JP2504959B2 - 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.

[Prior Art 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, if the product shape is such that the projected area is large and the thickness is thin like the optical disk substrate which is one kind of the optical transparent substrate, the following is manufactured by injection molding. It's quite difficult as detailed.

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 explained 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 a good transfer property of a bit or a guide groove, and having neither flashing nor coloring is obtained.

[Means for solving problems]

That is, the present invention provides a copolymer (a) of ethylene and a cyclic olefin, and a hydrocarbon compound having a molecular weight of 200 to 3000, which is liquid at room temperature, in an amount of 0.1 to 0.9 part by weight per 100 parts by weight of the copolymer (a). A transparent substrate for optics comprising a transparent thermoplastic resin composition containing (b).

[Work]

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.

It is completely unpredictable that the object of the present invention can be achieved by blending a small amount of a hydrocarbon compound having a molecular weight of 200 to 3000 and being liquid at room temperature. According to the constitution of the present invention, it is unclear why the object can be achieved, but according to the inference by the present inventors, a hydrocarbon compound liquid at room temperature having a molecular weight of 200 to 3000 is a transparent thermoplastic resin having a high Tg. It can be considered that one factor is that the resin is plasticized by being dispersed in the resin, and plays a role of lowering an apparent Tg in a microscopic view. As a result, the solidification of the resin surface in contact with the injection mold is slightly delayed, and the volatile components (decomposition of the resin,
Low boiling point substances generated by deterioration and trace monomers originally contained in the resin) can be easily reversed from the surface,
It is considered to prevent voids and flashing and improve the transferability of bits.

However, at this time, if the hydrocarbon compound is used in an excessively large amount, the plasticization tendency of the entire resin composition becomes strong, and the strength and heat resistance of the transparent substrate, especially as a transparent substrate for optical applications are impaired. Is the target transparent thermoplastic resin
0.1 to 0.9 parts by weight per 100 parts by weight, preferably 0.6 to 0.9
A range of parts by weight is preferred. It is one of the features of the present invention that the object can be achieved with such an extremely small amount of compounding. That is, according to the conventional knowledge, the amount of the plasticizer used for modifying or plasticizing the resin was several percent or more, but in the present invention, only the solidification time of the resin surface in contact with the mold at the time of injection molding is required. Therefore, the object can be achieved with a small amount of the above-mentioned compounding. One of the reasons why the amount can be achieved with such an amount is that the hydrocarbon compound has a low molecular weight, so that the mobility is high and the ratio and the hydrocarbon compound easily migrate to the resin surface during molding.
It is also considered that the effect of modifying the resin surface in contact with the mold is concentrated.

For this reason, in the present invention, those having a relatively low molecular weight, that is, a molecular weight of about 300 to 1000 are particularly preferable.

Examples of the hydrocarbon compound include aliphatic hydrocarbons having a straight chain or a side chain, alicyclic hydrocarbons, biphenyl, polyphenyl or condensed polycyclic aromatic aliphatic hydrocarbons and aromatic hydrocarbons. Partially hydrogenated compounds, or those obtained by substituting an alkyl group, an aryl group, an aralkyl group, or the like with a mother of any of these hydrocarbons can be exemplified. These hydrocarbons may be either natural products or synthetic products. More specifically, dodecylbenzene, polyalkylbenzene by-produced during the production of dodecylbenzene oil, dibenzylbenzene, alkylnaphthalene, polyphenylalkane oil, alkylated tetralin, ethylene oligomer, propylene oligomer, ethylene-propylene oligomer, polybutene. Examples include olefin polymers such as oligomers, fluid paraffin, squalane, mineral oil, and the like, but of course, hydrocarbon compounds not exemplified here can also be used.

In addition to the above, various antioxidants may be used in the present invention in order to measure the heat resistance stability of the resin. Furthermore, when using a transparent resin made of a halogen-containing catalyst such as Ziegler catalyst, a halogen scavenger should be used together so that the halogen contained in the residual catalyst residue does not damage the molding machine. Is.

The present invention will be described by taking an optical disk substrate as an example.
First, the resin and the above compound, if necessary, the other stabilizer in an amount that does not impair the effects of the present invention are mixed by a ribbon blender, a tumbler blender, a Henschel mixer, or the like, or an extruder, Banbury mixer, two rolls are mixed. 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, co-kneader, platey eater, mixer, twin-screw conical screw extruder, planetary screw extruder, gear type extruder, screwless extruder Injection molding is performed using a machine and the like, and molding is performed using a metal mold for disk molding (including a stamper for forming information 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), squalane (molecular weight 392) (B) and zinc stearate (C) were mixed and mixed with a Henschel mixer. A pellet was prepared at a temperature of 230 ° C. using a twin screw extruder having a screw diameter of 40 mm.

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 (Production of hydrocarbon compound) Volume 50 equipped with thermometer, stirrer, condenser and dropping funnel
In a 0 ml 4-neck flask, mix xylene (m-xylene 45
%, Ethylbenzene 51%, o- and p-xylene 4
%) 79.5 g (0.75 mol) of powdered anhydrous aluminum chloride 3 g is added under a nitrogen atmosphere. While stirring, 283.5 g (1.5 g mol) of a tricyclo [5.2.1.0 ^2,6 ] deca-3-ene-containing fraction (purity 70.9%) was added with a dropping funnel, and the mixture was heated with stirring at 60 ° C. for 2 hours. Methanol was added to terminate the reaction, and the reaction solution was washed until it became neutral. Then the pot temperature 150
Unreacted materials are removed at ℃ and pressure of 20mmHg, and Gardner hue 1
49 g of a viscous liquid having a viscosity of 10,800 cp at 0 and ²⁵ ° C. and a refractive index (n _D ²⁵ ) of 1.5482 was obtained. As a result of the analysis, tricyclo (5.2.1.
0 ^2,6] dec-3-ene: 1/1 adduct 59 wt% of mixed xylenes, the 2/1 adduct 33% by weight, can consist of other 8% by weight of divide.

Then, a hydrogenation reaction is performed on this viscous liquid to obtain a viscosity of 25 ° C.
39 g of a viscous liquid having a refractive index (n _D ²⁵ ) of 1.5028 and 10600 cp was obtained.
As a result of analysis, tricyclo [5.2.1.0 ^2,6 ] deca-3-ene: 59% by weight of 1/1 addition hydrogenated product of mixed xylene, 33% by weight of 2/1 addition hydrogenated product, and 8% by weight of others Average molecular weight of 32
It was found to be a hydrocarbon compound of 0.

(Test Example) The same procedure was carried out except that the hydrocarbon compound (D) obtained above was used instead of (B) in Example 1. The results are shown in Table 1.

Example 3 (Production of Hydrocarbon Compound) An ethylene / α-olefin random copolymer was continuously produced using a 4-glass reactor equipped with a stirring blade.
That is, hexane is 2 per hour, vanadium trichloride hexane solution (16 mmol /) per hour, ethylaluminum sesquichloride solution in hexane (96 mmol /)
Continuously feeding 1 per hour into the reactor from the top of the reactor,
On the other hand, the reaction liquid is continuously withdrawn from the lower part of the reactor so that the reaction liquid in the reactor is always 2. Also, a mixed gas of ethylene, propylene and hydrogen (44 ethylene / hour, 41 propylene / hour, 220 hydrogen / hour) is supplied from the upper part of the reactor. The reaction temperature was adjusted to 35 ° C. by circulating hot water in the jacket installed outside the reactor.
A small amount of methanol was added to the reaction liquid extracted from the lower part of the reactor to stop the reaction, and then the reaction liquid was washed with water three times. Then, the solvent hexane and low-boiling products were removed by distillation at a pot temperature of 100 ° C. under reduced pressure of 0.1 mmHg to obtain an ethylene / propylene random copolymer liquid at ordinary temperature.

The resulting ethylene-propylene random copolymer ¹³
The ethylene content measured by C-NMR method is 54 mol%,
When measured by gel permeation chromatography, n was 450 and w / n was 1.8. No melting point was observed with a differential scanning calorimeter, and melting energy was 0 cal.
It was / g.

(Test Example) The same procedure was carried out except that the random copolymer (E) obtained above was used instead of (B) in Example 1. The results are shown in Table 1.

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

Comparative Example 2 In Example 1, n-decane (F) was used instead of (B).
The same was done except using. The results are shown in Table 1.

Comparative Example 3 Instead of (B) in Example 1, polyethylene wats
Cus (Hijets 110P, Mitsui Petrochemical Industry) (G)
The same was done except using. Table 1 shows the results.

Comparative Example 4 The same procedure as in Example 1 was carried out except that a low crystalline ethylene / α-olefin copolymer (Tufmer P0680, Mitsui Petrochemical Industry) (H) was used instead of (B). The results are shown in Table 1.

EFFECTS OF THE INVENTION According to the present invention, there are no voids and no flushing, and the excellent transferability of the stamper pattern in the mold, for example, the bit part of the disk and the guide groove can be accurately transferred. Indicates.

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)

(57) [Claims] 1. A copolymer (a) of ethylene and a cyclic olefin, and a hydrocarbon compound having a molecular weight of 200 to 3000 and having a molecular weight of 200 to 3000 in an amount of 0.1 to 0.9 part by weight per 100 parts by weight of the copolymer (a). An optical transparent substrate comprising a transparent thermoplastic resin composition containing (b). 2. The hydrocarbon compound (b) has a molecular weight of 300 to 100.
The optical transparent substrate according to claim 1, which is a hydrocarbon compound of 0. 3. The glass transition temperature of the copolymer (a) is 100 ° C.
The optical transparent substrate according to claim 1 or 2, which is as described above. 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.