JPH0716959B2 - Method for producing transparent plastic body - Google Patents

Description

TECHNICAL FIELD The present invention is used in a method for producing an optical transparent plastic body such as an optical disk substrate, a lens, a prism, etc. as an information recording medium.

2. Description of the Related Art Conventional resin substrates for optical disks are made of injection-moldable polycarbonate resin (hereinafter abbreviated as PC) or polymethylmethacrylate resin (hereinafter abbreviated as PMMA). Depending on the type of the disk, casting PMMA may be used. Etc. are used. Also, for plastic lenses, PC, PMM
In addition to injection molding thermoplastic resins such as A, aryl,
Thermosetting resins such as epoxy and CR-39 (manufactured by UCC) have also been used.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The resin substrate for an optical disc is one that utilizes the change in the refractive index of light due to the phase transition of the recording film, and therefore heat resistance at around 200 ° C. is required. Light transmission homogeneity with small optical strain (such as birefringence) is required.

For this reason, a thermoplastic resin substrate is not sufficient, and a thermosetting resin or the like is about to be used. However, the thermosetting resin is slow and insufficient in terms of the curing speed, and has the first problem. Further, although a material that is cured by ultraviolet rays has a high curing speed, a material having high heat resistance has a second problem that the substrate is cracked when cured in the mold due to a large shrinkage of curing reaction.

Means for Solving the Problems The present invention, in order to solve the above problems, in a method for producing a transparent plastic body using an ultraviolet curable material, injecting the ultraviolet curable material into a mold capable of transmitting ultraviolet rays on both sides. Precuring by irradiating ultraviolet rays in an amount of ultraviolet rays within full curing from both sides, and then postcuring by irradiating ultraviolet rays from both sides of the demolded precure transparent plastic body until it is completely cured Is.

More specifically, the UV-curable material is preferably a compounded composition with a polyfunctional acrylate, and the polyfunctional acrylate compound has the following general formula: [In the formula, R ₁ is an alcohol residue having 2 to 50 carbon atoms, and R _{2 is}
Is H or CH ₃ and n is a number from 2 to 6. ] A compound represented by the following is used, which has a glass transition temperature of 110 ° C. or higher in a cured product obtained by radical polymerization of the compound.

Specific examples of such a polyfunctional acrylate compound include:
2,2'-bis [4- (β-methacryloxy) cyclohexyl] propane, 2,2'-bis [4- (β-methacryloyloxydiethoxy) cyclohexyl) propane,
Bis (oxymethyl) tricyclo [5.2.1.0 ^2,5 ] decane dimethacrylate, 1,4-bis (methacryloyloxymethyl) cyclohexane, trimethylolpropane tri (meth) acrylate, neopentyl glycol di (meth) acrylate, 1 , 6-hexanediol di (meth)
Acrylate, 1,3-butanediol di (meth) acrylate, diethylene glycol di (meth) acrylate, 2,2'-bis [4- (methacroyldiethoxy)
Examples thereof include methacrylic acid esters such as phenyl propane and acrylic acid ester compounds, and mixtures thereof. In terms of optical properties, 2,2'-bis [4-
(Β-methacryloyloxyethoxy) cyclohexyl]
Propane, bis (oxymethyl) tricyclo [5.2.1.0
^2,5 ] decane dimethacrylate and 1,4-bis (methacryloyloxymethyl) cyclohexane can be used. Here, (meth) acrylate is a generic term for both acrylate and methacrylate.

Further, in addition to the compound of the general formula (I) as described above, it is possible to use a radically polymerizable monomer generally used as a viscosity modifier in an amount of 10% by weight or less. Examples of such other polymerizable monomer include vinyl compounds such as styrene, chlorostyrene, dichlorostyrene, vinyltoluene, divinylbenzene, vinyl acetate and vinyl chloride, methyl methacrylate, phenyl (meth) acrylate, benzyl (meth) acrylate. , 2-phenoxyethyl (meth) acrylate, cyclohexyl (meth) acrylate, glycidyl (meth) acrylate,
Examples thereof include (meth) acrylic compounds such as epoxy (meth) acrylate and urethane (meth) acrylate, and allyl compounds such as diethylene glycol bisallyl carbonate and diallyl phthalate.

The radical initiator used in the polymerization of these monomers is not particularly limited, and 0.1 wt% to 10 wt% of at least one photosensitizer selected from benzophenone type, thioxanthone type, Michler's ketone type, etc. It suffices if they are blended within the range.

Action By irradiating ultraviolet rays within the amount of complete curing to cause a radical reaction to bring them into a pre-cure state, and by releasing the mold while the shrinkage is small, cracks may occur due to an imbalance in the adhesion force with the mold. It is possible to prevent the distortion. In addition, after removing the mold, post-curing by irradiating ultraviolet rays from both sides of the pre-cure transparent plastic body until it is completely cured, the contraction between both sides is particularly induced equally, and a transparent plastic body with little distortion is manufactured. can do. Also, since both sides are open during post cure, there is no risk of cracking.

Example FIG. 1 shows a plan view (a) and a front sectional view (b) of a liquid injection type used in the present invention. The glass molds 1 and 2 having an optical flat surface having a surface roughness of 0.02 μm or less have disk-shaped spaces formed by silicone rubber spacers 3 and 4 on the outer circumference and the inner circumference, and are fixed by a clamp 5. The materials in Comparative Examples 3 and 4 and Examples were gently injected by a syringe from the casting port 6 and air bubbles were expelled from the degassing port 7 as the end points, and Comparative Examples 3 and 4 were cured by heat, The example was irradiated with UV light to cure.

FIG. 2 shows the manufacturing method of the embodiment in the portion of the sectional view B of FIG.

UV rays are irradiated from both sides of the injected liquid (Fig. 2 (a)) to polymerize to a pre-cure condition (Fig. 2 (b)), and then demolded (Fig. 2 (c)), The pre-cure transparent plastic body 9 is taken out, and thereafter, ultraviolet rays UV are radiated in the state where the surroundings are replaced with N ₂ (FIG. 2 (d)) to obtain a post-cure transparent plastic body 10. The injection-molded transparent plastic bodies of PC and PMMA were used as Comparative Examples 1 and 2, and CR-39 and Table-
Table 1 shows the characteristics and productivity of the transparent plastic body obtained by thermosetting and photocuring the epoxy composition and the methacrylic composition shown in 2. From these results, it was found that the method for producing a photocurable transparent plastic body using a methacrylic composition is the most excellent in terms of heat resistance and productivity, although it is inferior in water absorption.

EFFECTS OF THE INVENTION As described above, in the method for producing a transparent plastic body, the present invention of performing pre-cure in the mold and performing post-cure after demolding can obtain a heat-resistant transparent plastic body with low distortion without cracking. The effect is great in that respect.

[Brief description of drawings]

FIG. 1 (a) is a plan view of a double-sided glass mold used in the present invention, FIG. 1 (b) is a front sectional view taken along the line AA ′ of FIG. 1 (a), and FIG. It is sectional drawing which shows the hardening process of the manufacturing method which paid its attention to the B section of a figure. 1,2 ... Mold, 8 ... Injected UV-curable material, 9 ...
… Precure transparent plastic body, 10 …… Transparent plastic body during post cure.

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Claims (1)

[Claims] 1. A method for producing a transparent plastic body using an ultraviolet curable material, which comprises injecting the ultraviolet curable material into a mold capable of transmitting ultraviolet rays on both sides, and irradiating both sides with ultraviolet rays in an amount of ultraviolet rays within the complete curing range. A method for producing a transparent plastic body which is pre-cured and then post-cured by irradiating ultraviolet rays from both sides of the pre-cured transparent plastic body that has been demolded until it is completely cured.