JPH04295643A - Manufacture of optical recording medium board - Google Patents

Abstract

PURPOSE:To provide a high grade optical record medium substrate which is excellent in transcription performance from a stamper due to low double refraction and effective to prevent defects from contamination deposited on a first roller. CONSTITUTION:Film-like plastics B3 are supplied to plastic A2 under a moleten state extruded from a T die 1 of a first roller 4 based on a three-roll process. Then, a laminated body 7 by the plastics A and B is prepared by way of a second roller 5 and a third roller 6 for molding service. The laminated body 7 is separated, thereby obtaining an optical record medium substrate comprised of plastics A.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method of manufacturing a substrate for an optical recording medium, and in particular to an optical recording medium used in the field of optical recording such as laser beam storage, capable of large-capacity storage, non-contact reading and writing. The present invention relates to a method of manufacturing a substrate with track guide grooves for use in the present invention.

0002

2. Description of the Related Art Conventionally, in a recording apparatus using a laser beam, there is a method in which grooves are formed in advance at regular intervals on the surface of a substrate for track servo for writing and reading. In this method, the grooves serve as a readout guide, which improves the accuracy of laser beam track control and enables faster access than conventional methods using grooveless optical recording medium substrates.

[0003] As methods for obtaining substrates for optical recording media provided with track guide grooves, heat pressing methods, injection methods, photocuring methods, etc. are widely used. Among these, the substrate material used in the heat press method and injection method is polymethyl methacrylate (hereinafter referred to as P
MMA) and polycarbonate are often used.

In addition, the photocuring method uses a PMMA, polycarbonate, glass substrate, etc., and injects a photocurable resin between the substrate and a stamper provided with an uneven surface for forming guide grooves. In this method, track guide grooves are formed on a substrate by photo-curing.

[0005] In addition, when obtaining a PMMA casting substrate, there is a method of obtaining a grooved casting substrate by using a stamper with an uneven surface on one side of the mold into which the monomer is poured, and a method of obtaining a grooved casting substrate by melting pellets of polycarbonate or the like. When forming a sheet by extrusion, a method has been proposed in which a roller is provided with an uneven surface to obtain a grooved sheet.

[0006]

[Problems to be Solved by the Invention] Currently, polycarbonate resin is the most widely used substrate for optical recording media. However, polycarbonate resin has the disadvantage that birefringence is likely to occur, and the value of birefringence increases immediately when strain occurs. Birefringence must be made as low as possible since it causes a loss of C/N ratio during recording and reproduction of optical recording media.

[0007] The causes of this birefringence include the following. For example, in a method of forming sheets from molten plastic using the melt extrusion method, the rollers used for extrusion forming are usually made of steel rolls plated with chromium. When a polycarbonate resin sheet is sandwiched between metal rollers and rolled, distortion occurs in the sheet, which causes birefringence. Also, the first
When the roller and sheet come into contact, birefringence may occur due to rapid cooling of the sheet due to the low temperature of the first roller. The set temperature range for each roller has become narrower, making temperature control during manufacturing difficult.

[0008] Furthermore, the formation of track guide grooves on substrates for optical recording media is also greatly affected by the cooling rate of the sheet by melt extrusion; if the cooling rate is fast, the movement of the resin during transfer from the stamper becomes slow. , the transferability deteriorates.

In addition, dirt due to the volatile content of the molten resin extruded from the T-die adheres to the first roller, and when it accumulates, unevenness occurs on the surface of the molded sheet, and the surface of the substrate becomes smooth. There is a problem that it disappears.

The present invention has been made in view of the above-mentioned problems, and has been made by melt extrusion to produce a first material that has low birefringence and good transferability from a stamper from a molten plastic.
It is an object of the present invention to provide a method for manufacturing a high-quality substrate for an optical recording medium, which prevents defects due to accumulation of dirt on rollers.

[0011]

[Means for Solving the Problems] That is, the present invention is a method for manufacturing a substrate for an optical recording medium from a molten plastic by a melt extrusion method, in which it is possible to form a substrate into a sheet or film extruded from an extruder. A track guide groove used for optical recording/reproduction is formed on one surface of plastic A in a molten state, and a film or sheet-like plastic B is brought into contact with the other surface to form a laminate. This is a method of manufacturing a substrate for an optical recording medium, which is characterized by peeling.

The present invention provides a method for manufacturing an optical recording medium substrate from a molten plastic by melt extrusion molding using a three-roll method, in which a substrate extruded from an extruder,
A film or sheet-like plastic B, which is incompatible with the molten plastic A, is supplied from the first roller of the three-roll method to the molten plastic A that can be formed into a sheet or film, and the plastic B is molded. plastic A through the second and third rollers for
By creating a laminate of and B, and separating this laminate in a subsequent process, an optical recording medium substrate can be obtained.

The present invention will be explained below based on the drawings. FIG. 1 is a schematic diagram showing one embodiment of the method for manufacturing an optical recording medium substrate of the present invention. FIG. 2 is an explanatory diagram showing a method of separating the laminate produced in FIG. 1 into sheet-like plastic A and film-like plastic B. FIG. 3 is a perspective view of FIG. 1 viewed from an oblique direction.

First, in FIG. 1, plastic A2 in a molten state is released from T-die 1 of an extruder by melt extrusion.
is extruded and inserted between the first roller 4 and the second roller 5. At this time, film-like plastic B3
is supplied from the first roller 4, and the first roller 4 and the second
A sheet-like laminate 7 is formed between the rollers 5 . As shown in FIG. 3, a stamper having a pattern 9 of a stamper of a guide groove for an optical recording medium is provided on the surface of the second roller 5, and the laminate 7 is in contact with the second roller 5. In the meantime, the transfer pattern 10 is transferred onto the sheet-like plastic A2a.

In order to separate the sheet-like laminate 7 onto which the transfer pattern 10 has been transferred into a sheet-like plastic A2a and a film-like plastic B3, as shown in FIG. It is sufficient to pass through the laminate 7 and separate the plastics A and B in opposite directions. Note that this separation may be performed when necessary; in a state where it is not separated, the film-like plastic B3 functions as a masking material that protects the surface of the sheet-like plastic A2a from dust and scratches during the manufacturing process.

This film-like plastic B3 is the first
By being supplied from the roller 4, the first roller 4
When the plastic A2 in a molten state is rolled and formed between the second roller 5 and the second roller 5, the pressure applied to the plastic A2 can be relaxed and the occurrence of large distortion can be suppressed. Moreover, since the film-like plastic B3 lowers the cooling rate of the molten plastic A2 extruded from the T-die 1, it is possible to obtain a sheet with low birefringence due to the slow cooling effect. Further, in terms of transferability, it is advantageous because the time during which the plastic A2 in the molten state is easily deformed becomes longer, and the quality as a substrate for an optical recording medium is also improved.

In addition, film-like plastic B3
This eliminates contamination of the first roll due to the volatile matter of the molten resin extruded from the T-die, making it possible to extend the continuous molding time.Furthermore, the film-like plastic B3 enables the masking process of the laminate at the same time. Therefore, it is possible to prevent dust and scratches from forming on the sheet-like plastic A2a, and therefore productivity can be greatly improved.

Plastic A used in the present invention
Of the plastics that can be used as a substrate for optical recording media, any plastic that can reduce birefringence during sheet molding may be used, such as polycarbonate, polystyrene, PMMA, polyetherketone, amorphous polyolefin, and polymethylpentene. , polysulfone, etc.

[0019] Furthermore, as the plastic B, a material that is incompatible with the molten plastic A is used,
For example, materials with good heat resistance such as polyethylene terephthalate, polybutylene terephthalate, polyamide, and polyimide are preferred. In particular, the plastic B may be a film or sheet in which additives such as fillers are added to improve heat resistance. The thickness of the film or sheet of plastic B is usually 100 μm or less, preferably in the range of 3 to 50 μm. If the thickness exceeds 100 μm, the optical properties of the plastic B film cannot be ignored, and in addition to adding conditions when selecting plastic B and narrowing the selection range, the increased thickness increases the frequency of transportation and handling, and the diameter of the supply roll. This is undesirable because it increases the size of the roll, shortens the roll replacement cycle, and increases costs.

[0020]

[Function] The present invention is a method for manufacturing a substrate for an optical recording medium from a molten plastic by a melt extrusion method using three rollers. Track guide grooves used for optical recording/reproduction are formed on one side of the molten plastic A, and the first three-roll method is formed on the other side.
Since the film or sheet-shaped plastic B supplied from the rollers is brought into contact with each other to form a laminate, the rapid temperature drop of the molten plastic A at the first roller is suppressed, forced rolling is also controlled, and complexity is reduced. You can get refractive sheets.

[0021]Furthermore, since the film-like plastic B prevents the first roll from being contaminated by the volatile matter of the molten plastic A extruded from the extruder, the continuous molding time can be extended.

Furthermore, since the film-like plastic B allows masking of the laminate at the same time, it is possible to prevent dust and scratches from forming on the sheet or film of the plastic A obtained.

[0023]

[Examples] The present invention will be specifically explained below with reference to Examples. Example 1 A substrate for an optical card medium was manufactured by using polycarbonate resin as plastic A and polyethylene terephthalate as plastic B using an apparatus as shown in FIG. First, polycarbonate resin (hereinafter referred to as PC) 4 melted at 300°C is extruded from the T-die 1. On the other hand, a polyethylene terephthalate film (hereinafter referred to as PET) 3 having a thickness of 5 μm is passed between the first roller 4 and the second roller 5 and sent to the third roller 6. P in molten state
C2 is fed between the first roller 4 and the second roller 5. At this time, the first roller 4, the second roller 5 and the third roller
The feed speed of the roller 6 was initially set to 4.0 m/min, and the roller surface temperatures were initially set to 105°C, 120°C, and 145°C, respectively.

A stamper pattern of guide grooves (parallel grooves) 9a for optical cards was provided on the surface of the second roller 5, as shown in FIG. Guide grooves for optical cards were transferred onto the surface of the sheet-like plastic A layer 2a of the laminate 7 thus obtained. The gap between the first roller 4 and the second roller 5 was adjusted, and a laminate 7 having a thickness of 0.4 mm was molded. This laminate 7 was separated into a PC sheet 2a and a PET film 3 by the method shown in FIG.

The birefringence of the obtained PC sheet 2a was measured and found to be 15 nm. In addition, the transfer pattern 10
The land width of the transfer pattern land portion 11 (see FIG. 4), which is the guide groove portion, was measured and divided by the groove width of the stamper groove portion 11a of the second roller 5 (see FIG. 5): Y.
X/Y≈0.9. Although this laminate 7 was molded continuously for 8 hours, there was no change in the birefringence value and the X/Y value. Note that the value of X/Y is hereinafter referred to as a transfer rate.

Comparative Example 1 An optical card medium substrate was manufactured using the materials and experimental conditions used in Example 1, but without using film-like plastic B3. When the birefringence was measured in the same manner as in Example 1, it was 30 nm.
The transfer rate was X/Y≈0.5. In addition, when continuous operation was performed under these experimental conditions, after about 3 hours, stains that were visible to the naked eye appeared on the surface of the first roller 4, and unevenness appeared on the surface of the molded sheet (Plastic A: 2a). .

As described above, in Example 1 and Comparative Example 1, as shown in FIG. 5, a stamper having a pattern 9a, which is a guide groove for an optical card, was used, but in the present invention, a stamper as shown in FIG. Alternatively, pattern 9, which is a circular guide groove for an optical disc, may be used, and any shape can be used without being influenced by the direction.

Further, as an application of the present invention, as shown in FIG.
You can also make it into a belt and use it over and over again. In this case, a cleaning roller 13 for cleaning the surface of the film-like plastic B3 and a cooler 14 may be provided as necessary. Further, the path of the film-like plastic B3 may be extended to the third roller 6.

[0029]

As explained above, according to the present invention, in a method for manufacturing an optical recording medium substrate from a molten plastic by a melt extrusion method, one of the molten plastics A extruded from an extruder A track guide groove used for optical recording/reproduction is formed on one surface, and three grooves are formed on the other surface.
Since the film or sheet-shaped plastic B supplied from the first roller of this roll method is brought into contact to form a laminate, it has low birefringence and good transferability from the stamper. A high-quality substrate for an optical recording medium that is free from defects can be manufactured with a high yield even by continuous molding over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing one embodiment of the method for manufacturing an optical recording medium substrate of the present invention.

FIG. 2 is an explanatory diagram showing a method of separating the laminate produced in FIG. 1 into sheet-like plastic A and film-like plastic B.

FIG. 3 is a perspective view of FIG. 1 viewed from an oblique direction.

FIG. 4 is a partial sectional view of a guide groove manufactured by an embodiment of the manufacturing method of the present invention.

FIG. 5 is a partial sectional view of a groove portion of a stamper used in an embodiment of the manufacturing method of the present invention.

FIG. 6 is an explanatory diagram showing a forming roller provided with a stamper used in one embodiment of the present invention.

FIG. 7 is a schematic diagram showing another embodiment of the invention.

[Explanation of symbols]

1 T-die 2 Molten plastic A (molten PC) 2a
Sheet-like plastic A (sheet-like PC) 3 Film-like plastic B (film-like PET) 4 First roller 5 Second roller (molding roller with stamper) 6
Third roller 7 Laminated bodies 8, 8a, 12 Support rollers 9, 9a Stamper pattern 10 Transfer pattern 11 Transfer pattern land portion 11a Stamper groove portion 13 Cleaning roller 14 Cooler

Claims (4)

[Claims] Claim 1: A method for manufacturing a substrate for an optical recording medium from a molten plastic by a melt extrusion method, comprising:
Track guide grooves used for optical recording and reproduction are formed on one side of the molten plastic A that can be formed into a sheet or film extruded from an extruder, and a film or sheet-shaped plastic is formed on the other side. A method for producing a substrate for an optical recording medium, comprising: forming a laminate by bringing plastic B into contact with each other, and then peeling off the plastic B. 2. When forming a laminate by passing plastic A and plastic B between rollers, a roller provided with a stamper is brought into contact with one surface of the plastic A to form track guide grooves used for optical recording and reproduction. 2. A method for manufacturing an optical recording medium substrate according to claim 1. 3. The thickness of the plastic B film or sheet is 100 μm or less.
The method for manufacturing the optical recording medium substrate described above. 4. The method for manufacturing an optical recording medium substrate according to claim 1, wherein the plastic A is a polycarbonate resin.