JP2504958B2 - 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 injection molding as described in detail below.

That is, transparent thermoplastic resins such as polymethylmethacrylate (PMMA), polycarbonate (PO), poly-4
Methylpentene 1 (PMP) and the like have high viscosities, but in injection molding, the resin temperature must be raised to lower the viscosity and improve the fluidity. But,
Even if the projected area is large, the resin having a small thickness has a small amount of resin, and therefore, the residence time of the resin in the injection molding machine becomes long. Further, since the steel sheet passes through a thin portion at a high speed in the mold, mechanical shear insulation is likely to occur. In this way, a resin that stays at a high temperature for a long time due to external heating and experiences internal heating such as shearing heat will naturally decompose and deteriorate, weakening the mechanical strength of the obtained 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 with the means of predrying the material resin and the method of venting air to the mold, which has been said to be effective in solving this type of problem, 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 completely different phenomenon from the siriburst leak, which shows 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 is
For example, it often occurs even when it takes a sufficient time to pre-dry the material resin which is said to be effective for preventing ordinary silver streaks, which 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 generated. However, the present invention has been achieved as a result of repeated studies on whether or not a product having good transferability of bits or guide grooves and free of flashing can be obtained.

[Means for solving problems]

That is, the present invention is characterized by comprising a transparent thermoplastic resin composition containing a phenolic antioxidant (a) having a cycloalkyl group and a copolymer (b) of ethylene and a cyclic olefin. Transparent substrate.

[Action]

As the base resin of the thermoplastic resin composition, a copolymer (b) of ethylene and a cyclic olefin is used. Examples of such a copolymer (b) include copolymers of cyclic olefins such as norbornene, tetracyclododecene and methyltetracyclododecene and ethylene (for example, JP-A-60-168708 and 61-115912). , Id 61-11
5916 and 61-120816).

The ethylene-cyclic olefin copolymer (b), which is a transparent thermoplastic resin particularly useful in the present invention, has a relatively high glass transition temperature (Tg), that is, about 100 ° C.
Those above, especially above 120 ℃. That is, T
When the g is high, the resin temperature of the resin surface that comes into contact with the mold when flowing 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, the resin preferably used is a copolymer of ethylene and cyclic olefin.

The cycloalkyl group-containing phenol-based antioxidant can be produced by nuclear-substituting the cycloalkyl group at a position below the hydroxyl group of the phenol ring portion of a known phenol-based antioxidant.

Particularly preferred as the present invention are compounds represented by the following formula.

(R ^{1 to} R ⁴ are hydrogen or an alkyl group and may be the same or different.) The cycloalkyl group-containing phenolic antioxidant may be a commercially available product, for example, 2,2 ′. -Dihydroxy-3,3'-dicyclohexyl-5,5'-dimethyl-diphenylmethane (Vulkanox ZKF, Bayer), 2,2'-
Dihydroxy-3,3'-di (α-methylcyclohexyl) -5,5'-dimethyl-diphenylmethane (Nonox WS
P, Seiko Chemical Co., Ltd.), 1,1-bis (4-hydroxyphenyl) cyclohexane (Nonox WSL, Seiko Chemical Co., Ltd.), 2-
There is (1-methylcyclohexyl) -4,6-dimethylphenol (Antigene W, Sumitomo Chemical Co., Ltd.). Among these, Vulkanox, ZKF and Nonox WSP are preferable.

It is unclear why the composition of the present invention is excellent in hue without flashing and the like, but it is estimated by the present inventors that a phenol-based 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. For this reason, phenolic antioxidants having a relatively low molecular weight, that is, a molecular weight of 600 or less are particularly preferable in the present invention.

The blending ratio of the phenolic antioxidant to the transparent thermoplastic resin is 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight, and more preferably 0.1 to 100 parts by weight of the resin.
~ 1 part by weight.

Incidentally, the range of the compounding amount of the above compound is such that if too much is compounded, the initial physical properties of the transparent substrate cannot be stably maintained for a long period of time, and if it is too small, the effect of the present invention is exhibited. It was set because it is difficult or even if it appears, it is not effective enough to withstand practical use.

In the resin composition of the present invention, when a transparent resin produced using a halogen-containing catalyst such as a Ziegler catalyst is used, the halogen contained in the remaining 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 and the above compound, and optionally, an amount of other stabilizer that does not impair the effects of the present invention are mixed with a ribbon blender, a tumbler blender, a Henschel mixer, or the like, or an extruder, Banbury mixer, two rolls, or the like after mixing. Melt-mix with or dissolve in hydrocarbon or aromatic solvent and mix with polymer solution, then single screw extruder, vent type extruder, two-screw extruder, three-screw extruder, conical two-screw extruder Machines, co-kneaders, plate equators, mixed extruders, twin-screw conical screw extruders, planetary screw extruders, gear-type extruders, screwless extruders, etc. (Including a set of stampers for forming bits and guide grooves).

Although various known gates may be used for the injection molding, a center pin gate or a center disk gate, preferably a gate diameter, is used in view of shrinkage and warpage.
It is preferable to use a center pin gate of 3 mm 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 Ethylene / tetracyclododecene copolymer having a melt flow rate (MFR: ASTM D 1238) of 35 kg / 10 min at a load of 2.15 kg and a temperature of 260 ° C. (ethylene content: 60 mol%, glass transition temperature Tg: 160 ° C.) ), Tetrakis [methylene-3
-(3,5-Di-tert-butyl-4-hydroxyphenyl) propionate] methane (A), 2,2'-dihydroxy-3,3'-dicyclohexyl-5,5'-dimethyl-diphenylmethane (B) And zinc stearate (C) are mixed and mixed with a Henschel mixer, then the screw diameter is 40
The pellets were made at a temperature of 230 ° C using a mm twin screw extruder.

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) were used.
A disk substrate having a diameter of 80 mm and a thickness of 1.0 mm was molded at a temperature of 0 ° C., and the items shown in Table 1 were evaluated. In addition, these items were evaluated visually, and the evaluation criterion was 1-5 bad.

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 The procedure of Example 1 was repeated except that 2,2′-dihydroxy-3,3′-di (α-methylcyclohexyl-5,5′-dimethyl-diphenylmethane (D) was used instead of (B). The results are shown in Table 1.

Comparative Example 1 The procedure of Example 1 was repeated except that (B) was not used in Example 1 and the amount of (A) was increased. The results are shown in Table 1.

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

Comparative Example 3 Instead of (A) in Comparative Example 1, 2,2'-oxamide bis [ethyl-3- (3,5-di-tert-butyl-4]
-Hydroxyphenyl) propionate] (F). The results are shown in Table 1.

Comparative Example 4 The same procedure as in Example 1 was carried out except that (E) was used instead of (B). The results are shown in Table 1.

Comparative Example 5 In Example 1, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene (G) is used in place of (B). Others went the same way. The results are shown in Table 1.

Comparative Example 6 Instead of (B) in Example 1, 3,5-di-tert-
The procedure of Example 1 was repeated except that butyl-4-hydroxytoluene (H) was used. 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, and transferability of a stamper pattern in a mold, for example, a bit part of a disk or a guide groove is accurately formed. It has an excellent effect that it can be 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 (9)

(57) [Claims] 1. An optical system comprising a transparent thermoplastic resin composition containing a phenolic antioxidant (a) having a cycloalkyl group, and a copolymer (b) of ethylene and a cyclic olefin. Transparent substrate. 2. The phenolic antioxidant (a) has a molecular weight of
The optical transparent substrate according to claim 1, which is a phenolic antioxidant of 600 or less. 3. The optical transparent material according to claim 1 or 2, wherein the phenolic antioxidant (a) has a cycloalkyl group which is nuclear-substituted at a position other than the hydroxyl group of the phenol ring. substrate. 4. The optical transparent substrate according to any one of claims 1 to 3, wherein the phenolic antioxidant (a) is represented by the following formula. (R ¹ , R ² , R ³ and R ⁴ are hydrogen or an alkyl group and may be the same or different) 5. The phenolic antioxidant represented by the general formula (I) is 2,2'-dihydroxy-3,3'-dicyclohexyl-5,5'-dimethyl-diphenylmethane or 2,2 '.
An optical transparent substrate according to claim 4, which is -dihydroxy-3,3'-di (α-methylcyclohexyl) -5,5'-dimethyl-diphenylmethane. 6. The glass transition temperature of the copolymer (b) is 100 ° C.
The optical transparent substrate according to any one of claims 1 to 5, which is as described above. 7. The optical transparent substrate according to any one of claims 1 to 6, wherein the optical transparent substrate has a large projected area and a small thickness. 8. The optical transparent substrate according to claim 1, wherein the optical transparent substrate is an optical disk substrate. 9. An optical transparent substrate according to any one of claims 1 to 8, which is manufactured by injection molding.