JPH01171815A - Manufacture of base for information recording mediums - Google Patents

Abstract

PURPOSE:To manufacture a base, optically isotropic and smooth, by injecting liquid resin into a mold for casting constituted of heat curing resin filled into the spaces between units and solidifying. CONSTITUTION:As for thermoplastic resin 4 filled between units, such resin as vinyl resin, styrene resin, acryl resin, polycarbonate resin, acetate resin, polyester resin, imide resin, fluorine group resin, olefin resin or the like is used, and its softening temperature is higher than the polymerization reaction temperature of the resin to be cast and should be heat-resistant. For liquid resin 7 injected into a mold for casting, transparent, uncured heat curing resin, photo- setting resin or unpolymerized thermoplastic resin is used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a substrate for an information recording medium having a concavo-convex preformat pattern.

[Prior Art] Conventionally, an information recording medium substrate has irregularities such as tracking grooves and information pits formed on its information recording surface. Methods for forming irregularities on the substrate include: (1) If the substrate is made of thermoplastic resin, a method of transferring stamper-type track grooves by injection method or heat press method, or (2) A method of transferring stamper-shaped track grooves using thermosetting resin. After applying a photocurable resin composition onto a transparent resin plate made of thermoplastic resin, a stamper mold is brought into close contact with the transparent resin plate and energy such as ultraviolet rays is applied from the side of the transparent resin plate to cure the photocurable resin composition. Let it harden and transfer the stamper type replica onto a transparent resin plate.
A method using the so-called 2P method.

Alternatively, there is a known method of casting a prepolymer containing a resin monomer or solvent using a casting mold with track grooves pre-formed on one or both sides. .

[Problems to be Solved by the Invention] However, the thermoplastic resin substrate obtained by the injection method or heat pressing method described in (1) above has problems with the substrate after molding due to residual stress and molecular orientation caused by the thermal history during molding. Since warpage and optical anisotropy may occur, problems remain as substrates for information recording media.

In addition, in the substrate obtained by the 2P method (2) above, the polymerization initiator and monomer used during photocuring tend to remain in the resin after photocuring, and these may affect the optical recording layer of the recording medium. , the problem of deterioration of recording characteristics often occurs.

As a method for manufacturing a substrate for an information recording medium that does not cause these problems, the above-mentioned cast molding method (2) is sometimes used.

The substrate obtained by this method requires almost no pressure to be applied during molding compared to the above methods Since resin can also be used, it is possible to select a resin that does not have a negative effect on the recording layer.

In the above cast molding method (2), the mold having irregularities such as tracking grooves and information bits used during cast molding is etched using a photoresist formed on a glass plate by a photolithography process as a mask. , those in which the irregularities are patterned, those in which the irregularities are patterned by laser cutting, or those in which the irregularities are formed on a glass plate or a metal plate by direct cutting with a diamond needle having a tip are known.

However, a problem with cast molding is that productivity is low because one processing time when manufacturing a substrate is very long. Therefore, for the purpose of improving productivity, a multi-cavity mold in which a plurality of pattern surfaces are formed on one mold is required as a mold used in the above-mentioned cast molding. However, as mentioned above, since micromachining is required to form irregularities on a casting mold, the manufacturing cost is extremely high when manufacturing a mold with multiple cavities. Moreover, if a defect occurs in one of the plurality of pattern surfaces, the entire mold with multiple molds cannot be used.

As a method to improve such defects, for example, a multi-cavity casting mold unit is formed by bonding multiple mold units with irregularities such as tracking grooves and information pits on the surface using a specific adhesive. By using a mold, if one of the units becomes defective, you only need to replace that one unit, improving the durability of the casting mold, making it optically isotropic, without warping, and with a flat surface. A method for manufacturing smooth substrates for information recording media with high productivity can be considered.

However, this method simply joins the mold units and does not take into account the relative position between the mold units of the substrate, so even if multiple substrates are obtained as a single unit by casting, Since each substrate is arranged in a staggered manner, it is not possible to carry out the next step of printing the recording layer as is, and it is necessary to cut each substrate before printing, making continuous production of recording media impossible. There are drawbacks.

Therefore, in order to improve this problem, a method can be considered in which a plurality of molding units are fixed to a backing member after the relative positions of the molding unit: (1) are specified using an appropriate adhesive.

However, in this method, the mold units are partially joined with adhesive, or gaps remain, so liquid resin enters the voids between the mold units during casting and solidifies. Therefore, a recording medium substrate having protrusions is created, and the protrusions obstruct post-processing and must be removed, making them unsuitable for continuous production of recording media. Also,
There was a problem in that the mold releasability between the end face of the mold unit and the cast resin substrate was not very good because of the protrusions formed by the gaps between the mold units.

The present invention has been made in order to improve the drawbacks of the prior art, and in a method of creating a substrate by cast molding, a plurality of mold units are attached to a backing member using an adhesive. By fixing and specifying the position and filling the gap between the plurality of mold units with thermoplastic resin,
It is an object of the present invention to provide a method for manufacturing with high productivity a substrate for an information recording medium that is optically isotropic, has no warpage, and has a flat and smooth surface.

[Means for Solving the Problems] That is, the present invention arranges and fixes a plurality of mold units having a concavo-convex preformat pattern on the surface thereof to a backing member, and then connects the plurality of mold units arranged between the plurality of mold units. After filling the gap with thermoplastic resin to form a casting mold,
The present invention relates to a method of manufacturing a substrate for an information recording medium, which is characterized in that a liquid resin is injected by a casting method using the casting mold, solidified, and then removed from the mold.

In the present invention, a plurality of mold units (hereinafter referred to as
After fixing the unit (hereinafter referred to as unit) to the backing member and specifying its position, the liquid resin is injected by the casting method into a casting mold made by filling the gap between the units with thermoplastic resin and solidified. It is characterized by being removed from the mold after being pressed.

The present invention will be explained in detail below.

The present invention provides (1) a substrate for an information recording medium by a cast molding method using a multi-cavity casting mold having a cross-sectional shape opposite to the shape of unevenness such as tracking grooves and information pits of an optical recording medium; This is a method for producing a casting mold in which a plurality of units each having one or more surfaces are arranged as a unit for the multi-cavity casting mold and fixed to a backing member. Fill the gaps between the units with thermoplastic resin.

The number of surfaces of these units is determined by the yield, cost, etc. of the information recording medium substrate manufactured by forming tracking grooves, information pits, and the like. For example, when manufacturing optical card substrates, a casting mold can be patterned on two sides using a 6-inch laser exposure machine, so these two sides can be used as one unit, and multiple units can be patterned. By using this, a casting mold with a multiple of 2 sides is produced.

Further, these units are fixed by adhesion using an ultraviolet curable adhesive. If, for example, a thermosetting adhesive is used as the adhesive used for this fixing, stress caused by contraction of the hardening resin may cause a problem of one position shift. Therefore, as a characteristic of this adhesive, after positioning,
It is necessary to fix it quickly without shifting the position. In the present invention, UV-curable adhesives are preferred as such adhesives.

In addition, the thermoplastic resins that fill the gaps between these units include vinyl resins, styrene resins, acrylic resins, polycarbonate resins, acetic acid resins, polyester resins, imide resins, fluorine resins, olefin resins, etc. , considering the mold releasability from the cast resin □
Olefin resins, Teflon resins, imide resins, etc. are preferred.

Furthermore, the thermoplastic resin to be filled must have a softening temperature higher than the polymerization reaction temperature of the resin to be cast, and must have heat resistance.

Although the gap between the units varies depending on the size of the unit, it is usually less than 10 m in width, preferably in the range of 2 to 5 square meters. If the number of layers exceeds 10, the gap becomes brittle and the amount of filler increases, which is not preferable.

In the present invention, the material of the unit is not particularly limited, and ordinary materials may be used, such as glass plates, ceramics, metals, etc.

In addition, there are no particular limitations on the backing member, and a wide range of materials can be used, but preferably the same material as the unit,
Alternatively, it is desirable to use a material with a thermal expansion coefficient similar to that of the unit; for example, a glass plate, ceramics, or metal with good thickness, precision, and flatness can be used.

Using the casting mold prepared as described above, a liquid transparent resin is injected into the casting mold by a normal casting method, solidified, and then removed from the mold to form a substrate for an information recording medium. Obtainable.

The liquid resin injected into the casting mold in the present invention is a transparent uncured thermosetting resin, a photocurable resin, or an unpolymerized thermoplastic resin. For example, thermosetting resins include phenolic resin, Examples of thermoplastic resins such as epoxy resins and polyester resins include vinyl resins, styrene resins, acrylic resins, polycarbonate resins, acetic acid resins, and polyester resins.

In this way, according to the manufacturing method of the present invention, optically isotropic, warp-free, flat and smooth substrates can be produced in large quantities, easily and inexpensively, and also have tracking grooves and information pits. A recording/reproducing type information recording medium substrate having a good shape can be obtained.

[Function] In the manufacturing method of the present invention, since the substrate is molded by a cast molding method, the obtained substrate for information recording medium has no optical anisotropy, is isotropic, has no warpage, and has a smooth surface. It becomes flat and smooth.

In addition, after producing a plurality of units of a plurality of casting molds, the positions are specified by arranging and fixing them to the backing member using adhesive, and then the positions are specified between the plurality of mold units. Since the gaps are filled with thermoplastic resin, the resulting plurality of substrates are arranged without any deviation in position, and the connecting portions are smooth without protrusions, making it easy to print the recording layer in the first step. In addition, compared to the conventional method of forming multiple pattern surfaces on a single mold, the manufacturing cost of casting molds is lower, yields are better, mold release is better, and productivity is higher. good.

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 FIGS. 1(a) to 1(e) are process diagrams showing an example of the method for manufacturing an information recording medium substrate of the present invention. All figures show cross-sectional views of the substrate.

Hereinafter, the manufacturing process will be explained in order based on the drawings.

First, in FIG. 1(a), a plurality of units 1 each made of a glass plate on which highly accurate grooves were formed by a photolithography process were prepared, and each unit was made into one unit.

Next, in FIG. 1(b), the unit 1 was placed on the backing member 3 using the adhesive 2.

At this time, an ultraviolet curing adhesive such as Diabond DA855G or UV130 (manufactured by Nogawa Chemical ■) was used as the adhesive.

Further, as the backing member 3, a glass plate with good thickness, precision and flatness was used.

Next, after correcting the position of the unit, it was immediately irradiated with ultraviolet light to fix the position of the unit. At this time, the ultraviolet rays may be irradiated from either the unit side or the backing member side, but the side to be irradiated must be formed so that the ultraviolet rays can pass through.

Next, in FIG. 1(C), a gap of about 3.5 mm in width between the units was filled with thermoplastic resin 4. As the thermoplastic resin, Sony Bond 5C608 (manufactured by Sony Chemical ■) was used. After filling, 100°C1180
The resin was solidified by heating for a minute.

Next, as shown in FIG. 1(d), the mold obtained as described above and another glass plate 5 whose surface has been optically polished are placed so as to face each other, and spacers 6 are provided around the periphery to form a cell. assembled.

A liquid epoxy resin having the following composition was injected into the cell as liquid resin 7, and cured at 100°C for 110 hours.

(Composition) Bisphenol A epoxy resin 100 parts by weight Methylhexahydrophthalic anhydride 88 parts by weight 2-ethyl-4-methylimidazole 0.5 parts by weight2
．． 1.0 parts by weight of 6-di-tert-butyl-p-cresol
As shown in e), the information recording medium substrate 8 is removed from the mold.
I got it.

In addition, when the birefringence of the obtained information recording medium substrate was investigated,
The retardation within the card substrate, which had a length of 54 mm, a width of 86 mm, and a thickness of 0.4+sm, was 0.1 to 5 nm, and no warping of the substrate was observed.

[Effects of the Invention] As explained above, according to the manufacturing method of the present invention, since a substrate is created by a cast molding method, information recording that is optically isotropic, has no warpage, and has a flat and smooth surface. It is possible to obtain a substrate for media.

Furthermore, by manufacturing substrates for information recording media by performing cast molding using casting molds made up of individual units, it was possible to improve productivity, which had been a drawback of cast molding.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1(a) to 1(e) are process diagrams showing one embodiment of the method for manufacturing an information recording medium substrate of the present invention. l... Unit 2... Adhesive 3... Backing member 4... Thermoplastic resin 5... Glass plate 6... Spacer 7... Liquid resin 8... Information recording medium board for

Claims (1)

[Claims] A plurality of mold units having a concavo-convex preformat pattern on the surface are arranged and fixed to a backing member, and then a thermoplastic resin is filled into the gaps between the plurality of arranged mold units to form a casting mold. After that, a liquid resin is injected by a casting method using the casting mold, solidified, and then removed from the mold.