JPS63197612A - Mold for cast molding - Google Patents

Abstract

PURPOSE:To obtain an optical disk base plate having a guide groove for optical recording with a low cast and in large quantities, by coating a metal stamper with a ultraviolet curing type resin, which is then spread under pressure by using a glass plate, cured and peeled off, obtaining thereby a two layer structure consisting of the ultraviolet cured resin where the shape of the metal stamper is accurately transferred and the glass plate, and using this as a mold for cast molding. CONSTITUTION:As a metal stamper, which are prepared by means of a nickel electroforming method, a plasmaethcing method, etc., are used. The metal stamper is coated with an ultraviolet curing type resin, which is then spread to a thickness of 0.1 mm or less to prevent peeling off by using a glass plate having a good flatness of a proper thickness. The glass plate which can be used has a thickness of 5 mm or more and good flatness and has no flaw and crack of 0.1 mm or more. To improve the adhesiveness with the ultraviolet curing type resin, it is preferable that the surface of the glass plate is roughened to a proper roughness. Then, the spread and closed ultraviolet cure resin layer is cured by exposing to an ultraviolet ray. It is preferable that the ultraviolet curing resin has a glass transition temp. which is higher than the curing temp. of the resin used for the cast molding.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cast molding mold for manufacturing an optical disc substrate having an optical recording guide groove by a cast molding method.

More specifically, it relates to a cast molding mold with a two-layer structure consisting of an ultraviolet curable resin and a glass plate, which is obtained by applying an ultraviolet curable resin onto a commonly obtained metal stamper and curing it with ultraviolet rays, and is used for optical discs. Our goal is to provide substrates efficiently and at low cost.

[Prior art]

The method for manufacturing a resin optical disk substrate having optical recording grooves is (1) incorporating a metal stamper with optical recording grooves into a mold, and molding it by injection or injection compression molding for use with optical disks with optical recording grooves. Method of forming a substrate. (2
) A method of applying an ultraviolet curable resin onto a stamper, compressing it with a flat optical disk substrate, irradiating it with ultraviolet rays to cure it, and then peeling off the stamper to obtain an optical disk substrate with guide grooves for optical recording (so-called 2P method) ). (3) There is a method of using a stamper as a cast molding mold to cure a thermosetting resin or ultraviolet curable resin and then removing the mold to form an optical disc substrate with guide grooves for optical recording. .

Method (1) has the advantage of excellent productivity, although the material for the substrate for optical discs is limited to thermoplastic resins, but these thermoplastic resins have hygroscopicity, dimensional change, and heat resistance. A resin with well-balanced properties such as optical birefringence and optical birefringence has not been found.

For example, polycarbonate has a large optical birefringence, and polymethyl methacrylate has a small optical birefringence but is inferior in heat resistance and moisture absorption.

The method (2) has the advantage that the transferability of the optical recording guide groove is good, but the resulting optical disc substrate has a two-layer structure, which causes warping, waviness, etc. Furthermore, in a long-term reliability test, a problem may arise in the adhesion between the ultraviolet curable resin layer on which the guide groove is formed and the flat optical disc substrate. Method (3) has the advantage of being able to use a thermosetting resin or ultraviolet curing resin with low optical birefringence, and that the optical recording guide groove forming portion is made of the same material, but it requires an expensive stamper. is used as a mold for cast molding, and it takes several hours to harden, especially when using epoxy resin.
Productivity is extremely poor and the product becomes expensive. In other words, since stampers are manufactured by electroforming or cutting, they are time-consuming and very expensive, and if cast molding is performed using these stampers, these stampers will be monopolized for a long time. However, in order to mass produce a large number of stampers, it is necessary to prepare a large number of stampers, and the maintenance of these stampers requires careful attention.The resulting substrate for optical disks with grooves for optical recording is extremely expensive. It had become a thing.

[Purpose of the invention]

The present invention was completed after intensive research into a method for producing a substrate for an optical disk with guide grooves for optical recording by a cast molding method, and a method for efficiently providing large quantities of cast molding molds with high precision, inexpensively, and efficiently. More specifically, it is made of an ultraviolet curable resin-glass plate in which the shape of the metal stamper is accurately transferred by applying an ultraviolet curable resin to a metal stamper, rolling it on a glass plate, curing it, and then peeling it off. The object of the present invention is to obtain a large quantity of optical disk substrates with guide grooves for optical recording at low cost by using a two-layer structure as a casting mold.

[Structure of the invention]

The present invention provides a method for obtaining an optical disc substrate with guide grooves for optical recording by a cast molding method, in which a cast mold forming a cavity coats an ultraviolet curing acrylate or methacrylate resin on a metal stamper. Cast molding with a two-layer structure of UV-curable acrylate or methacrylate resin-glass plate obtained by rolling with a glass plate, curing the UV-curable resin through the glass plate, and then peeling it from the metal stamper. This relates to a mold for molding.

The method for manufacturing a cast molding mold of the present invention will be described below.

First, the metal stamper that serves as the base mold is generally made by nickel electroforming, plasma etching, or the like, but stampers obtained by other methods may also be used. Since the optical recording guide groove performs transfer twice, in the case of a spiral shape, it is necessary to have a shape opposite to that used as a metal stamper in the 2P method or the like.

An ultraviolet curable resin is applied onto this metal stamper and rolled with a glass plate of appropriate thickness and good flatness. The thickness of the glass plate used is preferably 5M or more since it is used as a cast molding mold. Further, the surface condition of the glass plate only needs to be good in flatness, and a surface with normal surface roughness is sufficient. However, there must be no scratches or chips of 0.1M or more.

Further, in order to improve the adhesion with the ultraviolet curable resin, the surface of the glass plate may be roughened to an appropriate roughness within a maximum surface roughness of 0.1 s or less. Furthermore, if necessary, it is also an effective means to previously apply a suitable primer such as a silane coupling agent or a titanium coupling agent to the surface of the glass plate to increase adhesion.

The ultraviolet curable resin rolled on a glass plate is rolled and compressed to a thickness of 0.1 m or less to prevent peeling due to curing shrinkage, etc. For clamping, a load can be applied to the glass plate as appropriate.

Next, the rolled and pressed ultraviolet curable resin layer is cured by irradiating ultraviolet rays through a glass plate.

When the thermosetting resin is cured by the casting method in the subsequent process, the cast mold made of the ultraviolet curable resin and the glass plate created in this way will be deformed due to the curing temperature or deformed during demolding. , cracks etc. should not occur. For this reason, it is preferable that the UV-curable resin has a glass transition temperature (hereinafter referred to as Tg) higher than the curing temperature of the resin used for cast molding, and furthermore, Tg should be at least 5°C higher than the curing temperature of the resin used for cast molding. is necessary, and furthermore, it is desirable that the temperature be higher than 10°C.

Furthermore, when the radiation-curable resin is cured by a casting method in a subsequent step, deformation due to the heat generated during radiation irradiation or deformation or cracking during demolding must not occur. For this reason, UV-curable resins must have a Tg that is at least 5°C higher than the temperature caused by the heat generated by radiation irradiation.
It is desirable that the temperature be higher than ℃.

If the difference in Tg is less than 5°C, the optical disc substrate will be deformed, and the groove transferability will be poor, making it impossible to obtain a precise groove shape.
Furthermore, the mold cannot withstand repeated use as a casting mold.

Such ultraviolet curable resins are acrylate or methacrylate resins, including (A) polyfunctional acrylate, polyfunctional methacrylate, or acrylate oligomer, methacrylate oligomer (B) acrylate monomer, or methacrylate monomer (C) It consists of a photosensitizer. Examples of (^) include dipentaerythritol hexaacrylate, dipentaerythritol hexamethacrylate, dipentaerythritol pentaacrylate, dipentaerythritol pentamethacrylate, pentaerythritol tetraacrylate, polyester acrylate, polyester methacrylate, epoxy acrylate, but Gen acrylate, etc.

Examples of (B) include 1.4 butanediol diacrylate, 1.4 butanediol methacrylate, 1.6 hexanediol diacrylate, 1.6 hexanediol dimethacrylate, 1.10 decanediol diacrylate, 1. 10 Decanediol dimethacrylate, phenylethyl acrylate, phenylethyl methacrylate, tetrahydrofurfuryl acrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, neopendilicol diacrylate, diethylene glycol diacrylate, trimethylolpropane acrylate, bismethacrylooxy Contains ethyl phosphate, etc. Examples of (C) include benzyl compounds, benzoin alkyl ethers, benzophenone compounds, acetophenone compounds, and benzyl ketal compounds. The amount of (C) added is (A), (
A range of 1 to 5 parts by weight based on the total amount of B) is desirable.

Among these (A), (B), and (C), one whose T3 of the cured product is 10° C. or more higher than the curing temperature of the casting resin is selected. Furthermore, these cured acrylate or methacrylate resins may be appropriately annealed at a predetermined temperature in order to increase the crosslinking density. After the acrylate or methacrylate resin layer is cured in this way, the metal stamper is peeled off to obtain a casting mold made of an acrylate or methacrylate resin and a glass plate.

Cast molding is performed using these cast molding molds.

A mold release process is performed on these cast molds to form a cavity. The resin to be cast-molded as the resin for optical disc substrates must (1) have heat resistance of 100°C or higher;

(2) Good adhesion to the functional film.

(3) Have a transmittance of 88% or more for reading or writing laser light.

(4) Good heat and humidity resistance.

(5) Little dimensional change.

(6) Birefringence is 40nlll (double pass) or less.

Thermosetting resins include diallyl diglycol carbonate, diallyl phthalate containing prepolymers, epoxy resins, unsaturated polyester resins, etc., but are not particularly limited as long as they satisfy the above conditions. Further, as the radiation-curable resin, any UV-curable acrylate or methacrylate resin that satisfies the above conditions may be used, similar to those used to create the casting mold. . In some cases, a resin system consisting of a compound having an ethene group/polythiol/photosensitizer may also be used. In addition, an electron beam curing resin or the like may be used as long as it satisfies the above conditions. Furthermore, systems in which these thermosetting resins and ultraviolet curable resins are appropriately blended may also be used.

When a thermosetting resin system is used, the curing temperature must be 5° C. or more different from the Tg of the acrylate or methacrylate resin from which the casting mold is made. In addition, when using a radiation curing resin system, the Tg of the acrylate or methacrylate resin from which the cast molding mold is made is 5°C or more, which is higher than the temperature due to the heat generated on the irradiated surface during radiation irradiation. It is necessary.

〔Effect of the invention〕

According to the present invention, the same cast molding mold can be easily obtained in large quantities from one metal stamper, and by using this mold, an optical disc substrate with guide grooves for optical recording can be obtained at low cost. The industrial significance is extremely great.

〔Example〕

(Example 1) An ultraviolet curing resin having the following formulation was applied onto a metal stamper obtained by nickel electroforming and having an optical recording guide groove as a father.

Hydroxyethyl methacrylate 101.6 Hexanediol diacrylate 201-Hydroxyhexylbenzophenone 4 Then, an isopropanol solution containing 5% γ-acryloyloxypropyltrimethoxysilane was applied to the surface and treated at 100°C for 1 hour.Thickness The ultraviolet curing resin on the metal stamper was rolled using a Pyrex glass plate of 10711111, and
The mixture was irradiated with a W high-pressure mercury lamp from a height of 15 cm for 30 seconds to cure it, thereby obtaining a casting mold. The glass transition temperature of this ultraviolet curable resin was 140° C., and the groove transferability was 95% or more.

A cavity was made from the obtained casting mold and a glass flat plate that had been subjected to mold release treatment, and a resin with the following formulation was poured into the mold at 80°C.
2 hours, hardened at 130℃ for 3 hours to a thickness of 1.2#
An optical disk substrate with a guide groove for optical recording was obtained.

Methylhexahydrophthalic anhydride 862-Ethyl 4-methylimidazole 1 The obtained optical disk substrate is in no way better or better than the disk substrate of an optical disk obtained by directly using a metal stamper as a casting mold. It was excellent.

(Example 2) Using the metal stamper of Example 1, an ultraviolet curing resin having the following formulation was applied.

Hydroxyethyl methacrylate 20 Example 1
A casting mold was obtained by curing in the same manner as above.

The glass transition temperature of this ultraviolet curable resin was 150'C, and the groove transferability was 95% or more. A cavity was formed using this casting mold, and a resin with the following formulation was used to form a cavity.
It was cured at 0°C for 5 hours and at 140°Q for 3 hours.

Diallylisophthalate monomer 40 Dicumyl peroxide 1 The obtained optical disc substrate was the same as in Example 1.

(Example 3) Using the metal stamper of Example 1, an ultraviolet curing resin having the following formulation was applied.

Heteroalicyclic diacrylate 1001.6 Hexanediol diacrylate 5 Dimethacrylokidiethyl phosphate 51-Hydroxyhexylbenzophenone 3 It was cured in the same manner as in Example 1 to obtain a casting mold.

The glass transition temperature of this ultraviolet curable resin was 100° C., and the groove transferability was 95%.

A cavity was formed using the obtained casting mold, and a resin having the following formulation was cured by irradiation with ultraviolet rays.

Epoxy acrylate 60 1.6 Hexanediol diacrylate 401-Hydroxyhexylbenzophenone 3 The obtained optical disc substrate was of very good quality as in Example 1. The cast molding molds with recording guide grooves shown in the above examples have excellent transferability, and each mold can be cast 10 times or more. However, the grooved ultraviolet curing resin film was removed and there were no cracks.

Claims (1)

[Claims] When molding an optical disc substrate with guide grooves for optical recording by casting a thermosetting resin or a radiation curable resin, the glass transition temperature of the casting mold must be 5°C higher than the curing temperature of the resin that will become the optical disc substrate. It consists of a glass plate and a UV-curable acrylate or methacrylate resin with a high UV-curing temperature.The liquid UV-curable resin is applied onto a metal stamper, rolled with a glass plate, and then ultraviolet rays are irradiated from the glass plate side. A cast mold with a two-layer structure consisting of an acrylate or methacrylate resin and a glass plate obtained by curing the resin layer and then peeling off the metal stamper.