JPS62117153A - Production of substrate for optical disk having guide groove - Google Patents

Abstract

PURPOSE:To obtain the titled disk without any remaining molding strains and capable of regulating the refractive index by treating both surfaces of the substrate with a soln. contg. a silane compd. having an ethylenic double bond, heating the substrate, then pressing a stamper master disk and a glass sheet on both surfaces of the substrate through an UV curing resin, irradiating UV rays, simultaneously curing the two layers, and releasing the substrate from a die. CONSTITUTION:A mixture of gamma-methacryloxypropyltrimethoxysilane and ethanol in 1/8 weight ratio is used as a coupling agent and uniformly coated by dipping on both surfaces of the highly transparent epoxy substrate 2 obtained by cast molding. The material is heated in a drier at 100 deg.C for 1hr and then washed with acetone. The epoxy substrate 2, both surfaces of which are treated with the coupling agent, is thus obtained. Then an UV curing resin 3 is coated, the resin is cured, then the epoxy substrate 2 is released from the master disk 1 and a clamping plate 4, and the substrate for an optical disk with one surface having specified ruggedness and both surfaces coated with the UV curing resin 3 is obtained. The substrate has excellent adhesion and is not cambered.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an optical disc substrate with guide grooves, in which guide grooves are formed on one side of an epoxy resin cast substrate and a smooth tJV hardened layer is formed on the other side. This relates to a manufacturing method. More specifically, a solution of a silane compound having an ethylenic double bond, such as vinyl silane, is applied to both sides of an Ezegishi 1 transparent substrate, heat-dried, and then a UV hardened fat layer is placed on both sides. This invention relates to an optical disc substrate which is pressed between ε- and glass plates, and is cured by irradiating UV light from the glass surface to form a guide groove on one side and a smooth hardened layer on the other side.

[Prior art]

Conventionally, the substrates used in all optical recording media are glass or transparent synthetic resin substrates, and optically isotropic materials have been used to ensure no birefringence. polymethyl methacrylate, pyrisulfone,
Bori carbonate, golibinyl chloride, a copolymer of vinyl chloride and vinyl acetate, etc. have been proposed. However, among these, most of them are irimethyl methacrylate (PMM) in terms of moldability and optical transparency.
A) or polycarbonate (PC) is used. Polymethyl methacrylate (PMMA) substrates or PC substrates are generally obtained by injection molding.

However, as the recording density of the inner substrate increases and a higher degree of reliability is required of the medium, the following drawbacks become a major problem.

(2) In the case of N-type substrates, the heat resistance is poor, so when various functional films are deposited, the temperature of the substrate surface increases and deformation occurs.

Since both substrates are made of thermoplastic resin, creep may occur due to centrifugal force during high-speed rotation during access. Furthermore, if exposed to high temperatures during storage, deformation occurs and surface wobbling due to so-called rotation increases.

In the case of a θ or a P₫ substrate, the hygroscopicity is large, and problems arise such as deformation due to moisture absorption and promotion of oxidation of the functional film.

Since both substrates are manufactured by injection molding, molding distortion causes residual birefringence.

It is difficult to adjust the refractive index of both substrates, and the refractive index is limited to one.

etc.

[Structure of the invention]

In order to overcome such drawbacks, the inventors of the present application first investigated substrates using various resins, and cast an epoxy resin composition consisting of an epoxy resin, an organic polybasic acid anhydride, a curing accelerator, and a discoloration inhibitor. The present invention was filed with the applicant that a substrate obtained by thermoforming could be used as an optical recording medium to overcome the above-mentioned drawbacks.

Next, an ultraviolet curable resin is applied to the substrate to form guide grooves, and after the original plate is pressed against the substrate, a light beam is irradiated from the substrate surface side to harden the resin layer, and the mold is removed to transfer the unevenness. I tried the method.

However, it has been found that the conventional method has the following problems. In other words, since the resin constituting the substrate is an acid anhydride-cured epoxy resin, it has a significantly more hydrophilic interface than a general hard-curing resin due to the water groups in the resin skeleton, making it more difficult to use than a normal hard-curing resin. The system was unable to achieve adhesion to the substrate and was not suitable for practical use. In addition, in order to eliminate this drawback, when we used an acrylic monomer having 10H and -C0OH groups as a crosslinking monomer in the W curing resin system, it adhered closely to the Stanzu master disk having a hydrophilic interface and was easily removed from the mold. It was impossible.

Furthermore, due to curing shrinkage of the W cured resin layer, a phenomenon in which the substrate was warped by making the side fat layer concave also occurred.

The inventors of the present application have worked diligently to arrive at the present invention in order to solve this problem that arises because the substrate is an epoxy resin (greasy substrate).That is, the inventors of the present invention have worked hard to arrive at the present invention.That is, both surfaces of the substrate are treated with a solution containing a silane compound having an ethylenic double bond. , UV on both sides after heat treatment
The Stanno Z master and the glass plate are pressed against the substrate surface via the cured resin, and UV light is irradiated from the glass plate side to simultaneously cure the two layers, resulting in a cured layer that is harder than the Ebikishi cured product and removed from the mold. We have discovered a method of obtaining a substrate with guide grooves having a three-layer structure.

Any epoxy resin used to obtain the epoxy resin substrate of the present invention can be used as long as it is liquid at room temperature, such as liquid bisphenol A resin, alicyclic air resin, aliphatic epoxy resin, etc. resin is used. In addition, mixing and using these epoxies and resins is extremely effective in the present invention, and in particular, the mixing of alicyclic 17'' oxylipid and liquid bisphenol A-based resin is effective for refracting heavy metals in the cured product obtained by adjusting the mixing ratio. 1 is essential in that it can be adjusted as appropriate.

The mixing ratio is also important, and detailed research has revealed the interesting fact that there is a linear relationship between the mixing ratio and the I14 refractive index. For optical disc substrates, the ratio of aromatic resin to alicyclic resin is 9:1 to 1:
The range of 9 is preferable, and if the amount of aromatic resin exceeds this range, the refractive index will become large, and conversely, if the amount of alicyclic resin is large, the refractive index will become small. Furthermore, brominated epoxy resins can also be used as appropriate.

As the acid anhydride used as the curing agent to obtain the substrate used in the present invention, any acid anhydride can be used as long as it has excellent compatibility with the liquid epoxy resin, but hexahydrophthalic anhydride and tetrahydrophthalic anhydride are particularly applicable. ,
Aliphatic or alicyclic anhydride such as methyltetrahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, daliaceric anhydride, and maleic anhydride;
There are unsaturated aliphatic or aromatic curing agents such as phthalic anhydride, trimellitic anhydride, and pyromellitic anhydride, and for the same reasons as in the case of the above-mentioned resins, it is also effective to use a mixture of curing agents. A combination of an aromatic curing agent and an alicyclic curing agent is desirable. As for the curing agent, the higher the aromatic ring concentration, the higher the refractive index of the cured product.

The curing accelerator used to obtain the substrate used in the present invention includes 2-ethyl-4-methylimidazole, 2-ethyl-4-methylimidazole,
-Imidazoles such as methylimidazole and 1-benzyl-2-methylimidazole, 8th class amines, and the like, but imidazoles are preferred. Further, the anti-discoloration agent is important for obtaining the substrate used in the present invention, and contributes to light transmission stability. These discoloration inhibitors include 2-6
- Hindered phenols such as ditertiary-butylphenol, organic sulfides, organic phosphites,
Higher fatty acid salts and the like are used alone or in combination. Particularly in order to ensure discoloration stability under high temperatures, the effect of these combinations may be significant.

A substrate is obtained by a so-called cast molding method in which the thus obtained compound is cast into a mold, heated and cured, and then removed from the mold.

The mold is preferably a glass mold from the viewpoint of surface smoothness, and if necessary, it is also effective to appropriately release the mold from the glass surface.

Next, the substrate is treated with a solution in which a silane compound having an ethylenic double bond, such as vinylsilane or methacryloxyalkylsilane, is dissolved in an organic solvent. Treatment methods include dipping method, spin coater method, roll coater method,
This is carried out by a commonly used method such as a spray method.

Further, as the organic solvent for obtaining the solution, lower alcohols are preferable, and examples thereof include methanol, ethanol, propyl alcohol, isopropyl alcohol, and the like. The ratio of vinylsilane to lower alkonyl is preferably 1:8 to 1:10. In addition, the heating temperature is 50°C to 120°C, preferably 8°C.
The treatment is carried out at a temperature of 0 DEG C. to 100 DEG C., and the treatment time varies depending on the temperature, but is usually carried out in a range of 10 to 60 minutes.

Note that heat treatment is essential; without heat treatment, the substrate surface becomes sticky or the adhesion of the trv cured layer to the substrate surface deteriorates. Although the reason for this heating effect is not certain, it is presumed to be due to the reaction between the mono-CH group and the silanol group present in the 1-I sokin rejuvenating fat.

Next, an α-curing resin is placed on both sides of the treated surface. In this case, the UV-curing resin used is mainly composed of 7-mers or oligomers of monoesters, diesters, triesters, or tetraesters of acrylic acid or methacrylic acid. It is something.

Examples, ethyl acrylate, n-butyl acrylate, hexyl acrylate, octyl acrylate, 2
- alkyl acrylates, alkoxyalkyl acrylates, phenoxyalkyl acrylates and phenyl acrylates and diacrylates, such as ethylhexyl acrylate, octadecyl acrylate, ethoxyethyl acrylate and phenoxyethyl acrylate, e.g. tJf 1,3-pronogundiol diacrylate, Oligomers of alkanediol diacrylates and alkene glycol diacrylates and triacrylates such as diethylene glycol diacrylate and tetraethylene glycol diacrylate, such as trimethylolprono-and-dryacrylate and pentaerythritol triacrylate and tetraacrylate, such as R-ntaerythritol tetraacrylate. acrylic esters such as ethylene glycol acrylate, urethane acrylate, daryester acrylate, and epoxy acrylate.

Regarding the photoinitiator, it is important to pay attention to the light transmission characteristics of the transparent resin substrate, and since the epoxy resin substrate hardly transmits light with a wavelength of 290 nm or less,
Suitable photoinitiators having good sensitivity in a relatively long wavelength range, such as 2,2-dimethoxy-2-phenylacetophenone and benzoin isobutyl ether, or combinations thereof are preferred. Further, for the purpose of imparting toughness, 2 to 10, preferably about 5 parts by weight of a monothiol compound can be added to 100 parts by weight of the main component. If the amount exceeds 10 parts by weight, favorable results cannot be obtained in terms of heat resistance, hardness, glass transition point, etc.

Furthermore, if necessary, stabilizers, discoloration inhibitors, adhesion agents, etc. may be added to the ultraviolet curable resin system.

Next, the above-mentioned α-curing resin is placed on both sides of the treated epoxy substrate and pressed between a metal stun S- and a glass plate, and UV'' If: is irradiated from the glass plate surface to cure the two UVm resin layers. In this case, the surface of the treated substrate has ethylenic double bonds that react with the UV curing resin and form a strong bond.On the other hand, the surface of the metal stand and glass plate has an extremely hydrophilic interface as is well known. Therefore, it does not adhere to the α-curing resin at all, and the mold release transfer is performed extremely effectively.

The thus obtained substrate had grooves transferred to one side and a smooth cured resin layer on the other side, and was an extremely excellent substrate for optical/magnetic disks.

Examples are shown below.

〔Example〕

Example 1 Using γ-methacryloxypropyltrimethoxysilane/ethanol 1/8 (weight ratio) as a coupling treatment agent on an epoxy substrate with good transparency obtained by a casting method, both sides of the epoxy substrate were coated by a dipping method. Apply it evenly to 100℃,
This was heated in a dryer for 1 hour, and washed with acetone to obtain an epoxy substrate subjected to double-sided coupling treatment. Next, as shown in Figure 1, after coating with ultraviolet curable resin and curing the resin, the epoxy substrate is peeled off from the master (1) and the pressing plate (4). An optical disc substrate coated with an ultraviolet curing resin was obtained. The substrate had excellent adhesion and did not warp.0 Comparative Example 1 An epoxy substrate that had not been subjected to coupling treatment was coated with an ultraviolet curing resin and cured, but the coating resin and epoxy The adhesion of the substrate was poor, and a reliable optical disk substrate could not be obtained.

Comparative Example 2 Using an epoxy substrate with coupling treatment on one side,
In the same manner as in the example, an ultraviolet curable resin was applied only between the compacted surface and the master disk and cured to obtain an optical disk substrate having a predetermined unevenness on one side.

However, the obtained substrate was clearly warped, making it difficult to control tracking and focusing.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of manufacturing an optical disk substrate according to the present invention. In the figure, 1 is the master (Stanno!'), 2 is the epoxy board, and 3
is an ultraviolet curing resin, 4 is a silane compound layer, 5 is a glass plate, and 6 is an ultraviolet light source

Claims (2)

[Claims] (1) After obtaining a cast transparent cured flat plate of an epoxy resin consisting of an epoxy resin, an organic polybasic acid anhydride, a curing accelerator, and a discoloration inhibitor, both surfaces of the transparent substrate contain ethylenic double bonds. A step of applying a solution of a silane compound or immersing the substrate in a solution of a silane compound and then heat-treating at a temperature of 50°C or higher, and the hardness of the cured product on both treated surfaces is higher than the hardness of the cured product of the epoxy resin. An ultraviolet curable resin that can be obtained as a cured product is interposed, an original plate or a stamper with a guide groove on one side is loaded, a glass plate with a smooth surface is placed on the other side, and after the whole is pressed together, ultraviolet rays are applied from the glass plate side. A process of simultaneously curing the ultraviolet curable resin layers interposed on both sides by irradiation, and removing the original plate and glass plate having guide grooves, transferring the desired guide grooves to one side of the epoxy resin substrate, and simultaneously forming an ultraviolet curable smooth surface on the other side. 1. A method of manufacturing an optical disc substrate having a guide groove, the method comprising the steps of: (2) For an optical disk having a guide groove according to claim 1, wherein the ultraviolet curable resin is mainly composed of a monomer or oligomer of a monoester, diester, triester, or tetraester of acrylic acid or methacrylic acid. Substrate manufacturing method.