JP2002367224A - Optical disk substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk substrate which is excellent in rigidity, moldability, mold parting properties and transferability and is inexpensive. SOLUTION: The optical disk substrate which is (1) the optical disk substrate consisting of a styrene-(meth)acrylate base copolymer consisting of a styrene monomer, a (meth)acrylate base monomer and a vinyl base monomer copolymerizable therewith and which is described in (1) and is characterized in that (2) the MFR(melt flow rate) under 5 kg load at 200 deg.C is >=1.0 g/10 minute and the VSP(Vicat softening point) under 5 kg load is >=95 deg.C is constituted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc substrate which is excellent in releasability and warpage after molding.

[0002]

2. Description of the Related Art With the progress of the information-oriented society, the market has shifted from conventional magnetic tapes and magnetic disks to optical disks with higher integration as information recording media. Price reduction is required for versatility, and lower cost materials and improved productivity have been attempted.

[0003] As the optical disk referred to here, a signal recorded by converting a digitized signal such as audio or video into a plastic substrate surface with or without pits is read by a laser beam. Registered trademark)), VCD (video CD), music CD, CD-R
OM, CD-R, DVD-ROM, DVD-RAM, D
VD-R and the like.

[0004] As a method of forming pits, there are a mechanical method using a stamper and a method in which an organic dye existing on the board surface is reacted with light, but is not particularly limited.

[0005]

Polystyrene has been studied as such a material for an optical disk substrate. However, the rigidity is small, and the molded product is easily cracked at the time of mold release in the molding process. However, in order to obtain a molded product that does not cause warpage, it is necessary to extend the cooling time, and there has been a problem that the molding cycle becomes longer and the productivity is poor.

As a result of various studies to solve the above problems, the present inventors have found that styrene monomers, (meth) acrylate monomers, and vinyl monomers copolymerizable with these monomers. A styrene- (meth) acrylate-based copolymer composed of a monomer has been found to improve rigidity and heat resistance, and has completed the present invention.

[0007]

That is, the present invention provides (1)
Optical disc comprising styrene- (meth) acrylate-based copolymer comprising styrene-based monomer, (meth) acrylate-based monomer, and vinyl-based monomer copolymerizable with these monomers Substrate, (2) 200 ° C, 5kg
MFR (melt flow rate) under load ≧ 1.0 g / 1
0 minutes, VSP (Vicat softening point) under 5 kg load
The optical disk substrate according to (1), wherein P ≧ 95 ° C., (3) the styrene monomer, (meth)
Styrene- (meth) comprising acrylate monomers and vinyl monomers copolymerizable with these monomers
For 100 parts by mass of the acrylate copolymer,
The optical disc substrate according to (1) or (2), wherein 10 to 200 ppm of a lubricant is blended, (4) the lubricant is at least one or more selected from fatty acids, fatty acid metal salts and fatty acid amides. Optical disk substrate.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
As the styrene monomer used in the present invention, styrene, α-methylstyrene, p-methylstyrene, o-methylstyrene, m-methylstyrene, ethylstyrene,
Although pt-butylstyrene and the like can be mentioned, styrene is preferred. These styrene monomers may be used alone or in combination of two or more.

The (meth) acrylate-based monomers used in the present invention include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and methacrylate of 2-ethylhexyl (meth) acrylate. , Methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-methylhexyl acrylate, 2-ethylhexyl acrylate,
Acrylic esters such as decyl acrylate may be mentioned, but methyl (meth) acrylate or n-butyl acrylate is particularly preferable, and methyl (meth) acrylate is particularly preferable. These (meth) acrylate monomers may be used alone or in combination of two or more.

Further, vinyl monomers which can be copolymerized with these monomers as required include acrylic acid, methacrylic acid, acrylonitrile, methacrylonitrile,
N-phenylmaleimide, N-cyclohexylmaleimide and the like can be mentioned.

The method for producing the vinyl copolymer used in the present invention is not particularly limited, and for example, a polymerization method such as an emulsion polymerization method, a suspension polymerization method, a bulk polymerization method, and a solution polymerization method can be employed.

The properties of the styrene- (meth) acrylate copolymer used in the present invention are as follows.
the MFR under a g load is MFR ≧ 1.0 g / 10 min,
It is preferable that VSP under a load of 5 kg is VSP ≧ 95 ° C.

The amount of the lubricant used in the present invention depends on the amount of the styrene monomer, (meth) acrylate monomer,
It is preferable to mix 10 to 200 ppm with respect to 100 parts by mass of a styrene- (meth) acrylate-based copolymer composed of a vinyl monomer copolymerizable with these monomers. If it is less than 10 ppm, it is easily broken at the time of mold release, and if it exceeds 200 ppm, the transparency is lowered.

The types of the lubricant used in the present invention include fatty acids, fatty acid metal salts, and fatty acid amides. Fatty acids include stearic acid, behenic acid, erucic acid and the like. Fatty acid amides include ethylene bisstearyl amide. Fatty acid metal salts include zinc stearate (St-Zn), magnesium stearate (St-Mg), and calcium stearate (St-Mg).
-Ca) and the like. Particularly preferred is zinc stearate.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details will be described below using embodiments, but the present invention is not limited to the following embodiments.

Evaluation method MFR 200 according to JIS K-6874
It measured at 5 degreeC and 5 kg load. It was measured at a load of 5 kg according to VSP JIS K-7206. Rigidity In the molding process, the bending strength is 100 MPa as a measure of rigidity to prevent the molded product from cracking during mold release.
As described above (based on ASTM D790). Moldability The molding cycle should be less than 6 seconds,
A material with excellent productivity. Releasability The material having excellent releasability had the number of shots of 100 shots or more before cracking of a molded product due to poor release. Transferability If the pit groove depth was 100 nm or more when molded using a pit groove stamper for 160 nm, the material was excellent in transferability.

Example 1 An autoclave having a capacity of 250 liters was charged with 100 k of pure water.
0.5 g of sodium dodecylbenzenesulfonate
g, tricalcium phosphate 250 g, styrene 40 k
g, 60 kg of methyl methacrylate, and 100 g of t-butyl peroxyisobutyrate as a polymerization initiator.
g and t-dodecyl mercaptan (200 g) were added, and the mixture was dispersed with stirring at a rotation speed of 150 rpm. Then, the mixture is heated at 100 ° C. for 8 hours and at 130 ° C. for 2.5 hours.
The mixture was polymerized by heating for an hour. After completion of the reaction, washing, dehydration and drying were performed to obtain a beaded copolymer. This was designated as copolymer MS. The copolymer was mixed with 50 ppm of St-Zn as a lubricant, and the cylinder temperature was 220 ° C. and the screw speed was 100 rpm by a single screw extruder having a screw diameter of 40 mm.
m into pellets, then injection molding machine MDM-I manufactured by Meiki Co., Ltd.
By injection molding at a molding temperature of 240 ° C. and a mold temperature of 60 ° C., a diameter of 180 mm and a center hole of 15 m
An optical disk substrate having a thickness of 1.2 mm and a thickness of 1.2 mm was obtained. Next, the characteristics of the obtained optical disk substrate were evaluated. Table 1 shows the results.

Example 2 Pure water (100 k) was placed in an autoclave having a capacity of 250 liters.
0.5 g of sodium dodecylbenzenesulfonate
g, tricalcium phosphate 250 g, styrene 40 k
g, 60 kg of methyl methacrylate, and 100 g of t-butyl peroxyisobutyrate as a polymerization initiator.
g and 100 g of t-dodecyl mercaptan were added, and the mixture was dispersed with stirring at a rotation speed of 150 rpm. Then, the mixture is heated at 100 ° C. for 8 hours and at 130 ° C. for 2.5 hours.
The mixture was polymerized by heating for an hour. After completion of the reaction, washing, dehydration and drying were performed to obtain a beaded copolymer. This was designated as copolymer MS. To this copolymer, 50 ppm of St-Zn was added and mixed as a lubricant, and injection molding was performed using pellets in the same manner as in Example 1 to obtain an optical disk substrate. Next, the characteristics of the obtained optical disk substrate were evaluated. Table 1 shows the results.

Example 3 An autoclave having a capacity of 250 liters was charged with 100 k of pure water.
0.5 g of sodium dodecylbenzenesulfonate
g, tricalcium phosphate 250 g, styrene 60 k
g, 40 kg of methyl methacrylate, and 100 g of t-butyl peroxyisobutyrate as a polymerization initiator.
g and t-dodecyl mercaptan (200 g) were added, and the mixture was dispersed with stirring at a rotation speed of 150 rpm. Then, the mixture is heated at 100 ° C. for 8 hours and at 130 ° C. for 2.5 hours.
The mixture was polymerized by heating for an hour. After completion of the reaction, washing, dehydration and drying were performed to obtain a beaded copolymer. This was designated as copolymer MS. To this copolymer, 50 ppm of St-Zn was added and mixed as a lubricant, and injection molding was performed using pellets in the same manner as in Example 1 to obtain an optical disk substrate. Next, the characteristics of the obtained optical disk substrate were evaluated. Table 1 shows the results.

Example 4 An autoclave having a capacity of 250 liters was charged with 100 k of pure water.
0.5 g of sodium dodecylbenzenesulfonate
g, tricalcium phosphate 250 g, styrene 25 k
g, 70 kg of methyl methacrylate and 5 kg of acrylonitrile, 100 g of t-butylperoxyisobutyrate and 200 g of t-dodecylmercaptan were added as polymerization initiators, and the mixture was dispersed under stirring at a rotation speed of 150 rpm. Then, the mixed solution is heated at a temperature of 100
Polymerization was carried out by heating at 130 ° C. for 8 hours and at 130 ° C. for 2.5 hours. After completion of the reaction, washing, dehydration and drying were performed to obtain a beaded copolymer. This was designated as copolymer MS. To this copolymer, 50 ppm of St-Zn was added and mixed as a lubricant, and injection molding was performed using pellets in the same manner as in Example 1 to obtain an optical disk substrate. Next, the characteristics of the obtained optical disk substrate were evaluated. Table 1 shows the results.

Example 5 An optical disk substrate was obtained by subjecting the copolymer MS obtained in Example 1 to injection molding using pellets in the same manner as in Example 1 without adding a lubricant. Next, the characteristics of the obtained optical disk substrate were evaluated. Table 1 shows the results.

Example 6 St-Zn 2 was added to the copolymer MS obtained in Example 1 as a lubricant.
50 ppm was added and mixed, and injection molding was performed using pellets in the same manner as in Example 1 to obtain an optical disk substrate.
Next, the characteristics of the obtained optical disk substrate were evaluated. Table 1 shows the results.

Example 7 St-Mg50 was added to the copolymer MS obtained in Example 1 as a lubricant.
An optical disk substrate was obtained by adding and mixing ppm and performing injection molding using pellets in the same manner as in Example 1. Next, the characteristics of the obtained optical disk substrate were evaluated. Table 1 shows the results.

Example 8 St-Ca50 was added to the copolymer MS obtained in Example 1 as a lubricant.
An optical disk substrate was obtained by adding and mixing ppm and performing injection molding using pellets in the same manner as in Example 1. Next, the characteristics of the obtained optical disk substrate were evaluated. Table 1 shows the results.

Example 9 EBP 50 ppm was added to the copolymer MS obtained in Example 1 as a lubricant.
The mixture was added and mixed, and injection molding was performed using pellets in the same manner as in Example 1 to obtain an optical disk substrate. Next, the characteristics of the obtained optical disk substrate were evaluated. Table 1 shows the results.

Example 10 150 ppm of stearic acid was added as a lubricant to the copolymer MS obtained in Example 1 and mixed, followed by injection molding using pellets in the same manner as in Example 1 to obtain an optical disk substrate. Next, the characteristics of the obtained optical disk substrate were evaluated.
Table 1 shows the results.

Comparative Example 1 A reaction vessel equipped with a stirrer was charged with 100 parts of styrene, 2.5 parts of tribasic calcium phosphate, 0.5 parts of t-dodecylmercaptan, 0.2 parts of benzoyl peroxide and 250 parts of water. The temperature was raised to 100 ° C. to initiate polymerization. Seven hours after the start of the polymerization, the temperature was raised to 120 ° C. and maintained for 3 hours to complete the polymerization. The conversion reached 97%. The obtained reaction solution was neutralized with hydrochloric acid, dehydrated and dried to obtain a white bead-like copolymer. This was designated as copolymer PS. To this copolymer, 50 ppm of St-Zn was added and mixed as a lubricant, and injection molding was performed using pellets in the same manner as in Example 1 to obtain an optical disk substrate. Next, the characteristics of the obtained optical disk substrate were evaluated. Table 1 shows the results.

[0028]

[Table 1]

From Table 1, it can be seen that Experiment No. 1 to 10 are rigid,
Although it has excellent properties as an optical disc substrate such as moldability, mold release properties, and transfer properties, it was confirmed in Experiment Nos. No. 11 is inferior in characteristics as an optical disk substrate.

[0030]

According to the present invention, it is possible to provide an inexpensive optical disk substrate which is excellent in rigidity, moldability, release property and transferability.

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 4J100 AB02P AB03P AB04P AJ02R AL03Q AL04Q AL05Q AM02R AM47R AM48R BC04R CA04 CA05 DA23 DA42 JA36 5D029 KA02 KA18 KC10 KC13

Claims (4)

[Claims] 1. A styrene- (meth) acrylate-based copolymer comprising a styrene-based monomer, a (meth) acrylate-based monomer, and a vinyl-based monomer copolymerizable with these monomers. Optical disc substrate made of polymer. 2. MFR (melt flow rate) at 200 ° C., 5 kg load ≧ 1.0 g / 10 min, and VSP (Vicat softening point) at 5 kg load ≧ 95 ° C. 2. The optical disc substrate according to 1. 3. Styrene- (meth) acrylic acid comprising the styrene-based monomer, (meth) acrylate-based monomer, and a vinyl-based monomer copolymerizable with these monomers. 3. The optical disc substrate according to claim 1, wherein 10 to 200 ppm of a lubricant is blended with respect to 100 parts by mass of the ester copolymer. 4. The optical disc substrate according to claim 3, wherein the lubricant is at least one selected from fatty acids, fatty acid metal salts and fatty acid amides.