Patent Application
20070249143
The best mode for carrying out a method and a device of manufacturing a thin substrate of the present invention will now be described in detail with reference to the attached drawings.
When the turntable 102 is rotated in this state, air in the gap between the flexible sheet 101 and the turntable 102 moves by a centrifugal force from the inner periphery to an outer periphery beginning at the vicinity of an outer peripheral end of the spacer 104, and further, a steady-state air flow from the inner periphery to the outer periphery is generated by the air flowing into the gap from the through-hole 105. By the features, the local air entrainment phenomena caused by static electricity at the stationary time are totally removed. The space between the flexible sheet 101 and the turntable 102 made by the spacer 104 is usually desired to be 0.01 to 0.5 mm.
The through-hole 105 for air inflow may be provided in a doughnut-shaped plate itself of the turntable, and alternatively, it may be provided in a hub mounted concentrically to the center of the doughnut-shaped plate of the turntable. Since this makes air flow smoother, local surface wobbling can be reduced and a stable state with less surface wobbling can be kept. By uniformly providing a number of through-holes 105, a uniform air flow can be realized. In practice, a plurality of, preferably, 3 to 50 through-holes are desired to be disposed circumferentially to be symmetrical about the center of rotation. The diameter of the through-hole 105 is desirably 2 mm to 7 mm. However, the diameter and the number of the through-holes 105 are limited such that the strength of the turntable 102 does not become extremely low. While it is not shown in the drawing, the peripheral edge of the through-hole 105 is desired to be annealed so that an eddy is not generated or the substrate is not damaged due to the existence of the through-hole 105.
With respect to the turntable 102, by making the outside diameter the same as the outside diameter of the flexible sheet 101, or smaller by 5% or less than the outside diameter of the flexible sheet 101, the adhesive can be prevented from flowing into between the flexible sheet 101 and the turntable 102 on the occasion of spin-coating of the adhesive.
Next, the processes of manufacturing a thin substrate by using the equipment shown in
By the above processes, it is possible to manufacture the thin substrate according to the present invention which is enhanced in surface wobbling characteristics and surface wobbling acceleration characteristics. Hereinafter, more concrete example will be described.
A polycarbonate film having a thickness of 100 μm, an inside diameter of 15 mmφ and an outside diameter of 120 mmφ is prepared, and grooves and pits of DVD-R specifications are formed by a nanoimprint device made by Nanonics Corporation. Next, a dye recording layer, and a metal alloy reflection layer containing silver as a main constituent are stacked by 15 nm to produce two flexible sheets capable of optical recording and reproduction. As a turntable, an aluminum circular plate having a thickness of 1 mm, an inside diameter of 15 mmφ and an outside diameter of φ119 mm is prepared (this is defined as “a”), and in addition to this, the turntable on which eight inflow through-holes each of 6 mmφ are equidistantly disposed in a circumferential form at positions of 18 mm from the center was prepared (this is defined as “b”). Further, a spacer made of SUS304 with an outside diameter of 30 mmφ, an inside diameter of 15 mmφ and a thickness of 0.2 mm is prepared. In the following, the turntable on which the above described spacer and the above described “a” are concentrically fixed respectively is called a turntable 1, the turntable on which the above described spacer and the above described “b” are concentrically fixed respectively is called a turntable 2, and the turntable on which only the above described “a” is fixed is called a turntable 3.
The turntable used in this example is made of soda glass, but is more enhanced in effect by performing the following treatment. (1) Forming a nitride silicon or oxide silicon thin film of 1 nm or more on the soda glass. (2) Roughening the soda glass surface to have a mesh size of #6000 or smaller, more preferably #1000 or smaller. Alternatively, forming a very fine recessed and projected shape with 1 mm pitch or less. The treatment (1) mainly has the effect of reducing charged static electricity between the polycarbonate which is the material of the thin substrate and the turntable, and the treatment (2) mainly has the effect of enabling an air layer to readily enter between the thin substrate and the turntable. The above described treatments (1) and (2) may be individually used respectively, but by using those in combination, a larger effect can be exhibited.
Hereinafter, the procedure for bonding the flexible sheets together by this spin coat device will be described. First, one flexible sheet 402 is held by the vacuum chuck 407, and is disposed on the turntable 401 from above the spin coat device. Hereinafter, the flexible sheet is called a sheet A. Next, by the syringe 403, the ultraviolet curing adhesive is dropped onto the position of the inner periphery (r=18 to 23 mm) of the sheet A, and the adhesive is spread up to about r=35 mm in accordance with the coat conditions A shown in
Next, another flexible sheet (hereinafter, called a sheet B) is disposed so as to be overlaid on the sheet A on the turntable 401 by the vacuum chuck 407. A magnet clamp (not shown) is disposed from above the sheets A and B, and the adhesive between the sheets A and B is spun off in accordance with the coat conditions B shown in
Next, ultraviolet irradiation is applied to the bonded sheets using the ultraviolet ray irradiator 405, so that the adhesive is cured. When the adhesive is cured, the rotation of the turntable 401 is stopped, and the clamp is removed. When curing the adhesive, in order to make both surfaces of the bonded sheets uniform, it is preferable to irradiate one of the surfaces with ultraviolet irradiation intensity such that the one surface is cured in the order of about 30 to 70%, and thereafter, apply ultraviolet irradiation to the other surface by an amount of making up for a deficiency. Thereby, substrate deformation caused by a heat ray, and imbalance in the curing degree can be reduced, and therefore, a thin substrate with less surface wobbling can be obtained.
In the above described process, the adhesive layer is formed between the two flexible sheets each having a substrate thickness of 100 μm. Thereby, the thin substrate which is 210 μm thick at the inner periphery (r=20 mm), and 215 μm thick at the outer periphery (r=58 mm) has been produced. When the two flexible sheets are held with the magnet clamp, the clamp with an outside diameter of φ20 is used, and therefore, the adhesive layer is formed up to about r=10 mm which corresponds to the clamp outside diameter, while at the outer periphery, the adhesive layer is formed up to the substrate outermost periphery of r=60 mm by the spinning off process. Here, since the adhesive does not reach the above described clamp area, the two flexible sheets are bonded by any one of the following three kinds of methods as shown in
(1) Polyethylene terephthalate, polyethylene naphthalate or polycarbonate which is cut into a doughnut shape of a thickness of 25 μm with an outside diameter of φ9 and an inside diameter of φ7.5 is prepared, and this is sandwiched between a substrate A and a substrate B at the time of bonding (see an upper diagram in
(2) Ultraviolet irradiation or corona discharge treatment is performed only in the above described clamp area in advance to increase the surface energy, and further, thermocompression bonding (temperature of 140 degrees, pressure of 1 t) is performed only in the treated regions to bond the thin substrates together (see a central diagram in
(3) Hot melt sheet (model 3100; thickness of 30 μm, melting point of 130 degrees) made by DAICEL FINE CHEM LTD. which is additionally prepared is cut into the shape with the outside diameter of φ9 and the inside diameter of φ7.5, and this is sandwiched between the substrate A and the substrate B at the time of bonding. After the bonding layer is formed, the inner peripheral portions of the substrate A and the substrate B are bonded via the above described hot melt sheet by thermocompression bonding (temperature of 140 degrees, pressure of 1 t) (see a lower diagram in
Note that the above described various conditions are nothing but examples, and the kind of adhesive and the forming conditions of the bonding layer are not limited to these. Concerning the thickness (called T) of the completed thin substrate in the information area, as long as the thickness T is in the following range:
2×(t)×1.03<T<2×(t)×1.10
where the thickness of the original flexible sheet is set as t, the same effect as in this example can be obtained.
If the outside diameter of the turntable is made larger than the outside diameter of the thin substrate in the above described process, the adhesive flows into between the turntable and the thin substrate in the process of spinning off the adhesive. When the outside diameter of the turntable becomes smaller than the outside diameter of the thin substrate by 5% or more, wobbling of the substrate at the outer peripheral portion during rotation, that is, during formation of the bonding layer becomes especially large. Therefore, the distortion amount of the outer peripheral portion of the thin substrate which is completed also becomes remarkably large as a result. Accordingly, the outside diameter of the turntable is desirably the same as or smaller by 5% than the outside diameter of the thin substrate.
The thin substrate produced in this example (turntables 1 and 2) and the thin substrate produced by a conventional manufacturing method (turntable 3) are prepared, and their performances are compared.
First, with respect to these two kinds of thin substrates, the substrate displacements in a static state are measured by a CCD laser displacement meter made by Keyence Corporation which is additionally prepared.
Next, concerning the above described two kinds of thin substrates, the surface wobbling acceleration at the time of rotation of the substrate is measured by using the laser Doppler meter made by Sony Corporation.
The method and device of manufacturing the thin substrate of the present invention are described by showing the concrete embodiments thus far, but the present invention is not limited to those. A person skilled in the art can add various modifications and improvements to the construction and function of the invention according to the above described embodiments or other embodiments within a range which departs from the spirit of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-115609 | Apr 2006 | JP | national |
