JP2006249536A - Metal material to be mirror polished - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal material to be mirror polished by which the adverse influence of the existence of nonmetallic inclusions can be reduced and a sufficiently flat surface can be obtained. <P>SOLUTION: The existence ratio of the nonmetallic inclusions in the metal material is defined to be ≤0.05%. By controlling the amount of existence of the nonmetallic inclusions to a low concentration, the adverse influence of the nonmetallic inclusions can be reduced and sufficient flatness can be obtained. The hardness of a matrix of the metal material is defined to be ≥100 Vickers hardness. The difference in hardness between the metallic inclusions and the matrix can be decreased and the influence of the hidden nonmetallic inclusions can be reduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention uses surface polishing when manufacturing a stamper for manufacturing a large number of optical disks such as CD (Compact Disk) and DVD (Digital Versatile Disk), reflectors in various electronic devices, and ultra-precision molds. The present invention relates to a metal material for mirror polishing on which a mirror surface is formed.

  An optical disc such as a CD or DVD is manufactured by transferring an information recording surface having pits formed on an optical disc stamper to a resin substrate. Since the length and height of the pit are extremely small, the surface of the stamper is required to have high flatness.

  Conventionally, a plating method has been known as a method of manufacturing a stamper having high flatness. After applying a resist to a flat glass substrate that has been polished and thoroughly cleaned, the resist film is brought into close contact with the glass substrate by baking, and the resist film is electroformed in a nickel (Ni) bath to grow a nickel film. The stamper was manufactured.

  Further, unlike a method using electroforming plating, a method (first method) for manufacturing a stamper by polishing a rolled nickel plate has been proposed (for example, see Patent Document 1). Patent Document 1 discloses a technique for manufacturing a stamper by using a rolled nickel plate as a material, lapping the surface, performing chemical mechanical polishing, and forming a resist film thereon.

In addition, a stamper manufacturing method (second method) in which plating is added to the first method has been proposed (see, for example, Patent Document 2). In Patent Document 2, the surface of a rolled nickel plate is subjected to metal plating (for example, NiP alloy), the metal plating layer is subjected to chemical mechanical polishing, and a resist film is formed thereon, thereby forming a nickel rolled plate. A technique for manufacturing a stamper in which the influence of existing rolling mills and the like is suppressed is disclosed.
JP 2002-355749 A International Publication No. 2004/107335 Pamphlet

  When producing rolled nickel plates, it is common to produce slabs by solidifying metallic nickel melted in an electric furnace or the like in the casting process, and then subjecting the produced slabs to forging and rolling to finish them into thin plates. It is. In the present invention, when a stamper is produced using a nickel rolled sheet produced in such a process, the presence ratio (abundance) of non-metallic inclusions has a great influence on the surface quality after polishing treatment. Found out. This non-metallic inclusion is mainly composed of an oxide generated at the stage of melting and refining of nickel, and is entangled inside a metal material (base material).

  Patent Documents 1 and 2 do not consider the existence of such non-metallic inclusions at all, and there is a problem that sufficient planarization of the surface cannot be realized. Further, in Patent Document 2, when a large amount of non-metallic inclusions are present in a nickel rolled plate, a metal plating layer is not uniformly formed, so-called plating defects called pinholes are generated. There is a problem that the bonding between the rolled plate and the metal plating layer becomes brittle and the metal plating layer is peeled off during the polishing process.

  In addition, in the polishing process of Patent Document 1, since a part of the material is removed, the balance of the residual stress distribution in the material is lost. As a result, there is a problem that a phenomenon in which the material warps like a horseback saddle occurs after the polishing process.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a metal material for mirror polishing that can reduce the adverse effects of the presence of non-metallic inclusions and sufficiently flatten the surface. And

  Another object of the present invention is to provide a metal material for mirror polishing that can make the residual stress after the polishing treatment uniform and prevent the occurrence of warpage.

  The metal material for mirror polishing according to claim 1 is manufactured by rolling, and the mirror polishing metal material formed by surface polishing has a non-metallic inclusion content of 0.05% in the material. It is characterized by the following.

  In the first invention, the ratio of non-metallic inclusions in the metal material is 0.05% or less. Therefore, by controlling the abundance of nonmetallic inclusions at a low concentration, the adverse effects of nonmetallic inclusions are reduced and sufficient flatness can be obtained.

  The metal material for mirror polishing according to claim 2 is characterized in that, in claim 1, the hardness of the base material is 100 or more in terms of Vickers hardness.

  It is impossible to eliminate non-metallic inclusions existing on the surface and non-metallic inclusions newly appearing on the surface during the polishing process. In addition, the influence of the non-metallic inclusions hidden under the polishing surface on the polishing process cannot be ignored. Therefore, in the second invention, the hardness of the base material is increased in order to eliminate the influence of such non-metallic inclusions, particularly non-metallic inclusions hidden under the polished surface. Specifically, the hardness of the base material is set to 100 or more in terms of Vickers hardness. Therefore, the difference in hardness between the non-metallic inclusions and the base material is reduced, flatness is ensured when polished, and the influence of hidden non-metallic inclusions is reduced. Is obtained.

  The metal material for mirror polishing according to claim 3 is a metal material for mirror polishing in which a mirror surface is formed by surface polishing. In the metal material for mirror polishing, the elongation strain in the rolling longitudinal direction is 0.1% or more and 0.8% or less. Is added.

  In the third aspect of the invention, tensile strain is applied to the material before the polishing treatment with the surface plated with metal, specifically, 0.1% or more and 0.8% or less with respect to the base material after rolling. An elongation strain in the rolling longitudinal direction is given. Therefore, the residual stress after the polishing process is made uniform, the uniformity of the strain in the thickness direction is obtained, and the warpage is suppressed.

  A metal material for mirror polishing according to a fourth aspect is characterized in that the metal is plated on the surface in any one of the first to third aspects.

  In the fourth invention, the surface is metal-plated and the plated layer is polished, so that it is not affected by wrinkles generated during rolling. If there are many non-metallic inclusions on the rolled plate that will be the substrate, plating defects called pinholes will occur or, in extreme cases, the bonding between the rolled plate and the plated layer will be brittle However, since there are few non-metallic inclusions present in the third invention, such a situation does not occur and there are few pinhole defects and a sufficient flatness can be obtained.

  In the present invention, since the existence ratio of the nonmetallic inclusions in the metal material is set to 0.05% or less, the adverse effect of the nonmetallic inclusions can be reduced and sufficient flatness can be obtained. As a result, it is possible to provide a stamper for optical disks, a reflecting mirror in an electronic device, an ultra-precise mold, and the like that have excellent flatness accuracy. Moreover, the yield at the time of manufacture of these products can be improved.

  Further, in the present invention, since the hardness of the base material is set to 100 or more in terms of Vickers hardness, it is possible to reduce the adverse effects of non-metallic inclusions that are hidden not only on the surface but also directly under the polished surface, and more sufficiently Flatness can be obtained.

  In the present invention, since the elongation strain in the rolling longitudinal direction of 0.1% or more and 0.8% or less is given to the base material after rolling, the residual stress after polishing treatment is Uniformity can be obtained, uniformity of strain in the thickness direction can be obtained, and warpage can be suppressed.

  Further, in the present invention, the surface is plated with metal so that the influence of wrinkles generated during rolling can be avoided, and since there are few non-metallic inclusions, plating defects called pinholes are generated. thing. In extreme cases, the metal plating layer can be prevented from peeling off.

  It is a means of the present invention for solving the problems of the first method and the second method described above (it is difficult to ensure sufficient smoothness of the surface), and suppressing the existence ratio of non-metallic inclusions, The definition of hardness will be described in detail below.

(Regarding the suppression of the presence ratio of non-metallic inclusions (material cleanliness))
Hereinafter, the result of investigating the influence of the cleanliness of the material on the quality after the polishing process (see Table 1) and the reason for limiting the numerical value of the existence ratio of nonmetallic inclusions based on the investigation result will be described.

  The material used was pure nickel, which was collected from a slab produced by continuous casting after melting in an electric furnace. In order to investigate the influence of non-metallic inclusions, materials were collected from each of the front position, the center position, and the final solidification position in the longitudinal direction of the continuously cast slab. The concentration of nonmetallic inclusions is highest at the final solidification position, and the concentration of nonmetallic inclusions is low because steady solidification is performed at the central position.

  Further, a secondary melting slab was further collected from the material collected near the center in the longitudinal direction of the continuous casting slab, and arc welding (VAR melting) was performed in a vacuum. Specifically, a VAR material having a diameter of 100 mm and a length of 200 mm was collected and used as an electrode for VAR dissolution. The reason for applying this VAR dissolution is to further reduce the concentration of non-metallic inclusions.

  A hot-rolled slab having a thickness of 60 mm and a width of 100 mm was manufactured by hot forging from a total of four types of materials including three types of continuous cast slabs and one type of slab after VAR melting. The manufactured hot-rolled slab was heated to 1200 ° C. and then finished to a thickness of 4 mm by hot rolling. At this stage, a sample for cleanliness evaluation was collected. After the hot-rolled sheet of each sample was annealed at 750 ° C., the scale generated on the surface was removed by molten salt and pickling. Thereafter, intermediate annealing was performed once at a thickness of 1.00 mm, and then finished to a thickness of 0.95 mm by cold rolling.

  The rolled surface of a sample for cleanliness evaluation collected in the state of a cold-rolled sheet was embedded and polished, and the cleanliness was investigated. The cleanliness was evaluated according to the point calculation method of JISG0555. Table 1 shows the evaluation results of the cleanliness of each sample. Nonmetallic inclusions in nickel are classified into several types according to their morphology and composition, and Table 1 shows the total values.

  A disk-shaped material having a diameter of 180 mm was cut out from the material after cold rolling, and a polishing test was performed. The polishing test was performed on the one after cold rolling and the one plated on the surface. The plating treatment was electroless plating with a thickness of 10 μm.

  Each material was fixed on a surface plate, and then polished to finish by lapping polishing, polishing polishing and chemical mechanical polishing. The lapping polishing was performed using a diamond disk made of a copper foil in which diamond abrasive grains were fixed by nickel plating. Polishing polishing was performed with diamond slurry suspended in polishing oil. Further, in chemical mechanical polishing, a slurry in which colloidal silica is suspended is used. Polishing was performed by rotating the surface plate at a speed of 100 rpm and pressing the wrapping film against each material.

  For each material after the polishing treatment, a test piece for flatness evaluation was taken from a position of half the radius (position of 75 mm from the center), and the surface roughness was measured by AFM. In the measurement of the surface roughness, the average roughness (Ra) in the range of 100 μm × 100 μm was calculated. The calculation results are shown in Table 1. Moreover, in Table 1, when this average roughness (Ra) is 10 nm or less, it is judged that the abrasiveness is good and evaluated with “◯”, and when it exceeds 10 nm, the abrasiveness is poor. Judgment is made and evaluation is made with “×”.

  From the results in Table 1, only the material having a cleanness of 0.055% has poor polishing properties. In addition, the plated material can be polished more satisfactorily than the untreated material. Therefore, if the existing ratio (cleanness) of non-metallic inclusions in the material is 0.05% or less, the surface roughness after the polishing process will be 10 nm or less, regardless of the presence or absence of surface plating. I understand. Therefore, the surface can be sufficiently flattened by setting the existence ratio of the nonmetallic inclusions to 0.05% or less, and further improved by plating.

  The existence ratio (cleanness) of non-metallic inclusions in the material greatly affects the surface state after the polishing process even when the material is directly polished. This is because non-metallic inclusions appearing on the surface adversely affect the smoothing of the surface during the polishing process. That is, since the non-metallic inclusions are different in hardness from the base material, if they are mixed, the polishing is inevitably non-uniform and the surface after the polishing process is not smooth. In some cases, non-metallic inclusions with poor ductility themselves are destroyed during the polishing process and peeled off from the base material, and the peeled non-metallic inclusions are pressed against the material by the polishing pad. Smoothness cannot be obtained on the surface. When the presence ratio (cleanness) of non-metallic inclusions in the material exceeds 0.05%, non-metallic inclusions appearing on the surface increase, so that a flat and uniform surface cannot be obtained after polishing treatment. .

  In addition, although the flatness of the surface improves as the existence ratio (cleanness) becomes lower, on the other hand, an increase in cost for reducing the existence ratio (cleanness) is unavoidable. Therefore, the lower limit of the abundance ratio (cleanliness) of non-metallic inclusions in the material may be determined in consideration of economic background.

  Applying metal plating to the surface (front surface and / or back surface) of the material before polishing erases irregularities or undulations such as roll marks on the surface of the rolled material, and changes the surface shape after polishing. It is effective for further improvement. The thickness of the metal plating is not particularly limited, but the surface irregularities can be erased if the thickness is at least about 2 μm. On the other hand, the upper limit may be determined in consideration of the economic background, because the time of the plating process becomes longer when the plating is too thick, leading to an increase in cost. A thickness exceeding 1 is unnecessary.

(Regarding the hardness of the base material)
Hereinafter, the result of investigating the influence of the hardness of the base material on the quality after the polishing process (see Table 2) and the reason for limiting the numerical value of the hardness of the base material based on the result of the investigation will be described.

  As described above, based on the material collected from the center position of the slab in the longitudinal direction of the continuous cast slab, a material subjected to intermediate annealing with a thickness of 1.00 mm was obtained. This material was rolled from a minimum of 0.02 mm to a maximum of 0.5 mm, and subjected to a polishing test in the same manner as in the above example with the hardness of the base material changed.

  As for the hardness of the rolled plate, Vickers hardness was measured on the surface as a condition of a load of 1 kg. At this time, the hardness was measured at 5 points, and the average value thereof was calculated. Table 2 shows the calculation results and the evaluation of average roughness (Ra) and flatness after the polishing treatment. The method for obtaining the average roughness (Ra) and the evaluation criteria for the flatness are the same as in the above-described example.

  From the results in Table 2, it can be seen that a material having a Vickers hardness of the base material of 100 or more can obtain a surface having good smoothness. Therefore, the surface can be further flattened by setting the Vickers hardness of the base material to 100 or more.

  The hardness of the base material greatly affects the smoothness of the surface after the polishing treatment. If the base material has a low hardness and is soft, the material is easily damaged by the handling in the polishing process or in the preceding and subsequent processes. In addition, damage caused when foreign matter is mixed in the polishing slurry is greatly affected by a soft material. From such a point, when the base material has a Vickers hardness of less than 100, polishing wrinkles are large and easily remain. Therefore, it is necessary to set the base material hardness to 100 or more in terms of Vickers hardness by a method such as work hardening prior to polishing. The upper limit of the hardness is not particularly specified because polishing becomes easier as the hardness increases.

  Next, the application of elongation strain, which is a means of the present invention for solving the above-described problem (warp generation) of the first method, will be described in detail below.

(Regarding elongation strain after rolling)
Hereinafter, the result of investigating the influence of the elongation strain after rolling on the quality after the polishing treatment (see Table 3) and the reason for limiting the numerical value of the elongation strain based on the investigation result will be described.

  A cold rolled coil having a width of 500 mm and a thickness of 0.3 mm having a SUS304 component was used as a material. Various elongation strains were applied to this coil in the longitudinal direction of rolling with a tension leveler or stretcher. Table 3 shows the conditions for the elongation strain. And the grinding | polishing process was performed on the conditions similar to the example mentioned above.

  After the polishing process is completed, the polishing plate is placed on the surface plate, and one end thereof is fixed to the surface plate. Further, it was examined whether or not a spacer having a width of 5 mm and a thickness of 0.5 mm could be inserted between the other end of the polishing plate raised from the surface plate and the surface plate. That is, it was examined whether or not a warp having a height of 0.5 mm or more occurred on the edge of the polishing plate on the surface plate. In Table 3, when it is not possible to insert a spacer, it is judged that a warp of 0.5 mm or more has not occurred, and evaluated as “◯”. When a spacer can be inserted, a warp of 0.5 mm or more occurs. It is judged that it is judged as “×”.

  From the results of Table 3, warping of 0.5 mm or more occurs in the material not applied with elongation strain, and warping of 0.5 mm or more occurs in the material applied with elongation strain of 0.1% or more. Absent. Therefore, warpage can be prevented from occurring by adding an elongation strain of 0.1% or more in the longitudinal direction of the rolled material.

  In the material after rolling, the residual stress exists non-uniformly due to local fluctuations in the friction coefficient between the material and the roll in rolling. When such a material is polished, the balance of the residual stress balanced in the material is lost, and a phenomenon may occur in which the material greatly warps after completion of the polishing process.

  In order to suppress such warpage, it is only necessary to make the residual stress existing in the material uniform. To make this uniform, it is effective to add elongation strain in the rolling direction to the base material. However, when the amount of the elongation strain is less than 0.1%, effective uniformity of the residual stress cannot be obtained, and the base material after the polishing treatment is warped. On the other hand, if the amount of elongation strain exceeds 0.8%, the material is wrinkled in the direction parallel to the elongation strain direction in the step of applying the elongation strain, which is a problem. Therefore, the amount of elongation strain is suitably in the range of 0.1% to 0.8%, particularly about 0.5%. This result was the same with a pure nickel plate.

  In the above example, pure nickel and SUS304 were used as materials, but in addition to this, pure titanium for industrial use, austenitic or ferritic stainless steel, iron-nickel alloy containing 36% or 42% nickel, Or even if it is materials, such as copper or copper alloy, aluminum, or an aluminum alloy, as long as the conditions of this invention are satisfy | filled, it is natural that there exists an effect similar to the case of pure nickel.

Claims (4)

  A mirror-polished metal produced by rolling, wherein a mirror-polished metal material having a mirror surface formed by surface polishing has a non-metallic inclusion content of 0.05% or less in the material. Material.   The metal material for mirror polishing according to claim 1, wherein the hardness of the base material is 100 or more in terms of Vickers hardness.   A mirror-polishing metal material in which a mirror surface is formed by surface polishing, wherein elongation strain is applied in the rolling longitudinal direction under conditions of 0.1% or more and 0.8% or less. Metal material.   The metal material for mirror polishing according to any one of claims 1 to 3, wherein the surface is plated with a metal.