JPH0687318B2 - Optical transparent substrate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical transparent substrate, and particularly to an optical transparent substrate having a large projected area and a thin thickness, which exhibits a good appearance by injection molding, such as an optical substrate. Disc substrate.

[Conventional technology and its problems]

Various molding methods for producing an optical transparent substrate using a transparent thermoplastic resin are known. Among them, the injection molding method is the most industrially utilized means in terms of productivity, that is, molding of a large amount of products at a high production rate.

By the way, like an optical disk substrate, which is a kind of optical transparent substrate, its product shape has a large projected area, and
If it is thin, it is difficult to manufacture it by the injection molding method as described in detail below.

That is, many of the transparent thermoplastic resins such as polymethylmethacrylate (PMMA), polycarbonate (PC), and poly-4methylpentene-1 (PMP) have high viscosity, but in injection molding, the resin temperature must be raised. Viscosity must be reduced and fluidity must be improved. However, even if the projected area is large, the thin one has a small amount of resin,
Therefore, the residence time of the resin in the injection molding machine becomes long. In addition, mechanical shearing is likely to occur because the material passes through a thin portion at a high speed in the mold. In this way, resins that stay for a long time under high temperature due to external heating and experience internal heating such as shearing heat will naturally decompose and deteriorate, weakening the mechanical strength of the resulting product and mixing burns. However, there is a problem in that the optical disk substrate cannot be used as an optical disk substrate.

Another problem is the fact that minute voids are often generated in the manufactured disk substrate. It can be said that this phenomenon can be said to be applicable to injection molding in general, but in the method of predrying the material resin and bleeding air in the mold, which has been said to be effective for solving this type of problem, the low fluidity resin described above is used. It is not sufficient to manufacture a disk substrate by high-temperature injection molding using.

Another problem is that the pit portion and the guide groove of the disk are not accurately transferred to the disk substrate.

Yet another problem is that a phenomenon called flashing may occur on the surface or inside the disk substrate. Here, flashlash is a phenomenon that produces an irregularly shaped cloud along the radial direction of the disk, and is a phenomenon completely different from silver streak, which has a relatively clear streak shape. Although such a phenomenon may be less problematic in an ordinary molded product, it is absolutely not necessary in an application such as a transparent substrate. This phenomenon often occurs even if it takes sufficient time to pre-dry the material resin, which is said to be effective for preventing ordinary thrust leak, and is a headache for those skilled in the art.

Still another problem is that the transparent substrate obtained by molding is colored yellow.

[Problems to be solved by the invention]

In view of the current situation, the inventors of the present invention do not deteriorate mechanical properties even when injection-molding a transparent substrate for optics, in particular, an optical disc substrate having a large projected area and a small thickness, and a void is not generated. However, the present invention has been achieved as a result of repeated studies on whether or not a product having good transfer of the bit or the guide groove, good flash generation and no coloring can be obtained.

[Means for solving problems]

That is, the present invention is a β- (3,5-di-ter-butyl-4-hydroxyphenyl) propionic acid alkyl ester (I) in which the alkyl group forming the ester portion is an alkyl group having 10 or less carbon atoms, It is a transparent substrate for optics characterized by comprising a copolymer (II) of ethylene and a cyclic olefin.

(Function) In the present invention, a copolymer (II) of ethylene and a cyclic olefin which is a transparent thermoplastic resin is used. Examples of the copolymer of ethylene and cyclic olefin include copolymers of cyclic olefin such as norbornene, tetracyclododecene, and methyltetracyclododecene and ethylene (for example, JP-A-60-168708). Bulletin,
61-115912, 61-115916, 61-120816
(See the official gazette).

In the present invention, an ethylene / cyclic olefin copolymer is used as the transparent thermoplastic resin as described above,
A transparent thermoplastic resin having a particularly excellent effect by blending the β- (3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid alkyl ester as described above has a glass transition temperature (Tg). Is relatively high, that is, above about 100 ° C, especially above 120 ° C.
That is, when the Tg is high, the resin temperature of the resin surface that comes into contact with the mold when it flows into the mold by injection molding decreases, and the surface solidifies relatively quickly. Therefore, it is presumed that the volatile components and the like, which are presumed to be due to the oxidative deterioration of the resin, are trapped inside the resin, which causes the flashing described above. That is, as the Tg is higher, the surface is solidified more quickly and the flash becomes more remarkable. Therefore, when the present invention is applied to such a resin, the flash is prevented and useful.
Therefore, preferably the resin used is a copolymer of ethylene and cyclic olefin.

β- (3,5-di-tert-butyl-4-hydroxyphenyl)
The alkyl group of alkyl propionate has carbon number
It is most preferably 10 or less, especially 5 or less, and more preferably a methyl group. Even with the same alkyl ester, for example, the octadecyl group with 18 carbon atoms, which is usually most likely to be used, has a higher silver streak prevention, flash prevention, void prevention, hue and bit transferability than a methyl group. It is inferior in both respects. In addition, none of the other antioxidants outperforms the constitution of the present invention in all of these points.

Although it is unclear why the composition of the present invention is excellent in hue without flashing and the like, it is presumed by the present inventors that a phenolic antioxidant having a structure as used in the present invention is highly effective. Tg acts as a plasticizer on transparent thermoplastic resin, lowers the apparent Tg at least near the resin surface, and reduces the volatile components on the resin surface that come into contact with the mold (resin generation and degradation caused by resin degradation). It is also considered that one of the reasons is that the boiling point substances and trace monomers originally contained in the resin) can easily escape from the surface.

β- (3,5-di-tert-butyl-4-hydroxyphenyl)
The compounding amount of the alkyl propionate is 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight, and more preferably 0.1 to 1 part by weight with respect to 100 parts by weight of the resin.

The range of the compounding amount of the compound is such that if the compounding amount is too large, the initial physical properties of the transparent substrate cannot be kept stable for a long period of time, and if it is too small, the desired effect of the present invention is not easily expressed. Or, even if it appears, it is set because it has no practical effect.

In the resin composition of the present invention, when using a transparent resin produced with a halogen-containing catalyst such as a Ziegler catalyst, halogen contained in the residual catalyst residue does not damage the molding machine, A halogen scavenger should be used in combination.

The present invention will be described by taking an optical disk substrate as an example. First, a resin, the above-mentioned compound, and if necessary, an amount of another stabilizer which does not impair the effects of the present invention, a ribbon blender, a tumbler blender, and a Henschel mixer. Mix with or after mixing with an extruder, Banbury mixer, two rolls, etc. or dissolve in hydrocarbon or aromatic solvent and mix with polymer solution, then single screw extruder, vent type extruder, two Screw extruder, triple screw extruder, conical twin screw extruder, co-kneader, platen dictator, mixer, twin screw conical screw extruder, planetary screw extruder, gear type extruder, screwless extruder, etc. Injection molding is performed by using a metal mold for disk molding (also a set of stampers for forming information bits and guide grooves By the free) go-between for molding.

The gate used in the injection molding may be various known ones, but from the viewpoint of shrinkage and warpage, a center pin gate or a center disk gate, preferably a gate diameter of 3 m
It is preferable to use a center pin gate of m or less, especially 0.5 to 2.0 mm, and a center disk gate of 1 mm or less, especially 0.2 to 0.8 mm.

The disk substrate obtained by injection molding is then formed with a recording layer or a metal layer for reflecting a laser beam by a known method such as a vapor deposition method or a sputtering method, and further provided with a protective layer if necessary. Will be completed.

〔Example〕

The contents of the present invention will be shown below by way of preferred examples, but the present invention is not limited to these examples unless otherwise specified.

Example 1 Melt flow rate at a load of 2.15 kg and a temperature of 260 ° C. (M
FR: ASTM D 1238) is 35g / 10min ethylene-tetracyclododecene copolymer (ethylene content 60mol%, intrinsic viscosity [η]: 0.45d1 / g (135 ° C, decalin solvent)) and tetrakis [methylene -3- (3,5-di-tert-butyl-4-
Hydroxyphenyl) propionate] methane (A): , Methyl-β- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate (B) and zinc stearate (C) are mixed, mixed with a Hensiel mixer, and then screwed with a screw diameter of 40 mm. The pellets were made using an extruder at a temperature of 230 ° C.

Using this pellet as a raw material, a Sumitomo Heavy Industries P40 / 25A injection molding machine and a center disk gate mold (mold with a stamper for forming information pits) are used.
A disk substrate having a diameter of 80 mm and a thickness of 1.0 mm was molded at a temperature of ° C, and the items shown in Table 1 were evaluated. In addition, these items were visually evaluated, and the evaluation standard was set as bad 1 → 5 good.

The compounding amount of the stabilizer is shown in parts by weight with respect to 100 parts by weight of the raw material resin.

Example 2 Instead of (A), n-octadecyl-β- (3,5-di-tert
The procedure was as in Example 1 except that -butyl-4-hydroxyphenyl) propionate (D) was used. The results are shown in Table 1.

Example 3 Instead of (A), 2,2'-oxamide bis [ethyl-3-
(3,5-Di-tert-butyl-4-hydroxyphenyl) propionate] (E) was used, but the procedure was the same as in Example 1. The results are shown in Table 1.

Example 4 In Example 1, tetrakis [methylene-3- (3,5
-Di-tert-butyl-4-hydroxyphenyl) propylnate] methane (A) and zinc stearate (C)
The same procedure as in Example 1 was carried out except that No. The results are shown in Table 1.

Comparative Example 1 The procedure of Example 1 was repeated except that (D) was used instead of (B). The results are shown in Table 1.

Comparative Example 2 The procedure of Example 1 was repeated except that the amount of (A) was increased without using (B). The results are shown in Table 1.

Comparative Example 3 The procedure of Example 3 was repeated, except that the amount of (E) was increased without using (B). The results are shown in Table 1.

Comparative Example 4 Instead of (B) in Example 1, 1,3,5-trimethyl-
The procedure of Example 1 was repeated except that 2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene (F) was used. The results are shown in Table 1.

Comparative Example 5 The procedure of Example 1 was repeated except that 3,5-di-tert-butyl-4-hydroxytoluene (G) was used in place of (B) in Example 1. The results are shown in Table 1.

EFFECTS OF THE INVENTION According to the present invention, mechanical properties are excellent, voids are not generated, flashing is not generated, coloring is not generated, and transferability of a stamper pattern in a mold, for example, a bit part of a disk or a guide is provided. It exhibits an excellent effect that the groove can be accurately transferred.

Therefore, the optical disk substrate, the large-sized display substrate, the transparent electrode substrate, the transparent electric circuit substrate, and the CRT cover for VD work have a large projected area but can be suitably used for manufacturing a thin optical transparent substrate product.

Claims (6)

[Claims] 1. A β- (3,5-di-tert-, wherein the alkyl group forming the ester moiety (I) is an alkyl group having 10 or less carbon atoms.
A transparent optical substrate comprising an alkyl ester of butyl-4-hydroxyphenyl) propionic acid and (II) a copolymer of ethylene and a cyclic olefin. 2. The optical transparent substrate according to claim 1, wherein the alkyl group is an alkyl group having 5 or less carbon atoms. 3. A glass transition temperature of a copolymer of ethylene and a cyclic olefin is 100 ° C. or higher.
Item 2. The optical transparent substrate according to Item 2 or Item 2. 4. The optical transparent substrate according to any one of claims 1 to 3, wherein the optical transparent substrate has a large projected area and a small thickness. 5. The optical transparent substrate according to any one of claims 1 to 4, wherein the optical transparent substrate is an optical disk substrate. 6. The optical transparent substrate according to any one of claims 1 to 5, which is manufactured by injection molding.