JPH0630181B2 - Method for manufacturing substrate of optical recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method of manufacturing a substrate having a guide groove for an optical recording medium capable of recording and reproducing by a light beam.

[Conventional technology]

It is necessary to form an optical guide groove on the substrate of the optical recording medium in order to perform high-density recording, and several methods have been conventionally known as the forming method. One method is to apply a curable resin onto a mold called a stamper provided with irregularities corresponding to the shape of the guide groove, place the substrate on this, and then irradiate the resin with resin. There is a method of forming a guide groove and fixing the guide groove to the substrate by curing the resin.

[Problems to be solved by the invention]

The substrate manufactured by this method has an excellent transfer property of the guide groove shape, and has an advantage that optical distortion of the substrate with the guide groove can be reduced as compared with other guide groove forming methods. However, in addition to being inferior to other methods in terms of mass productivity, the following problems have not been solved.

FIG. 5 is a view showing a state after the resin is cured when the guide groove is formed by the above conventional method. In this conventional method, the resin 3 before curing may flow out from the endmost portion of the substrate 2 because it has fluidity, and the protruding portion is cured as it is due to light irradiation or the like and is exposed to the outside of the substrate 2. Burrs having pointed ends as shown in the figure often occur.

In addition, since there is a minute gap in the fitting portion between the central axis 1 arranged at the center of the stamper 4 and the substrate 2, the resin also squeezes out and hardens even in this portion, causing a small burr,
It has been difficult to separate the stamper 4 from the substrate 2 having the guide groove fixed thereto.

When releasing the guide grooved substrate 2 and the stamper 4 in which burrs are generated, burrs having pointed ends are easily chipped, and the chipped burs are separated as dust, and static electricity is generated by electrification. It often adhered to the surface. Also, when removing burrs, the removed burrs sometimes become dust and adhere to the substrate surface. When the recording layer is laminated on the guide groove to which the dust is attached in this way, the dust portion has a step and cannot be completely covered by the laminated film and becomes a pinhole. There has been a problem that the recording characteristics are deteriorated due to the fact that water or oxygen enters through the pinholes and corrodes the recording layer.

The present invention has been made in view of the above problems, and an object thereof is to prevent dust from adhering to a substrate surface by suppressing the occurrence of burrs when manufacturing a substrate with a guide groove using a stamper. It is an object of the present invention to provide a method of manufacturing a substrate for an optical recording medium which can be prevented.

[Means for solving problems]

The method for producing a substrate for an optical recording medium of the present invention is a method in which a curable resin and a substrate are sequentially laminated on a mold having irregularities corresponding to the shape of the guide groove, and the resin is solidified to form a guide groove. In the method of manufacturing a substrate for an optical recording medium, a mask having a donut-shaped light-shielding portion whose inner circumference is larger than the central hole of the substrate and whose outer circumference is smaller than the outer circumference of the substrate is placed on the substrate. The substrate, and then pressing down the substrate while irradiating the substrate with light that can pass through the mask from above, so that the substrate is previously coated below the light-shielding portion and between the mold and the substrate. A step of spreading a curable resin by irradiation of light, and curing the resin expanded to a position where light is irradiated; removing the mask; and irradiating the resin with the light, The process of curing the entire resin Characterized in that it.

〔Example〕

FIG. 1 is a plan view showing an example of the mask 5 used in the method of the present invention. The mask 5 has light-transmitting portions 6 that transmit light inside and outside a light-shielding portion 7 that has a donut shape that blocks light.

The inner circumference 7a of the light shielding portion 7 is larger than the central hole (fitting portion with the central axis 1 of the stamper) of the substrate 2 shown in FIG. 2 which is used when carrying out the method of the present invention. Outer circumference 7b
Is smaller than the outer circumference of the substrate 2. That is, when the mask 5 is placed on the substrate 2, the light-shielding portion 7 serves as the inner end portion of the substrate (the end portion in the present invention means a portion having a certain width from the end portion). The outer ends are not covered, and only the intermediate part between these ends can be covered.

According to the method of the present invention, since the resin layer forming the guide groove having the same shape as the light-shielding portion 7 and having substantially the same size can be fixed to the substrate, the light-shielding portion 7 is within a range satisfying the above-mentioned size. The mask 5 is provided according to the shape and size of the resin layer to be formed.

Although the inner and outer peripheries of the light shielding portion 7 of the mask 5 in this example are circular, their shape is not limited to circular and may be polygonal or the like. In the present invention, the shading portions having these shapes are all referred to as a donut-shaped shading portion.

The stamper used in the method of the present invention may be the same as the conventional one shown in FIG. 5, but a hole 8 for inserting the central axis of the stamper is provided at the center of the mask. There is. The center hole 8 is preferably substantially the same size as the center axis of the stamper so that the mask 5 can be easily positioned on the stamper, and can be fitted into the center hole 8. The light-transmitting portion 6 outside the light-shielding portion 7 is provided merely for the reason of manufacturing the mask, and is not always necessary.

The method of the present invention will be described in detail below by taking the case of using the above mask as an example. 2 and 3 are diagrams showing an embodiment of the present invention.

In this embodiment, first, the ultraviolet curable resin 3 is applied onto the stamper 4. The resin is applied so that when the mask 5 is set above the resin 3 in the next step, the resin 3 exists below the doughnut-shaped light-shielding portion and does not protrude below the light-transmitting portion. It is necessary to.

Incidentally, the resin is not limited to the ultraviolet curable type, but other types of resin which are cured by another type of light may be used, and in this case, the light used may be one corresponding to this resin. Good.

Next, the substrate 2 which can transmit the used light, that is, the ultraviolet ray is fitted into the central shaft 1 arranged at the center of the stamper 4, and the mask 5 is fitted into the central shaft 1 to place the substrate 2 above the resin 3.
And mask 5 are set.

Next, the substrate 2 and the mask 5 placed on this are slowly lowered, and when the substrate 2 is touched by the resin 3, the ultraviolet lamp 10 covered by the reflector 9 is turned on to turn the substrate 2 and the mask 5 on. It descends more slowly (Fig. 2). Since the ultraviolet rays 11 do not reach below the light-shielding portion of the mask, the resin previously applied below the light-shielding portion is gradually spread without being cured regardless of whether the ultraviolet lamp 10 is turned on. The resin that has reached is cured by being exposed to light. Even if there is some unevenness in the way the resin 3 spreads, the resin 3 will stop expanding along the inner and outer circumferences of the light-shielding portion of the mask upon curing. After that, the mask is removed and the resin 3 is completely cured by irradiating the substrate 2 with ultraviolet rays 11 completely,
A guide groove made of hardened resin is formed and fixed to the substrate (Fig. 3).

By the above method, it is possible to prevent burrs from being generated in the guide groove made of the cured resin.

In the above-described embodiment using the mask shown in FIG. 1, since the transparent portion of the mask is wide, the ultraviolet rays transmitted through this portion wrap around due to diffraction, and the resin 3 reaches the end portion of the light shielding portion of the mask. It may be cured before and the accuracy of the stop position of the resin 3 may be slightly deteriorated. To improve this accuracy, a mask as shown in FIG. 4 may be used. Since the transparent portion 6 of this mask is a doughnut-shaped slit having a narrow width, the amount of ultraviolet rays that pass through the mask is small and wraparound does not substantially occur. For this reason, the resin is used as the translucent portion 6.
The resin 3 can be stopped at the position of the light-transmitting portion 6 with almost no error before reaching the position, and the accuracy of the stop position of the resin 3 can be increased.

Next, an example of actually carrying out the method of the present invention will be shown.

A blue glass substrate with an outer diameter of 200 mm, an inner diameter of 30 mm, and a thickness of 1.1 mm, and a donut-shaped light-shielding portion with an inner diameter of 65 mm and an outer diameter of 195 mm provided on a glass disk by chrome coating are shown in Fig. 1. Such a mask, a mixture of pentaerythritol tetramercaptoacetate and diarylidene pentaerythritol [trade name: Spyrac T-502 (Showa High Polymer)] and 2-hydroxypropyl-1,3-dimethacrylate [trade name: 701A (new Nakamura Kagaku)] is mixed at a ratio of 1: 2 and benzoin isopropyl ether is used as a photopolymerization initiator in an amount of 2
%, An ultraviolet curable resin was used to produce a substrate with guide grooves by the method of the present invention. The resin layer that forms the guide groove of this board has an inner diameter of 70 mm (± 1.5 mm) and an outer diameter of 190 mm.
It was a donut shape (± 1.5 mm).

In addition to the light shielding part under the same conditions as the above mask, the inner diameter from the center
Same as above except that a mask with a light-shielding part is provided on the part up to 60 mm and the part outside the outer diameter of 200 mm, that is, the mask shown in Fig. 4 having the slit-shaped light transmitting part with a width of 5 mm. A substrate with a guide groove was manufactured under the conditions by the method of the present invention. The resin layer of this board has an inner diameter of 65 mm (± 1 mm) and an outer diameter of 195
It was a doughnut-shaped one having a size of mm (± 1 mm), and could be formed in the same shape and size as the light-shielding portion.

〔The invention's effect〕

As described above, according to the method of the present invention, before the resin reaches the innermost and outermost end portions of the substrate, it can be cured at a desired position, and a resin layer serving as a guide groove is formed near the inner and outer peripheries of the substrate. It became possible not to fix. Therefore, since the resin is formed by protruding from below the substrate and burrs, which are the main source of dust, do not occur, the adhesion of dust to the substrate with guide grooves is greatly reduced, and high reliability for recording media A substrate suitable for use as a substrate can now be manufactured.

Further, since the resin does not adhere to the central axis of the stamper, the stamper and the substrate with the guide groove can be easily released from the mold, and the step of removing burrs is not necessary, so that the manufacturing efficiency is improved.

Furthermore, when a recording medium is manufactured using a substrate with a guide groove manufactured by the method of the present invention, a recording layer is laminated only on the resin layer forming the guide groove, and then a protective layer is formed on the entire surface of the substrate. The protective layer covers not only the recording layer but also the side surface at the end of the resin layer, so that water may invade from the side surface at the end of the resin layer as in the case of a substrate made by a conventional method. The effect of improving the durability of the recording layer can be expected.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of a mask used in the method of the present invention, FIGS. 2 and 3 are views showing an embodiment of the method of the present invention, and FIG. 4 is used in the method of the present invention. It is a top view which shows another example of a mask. FIG. 5 is a diagram showing a state after resin curing when a guide groove is formed by a conventional method using a stamper. 1: Central axis, 2: Substrate 3: Resin, 4: Stamper 5: Mask, 6: Light transmitting part 7: Light shielding part, 7a: Inner circumference 7b: Outer circumference, 8: Center hole 9: Reflector, 10: UV lamp 11: UV

Claims (1)

[Claims] 1. A photocurable resin and a substrate are sequentially laminated on a mold having irregularities corresponding to the shape of the guide groove, and the resin is cured to form a substrate for an optical recording medium with a guide groove. In the method of manufacturing, first, light is applied only to the resin in the position corresponding to the peripheral portion of the substrate to cure the resin in this portion, and then the remaining resin surrounded by the cured resin. Illuminate the
A method for manufacturing a substrate of an optical recording medium, which comprises curing the remaining resin.