JP4174270B2 - Glass molding product press molding method / apparatus, glass substrate manufacturing method / apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a glass molding product press molding method and a press molding apparatus. The present invention also relates to a method and an apparatus for manufacturing an ultra-smooth glass substrate mainly for information recording media.
[0002]
[Prior art]
High-density recording performance in information recording media such as magnetic disks greatly depends on the substrate material. Glass is attracting attention as a substrate material suitable for information recording media. This is because glass has high strength and good heat resistance, and has high surface hardness and high-precision precision polishing using cerium oxide or the like, so that excellent smoothness can be obtained. These characteristics contribute to downsizing the external storage device, improving the coercive force, and lowering the flying height (lowering flying height) of the magnetic head.
[0003]
A method for press-molding a glass substrate for an information recording medium is a method in which a glass material is subjected to press-molding with heating using a molding die to transfer an ultra-smooth surface of the die. This press molding method has advantages such as stable quality, no post-processing, and high productivity.
[0004]
In the molding method in which the above-described press molding is performed on such an information recording medium, molding is performed as follows.
[0005]
FIG. 6 shows a schematic configuration of a conventional glass substrate press molding apparatus for an information recording medium. In FIG. 6, 1 is an upper mold, 2 is a lower mold, 3 is an upper stage (press head) that holds the upper mold 1, and 4 is a lower stage (press head) that holds the lower mold 2. 5, 6 are heaters built in the stages 3 and 4, 7 is a plunger, and 8 is a glass material.
[0006]
The glass material 8 is placed on the lower mold 2, the plunger 7 is operated to move the upper mold 1 downward, and the glass material 8 is sandwiched between the upper mold 1 and the lower mold 2 from above and below. When the heaters 5 and 6 are heated, the glass material 8 is heated to near the softening point temperature through the stages 3 and 4 and the upper mold 1 and the lower mold 2. Next, the glass material 8 is pressed to a required thickness by pressing the plunger 7. Then, after cooling in the mold-clamped state, the mold is opened and the molded glass substrate is taken out.
[0007]
The glass substrate in the information recording medium may be a glass substrate with a shaft in which a central shaft portion is integrated in order to ensure high rigidity against high-speed rotation. The mold used when press-molding this glass substrate with a shaft has a recess at the center. The recess is for forming a shaft portion in the glass substrate with a shaft.
[0008]
FIGS. 7A and 7B show a mold configuration for a glass substrate with a shaft. Protective films 1 a and 2 a are formed on the press surfaces of the upper mold 1 and the lower mold 2. A recess 2b is formed at the center of the lower mold 2 corresponding to the shaft portion of the glass substrate. A glass substrate 9 having a shaft portion 9a corresponding to the recess 2b is obtained by press-molding the glass material 8 in the same manner as described above.
[0009]
The protective films 1a and 2a formed on the press surface of the mold base material through an underlayer include tungsten (W), platinum (Pt), palladium (Pd), rhodium (Rh), and ruthenium (Ru). Metal thin films having high hardness such as iridium (Ir), osmium (Os), rhenium (Re), and tantalum (Ta) are used. The protective film prevents breakage of the press surface due to repetitive molding, and prevents reaction with the glass material to be molded to enhance mold release properties.
[0010]
[Problems to be solved by the invention]
However, there is a problem that the protective film on the die press surface deteriorates while repeatedly performing press molding using the same die. Deterioration of the protective film causes an increase in the surface roughness of the press surface, that is, surface roughness, and as a result, the high surface smoothness and flatness required for the press-formed product (glass substrate) are hindered. That is, it affects the durability and life of the mold.
[0011]
The present invention was devised in view of such circumstances, and by taking measures through investigating the cause of protective film deterioration in repeated press molding with heating, even in repeated press molding over a long period of time. The purpose is to suppress the deterioration of the protective film, improve the durability and life of the mold, and improve the productivity of the glass molded product.
[0012]
[Means for Solving the Problems]
The inventors of the present invention have intensively studied to investigate the cause of the protective film deterioration. As a result, the following knowledge was obtained. That is, when the glass material is forcedly deformed by a pair of molds under severe high temperature and high pressure, the water contained in the glass is ejected as an active corrosive gas. This active corrosive gas (H ₂ O) comes into contact with the protective film (metal thin film) on the die press surface and causes a chemical reaction to corrode the protective film. As a result, the surface roughness of the die press surface is deteriorated, which adversely affects the die life.
[0013]
Therefore, based on this knowledge, the present invention aims to solve the above problems by taking the following measures.
[0014]
In order to produce the target glass molded product (target molded product) using the glass material as the starting material, instead of pressing the target molded product at once from the glass material under high temperature and high pressure of the conventional method, The present invention adopts a new two-stage system. The two-stage holding system includes a first process and a second process. In the first step, a press material (intermediate member) approximating the shape of the target glass molded product is produced from the glass material. In the second step, a target glass molded product is produced by subjecting the press material having the target approximate shape to press forming with heating. The first step mainly forms the overall shape, and the second step mainly transfers the highly smooth mold press surface precisely to the press-formed product. Function separation is performed in the first step and the second step. Note that the press material itself in the first step is not necessarily produced by press molding.
[0015]
In the process of press molding a glass material into a predetermined shape and a predetermined size with a pair of molds at high temperature and high pressure, active corrosive gas (H ₂ It is presumed that the condition that O) is ejected is that the deformation rate of the glass material shrinkage exceeds a certain reference value (critical value) in the history studied by the present inventors. Although temperature and pressure may be factors, it is thought that it is a deformation rate directly.
[0016]
Here, it is conceivable to take measures to prevent active corrosive gas from being ejected by limiting the deformation rate of the glass material to be smaller than the critical value when obtaining the target molded product. The present invention adopts the above-mentioned two-stage system as a technique for obtaining a target molded product having a predetermined shape and a predetermined dimension by press molding after limiting the deformation rate to be smaller than a critical value.
[0017]
If the glass material to the target molded product are press-formed at once, the deformation rate exceeds the critical value. Therefore, a press material (intermediate member) that approximates the shape of the target molded product is prepared in advance. The press material having the target approximate shape has its shape and dimensions set under the following conditions. The condition is that the deformation rate when press-molding from this press material to the target molded product is below a critical value. The press material as the intermediate member does not exceed the critical value even if it is press-molded to the target molded product. Therefore, the active corrosive gas (H ₂ O) does not erupt.
[0018]
For such a requirement, the press material as the intermediate member is made from the glass material in the first step. That is, a press material that approximates the shape of the target molded product is produced from a glass material. What is required of the press material as the intermediate member is the critical value of the deformation rate, and the surface smoothness is not necessarily required for the press material.
[0019]
As described above, even if press forming with heating is performed on a press material with a target approximate shape and the target molded product is press formed, the deformation rate does not exceed the critical value, and corrosive gas is ejected from the press material. Does not occur.
[0020]
However, when press molding is adopted in the first step, the following concept is the basis. When press-molding a glass material to produce a press material with a target approximate shape, an active corrosive gas (H ₂ O) may erupt. This corrosive gas deteriorates the mold protective film. Here, according to the present invention, the ejection of the corrosive gas in the first step and the accompanying protective film deterioration are allowed to be unavoidable. What is ultimately required is a glass molded article with a high level of surface smoothness, but this glass molded article is obtained directly by press molding from a press material. It is not obtained by press molding. Therefore, the mold used in the first process and the mold used in the second process may be separated. Even if the corrosive gas ejected when press-molding the press material from the glass material in the first step deteriorates the die press surface, when the glass molded product is press-molded from the press material in the second step, By using another mold that is not present, press molding with high surface smoothness can be performed. Further, in the second step, since the deformation rate does not exceed the critical value, no corrosive gas is ejected from the press material, and therefore the die press surface used in the second step does not deteriorate. Even if the mold in the first step may be deteriorated, the mold in the second step is free from deterioration. The press material obtained by performing press molding using the mold deteriorated in the first step may have inferior surface smoothness. However, this press material is an intermediate member, which does not necessarily require a high degree of smoothness. Even if it becomes a press material whose surface smoothness is somewhat inferior, it can be made to shift to the state excellent in surface smoothness highly through the 2nd process. This is because, in the second step, no corrosive gas is ejected, the press surface deterioration is avoided, and high smoothness of the press surface can be maintained. A glass molded product obtained by transferring the high smoothness of the mold has a high level of surface smoothness. This is maintained in repeated press molding.
[0021]
As described above, in the repetition of press molding involving the first step and the second step, at least the second step prevents deterioration of the protective film of the die and improves the durability and life of the die. Thus, a high-quality glass molded product can be produced with high productivity over a long period of time.
[0022]
The above deformation critical value will be specifically considered. The thickness of the target molded product is t ₀ The thickness t of the press material as the intermediate member is [t ≦ 1.3 × t ₀ And preferably [t ≦ 1.2 × t ₀ More preferably, [t ≦ 1.1 × t ₀ ] Is good. That is, for the press material thickness t, the target molded product thickness t ₀ The thickness is limited to a thickness not exceeding 1.3 times. 1.3 times slightly corrosive gas (H ₂ This is because the ejection amount O) is observed, but the ejection amount is below an allowable level in the degree of deterioration of the die press surface. If you want to extend the service life of the mold in the second step, the target molded product thickness t ₀ It is better to keep it below 1.2 times. Corrosive gas (H ₂ The ejection amount of O) decreases as the deformation rate decreases. In order to substantially eliminate corrosive gas ejection, the target molded product thickness t ₀ And 1.1 times or less. In this case, the mold life is sufficiently long. The lower limit of the press material thickness t is the target molded product thickness t. ₀ The value exceeds. The press material thickness t is the target molded product thickness t. ₀ A value greater than t ₀ A value as close as possible is preferable.
[0023]
About the press molding apparatus used when implementing said press molding method, a 1st pair of metal mold | die which press-molds the press raw material which approximates the shape of the target glass molded product by heat-pressing glass material. And a second pair of molds for press-molding a target glass molded product by heating and pressurizing the press material having the target approximate shape. Alternatively, a combination of a second pair of molds and a direct molding mold apparatus or a glass material cutting apparatus may be used.
[0024]
Considering a pair of molds used in the first step and a pair of molds used in the second step in the above glass molding product press molding apparatus, the mold in the first step is caused by corrosive gas. Since there is a high possibility that the deterioration will proceed, it is considered that it should not be diverted to the second step. However, in a glass molded product obtained by press molding, if the entire outer peripheral surface is not required to have a high level of smoothness evenly, it is allowed to be diverted to the second step for the mold on the side that is not required. Is done. For a mold on the side that requires high smoothness, a mold different from that in the first process is used in the second process.
[0025]
When a pair of molds is represented by an upper mold and a lower mold, one of the pair of lower mold and upper mold is configured as a dual mold. In mold opening, the press material is generally placed on a lower mold. Therefore, the upper mold side is a mold for high smoothness, the upper mold is changed in the first step and the second step, and the lower mold is the first step and the second step. It is to be shared with the process. If it does in this way, it will become possible to transfer to a 2nd process from a 1st process, with a press raw material mounted on a lower metallic mold, and it will work on productivity improvement.
[0026]
There are the following two types of configurations in which the above-described dual-purpose mold is shared in the first step and the second step. One is to configure the dual-purpose mold in a position variable manner. The other is that the dual-purpose mold is fixed in position, and each of the non-multiple molds paired with the dual-purpose mold is configured to be variable in position. When the lower mold is used as a combined mold, the former reciprocates the lower mold between the first process and the second process, and the latter reciprocates the upper mold. The reciprocating movement may be a linear movement or a turning movement. Instead of reciprocal movement, cyclic rotational movement may be used.
[0027]
In the above, the second step is preferably performed under reduced pressure in the atmosphere. When the surface of the press material of the target approximate shape obtained in the first step is smoothed to some extent, when the mold is clamped again in the second step with respect to this press material, the die press surface is pressed. When contacting the surface of the material, gas in the atmosphere is enclosed between the two, and when press molding is performed in that state, the enclosed gas molecules are pressed into the surface layer portion of the glass molded product, generating bubbles. End up. This impairs the surface smoothness of the press-formed product. On the other hand, if the pressure of the press molding is reduced, the number of gas molecules in the atmosphere decreases, and gas sealing is performed between the mold press surface and the press material surface during the new clamping. Is substantially prevented. Therefore, the deterioration of the surface smoothness due to the generation of bubbles is prevented, and a glass molded product having a highly excellent surface smoothness can be produced.
[0028]
When the above-mentioned method for press-molding a glass molded product is applied to press-molding a glass substrate for an information recording medium, the effect can be fully exhibited. In this case, the target glass molded product is a disk-shaped glass substrate. A glass substrate with a shaft may be used.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a glass molding product press molding method / apparatus according to the present invention will be described in detail with reference to the drawings. Here, a case of application to a glass substrate with a shaft for an information recording medium will be described.
[0030]
FIG. 1 is a front view showing the main part of the configuration of a glass substrate manufacturing apparatus (press molding apparatus) for an information recording medium in an embodiment of the present invention. FIG. 2 is an explanatory diagram of a first step in the embodiment, and FIG. 3 is an explanatory diagram of a second step in the embodiment. Here, as a specific example of the target glass molded article, a glass substrate with a shaft having a diameter of 64 mm and a thickness of 0.64 mm is assumed.
[0031]
In FIG. 1, 10 is a vacuum chamber, 11 is a lower mold, 20 is a first upper mold unit, and 30 is a second upper mold unit. The lower mold 11 is configured to be used for both the first process and the second process. The lower mold 11 is placed and fixed on the upper surface of a stage (press head) 13 with a built-in heater 12. The stage 13 is configured to be reciprocally movable by a reciprocating mold moving mechanism 14. The mold moving mechanism 14 is configured to reciprocate the stage 13 and the lower mold 11 between the first press position P1 in the first step and the second press position P2 in the second step. . A first upper mold unit 20 is arranged corresponding to the lower mold 11 at the first press position P1, and a second upper mold corresponding to the lower mold 11 at the second press position P2. A mold unit 30 is arranged.
[0032]
The first upper mold unit 20 includes a first upper mold 21, a stage (press head) 23 incorporating a heater 22, and a first pressure plunger 24. The second upper mold unit 30 includes a second upper mold 31, a stage (press head) 33 including a heater 32, and a second pressure plunger 34. The upper molds 21 and 31 are respectively held on the lower surfaces of the stages 23 and 33, and the stages 23 and 33 are attached to the lower surfaces of the pressure plungers 24 and 34, respectively. A recess 11a corresponding to the shaft portion of the glass substrate with shaft is formed in the center portion of the lower mold 11 because the glass substrate with shaft is a target molded product. In the case of a glass substrate without a shaft, the recess is not necessary. Each of the lower mold 11, the first upper mold 21, and the second upper mold 31 has a protective film formed on the press surface of the mold base material.
[0033]
First, as a preliminary process, a glass material 41 is placed on the lower mold 11 in a state where the lower mold 11 is positioned at the first press position P1 by the mold moving mechanism 14 (see FIG. 1). Next, the vacuum chamber 10 is evacuated to reduce the atmosphere, and a vacuum state of 1000 Pascals or less is maintained.
[0034]
Subsequently, the first step is performed. As shown in FIG. 2, the pressurizing plunger 24 in the first upper mold unit 20 is extended with respect to the lower mold 11 positioned at the first press position P1 and on which the glass material 41 is placed. The glass material 41 is sandwiched between the upper mold 21 and the lower mold 11 from above and below. Then, the stages 13 and 23 are heated by the heaters 12 and 22, and the temperature of the lower mold 11 and the first upper mold 21 is set to the glass softening point temperature (10 ^7.65 poise) temperature control. When the temperature is raised to near the glass softening point temperature, the pressure plunger 24 then pressurizes in the direction indicated by the arrow A, and the glass material 41 is deformed to perform molding. The thickness control in this molding is as follows.
[0035]
Thickness (target molded product thickness) t of the glass substrate 43 (see FIG. 3), which is a target molded product to be obtained by press molding in the second step to be described later ₀ On the other hand, the thickness t of the press material 42 as an intermediate member to be obtained in the first step is 1.1 times or less. Here, as an example, the target molded product thickness t ₀ = 0.64 mm, and press material thickness t = 0.70 mm (the magnification in this case is about 1.094). That is, pressing is performed until the thickness of the press material 42 shown in FIG. 2 reaches a predetermined dimension of 0.70 mm. Thereafter, the press material 42 is cooled to the glass transition temperature or lower in the mold-clamped state. The molded glass in this state is the press material 42. The center part of the lower surface of the press material 42 is pushed into the recess 11a of the lower mold 11 and becomes a shaft part.
[0036]
Next, the transition process to a 2nd process is performed. That is, as shown in FIG. 3, the pressurizing plunger 24 is retracted in the direction of arrow B to perform mold opening, and the first upper mold 21 is detached. Further, the mold moving mechanism 14 is operated to move the lower mold 11 in the direction of arrow C, the lower mold 11 is stopped at the second press position P2, and the second upper mold unit 30 in the second upper mold unit 30 is moved. 2 is positioned at a position facing the upper mold 31.
[0037]
Then, the second step is performed. Even in the second step, the atmosphere decompression state (1000 Pascal or less) of the first step is maintained. As shown in FIG. 3, the pressurizing plunger 34 in the second upper mold unit 30 is extended with respect to the lower mold 11 positioned at the second press position P2 and placing the press material 42 thereon. The press material 42 is sandwiched between the upper mold 31 and the lower mold 11 from above and below. At this time, the ultra-smooth press surface of the second upper mold 31 comes into contact with the upper surface of the press material 42. However, since the atmosphere is under reduced pressure, gas molecules are not pressed into the surface layer portion of the press material 42 and become bubbles. According to experiments, the atmosphere during molding is atmospheric pressure (1.013 × 10 ^Five It was confirmed that if it was set to 1/100 or less of Pa), bubbles that would be a practical problem were not generated. Therefore, the atmosphere during molding is kept below 1000 Pascals.
[0038]
Then, the stages 13 and 33 are heated by the heaters 12 and 32, and the temperatures of the lower mold 11 and the second upper mold 31 become the glass softening point temperature (10 ^7.65 poise) temperature control. When the temperature is raised to near the glass softening point, pressurization is performed in the direction indicated by the arrow D by the pressurization plunger 34, and the press material 42 is deformed to perform molding. In this molding, the thickness dimension of the glass substrate 43 that is the target molded product is the target molded product thickness t. ₀ Press until 0.64 mm. Thereafter, the glass substrate 43 is cooled to a glass transition point temperature or lower while the mold is clamped. The molded glass in this state is the glass substrate 43. In this second step, since the thickness control of press molding is strictly performed, an active corrosive gas (H ₂ O) is not ejected, and the mold protective film is not deteriorated by the corrosive gas.
[0039]
Next, a return process to the first step is executed. That is, the pressure plunger 34 is retracted to perform mold opening, and the second upper mold 31 is separated upward. Further, the mold moving mechanism 14 is operated to move the lower mold 11 in the direction opposite to the arrow C, the lower mold 11 is stopped at the first press position P1, and the first upper mold unit 20 is moved. Is positioned at a position facing the first upper mold 21 (see FIG. 1).
[0040]
The glass substrate 43 with a shaft is a substrate for an information recording medium such as a magnetic disk. Since the upper surface without the shaft portion serves as an information recording surface, high surface smoothness and flatness are required. Therefore, the upper surface of the press material 42 must be a surface to be transferred in the second step. On the other hand, the lower surface where the shaft portion 43a of the glass substrate 43 is not an information recording surface. Therefore, surface smoothness and flatness are not required as much as the upper surface. Therefore, the lower surface of the press material 42 does not necessarily have to be a transfer surface in the second step. Therefore, the mold moving mechanism 14 is operated while the press material 42 is placed on the lower mold 11 corresponding to the shaft portion 43a side of the glass substrate 43, and the lower mold 11 is moved to the first step (first step). It is moved from the press position P1) to the second step (second press position P2). That is, the lower mold 11 is used in both the first process and the second process.
[0041]
Such combined use of the lower mold 11 brings about an improvement in productivity. The reason is as follows. If the lower mold of the first process and the lower mold of the second process are separated, the molded press material 42 is removed from the lower mold when the mold is opened at the end of the first process. In addition, it is necessary to set in another lower mold. In the set, the shaft portion must be fitted into the recess of the lower mold. This troublesome demolding and re-installation with shaft insertion reduces efficiency. If the lower mold is also used, there is no such trouble and efficiency is improved.
[0042]
In the above, since the thickness control at the time of press molding is not strict in the first step, an active corrosive gas (H from the glass material 41 during press molding with heating to the glass material 41 is performed. ₂ O) may be ejected, and when the corrosive gas is ejected, the mold protective film may be deteriorated by the corrosive gas. However, deterioration of the mold protective film in the first step is allowed, and the mold is replaced or regenerated every time the number of press molding repetitions reaches a predetermined number or depending on the degree of deterioration. That's fine.
[0043]
FIG. 4 is a graph showing the relationship between the deformation rate of glass and the amount of gas generated from the glass. The deformation rate γ on the horizontal axis indicates the thickness t of the press material 42 as the intermediate member and the thickness t of the glass substrate 43 as the target molded product. ₀ (Γ = t / t ₀ ). The gas amount Vi on the vertical axis is the result of measuring the amount of gas generated during press molding with a gas analyzer (obtained in terms of current value (mA)).
[0044]
FIG. 4 shows that the generated gas amount Vi has a linear characteristic with respect to the deformation rate γ, and decreases as the deformation rate γ decreases. In particular, in the region where the deformation rate γ is 1.1 or less, almost no gas is generated. Considering that the deformation rate in the conventional example corresponds to at least 2 or more, it can be seen that the molding method in the present embodiment can greatly reduce the amount of gas generated in the second step.
[0045]
When the deformation rate γ = 1.3, the gas amount Vi = 2.4 (mA), and if it is less than this, deterioration of the mold can be suppressed to some extent. When the deformation rate γ = 1.2, the gas amount Vi = 1.0 (mA), and if it is less than this, the deterioration of the mold can be surely suppressed. The deformation rate γ = 1.1 and the gas amount Vi = 0 (mA). Ideally, the deformation rate γ should be 1.1 or less.
[0046]
FIG. 5 is a graph showing the transition of mold deterioration in the present embodiment. The horizontal axis represents the number of moldings (number of shots). The vertical axis represents the surface roughness (Ra (center line average roughness): nm) in the mold. In the graph, those indicated by black dots and solid lines are the results in this embodiment. For comparison, the results in the conventional example are indicated by white circles and broken lines. In the case of the comparative example, the surface roughness Ra = 8 nm in 100 shots, which greatly exceeds the allowable limit. In the case of the embodiment of the present invention, although not shown, the surface roughness Ra = 1 nm was maintained with almost no change even after 1000 shots.
[0047]
From FIG. 5, it can be seen that in this embodiment, the surface roughness hardly changes, and the deterioration of the mold is extremely small as compared with the conventional example.
[0048]
As described above, in the present embodiment, the first step of forming the molding process substantially in the shape of a glass substrate, and the second step of precisely transferring the press surface of the mold to form a smooth substrate surface. In addition, the glass deformation rate in the second step is managed. As a result, the amount of gas generated can be remarkably reduced in the second step where it is required to maintain a precise mold surface, and corrosion of the mold can be greatly suppressed. As a result, the life of the mold can be extended.
[0049]
In addition, as described above, the molding apparatus of the present embodiment is configured to maintain the molding atmosphere under reduced pressure (for example, 1000 Pascal or less), and prevents generation of bubbles due to intrusion of gas molecules, so that high-quality glass is used. A substrate can be manufactured.
[0050]
In the molding apparatus of the present embodiment, the so-called reheat molding method similar to that of the second step is used as a method for producing the press material of the intermediate member in the first step. The manufacturing method is not limited and may be a so-called direct molding method. . above Even in this case, if the deformation rate γ from the press material of the intermediate member to the glass substrate is managed in the same manner as described above, the same effect as in the present embodiment can be obtained.
[0051]
In the above description, the lower mold 11, the first upper mold 21 and the second upper mold 31 are all made of a constituent material having excellent high-temperature mechanical strength and oxidation resistance. In particular, there are:
[0052]
(1) Cemented carbide with tungsten carbide (WC) as the main component
(2) Titanium nitride (TiN), titanium carbide (TiC), chromium carbide (Cr _Three C ₂ ), Alumina, Sapphire (Al ₂ O _Three ), Silicon carbide (SiC), boron nitride (BN), or aluminum nitride (AlN)
(3) Cermet (composite material of ceramics and sintered metal) mainly comprising any of the above (2)
(4) Stainless steel, nickel (Ni), nickel alloy, molybdenum (Mo), molybdenum alloy, cobalt (Co), cobalt alloy, chromium (Cr), chromium alloy, titanium (Ti), titanium alloy, tantalum (Ta), Tantalum alloy, tungsten (W), tungsten alloy
In the above, the protective film is a constituent material excellent in high-temperature mechanical strength and glass resistance, and specifically includes the following.
[0053]
(1) Platinum (Pt), palladium (Pd), iridium (Ir), rhodium (Rh), osmium (Os), ruthenium (Ru), rhenium (Re), tungsten (W), tantalum (Ta), titanium ( Ti), chromium (Cr), molybdenum (Mo), nickel (Ni), cobalt (Co)
(2) An alloy containing at least one kind of metal in (1) above
[0054]
【The invention's effect】
As described above, according to the present invention, the press molding process mainly includes the first step of forming the overall shape, and the first step of precisely transferring a highly smooth mold press surface to the press molded product. Since the function is separated into two steps and the thickness control in the second step, the active corrosive gas (H ₂ O) can be suppressed and corrosion of the mold can be surely prevented, and as a result, the life of the mold can be extended. That is, in the repetition of the press molding involving the first step and the second step, at least in the second step, the deterioration of the protective film of the die can be prevented, and the durability and life of the die can be improved. It is possible to produce a good-quality glass molded product with high productivity over a long period.
[0055]
Furthermore, by carrying out the second step under reduced pressure in the atmosphere, it is possible to prevent the enclosing of bubbles at the time of mold clamping again and to produce a glass molded product having a high surface smoothness.
[0056]
The present invention has a great effect when applied to the formation of a glass substrate for an information recording medium as a glass molded product.
[Brief description of the drawings]
FIG. 1 is a front view showing the main part of the configuration of a glass substrate manufacturing apparatus (press molding apparatus) for an information recording medium in an embodiment of the present invention.
FIG. 2 is an explanatory diagram of a first step in the embodiment of the present invention.
FIG. 3 is an explanatory diagram of a second step in the embodiment of the present invention.
FIG. 4 is a graph showing the relationship between the deformation rate of glass and the amount of gas generated from glass in an embodiment of the present invention.
FIG. 5 is a graph showing the transition of mold deterioration in the embodiment of the present invention.
FIG. 6 is a front view showing a schematic configuration of a conventional glass substrate press molding apparatus for an information recording medium.
FIG. 7 is a front view showing a mold configuration for a glass substrate with a shaft.
[Explanation of symbols]
10 Vacuum chamber
11 Lower mold
11a recess
12 Heater
13 stage (press head)
14 Mold moving mechanism
20 First upper mold unit
21 First upper mold
22 Heater
23 stage (press head)
24 First pressure plunger
30 Second upper mold unit
31 Second upper mold
32 Heater
33 stage (press head)
34 Second pressure plunger
41 Glass material
42 Press material
43 Glass substrate
43a Shaft
P1 First press position
P2 Second press position

Claims (9)

A first step of producing a press material that approximates the shape of a target glass molded product from a glass material;
A second step of producing the target glass molded product by performing press molding with heating on the press material of the target approximate shape,
In the first step, the glass material is subjected to press molding with heating to produce a press material having the target approximate shape, and the thickness of the press material having the target approximate shape is the target. The press material is produced under the condition of 1.1 times the thickness of the product ,
The second step is performed by changing at least one of the pair of dies used in the first step, and performing the press molding method of a glass molded product. The said 2nd process is a press molding method of the glass molded product of Claim 1 implemented under atmospheric pressure reduction. The glass molding product press molding method according to claim 1 or 2 , wherein the target glass molding product is a disk-shaped glass substrate. The manufacturing method of the glass substrate which manufactures the glass substrate for information recording media as said glass molded article using the press molding method in any one of Claim 1- Claim 3 . A first pair of molds for press-molding a press material that approximates the shape of a target glass molded product by heating and pressing the glass material;
A second pair of molds for press-molding a target glass molded product by heating and pressurizing the press material of the target approximate shape,
The first pair of molds press-molds the press material under a condition that the thickness of the press material having the target approximate shape is 1.1 times or less the thickness of the target glass molded product. A press-molding device for glass molded products. In said second pair of molds with the first pair of molds, according to claim 5 which constitutes one of the mold of the lower mold and the upper mold forming a pair of molds combined Press molding equipment for glass molded products. The glass molding product press molding apparatus according to claim 6 , wherein the dual-purpose mold is configured to be variable in position. The glass molding product press molding apparatus according to claim 6 , wherein the dual-purpose mold is fixed in position, and each of the non-shared molds paired with the dual-purpose mold is configured to be variable in position. An apparatus for manufacturing a glass substrate, comprising the press molding apparatus according to any one of claims 5 to 8, and manufacturing a glass substrate for an information recording medium as the glass molded product.

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