JPH03115349A - Hydrogenated vinyl arom. hydrocarbon polymer composition, and optical disc board - Google Patents

Abstract

PURPOSE:To prepare a polymer compsn. excellent in the heat resistance, optical properties, and adhesion to a recording film layer and suitable for an optical disc board by compounding a hydrogenated vinyl arom. hydrocarbon-conjugated diene block copolymer a hydrogenated vinyl arom. hydrocarbon polymer, etc. CONSTITUTION:The title compsn. comprises 10-100wt.% vinyl arom. hydrocarbon-conjugated diene block copolymer (A) wherein 75-98mol% of the total double bonds and arom. rings in the polymer have been hydrogenated; 0-95wt.% vinyl arom. hydrocarbon polymer (B) wherein 80mol% or higher of the arom. rings have been hydrogenated; and/or 0-20wt.% satd. hydrocarbon resin (C) having a number-average mol.wt. of 500-5000 and a softening point of 40 deg.C or higher, wherein the sum of B and C is higher than 0wt.%.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention provides a method for producing a material having excellent transparency, heat resistance, and adhesion to metals, etc.
The present invention relates to a hydrogenated vinyl aromatic hydrocarbon resin composition, and more particularly to an optical disc substrate obtained using such a hydrogenated vinyl aromatic hydrocarbon resin composition.

[Conventional technology] Optical recording using lasers enables high-density information recording, storage,
Since it can be recycled and regenerated, its development has been actively carried out in recent years. An optical disk can be cited as an example of such optical recording.

In general, optical discs basically consist of a transparent substrate and various recording media coated thereon.

Colorless and transparent synthetic resins are often used for the transparent substrates of optical discs, and typical examples include polycarbonate (hereinafter abbreviated as rPcJ) or polymethyl methacrylate (hereinafter abbreviated as rP, MMAJ).
can be mentioned. Although these resins are colorless and transparent and have other excellent properties, they do not meet all the requirements for optical materials, especially optical disk substrates, and there are problems that need to be solved. It has points. For example, PC has a problem with birefringence due to its aromatic ring, and also has problems with water absorption or water permeability. On the other hand, PMMA has heat resistance,
Problems with water absorption and toughness have been pointed out for some time.

In this way, these resins are used with their own inherent problems, but in reality, there are also
In relation to recording media coated on transparent substrates made of these resins, new problems have arisen as described below.

On the other hand, regarding recording media, a wide variety of developments have been carried out in response to the uses of optical discs. for example,
The write-once type is a hole-drilling type that is only for recording and playback, and the erasable type is a phase change type that uses a crystal transition phenomenon, and the type that is for recording, playback, erasing, and rewriting is the write-once type. Magneto-optical types that utilize magnetic effects are known. These recording media materials include tellurium or its oxide, alloy compound, etc. for the write-once type, and GdFe, GdFe, etc. for the erasable type.
TbFe, GdFeCo, TbFeC.

Inorganic materials such as rare earth-transition metal amorphous alloy compounds are mainstream, and are generally formed by forming a film on a transparent substrate by a dry process such as sputtering under a high vacuum.

By the way, the hygroscopicity and water permeability of PC and PMMA, on the one hand, cause the problem of warpage due to the expansion of the substrate itself when it absorbs moisture, but on the other hand, the permeation of moisture through the substrate causes corrosion of the recording medium, and the optical disc This causes a shortened lifespan.

Further, regarding the heat resistance of the substrate resin, there are the following problems. That is, optical discs, especially light discs,
For optical discs such as once type and erasable type,
The temperature of the recording medium during writing and erasing of records reaches 200° C. or higher. For this reason, even though this heat is not directly applied to the disk substrate, it is expected that the substrate will reach a considerably high temperature when writing and erasing records, and resins with low heat resistance may cause deformation of the substrate or group formation. Problems such as deformation may occur.

On the other hand, in the production process of optical discs, a heat treatment process is often incorporated in order to prevent aging of the substrate or recording medium. It is desirable to shorten the time.

From this point of view as well, if the heat resistance of the resin is low, a high treatment temperature cannot be used and productivity cannot be increased.

For these reasons, PMMA, which has low heat resistance, is insufficient to withstand the high temperatures of the optical disc production process and usage conditions, and conventionally, PC, which has higher heat resistance, has been used exclusively as a transparent substrate material. However, even PC is not necessarily evaluated as having sufficient heat resistance, and the emergence of resin materials with higher heat resistance is desired.

In order to compensate for the drawbacks of conventional resins such as PC and PMMA, there is a method of using transparent resins that are mainly composed of carbon and hydrogen and have a high softening point.
No. 149,845 and others have proposed hydrogenated vinyl aromatic hydrocarbon polymers.

[Problem that the invention is trying to solve] However,
The above-mentioned hydrogenated vinyl aromatic hydrocarbon polymer has the same problem as the low adhesion of so-called polyolefins, in that it has poor adhesion to the recording film and cannot have a sufficient lifespan as an optical disc.

[Means for Solving the Problems] Therefore, the inventors of the present invention conducted extensive studies on improving the resin to improve the adhesion with the recording film layer described above, and as a result, the present inventors developed a hydrogenated vinyl aromatic hydrocarbon polymer. As a method, a hydrogenated vinyl aromatic hydrocarbon-conjugated diene block copolymer with a specific hydrogenation rate is used, or a hydrogenated vinyl aromatic hydrocarbon polymer and a hydrogenation rate with a specific value are used. Hydrogenation obtained by mixing a hydrogenated vinyl aromatic hydrocarbon-conjugated diene block copolymer and optionally adding a saturated hydrocarbon resin with a number average molecular weight of less than 5000 and a softening point of 40°C or higher. By using a vinyl aromatic hydrocarbon polymer composition, it is possible to obtain an optical disc substrate that has excellent adhesion to the recording film layer while maintaining the high heat resistance originally possessed by hydrogenated vinyl aromatic hydrocarbon polymers. This discovery led to the present invention.

That is, the gist of the present invention is as follows: (a) 75 mol to 98 mol of all double bonds and aromatic nuclei in the vinyl aromatic hydrocarbon-conjugated diene block copolymer;
Polymer 1-1 obtained by hydrogenating mol%, less than OO% by weight) 80 mo of aromatic nuclei in vinyl aromatic hydrocarbon polymer
0 to 95% by weight of a polymer obtained by hydrogenating lfi% or more and/or (c) number average molecular weight of 500 to 5,000, softening point of 4
0 to 20% by weight of saturated hydrocarbon resin at 0°C or higher (however,
The total of components (b) and (c) exceeds 0% by weight). It is used as an optical disc substrate that has excellent adhesion to materials and polar group-containing polymer compounds, and particularly excellent adhesion to recording film layers.

The present invention will be explained in detail below.

Component (a) of the composition of the present invention is a hydrogenated vinyl aromatic hydrocarbon-conjugated dienepro-link copolymer.

The vinyl aromatic hydrocarbon monomer in the vinyl aromatic hydrocarbon polymer segment in the raw material vinyl aromatic hydrocarbon-conjugated diene block copolymer includes styrene,
Examples include P-methylstyrene and α-methylstyrene, with styrene being a particularly representative example.

Examples of the vinyl aromatic hydrocarbon polymer segment include a homopolymer or a copolymer of two or more of these vinyl aromatic hydrocarbons. Further, other monomers copolymerizable with the above-mentioned vinyl aromatic hydrocarbon may be contained within a range such that the characteristics of the vinyl aromatic hydrocarbon polymer are not lost. Such monomers include acrylic acid,
Acrylic esters, methacrylic acid, methacrylic esters, maleic acid, maleic anhydride, acrolein, vinyl esters, vinyl ethers, vinyl ketones,
Examples include acrylonitrile.

The conjugated dienes in the conjugated diene polymer segment include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1.3pentadiene, 1,3
-hexadiene, etc., and 1,3-butadiene and isoprene are particularly common. A block copolymer consisting of two or more types of segments can be produced by a known method called living anionic polymerization, such as a method in which polymerization is performed using an organic lithium compound as an initiator in a hydrocarbon solvent such as hexane or heptane. can be obtained easily.

The content of the vinyl aromatic hydrocarbon polymer segment in such a block copolymer is 20% by weight or more, preferably 40% by weight or more, and more preferably 60% by weight or more. Further, the content of the conjugated diene polymer segment is 20% by weight or less of the total composition of the present invention.

If the content of the conjugated diene polymer segment is too large in the composition, the heat resistance and rigidity of the composition will decrease, making it unsuitable for use as an optical disc substrate.

The number average molecular weight of such raw material vinyl aromatic hydrocarbon-conjugated diene plotter copolymer is 30,000 to 400,000, preferably 50,000 to 400,000.

The hydrogenated vinyl aromatic-conjugated diene block copolymer, which is the component (a) of the composition of the present invention, is prepared by hydrogenating such a block copolymer in the presence of a hydrogenation catalyst capable of hydrogenating aromatics. You can get it.

Examples of hydrogenation catalysts used here include metals such as nickel, cobalt, ruthenium, rhodium, platinum, and palladium, or their oxides, salts, and complexes, and those supported on carriers such as activated carbon, diatomaceous earth, and alumina. etc. Among these, Raney nickel, Raney cobalt, stabilized nickel and ruthenium, rhodium or platinum supported catalysts on carbon or alumina are particularly preferred from the viewpoint of reactivity.

The hydrogenation reaction is carried out at a pressure of 50 to 250 kg/afl, 100
At a temperature of ~200°C, cyclohexane as a solvent,
Saturated hydrocarbon solvents such as methylcyclohexane, n-octane, decalin, tetralin, naphtha, or THF
It is preferable to use an ether solvent such as . Regarding the hydrogenation rate, the hydrogenation rate of the double bonds originating from the conjugated diene segment is substantially 100%. The hydrogenation rate of aromatic nuclei is 98 mol% or less, preferably 95 mol% or less, more preferably 90 mol% or less. The lower limit of the hydrogenation rate of aromatic nuclei is 75 mol%, preferably 80 mol%. If the nuclear hydrogenation rate is higher than the above value, the adhesion with the recording film is insufficient, and if it is lower, it may cause a decrease in heat resistance, an increase in birefringence, a decrease in compatibility with component (b), etc. There's a problem.

The number average molecular weight of the hydrogenated vinyl aromatic hydrocarbon-conjugated diene block copolymer of component (a) obtained as described above is 20,000 to 300,000, preferably 50,000 to 200,000. If the molecular weight is too low, the strength will be insufficient, and if the molecular weight is too high, the moldability and optical uniformity will deteriorate.

Component (b) of the composition in the present invention is a hydrogenated vinyl aromatic hydrocarbon polymer.

The raw material vinyl aromatic hydrocarbon polymer is the above-mentioned (a)
Examples include polymers similar to the vinyl aromatic hydrocarbon polymer segments in the raw materials for the components. The polymerization method is not particularly limited as long as an amorphous polymer can be obtained, but radical polymerization, anionic polymerization, etc. are usually used. The molecular weight of this raw material vinyl aromatic hydrocarbon polymer is preferably 50,000 or more in terms of number average molecular weight. If the molecular weight is too low, the heat resistance and toughness of the resin obtained after hydrogenation will decrease.

On the other hand, there is no particular restriction on the upper limit of the molecular weight, but it is usually preferably 400,000 or less.

Such a vinyl aromatic hydrocarbon polymer may be used as described in (a) above.
Nuclear hydrogenation is carried out in a manner similar to the hydrogenation of components.

The nuclear hydrogenation rate of aromatic nuclei due to nuclear hydrogenation reaction is 80 mojl! %
That's all. If the hydrogenation rate is low, the heat resistance will decrease and the birefringence as an optical material will increase, which is not preferable. The nuclear hydrogenation rate of this component is preferably 90 moA% or more, more preferably 95 mol% or more.

The number average molecular weight of the hydrogenated vinyl aromatic hydrocarbon polymer obtained as described above is from 50,000 to 300,000, preferably from 60,000 to 250,000. If the number average molecular weight is less than 50,000, the strength will be insufficient, which is undesirable, and if it exceeds 300,000, moldability and optical uniformity will be impaired, which is not preferred.

Component (c) of the present invention has a number average molecular weight of 500 to 5000,
It is a saturated hydrocarbon resin with a softening point of 40'C or higher.

Preferably, the number average molecular weight is 500 to 2000 and the softening point is 60 to 200°C. Component (c) is a component that contributes to improving adhesiveness. If the molecular weight of component (c) is too high, the effect of improving adhesion is insufficient. If it is too low, there will be problems such as scattering and bleeding during molding, making it unusable. Moreover, if the softening point is too low, the heat resistance of the composition will decrease. The hydrogenation rate of the resin component (c) is 95% or more, preferably 98% or more. Examples of such saturated hydrocarbon resins include hydrogenated petroleum resins, hydrogenated dicyclopentadiene resins, and low molecular weight polyvinylcyclohexane resins.

The content of each component in the composition is 1 to less than 100% by weight, preferably 10 to 99% by weight of component (a). (b)
The amount of components is 0-95% by weight, preferably 0-90% by weight
It is. The content of component (c) is 0 to 20% by weight, preferably 0 to 10% by weight. (just c) component and (c
) The sum of the components exceeds 0% by weight. ) There are no particular restrictions on the mixing of the above components, but usually the above components are dissolved in a solvent and then put into a poor solvent or co-precipitated by distilling off the solvent, etc., or an extruder. , Brabender Plastograph, Banbury mixer, or other kneading machines may be used.

Furthermore, a method of melting and kneading after solution mixing is also preferred.

In the present invention, a heat stabilizer is usually added to the resin obtained as described above and then molded.

As heat stabilizers, hindered phenol heat stabilizers,
Examples include sulfur-based heat stabilizers and phosphorus-based heat stabilizers. A combination of a hindered phenol heat stabilizer and a phosphorus heat stabilizer is preferred from the viewpoint of improving heat deterioration resistance.

The hindered phenol heat stabilizer employed in the present invention includes tetrakis[methylene-5(3,5-di-t-
Butyl-4-hydroxyphenyl)propionate methane, 3.9-bis[1゜1-dimethyl-2-(β-(3
-t-butyl-4-hydroxy-5-methylphenyl)
propionyloxy)ethyl)-2,4,8,10-tetraoxaspiro(5,5)undecane, 1,3.5 tris(3,5-di-L-butyl-4-hydroxybenzyl-5-t-lyazine- 2,4,6(IH,3H,5H
)-) ion, 1.3.5-trimethyl-2,4,6-
) lis(3,5-di-L-butyl-4-hydroxybenzyl)benzene and the like.

In addition, as a phosphorus-based heat stabilizer, tetrakis (2,4-
Examples thereof include di-butylphenyl)-4,4'-biphenylene phosphonite, bis(2,6-butyl-4-methylphenyl)pentaerythritol-di-phosphite, and the like.

A suitable amount of each of these stabilizers added is 0.01 to 1 part by weight.

There are no particular restrictions on the method of mixing these stabilizers with the resin composition of the present invention, but usually the resin and stabilizer are mixed using a ribbon blender, tumbler blender, Henschel mixer, etc., and then a Banbury mixer is used. - Mix by melt-kneading using a screw extruder, twin-screw extruder, etc. to form pellets. Using the pellet thus obtained, for example, to obtain an optical disc substrate, the molding temperature is 270.
By injection molding at ~350°C, especially at 280~340°C, it is possible to obtain an optical disk substrate that has excellent transparency, heat resistance, etc., is free from coloring, and has extremely low optical distortion.

When manufacturing an optical disk using an optical disk substrate obtained from the hydrogenated vinyl aromatic hydrocarbon polymer composition of the present invention, SN, Tag is applied to the surface of the substrate by a method such as sputtering or vapor deposition.

It is possible to adopt a method such as forming a film such as the above film, further forming a recording layer such as TbFeCo on the film, and finally covering the film with a protective film.

Since the optical disc substrate made of the polymer composition of the present invention has excellent adhesion to the recording layer, it can have a sufficient life as an optical disc.

Further, the polymer composition of the present invention can be used as a molding material for optical lenses, optical cards, etc. in addition to optical discs by taking advantage of its excellent heat resistance and optical properties. Even in that case, the excellent adhesive properties of the polymer composition of the present invention are effective.

〔Example〕

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

In addition, various physical properties in the following Examples and Comparative Examples were measured by the following methods.

■ Number average molecular weight Nigel permeation chromatography (GP
C), the number average molecular weight in terms of polystyrene was determined by measuring in the same manner as polystyrene using THF as a solvent.

(2) Nuclear hydrogenation rate (%): Polyvinylcyclohexane resin was dissolved in tetrahydrofuran (THF) and measured by UV absorption.

■ Softening temperature C''C): Dup On was measured using a thermomechanical analyzer manufactured by Thermo Mechanical Analyzer and a load of 5g using a probe for needle insertion mode.
The softening temperature was measured at a heating rate of °C/min. The thickness of the test piece was 3M.

Resin production example-1 Styrene homopolymer (HH-1 manufactured by Mitsubishi Monsite Kasei Co., Ltd.
02 number average molecular weight (N100,000) was dissolved in tetrahydrofuran, 5% Pd/C was added as a catalyst, and a hydrogenation reaction was carried out at a temperature of 170° C. and a hydrogen pressure of 100 kg/c-j for 6 hours. Hydrogenated polystyrene with a number average molecular weight of 68,000 and a nuclear hydrogenation rate of 99.0% was obtained.

Resin production example-2 Resin except that a styrene-butadiene block copolymer (number average molecular weight 10,000,000 butadiene content 20% by weight) obtained by an anionic polymerization method was used at a hydrogen pressure of 70 kg/cm. Hydrogenated styrene with a number average molecular weight of 87,000 and a hydrogenation rate of 87.5% was hydrogenated in the same manner as in Production Example-1.
A butadiene block copolymer was obtained.

Resin Production Example-3 A styrene-butadiene block copolymer (number average molecular weight: 105,000 butadiene content: 5% by weight) obtained by anionic polymerization was hydrogenated in the same manner as in Resin Production Example-1. A hydrogenated styrene-butadiene block copolymer having a number average molecular weight of 89,000 and a hydrogenation rate of 93.5% was obtained.

Resin Production Example-4 A styrene-butadiene block copolymer (number average molecular weight: 120,000 butadiene content: 40% by weight) obtained by an anionic polymerization method was hydrogenated in the same manner as in Resin Production Example-2 to obtain a number-average A hydrogenated styrene-butadiene block copolymer with a molecular weight of 95,000 and a hydrogenation rate of 85.5% was obtained.

Resin Production Example-5 A styrene-methyl methacrylate copolymer (styrene content: 85% by weight, number average molecular weight: 184,000) obtained by radical polymerization was hydrogenated in the same manner as in Resin Production Example-1. As a result, the hydrogenation rate was 100% and the number average molecular weight was 14.
40,000 hydrogenated polymers were obtained. Ester groups were not hydrogenated.

Resin production example-6 Styrene homopolymer (HH-1 manufactured by Mitsubishi Monsite Kasei Co., Ltd.
02 number average molecule ff 1,130,000) was dissolved in tetrahydrofuran, 5% Pd/C was added as a catalyst, and the temperature was 170°C.
A hydrogenation reaction was carried out at a hydrogen pressure of 60 kg/ci for one hour. Hydrogenated polystyrene with a number average molecular weight of 75,000 and a nuclear hydrogenation rate of 2% was obtained.

Example-1 3.75 kg of the polymer obtained in Resin Production Example-1, 1.25 kg of the polymer obtained in Resin Production Example-2, and hydrogenated petroleum resin (Aruyo Kagaku Co., Ltd. Alcon P- 100) 250
g was dissolved in tetrahydrofuran and then co-precipitated into methanol. As an additive, 1,35-trimethyl-2,4,6-)lis-(3,5-di-t-butyl-4-hydroxybenzyl)benzene (Nrgano
30'') and (2,6-di-butyl-4-methylphenyl)pentaerythritol-siphosphite)
(rMARKPEP-36J manufactured by Adeka Argus) 0 each
．． After adding 05 parts by weight, the mixture was dried. Then, the mixture was melt-kneaded using an extruder at 260'C to form pellets.

This pellet is molded into an injection molding machine (“M140A” manufactured by Takisha Co., Ltd.)
Attach a stand bar with a group to the movable mold side using
A disc-shaped optical disk substrate of mm was molded.

The softening temperature of the substrate resin is 163℃, the single flexural modulus is 2B, O
It was OOkg/cIIN.

The obtained substrate is loaded into a sputtering device, and first 8
The atmosphere was evacuated to below X 10-'torr, and a Ta target was reactively sputtered using a mixed gas of Ar and 0□ to form an interference layer (thickness: 800 mm) consisting of Ta and O. Next, by simultaneous binary sputtering with Ar gas using a Tb target and a FeCo target, Tb
A FeCo recording layer (300 layers thick) was provided. Furthermore, T
The A2 target on which the i-chip was placed was sputtered in Ar gas to form a reflective layer with a thickness of 300 mm. On the mirror surface of the substrate on which this film is provided, draw 10 lines each in an area of 1 cm x 11. Apply Teraoka's adhesive tape (imide film base) to the resulting substrate grating area, and then pull it. The adhesion strength between the substrate and the tantalum oxide film was evaluated by peeling it off.

As a result, not one of the 100 test pieces in the shape of a substrate measuring 1 mm x 1 mm square was peeled off.

Example-2 5 kg of the hydrogenated polymer obtained in Resin Production Example-3 was added with low molecular weight polyvinylcyclohexane (A/L/
17P-125 Softening point 125'C1 Molecular weight 820) 1
50 g was added, and pelletization, injection molding, and sputtering were performed in the same manner as in Example 1, including additives and the like. The softening temperature of the substrate resin is 168°C and the elastic modulus is 29. OOOk
g/cffl. As a result of performing a tape peeling test in the same manner as in Example 1, not one out of 100 sheets peeled off.

Example-3 2.5 kg of hydrogenated polymer obtained in Resin Production Example-1,
and 2.5 kg of hydrogenated polymer obtained in Resin Production Example-2
Pelletization, injection molding, and sputtering were performed in the same manner as in Example-2. The softening temperature of the substrate resin was 158° C., and the elastic modulus was 23,000 kg/ci. As a result of the tape peel test, not one out of 100 tapes peeled off.

Example-4 An optical disk substrate was obtained in the same manner as in Example-1 except that the polymer obtained in Resin Production Example-5 was used instead of the polymer obtained in Resin Production Example-1, and sputtering was performed. Ta.

The softening temperature of the substrate resin is 161°C, and the elastic modulus is 28°000.
kg/ad. As a result of tape peeling test, peeling was 1
There wasn't even one out of 00.

Example-5 4.25 kg of the polymer obtained in Resin Production Example-1, 0.75 kg of the polymer obtained in Resin Production Example-4, and Example-
An optical disc substrate was obtained in the same manner as in Example 1 except that 250 g of Alcon P-100 used in Example 1 was used, and sputtering was performed.

The softening temperature of the substrate resin is 160℃, and the elastic modulus is 27000k.
g/csll. As a result of the tape peel test, not one out of 100 tapes peeled off.

Comparative Example 1 Additives similar to those in Example 1 were added to 5.0 kg of the polymer obtained in Resin Production Example 1, and pelletization, injection molding, and sputtering were performed in the same manner. The softening temperature of the substrate resin was 172°C, and the elastic modulus was 32,000 kg/ci.

As a result of the tape peel test, all of the 100 pieces were peeled off.

Comparative Example-2 In Example-1, instead of using the hydrogenated polymer obtained in Resin Production Example-2, a hydrogenated polymer with a hydrogenation rate of 99.5% in Resin Production Example-2 was used. Pelletization, injection molding, and sputtering were performed in the same manner as in Example-1 except for this.

The softening temperature of the substrate resin is 163" and the C1 elastic modulus is 28°0.
00 kg/C1fl. As a result of the tape peel test, 98 out of 100 tapes were peeled off.

Comparative Example 3 The same additives as in Example 1 were added to 5.0 kg of the polymer obtained in Resin Production Example 6, and pelletization, injection molding, and sputtering were performed in the same manner. The softening temperature of the substrate resin was 150°c1, and the elastic modulus was 32,000 kg/d.

As a result of the tape peel test, 5 out of 100 tapes peeled off, indicating that the heat resistance was significantly reduced and the adhesive strength was still insufficient.

The results of Examples and Comparative Examples are summarized in Table 1.

Table 1 [Effects of the Invention] The composition of the present invention has excellent heat resistance, optical properties, and adhesion to recording film layers, and can be used for optical disc substrates and other optical materials.

Claims (3)

[Claims] (1) (a) 1 to less than 100% by weight of a polymer obtained by hydrogenating 75 mol to 98 mol% of all double bonds and aromatic nuclei in the vinyl aromatic hydrocarbon-conjugated diene block copolymer; and (b) 80m of aromatic nuclei in vinyl aromatic hydrocarbon polymer
0 to 95% by weight of polymer obtained by hydrogenating ol% or more
and/or (c) number average molecular weight 500-5,000, softening point 40°C
A hydrogenated vinyl aromatic hydrocarbon polymer composition comprising two or three components of the above saturated hydrocarbon resins from 0 to 20% by weight (however, the total of components (b) and (c) exceeds 0% by weight). . (2) The hydrogenated vinyl aromatic hydrocarbon polymer composition according to claim 1, which is used as an optical material. (3) An optical disc substrate comprising the hydrogenated vinyl aromatic hydrocarbon polymer composition according to claim 1.