JPH0729313B2 - Molding method for transparent plastic board - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for molding a transparent plastic plate used for optical disks, magneto-optical disks, thin plastic lenses, and the like.

2. Description of the Related Art As a method of molding a transparent plastic plate used for optical disks, magneto-optical disks, etc., an ultraviolet curable liquid resin is used as a material, and the liquid resin injected into a mold is irradiated with ultraviolet rays to form a transparent film having a desired shape. A method for molding a plastic plate is proposed in Japanese Patent Laid-Open No. 60-112409.

Problems to be Solved by the Invention However, in the conventional molding method, UV irradiation is completed, warpage occurs in the transparent plastic plate taken out from the mold, and optical distortion (birefringence etc.) becomes large. There was a problem. The first cause is that the amount of received ultraviolet rays radiated to the transparent plastic plate in the mold is large on the surface side of the transparent plastic plate and small on the inside side, and as a result, the difference in the photopolymerization rate in the thickness direction of the transparent plastic plate is Is considered to occur and mechanical distortion or optical distortion occurs. The second cause is that when completely cured in the mold,
It is conceivable that the resin inside contracts and causes imbalance in the adhesion between the resin and the die, resulting in mechanical strain.

In order to reduce such mechanical distortion and optical distortion,
Although it is conceivable to reduce the irradiation amount of ultraviolet rays, in this case, it is necessary to irradiate ultraviolet rays for a long time, which causes a problem that production efficiency is deteriorated.

In addition, when the liquid resin is cured by irradiating ultraviolet rays from only one side, there is a problem that the mechanical strain and the optical strain are more remarkable.

Means for Solving the Problems The first invention is to inject an ultraviolet curable liquid resin into an ultraviolet permeable mold, irradiate the liquid resin with a light ray having a wavelength of more than 300 nm, and then perform precure. After demolding
It is characterized in that both sides of the incompletely cured transparent plastic plate obtained by the pre-cure are irradiated with a light beam having a wavelength of 300 nm or less to perform post-cure.

A second aspect of the invention is obtained by injecting an ultraviolet curable liquid resin into an ultraviolet permeable mold, irradiating the liquid resin with a first ultraviolet ray to perform pre-cure, and then removing the mold, and then obtaining the pre-cure. It is characterized in that both sides of an incompletely cured transparent plastic plate are irradiated with a second ultraviolet ray for post-curing, and the irradiation amount of the first ultraviolet ray is smaller than that of the second ultraviolet ray. .

Action According to the first aspect of the invention, a light beam having a wavelength of more than 300 nm is irradiated during pre-cure to cure the liquid resin in the mold to a certain degree of curing state. Since the transmittance of light having a wavelength of more than 300 nm to the liquid resin is good, it is possible to uniformly cure the entire liquid resin, prevent mechanical strain and optical strain from occurring, and perform precure. . Further, since the transparent plastic plate in the pre-cure state is taken out from the mold, it is possible to prevent the occurrence of mechanical strain due to the unbalanced adhesion between the plate and the mold. Furthermore, the post-cure performed after demolding has a wavelength on both sides of the incompletely cured transparent plastic plate obtained by pre-cure.
Since irradiation is performed by irradiating light of 300 nm or less, contraction between both surfaces can be equally induced and the occurrence of mechanical strain can be reduced,
Since the UV irradiation is performed after the pre-cure, the occurrence of optical distortion can be reduced. Moreover, in the post cure, the light having a wavelength of 300 nm or less is irradiated, so that the transparent plastic plate can be completely cured in a short time.

According to the second aspect of the invention, the liquid resin in the mold is cured to a certain degree of curing state by irradiating the ultraviolet ray in an amount smaller than the irradiation amount of the ultraviolet ray irradiated in the post-cure during the pre-cure. Therefore, the photopolymerization action does not occur rapidly and the entire liquid resin is gradually hardened, so that the occurrence of mechanical strain or optical strain can be reduced and precuring can be performed. Further, since the transparent plastic plate in the pre-cure state is taken out from the mold, it is possible to prevent the occurrence of mechanical strain due to the unbalanced adhesion between the plate and the mold. Furthermore, post-curing performed after demolding is performed by irradiating both sides of the incompletely cured transparent plastic plate obtained by pre-cure with ultraviolet rays in an amount higher than the irradiation amount of ultraviolet rays irradiated during pre-cure. Can be induced equally and the occurrence of mechanical strain can be reduced, and the generation of optical strain can be reduced because of ultraviolet irradiation after pre-cure. Moreover, in the post-cure, the transparent plastic plate can be completely cured in a short time because the ultraviolet irradiation is performed in an amount larger than the ultraviolet irradiation amount in the pre-cure.

First Embodiment A first embodiment of the present invention will be described with reference to the drawings. This first
The embodiment relates to a method of molding a transparent plastic plate for an optical disc, and uses a mold 1 shown in FIGS. 1 and 2 at the time of pre-cure. The mold 1 is composed of a pair of transparent glass plates 1a and 1b having optical flat surfaces, a cylinder rubber spacer 1c, a clamp 1d, and the like, and an ultraviolet curable liquid resin 2a is poured into the inside (first part).
Figure).

As the ultraviolet curable liquid resin 2, a compounded composition with a polyfunctional acrylate compound is suitable. Specific examples of the polyfunctional acrylate compound include 2,2′-bis [4- (β-methacryloyloxyethoxy) cyclohexyl] propane and bis (oxymethyl) tricyclo [5.
2.1.0 ^2,5 ] decane dimethacrylate and 1,4-bis (methacryloyloxymethyl) cyclohexane.

In addition to the above-mentioned polyfunctional acrylate compound, a radical polymerization monomer which is generally used as a viscosity modifier is added.
It is possible to use it in the range of not more than wt%. Examples of such other polymerized monomers include vinyl compounds such as styrene, chlorostyrene, dichlorostyrene, vinyltoluene, divinylbenzene, vinyl acetate and vinyl chloride,
Examples thereof include (meth) acrylic compounds such as methyl methacrylate and phenyl (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 a photosensitizer selected from benzophenone-based, thioxanthone-based, Michler's ketone-based, etc. is added in the range of 0.1% ^WT to 10 ^WT %. I'm good.

In this embodiment, at least two kinds of the photosensitizers are blended, and one of them is used which has a sensitizing effect in the wavelength region of 300 nm or more.

After the UV curable liquid resin 2a as described above is poured into the UV permeable mold 1, as shown in FIG.
UV ₁ is irradiated from both sides. The ultraviolet rays UV ₁ are ultraviolet rays on the long wavelength side in which light rays having a wavelength of 300 nm or less are cut, and have good transparency. Therefore, liquid resin
The amount of light received on the surface side and inside of 2a is approximately equal,
With the help of a photosensitizer with a sensitizing effect in the above wavelength range,
The entire liquid resin 2a is hardened substantially uniformly to form the transparent plastic plate 2b in the pre-cure completed state.

Next, as shown in FIG. 3, the mold is removed, and the incompletely cured transparent plastic plate 2b obtained by pre-cure is taken out, and post-cure is performed as shown in FIG. Post curing is in a state of replacing the ambient in N ₂ gas is carried out by irradiating the conventional ultraviolet UV ₂ on both surfaces of the transparent plastic plate 2b. By irradiating with this ultraviolet ray UV ₂ , the transparent plastic plate 2c which is completely cured in a short time can be obtained.

At the time of post cure, for example, ultraviolet rays on the short wavelength side in which light rays of 300 nm or more are cut may be irradiated.

In the first embodiment, both surfaces of the liquid resin 2a are irradiated with the ultraviolet ray UV ₁ on the long wavelength side during the precure, but it is also possible to irradiate the ultraviolet ray UV ₁ on only one surface of the liquid resin 2a. For example, when the mold 1 including the stamper and the transparent glass plate is used, the ultraviolet rays UV ₁ are applied to only one surface of the liquid resin 2a.

Next, a second embodiment of the present invention will be described. The ultraviolet curable liquid resin 2a and the mold 1 are the same as those used in the first embodiment. However, it is not necessary to use the photosensitizer having the sensitizing effect in the wavelength region of 300 nm or more in the first embodiment.

At the time of pre-cure, the liquid resin 2a is irradiated with low energy ultraviolet rays. That is, the irradiation amount of ultraviolet rays at the time of pre-cure is remarkably reduced as compared with the irradiation amount of ultraviolet rays at the time of post-cure, for example, 1/10. Therefore, in the second embodiment,
The time required for precure becomes relatively long. As a result, the liquid resin 2a is gradually hardened, and the whole is hardened substantially uniformly.

The next post-cure is performed by irradiating both sides of the incompletely cured transparent plastic plate 2b that has been demolded after completion of the pre-cure, with substantially the same post-cure as in the first embodiment. Work is done. By this post-cure, the completely cured transparent plastic plate 2c can be obtained in a short time.

EFFECTS OF THE INVENTION According to the present invention, it is possible to mold a transparent plastic plate with low mechanical strain and optical strain with high efficiency.

[Brief description of drawings]

1 to 4 show respective molding steps according to an embodiment of the present invention, FIG. 1 is a sectional view showing a state where liquid resin is poured into a mold, FIG. 2 is a sectional view showing a state of pre-cure, FIG. 3 is a sectional view showing a demolded state, and FIG. 4 is a sectional view showing a post-cure state. 1 …… Type 2a …… Liquid resin 2c …… Transparent plastic plate UV ₁ , UV ₂ … UV rays.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location B29K 105: 24 105: 32 B29L 11:00 17:00

Claims (2)

[Claims] 1. A UV-curable liquid resin is poured into a mold capable of transmitting UV rays, and the liquid resin is irradiated with a light ray having a wavelength of more than 300 nm to perform pre-cure, and then demolded, and then obtained by the pre-cure. A method for molding a transparent plastic plate, which comprises post-curing by irradiating a light beam having a wavelength of 300 nm or less on both surfaces of the incompletely cured transparent plastic plate. 2. An ultraviolet-curable liquid resin is poured into a mold capable of transmitting ultraviolet rays, the liquid resin is irradiated with a first ultraviolet ray to perform pre-cure, and then the mold is removed, followed by the pre-cure. Transparent, characterized in that both sides of an incompletely cured transparent plastic plate are irradiated with a second ultraviolet ray for post-curing, and the irradiation amount of the first ultraviolet ray is smaller than that of the second ultraviolet ray. Molding method for plastic plate.