually cooled to room temperature. Subsequently, in preparation for re-pressing, when the lower die 16 moves to the stop positions P10 to 12 and stops at these positions, the temperature of the press surface is heated to a temperature suitable for the press. The lower mold preheating step is performed.

  The rotation speed of the turntable 12 can be selected as appropriate. However, from the viewpoint of achieving a balance between mass production stability and production speed improvement, it is usually preferable to set the rotation speed to about 2 to 3 rotations / minute. In addition, the stop time of the lower mold 16 at each stop position P1 to P12 is not particularly limited, but from the viewpoint of ensuring the improvement of the production speed while securing the time required for the implementation of each process. 1.7 seconds are preferable, and 1.2 seconds to 1.5 seconds are preferable.

  Next, each step will be described more specifically. First, in the glass supply step, a glass supply means including at least an outflow nozzle for flowing the molten glass to the press surface of the lower mold 16 and a cutting machine for cutting the molten glass continuously flowed out from the outflow nozzle. The molten glass is supplied onto the press surface of the lower die 16. Specifically, a glass supply process is implemented as follows. First, molten glass made of these glass materials that has been melted, clarified, and stirred and homogenized is continuously discharged from the outflow nozzle at a constant outflow speed, and this molten glass flow is always kept at a constant mass by a cutting machine called shear. Periodically cut to obtain a molten glass lump. Then, the cut molten glass lump is supplied (cast) onto the press surface of the lower die 16 waiting at the stop position P1 immediately below the outflow nozzle. The molten glass discharged from the outflow nozzle is in a softened state and has a viscosity of about 0.3 to 100 Pa · s. The molten glass is rounded by the surface tension on the press surface of the lower mold 16 and becomes a lump-like glass. In addition, although the temperature of the press surface of the lower mold | type 16 is lower than the temperature of a glass lump, it is adjusted so that a substantially plate-shaped glass may not be broken by supercooling a lump glass.

  After the casting is finished, the lower mold 16 on which the massive glass is placed on the press surface moves to the stop position P2 and stops. And a shaping | molding process is implemented in the stop position P2, and glass is press-molded in substantially plate shape. At this time, the temperature, pressing pressure, and pressing time of the upper die 16 and the lower die 16 are appropriately set in consideration of the thermal properties of the glass such as the glass transition temperature, the diameter and thickness of the substantially plate-like glass to be produced, and the like. For example, the temperature of the upper mold can be adjusted to 250 to 400 ° C., and the temperature of the lower mold 16 can be set to 420 to 470 ° C. About a press thrust, it can select suitably according to the shape of substantially plate-like glass. For example, about 3 to 7 tons can be used as a guideline for the thrust at the time of pressing a 2.5-inch equivalent product of the information recording medium substrate.

  When the press molding is completed, the upper surface of the glass molded product having a substantially plate-like shape is released from the upper die, and the lower die 16 on which the substantially plate-like glass in a high-temperature state immediately after pressing is placed is moved from the stop position P3. Then, it moves to the stop position P9 where the take-out process (takeout) is performed while repeating the pause at each stop position. Then, in the process in which the lower mold 16 moves from the stop position P3 to the stop position P9, the entire substantially plate-like glass in a high temperature state immediately after pressing is soaked and cooled (soaking / cooling step). In this soaking / cooling step, the state in which the upper surface cooling rate adjusting member 26 is provided so as to cover the upper surface of the substantially plate-like glass as described above is maintained at least in a part of the entire period of the step. Is done.

  Subsequently, at the stop position P9, an extraction process (takeout) for taking out the substantially plate-like glass from the lower mold 16 is performed. This take-out can be performed by adsorbing and holding the upper surface of the substantially plate-like glass with an adsorbing means. The taken-out substantially plate-like glass is quenched in the atmosphere, and then placed in an annealing furnace and annealed for strain removal. And substantially plate-like glass can be obtained by passing through such a series of processes.

  In addition, the surface temperature of the press surface of the lower mold | type 16 stopped at the stop position P9 after finishing the taking-out process has fallen to the temperature unsuitable for a press process. For this reason, the lower mold 16 is heated so that the temperature of the press surface of the lower mold 16 becomes a temperature suitable for the pressing process by using a heater until the lower mold 16 moves to the stop position P12. (Lower mold preheating process). Thereafter, the lower die 16 moves from the stop position P12 to the next stop position P1, and the next press molding is performed.

-Manufacturing method of substrate for information recording medium-
Next, a case where an information recording medium substrate (hereinafter sometimes simply referred to as “substrate”) is manufactured using the substantially plate glass obtained by the substantially plate glass manufacturing method of the present embodiment will be described. . About the substantially plate-like glass produced by the method for producing the substantially plate-like glass of the present embodiment, an information recording medium substrate is produced through at least a grinding / polishing step of grinding / polishing the main surface of the substantially plate-like glass. To do. Moreover, when the glass which comprises substantially plate-shaped glass has a glass composition which can be crystallized by heat processing, the crystallization process to crystallize by heating substantially plate-shaped glass other than the said process can also be combined. . As typical examples of manufacturing the information recording medium substrate, for example, (1) a first lapping step, (2) a cutting step (coring, forming), (3) an end surface grinding step, (4) a second The lapping step, (5) end surface polishing step, (6) main surface polishing step, (7) chemical strengthening step and cooling step, and (8) precision cleaning step can be performed in this order. Hereinafter, these eight steps will be described more specifically. The disk-shaped glass having a diameter sufficiently larger than the diameter of the substrate is press-molded, the concentric disk-shaped glass is taken out from the disk-shaped glass by scribing, and the taken-out disk-shaped glass is taken from the above (1) to (8 ) Can be formed into a substrate.

(1) 1st lapping process In a 1st lapping process, a disk-shaped glass base plate is obtained by lapping the both main surfaces of substantially plate-shaped glass. This lapping process can be performed using alumina free abrasive grains with a double-sided lapping apparatus using a planetary gear mechanism. Specifically, the lapping platen is pressed on both sides of the glass base plate from above and below, and a grinding liquid containing free abrasive grains is supplied onto the main surface of the glass base plate, and these are moved relatively to perform lapping processing. It can be carried out. By this lapping process, a glass base plate having a flat main surface is obtained.

(2) Cutting process (coring, forming)
Next, the glass base plate is cut using a diamond cutter, and a disk-shaped glass substrate is cut out from the glass base plate. Next, using a cylindrical diamond drill, a circular hole is formed in the center of the glass substrate to obtain a donut-shaped glass substrate (coring).

(3) End surface grinding process And an inner peripheral end surface and an outer peripheral end surface are ground with a diamond grindstone, and a predetermined chamfering process is performed (forming).

(4) Second Lapping Step Next, a second lapping process is performed on both main surfaces of the obtained glass substrate in the same manner as in the first lapping step. By performing this second lapping step, it is possible to remove in advance the fine unevenness formed on the main surface in the cutting step and end surface polishing step, which are the previous steps, and shorten the subsequent polishing step on the main surface. Can be completed in time.

(5) End surface polishing step Next, the end surface of the glass substrate is mirror-polished by a brush polishing method. At this time, as the abrasive grains, a slurry (free abrasive grains) containing cerium oxide abrasive grains can be used. By this end surface polishing step, generation of particles and the like from the end surface of the glass substrate can be prevented.

(6) Main surface polishing step As the first half step of the main surface polishing step, a first polishing step is first performed. This first polishing process is mainly intended to remove scratches and distortions remaining on the main surface in the lapping process described above. In the first polishing step, the main surface is polished using a hard resin polisher by a double-side polishing apparatus having a planetary gear mechanism. For example, cerium oxide abrasive grains can be used as the polishing liquid. And the glass substrate which finished this 1st grinding | polishing process is immersed in each washing tank of a neutral detergent, a pure water, and IPA (isopropyl alcohol) sequentially, and is wash | cleaned.

  Next, a second polishing step is performed as the latter half of the main surface polishing step. The purpose of this second polishing step is to finish the main surface into a mirror surface. In the second polishing step, the main surface can be mirror-polished using a soft foam resin polisher by a double-side polishing apparatus having a planetary gear mechanism. As the polishing liquid, cerium oxide abrasive grains finer than the cerium oxide abrasive grains used in the first polishing step can be used. The glass substrate that has finished the second polishing step is sequentially immersed in each cleaning bath of neutral detergent, pure water, and IPA (isopropyl alcohol) to be cleaned. An ultrasonic wave is applied to each cleaning tank.

(7) Chemical strengthening step and cooling step When the substantially plate-like glass used for the production of the substrate for information recording medium is made of glass containing an alkali metal such as lithium or sodium, the glass after the lapping step and the polishing step are finished. The substrate is preferably chemically strengthened. By performing the chemical strengthening step, a high compressive stress can be generated in the surface layer portion of the information recording medium substrate. For this reason, the impact resistance of the surface of the information recording medium substrate can be improved. Such chemical strengthening treatment is very suitable for producing a magnetic recording medium in which a head for recording / reproducing information may mechanically come into contact with the surface of the information recording medium.

  The chemical strengthening is performed by preparing a chemical strengthening solution in which potassium nitrate and sodium nitrate are mixed, heating the chemical strengthening solution, preheating the cleaned glass substrate, and immersing it in the chemical strengthening solution. Thus, by immersing in the chemical strengthening solution, the lithium ions and sodium ions in the surface layer of the glass substrate are replaced with sodium ions and potassium ions in the chemical strengthening solution, respectively, and the glass substrate is strengthened.

  Then, the glass substrate which finished the chemical strengthening process is immersed in a water bath, cooled, and maintained for a while. Then, the cooled glass substrate is cleaned by immersing it in heated concentrated sulfuric acid. Further, the glass substrate after the sulfuric acid cleaning is cleaned by immersing in a cleaning bath of pure water and IPA (isopropyl alcohol) sequentially. In addition, an ultrasonic wave is applied to each washing tank.

(8) Precision cleaning step Next, it is preferable to carry out a precision cleaning step in order to remove abrasive residues and foreign iron-based contaminants, and to make the surface of the glass substrate smoother and cleaner. Such a precision cleaning process is very suitable for producing a magnetic recording medium in which a head for recording / reproducing information may mechanically contact the surface of the information recording medium. This is because the occurrence of head crashes and thermal asperities can be suppressed by carrying out precision cleaning. In addition, as a precision washing | cleaning process, you may make it perform a water rinse washing | cleaning and IPA washing | cleaning process after washing | cleaning by alkaline aqueous solution.

  The surface roughness of the information recording medium produced through these series of steps can be on the order of sub-nanometers with Ra. The surface roughness can be appropriately adjusted by selecting main surface polishing conditions and cleaning conditions. The information recording medium substrate obtained through the above-described eight steps can be used for production of an information recording medium employing various known recording methods such as known magnetic recording, optical recording, and magneto-optical recording. However, it is particularly suitable for use in producing a magnetic recording medium. Further, in the case of an information recording medium substrate that is not required to have cleanness, smoothness, and impact resistance on the surface of the information recording medium substrate as much as the magnetic recording medium substrate, one of the above eight steps is performed as necessary. The steps may not be performed, and each process may be simplified or performed under rougher conditions.

-Manufacturing method of information recording medium-
The information recording medium can be manufactured by performing at least an information recording layer forming step of forming an information recording layer on at least one surface of the information recording medium substrate thus obtained. When a magnetic recording medium is manufactured, a magnetic recording layer is provided as an information recording layer. The magnetic recording medium may be either a horizontal magnetic recording system or a perpendicular magnetic recording system, but is preferably a perpendicular magnetic recording system. When a perpendicular magnetic recording type magnetic recording medium is manufactured, for example, an adhesion layer made of Cr alloy, a soft magnetic layer made of FeCoCrB alloy, an underlayer made of Ru, and CoCrPt—TiO _{2 on} both surfaces of an information recording medium substrate. A perpendicular magnetic recording layer made of an alloy, a protective layer made of hydrogenated carbon, and a lubricating layer made of perfluoropolyether can be sequentially formed in this order. The adhesion layer, the soft magnetic layer, the underlayer, and the perpendicular magnetic recording layer can be formed by a sputtering method, and the protective layer can be formed by a sputtering method or a CVD method (Chemical Vapor Deposition method). The lubricating layer can be formed by a dip coating method. Further, in-line type or single-wafer type sputtering apparatus capable of continuous film formation of each layer can be used for film formation from the adhesion layer to the protective layer, and immersion coating apparatus can be used for film formation of the lubricating layer. .

-Optical component manufacturing method-
Next, the case where an optical component is manufactured using the substantially plate glass obtained by the substantially plate glass manufacturing method of this embodiment is demonstrated. About the substantially plate glass produced by the manufacturing method of the substantially plate glass of this embodiment, a desired optical component is produced through at least a grinding / polishing step of grinding / polishing the main surface of the substantially plate glass. be able to. Examples of such optical components include convex meniscus lenses, plano-convex lenses, biconvex lenses, concave meniscus lenses, plano-concave lenses, biconcave lenses, microlenses, various lenses such as lens arrays, prisms, and the like. Further, the surface of these optical components may be coated with an antireflection film or the like as necessary. The optical component thus obtained is suitable as an optical component constituting a projection optical system such as a high-definition imaging optical system, for example, a digital still camera, a digital video camera, a surveillance camera, an in-vehicle camera, or a projector.

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

Example 1
After the molten glass obtained by melting the aluminosilicate glass is supplied onto the pressing surface of the lower die 16, it is pressed by the upper die and the lower die 16 to obtain a substantially plate-like glass (thickness = 1.2 mm, diameter d = 66 mm). 1000 were produced continuously.

  In addition, the glass shaping | molding apparatus used at the time of preparation of this substantially plate glass used the apparatus comprised so that substantially plate glass could be manufactured with a process as shown in Table 1. Specifically, as shown in FIGS. 1 and 2, the main part of this apparatus is arranged on a base portion 10 and includes a rotary table 12 having twelve lower molds 16, and a stop position P <b> 1. A glass supply means for supplying molten glass to the lower mold 16, an upper mold disposed immediately above the press surface of the lower mold 16 at the stop position P2, and a substantially plate shape on the press surface of the lower mold 16 at the stop position P8. Attaching means for taking out the glass, a heater for preheating the lower mold 16 while the lower mold 16 moves from the stop position P9 to P12, and a main shaft 14 corresponding to the 12 lower molds 16, And a support portion 18 having an upper surface cooling rate adjusting member 26 at the tip. The upper surface cooling rate adjusting member 26 can be heated to a desired temperature by a heater.

The execution order (manufacturing process) of each step when producing substantially plate-like glass in Example 1 was as shown in Table 1. The main production conditions other than those shown in Table 1 were as follows.
Glass transition temperature Tg: 485 ° C
-Average linear expansion coefficient of glass: 95 × 10 ⁻⁷ / K (100 to 300 ° C.), 98 × 10 ⁻⁷ / K (300 to Tg ° C.), 37 × 10 ⁻⁶ / K (Tg to 530 ° C.)
-Temperature of the press surface when supplying molten glass onto the press surface of the lower die 16: 500 ° C
・ Temperature of upper die press surface during pressing: 450 ℃
-Viscosity of molten glass put on lower mold 16: 40 Pa · s
・ Pressing time (time for applying pressure to glass): 1 second ・ Material constituting the pressing surface of the upper die 16 and the lower die 16: cast iron (no coating treatment)
-Material constituting the upper surface cooling rate adjusting member 26: stainless steel-Temperature of the upper surface cooling rate adjusting member 26 when the upper surface cooling rate adjusting member 26 is arranged in contact with the upper surface of the substantially plate-like glass: 500 ° C
The temperature of the substantially plate glass when taking out the substantially plate glass from the lower mold 16: 520 ° C.
・ Leaving environment of plate-shaped glass after take-out: normal temperature air environment

(Comparative Example 1)
In the first embodiment, the upper surface cooling rate adjusting member 26 is disposed on the upper surface of the substantially plate-like glass at the stop position P3 instead of the upper surface cooling rate adjusting member 26 being always supported by being attached to the tip of the support portion 18. At the stop position P8, the upper surface cooling rate adjusting member 26 alone was separated from the upper surface of the substantially plate glass. That is, while the lower mold | type 16 moved to the stop positions P3-P8, the upper surface cooling rate adjustment member 26 arrange | positioned at the upper surface of substantially plate-shaped glass was made into the state which is not supported by another member. Except this, a substantially plate-like glass was produced in the same manner as in Example 1.

(Comparative Example 2)
In Example 1, the upper surface cooling rate adjusting member 26 was not disposed on the upper surface of the substantially plate glass while the lower mold 16 passed the stop positions P3 to P8. That is, while the lower mold 16 moves between the stop positions P3 to P8, the upper surface of the substantially plate-like glass is exposed to air at normal temperature. Except this, a substantially plate-like glass was produced in the same manner as in Example 1.

(Comparative Example 3)
The substantially plate-like glass obtained in Comparative Example 2 was subjected to a warp correction press by being pressed from both sides with a flat plate-like stainless steel member in a state where it was heat-treated again to about 540 ° C. Except this, a substantially plate-like glass was produced in the same manner as in Comparative Example 2.

<Evaluation>
In the evaluation, the flatness of 10 samples obtained in each example and comparative example was measured, and the average value was obtained. The flatness was obtained by measuring the displacement at a 1 mm pitch with a laser focus displacement meter while moving the sample placed on the XY stage. Then, the difference between the maximum value and the minimum value of the displacement obtained after correcting the inclination of the measured value was obtained for each sample, and the average value of these values was defined as the flatness. The results are shown in Table 2 below.

DESCRIPTION OF SYMBOLS 1 Press molding apparatus 2 Floor surface 10 Base part 12 Rotary table 14 Spindle 16 Lower mold 18 Support part 20 Support part main body 22 Movable arm support part 24 Movable arm 26 Upper surface cooling rate adjustment member

Claims (10)

By pressing the molten glass supplied on the lower mold press surface with the lower mold press surface and the upper mold press surface arranged opposite to the lower mold press surface, the substantially flat plate shape is obtained. Molding process to mold;
Including at least a soaking / cooling step of cooling and soaking the substantially flat plate-like glass after separating the upper mold from the upper surface of the glass formed into the substantially flat plate shape,
The upper surface cooling rate adjusting member is in contact with or close to the upper surface of the substantially plate-like glass located on the lower die press surface in at least a part of the entire process in which the soaking / cooling step is performed. A method for producing a substantially plate-like glass, wherein the upper surface cooling rate adjusting member is supported by a support portion that is directly or indirectly fixed to a floor surface. In the manufacturing method of the substantially plate-shaped glass of Claim 1,
A method for producing a substantially plate-like glass, wherein the temperature of the upper surface cooling rate adjusting member is controlled by at least one temperature control means selected from a heating means and a cooling means. In the manufacturing method of the substantially plate-shaped glass of Claim 1 or 2,
The method of producing substantially plate-like glass, wherein the curvature of the surface of the upper surface cooling rate adjusting member contacting the upper surface of the substantially plate-like glass and the curvature of the upper surface of the substantially plate-like glass are the same. . In the manufacturing method of the substantially plate-shaped glass as described in any one of Claims 1-3,
The glass forming step and the soaking / cooling step are performed after the glass supply step of cutting the molten glass continuously flowing out from the nozzle into predetermined volumes and supplying the molten glass onto the press surface of the lower die. In order,
Then, the extraction process which takes out the said substantially plate-shaped glass on the press surface of the said lower mold from the said lower mold is implemented, The manufacturing method of the substantially plate-shaped glass characterized by the above-mentioned. In the manufacturing method of the substantially plate-shaped glass of Claim 4,
The lower mold moves while alternately repeating movement and stop in the circulation direction, and performs the glass supply step at any one stop position,
Based on the stop position where the glass supply step is performed as a reference, the molding step is performed at the stop position located downstream in the circulation direction
The soaking / cooling step is performed from the stop position at which the forming step is performed to the stop position at which the take-out step is performed through one or more stop positions located on the downstream side in the circulation direction. A method for producing a substantially plate-like glass. One upper mold and a plurality of lower molds having a press surface for press-molding a predetermined volume of molten glass;
A main shaft serving as a rotation center is provided, and the plurality of lower molds are arranged on the peripheral edge at equal intervals, and the rotation and stop in one direction are repeated for each rotation angle obtained by dividing 360 degrees by the number of the lower molds. A circular rotary table,
Glass supply for supplying molten glass continuously flowing out from a nozzle connected to a molten glass supply source onto a press surface of a lower die that is cut at a predetermined capacity and stopped at one stop position of the rotary table. Means,
With respect to any one of the stop positions, the lower mold is disposed so as to be opposed to the press surface of the lower mold that stops at the stop position downstream in the rotation direction of the rotary table and is movable in the vertical direction. An upper die provided with a press surface for pressing the molten glass located on the press surface to form a substantially plate shape;
The substantially plate-like shape that is located on the lower press surface of the stop position that is located on the downstream side in the rotation direction of the rotary table, with one or more stop positions sandwiched from the stop position where the upper mold is disposed Taking out the glass of the above from the lower mold,
The main shaft located on the upper surface side of the turntable extends from the main shaft to the outer peripheral side of the turntable, and at the tip thereof, between the vicinity of the lower die press surface and the upper die side between the lower die press surface. A support portion provided with an upper surface cooling rate adjustment member provided movably,
Comprising at least
In a section in which the lower mold moves from after passing through the stop position where the upper mold is arranged until it reaches the stop position where the take-out means is arranged along the downstream side in the rotation direction of the rotary table. ,
The upper surface cooling rate adjusting member is disposed so as to be in contact with or close to the upper surface of the substantially plate-like glass located on the lower die press surface in at least a part of the interval. apparatus. The press molding apparatus according to claim 6, further comprising at least one temperature control means selected from a heating means and a cooling means for controlling a temperature of the upper surface cooling rate adjusting member.   The substrate for an information recording medium is subjected to at least a grinding / polishing step of grinding / polishing the main surface of the substantially plate-like glass produced by the method for producing a substantially plate-like glass according to claim 1. A method of manufacturing a substrate for an information recording medium, characterized by being manufactured.   An information recording medium is manufactured through at least an information recording layer forming step of forming an information recording layer on the main surface of the information recording medium substrate manufactured by the information recording medium substrate manufacturing method according to claim 8. An information recording medium manufacturing method.   An optical component is manufactured through at least a grinding / polishing step of grinding / polishing the main surface of the substantially plate-like glass produced by the method for producing a substantially plate-like glass according to claim 1. A method of manufacturing an optical component characterized by the above.

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