JPS6323102A - Transparent substrate for optical use - Google Patents

Abstract

PURPOSE:To prevent the deterioration of the mechanical properties of a transparent substrate and the formation of voids and to improve the transferability of pits or guide grooves by using a transparent thermoplastic resin blended with a hydrocarbon compound having 200-3,000mol.wt. and a liq. state at ordinary temp. by 0.01-1 part by weight per 100 parts resin. CONSTITUTION:A transparent substrate is made of a transparent thermoplastic resin blended with a hydrocarbon compound having 200-3,000mol.wt. and a liq. state at ordinary temp. by 0.01-1 part by weight per 100 parts resin. Polmethyl methacrylate (PMMA), polycarbonate (PC) or poly-4-methylpentene-1 (PMP) is generally used as the transparent thermoplastic resin. The thermoplastic resin may be polystyrene or a product produced by hydrogenating a ring opened homopolymer of tetracyclododecene or a ring opened copolymer of tetracyclododecene with norbornene. The hydrocarbon compound plasticizes the transparent thermoplastic resin having high Tg by dispersion in the resin and can microscopically lower the apparent Tg. The especially preferred mol.wt. of the hydrocarbon compound is about 300-1,000.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to optical transparent substrates, and in particular, to optical transparent substrates that have a large projected area and a thin thickness that exhibit a good appearance by injection molding, such as optical disk substrates. Regarding.

[Conventional technology and its problems]

Various molding methods are known for manufacturing optical transparent substrates using transparent thermoplastic resins. Among them, injection molding is the method most used industrially because of its productivity, that is, the ability to mold a large amount of products at a high production rate.

By the way, the product shape has a large projected area, such as an optical disk substrate, which is a type of optical transparent substrate, and
If the material is thin, it is difficult to manufacture it by injection molding (as detailed below).

In other words, transparent thermoplastic resins such as polymethyl methacrylate (PMM8), polycarbonate (PO), and poly4methylpentene (PMP) have high viscosity, so during injection molding, the resin temperature must be raised to lower the viscosity. We need to improve liquidity.

However, even if the projected area is large, if the thickness is thin, the amount of resin is small, and the residence time of the resin in the injection molding machine is therefore long. , mechanical shear heat is also likely to occur.In this way, resins that remain at high temperatures for a long time due to external heating and also experience internal heating such as shear heat will naturally decompose and deteriorate, and the resulting product will deteriorate. There are problems in that the mechanical strength is weakened and scorches are mixed in, making it impossible to use it as an optical disc substrate.

Another problem is the fact that manufactured disk substrates often have small voids. Although it can be accepted that this phenomenon applies to injection molding in general, methods such as pre-drying the material resin or adding air vents to the mold, which have been considered effective in solving this type of problem, cannot achieve the low flow rate described above. The production of disk substrates by high-temperature injection molding using plastic resins is insufficient.

Another problem is that the pits and guide grooves of the disk are not accurately transferred to the disk substrate.

Yet another problem is that a phenomenon called flash may occur on or inside the disk substrate. Here, the flash is a phenomenon that produces irregularly shaped clouds along the radial direction of the disk, and is a completely different phenomenon from the silver streak that shows a relatively clear streak-like shape.

Although such a phenomenon may not be much of a problem in ordinary molded products, it must never occur in applications such as transparent substrates. This phenomenon often occurs even after sufficient time has been taken to pre-dry the material resin, which is said to be effective in preventing, for example, common silver streaks, and is a source of headache for those skilled in the art.

Yet another problem is that the transparent substrate obtained by molding becomes yellow (colored).

[Problem that the invention seeks to solve]

In view of the current situation, the present inventors have discovered that even if an optical transparent substrate, especially one having a large projected area and a small thickness such as an optical disk substrate, is injection molded, the mechanical properties will not deteriorate and voids will not occur. The present invention was arrived at as a result of repeated research into whether it was possible to obtain a product that does not have any problems, has good transferability of bits or guide grooves, and does not cause flash (and is not colored).

[Means for solving problems]

That is, in the present invention, a hydrocarbon compound having a molecular weight of 200 to 3,000 and which is liquid at room temperature is added to o, oi per 100 parts by weight of resin.
This is an optical transparent substrate characterized by being made of a transparent thermoplastic resin containing ~1 part by weight.

[For production]

Examples of transparent thermoplastic resins include the aforementioned PMM^ and PC.
, In addition to PMP, polystyrene (PS), or hydrogenated ring-opening polymers of tetracyclododecenes or ring-opening copolymers with norbornenes as shown in JP-A-60-26024, In addition, copolymers of ethylene and cyclic olefins such as norbornene, tetracyclododecene, and methyltetracyclododecene (for example,
0-168708, 61-1) 5912, 61-
1) 5916, 6l-120816), etc.

Transparent thermoplastic resins that are particularly useful in the present invention are those with relatively high glass transition temperatures (Tg) of about 100
℃ or above and 120°C or above.In other words, when the Tg is high, the temperature of the resin surface that comes into contact with the mold when it flows into the mold during injection molding decreases, and the temperature of the resin melts relatively quickly. The surface solidifies.For this reason, volatile components estimated to be due to oxidative deterioration of the resin are trapped inside the resin, causing the aforementioned flash.In other words, the higher the Tg, the faster the surface solidifies. occurs,
Therefore, applying the present invention to such resins is useful because it prevents flash. Therefore, the resin preferably used is a copolymer of ethylene and cyclic olefin.

It is completely unexpected that the object of the present invention can be achieved by blending a small amount of a hydrocarbon compound with a molecular M2O of 0 to 3000 that is liquid at room temperature. It is unclear why the structure of the present invention can achieve the object, but according to the inventors' speculation, a hydrocarbon compound that is liquid at room temperature and has a molecular i of 200 to 3000 can be a transparent thermoplastic with a high Tg. It can be considered that one of the reasons is that it plasticizes the resin by dispersing it in the resin, and plays the role of lowering the apparent Tg when viewed microscopically. As a result, the solidification of the resin surface in contact with the injection mold is slightly delayed, and volatile components generated inside the resin (low boiling point substances generated due to decomposition and deterioration of the resin and trace amounts of upper particles originally contained in the resin) -, etc.) from the surface, prevents voids and flashes, and improves bit transferability.

However, if a too large amount of hydrocarbon compound is used at this time, the resin composition as a whole will tend to become more visible, which will affect the strength and heat resistance of the transparent substrate, especially as a transparent substrate for optical applications. The amount is the target transparent thermoplastic resin 1
0.01 to 1 part by weight, especially 0.1 to 1 part by weight per 00 parts by weight
A range of 0.9 parts by weight is preferred. It is also one of the features of the present invention that the objective can be achieved with such a very small amount of blending. In other words, in the conventional knowledge, the amount of plasticizer used for modifying or plasticizing the resin was several percent or more, but in the present invention, the amount of plasticizer used for modifying or plasticizing the resin was determined by reducing the solidification time of the resin surface in contact with the mold during injection molding. Since it is only necessary to slightly delay the reaction, the purpose can be achieved with a small amount of addition as described above. One of the reasons why the objective can be achieved with such an amount is that the hydrocarbon compound has high mobility due to its low molecular weight, which makes it easy for the hydrocarbon compound to migrate to the resin surface during molding and come into contact with the mold. This is also thought to be because it intensively achieves the effect of modifying the resin surface.

For these reasons, in the present invention, those having a relatively low molecular weight, that is, about 300 to 1000, are suitable for the tomato.

Examples of hydrocarbon compounds include aliphatic hydrocarbons having straight or side chains, alicyclic hydrocarbons, aliphatic hydrocarbons such as biphenyl, polyphenyl, or fused polycyclic aromatics, and aromatic hydrocarbons. partially hydrogenated compounds, or these various hydrocarbons as base materials, alkyl groups,
Examples include those substituted with an aryl group, an aralkyl group, etc.

Both natural and synthetic hydrocarbons can be used. More specifically, dodecylbenzene, polyalkylbenzene, dibenzylbenzene, alkylnaphthalene, polyphenylalkane oil, alkylated tetralin, ethylene oligomer, propylene oligomer, ethylene-propylene oligomer, polybutene that is produced as a by-product during the production of dodecylbenzene oil. Examples include olefin polymers such as oligomers, liquid paraffin, squalane, mineral oil, etc., but of course hydrocarbon compounds not exemplified here can also be used.

In the present invention, various antioxidants may also be used in order to measure the heat resistance stability of the resin.

Furthermore, when using a transparent resin made with a halogen-containing catalyst such as Ziegler's catalyst, a halogen scavenger should be used in combination to prevent the halogen contained in the remaining catalyst residue from damaging the molding machine. It is.

To explain the present invention using an optical disk substrate as an example, first, the resin and the above compound, and if necessary, other stabilizers in an amount that does not reduce the effect of the present invention, are mixed in a ribbon blender, tumbler blender, Henschel mixer, etc. After mixing, melt-mix using an extruder, Banbury mixer - 1 or two rolls, or dissolve it in a hydrocarbon or aromatic solvent and mix it into a polymer solution, and then use a single-screw extruder, vented extruder, or twin-screw extruder. , three-screw extruder, conical two-screw extruder, co-kneader, plateificator, mixtruder, twin-screw conical screw extruder, planetary screw extruder, gear-type extruder, screwless extruder, etc. Injection molding is performed using a disk mold (including one equipped with a stamp bar for forming information bits and guide grooves).

Various known gates may be used for injection molding, but in view of shrinkage and warping, center pin gates and center disc gates, preferably gate diameter 3.
III1) or less, especially a center pin gate of 0.5 to 2.0 mm, gate thickness 1fflI1) or less, especially 0.5 to 2.0 mm.
It is preferable to use a center disk gate of 2 to 0.8 mm.

The disk substrate obtained by injection molding is then completed by forming a recording layer or a metal layer for reflecting laser beams by a known method such as vapor deposition or sputtering, and further providing a protective layer if necessary. .

〔Example〕

The content of the present invention will be illustrated below with preferred examples, but the present invention is not limited to these examples unless otherwise specified.

Example 1 +r at load 2.15, melt flow rate (MFR: ASTM D 1238) at 260°C A degree is 3
Tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate comethane (A ), squalane (molecular weight 392) (B) and zinc stearate (C) were mixed in a Henschel mixer, and then pellets were created at a temperature of 230°C using a twin-screw extruder with a screw diameter of 401) m. .

Using these pellets as raw material, using a Sumitomo Heavy Industries P40/25A injection molding machine and a center disk gate mold (a mold equipped with a stand bar for forming information bits), the pellets were heated to a diameter of 80 nuw and a thickness of 80 nuw at a temperature of 280°C. 1.0III
The disk substrate of 1) was molded, and the items shown in Table 1 were evaluated. Note that these items were evaluated visually, and the evaluation criteria were 1 to 5 good.

The amount of the stabilizer is expressed in parts by weight based on 100 parts by weight of the raw material resin.

Example 2 (Production of hydrocarbon compounds) A container ffi equipped with a thermometer, a stirrer, a condenser and a dropping funnel
Mixed xylene (m-
xylene 45%, ethylbenzene 51%, 0- and p
3 g of powdered anhydrous aluminum chloride are added to 79.5 g (0.75 mol) of xylene (4%) under a nitrogen atmosphere. Tricyclo(5,2
, 1,0”) Deca-3-x7 content (purity 70.9
%) 283.5g (1.5g mol) was added and heated to 60°C.
Heat and stir for 2 hours. The reaction was terminated by adding methanol, and the reaction solution was washed until it became neutral. Next, pot temperature 1
Unreacted substances were removed at 50°C and a pressure of 20mmHg to obtain 49g of a viscous liquid with a Gardner hue of 10.25°C, a viscosity of 10.800cp, and a refractive index (no'') of 1.5482.As a result of analysis, tricyclo[ 5, 2,
It was found that it consisted of 33% by weight of the 2/1 adduct and 8% by weight of others.

Next, this viscous liquid was subjected to a hydrogenation reaction, and the viscosity at 25°C was 10,600 cp and the refractive index (nDzs) was 1.5028.
39 g of viscous liquid was obtained. As a result of the analysis, tricyclo [5
゜2.1.0''') Dec-3-ene: 1 of mixed xylene
It was found to be a hydrocarbon compound with an average molecular weight of 320, consisting of 59% by weight of /1 addition hydrogenated product, 33% by weight of 2/1 addition hydrogenated product, and 8% by weight of others.

(Test Example) The hydrocarbon compound (D) obtained above was added to (B) of Example 1.
) was used in the same manner.

The results are shown in Table 1.

Example 3 (Production of hydrocarbon compound) An ethylene/α-olefin random copolymer was continuously produced using a 41 glass reactor equipped with a stirring blade. Namely, hexane solution (16 mmol/l) per hour, hexane solution of vanadium trichloride (16 mmol/l) per hour, hexane solution of ethylaluminum sesquichloride (96 mmol/7 hourly)
1) per hour is continuously fed into the reactor from the upper part of the reactor, while the reaction liquid is continuously withdrawn from the lower part of the reactor so that the reaction liquid in the reactor is always 21. A mixed gas of ethylene, propylene and hydrogen (ethylene 4i/hour, propylene 41A/hour, hydrogen 220
1'). The reaction temperature was maintained at 35°C by circulating hot water through a jacket attached to the outside of the reactor.
It was adjusted to A small amount of methanol was added to the reaction liquid taken out from the bottom of the reactor to stop the reaction, and then the reaction liquid was washed three times with water.

After that, the pot temperature is 100℃ with Q, 1mm 1)g vacuum.
The hexane solvent and low-boiling products were removed by distillation to obtain an ethylene-propylene random copolymer that was liquid at room temperature.

The generated ethylene/propylene random copolymer
As measured by C-NMR, the ethylene content was 54 mol%, as measured by gel permeation chromatography, n was 450, and Mh/Tin was 1.8. No melting point was observed and the melting energy was Ocal/g.

(Test Example) The random copolymer (E) obtained above was used in Example I (
The same procedure was performed except that B) was used instead of B).

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 amount of (A) was increased. The results are shown in Table 1.

Comparative Example 2 The same procedure as in Example 1 was carried out except that n-decane (F) was used instead of (B). The results are shown in Table 1.

Comparative Example 3 In Example 1, instead of (B), polyethylene wax (HIZEX O1) 0P, Mitsui Petrochemical Industries) (G
) was used in the same manner. The results are shown in Table 1.

Comparative Example 4 Low crystalline ethylene was used instead of (B) in Example 1.
The same procedure was carried out except that α-olefin copolymer (Tafmer PO680, Mitsui Petrochemical Industries, Ltd.) (II) was used. The results are shown in Table 1.

〔Effect of the invention〕

According to the present invention, there is no generation of voids or flash, and furthermore, it exhibits excellent effects in that it is possible to accurately transfer the stubber pattern in the mold, such as the bit portions and guide grooves of the disk.

Therefore, it can be suitably used for manufacturing optical transparent substrate products that have a large projected area but are thin, such as optical disk substrates, large display substrates, transparent electric bridge substrates, transparent electric circuit boards, and CRT covers for VD work.

Claims (6)

[Claims] (1) A transparent optical substrate characterized by being made of a transparent thermoplastic resin containing 0.01 to 1 part by weight of a hydrocarbon compound having a molecular weight of 200 to 3,000 and liquid at room temperature per 100 parts by weight of the resin. (2) The optical transparent substrate according to claim 1, which is a hydrocarbon compound having a molecular weight of 300 to 1,000. (3) The optical transparent substrate according to claim 1 or 2, wherein the transparent thermoplastic resin has a glass transition temperature of 100° C. or higher. (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) Claim 1 manufactured by injection molding
The optical transparent substrate according to any one of items 5 to 6.