JPH04277557A - Resin composition for optical disk substrate - Google Patents

Abstract

PURPOSE:To produce the title compsn. which transmits laser light sufficiently, adheres well to an inorg. thin film formed thereon as an information recording layer, and has an excellent heat resistance when used in a magneto-optical disc utilizing magnetic change or in a phase-change optical disc. CONSTITUTION:The title compsn. is obtd. by compounding 100 pts.wt. matrix resin (e.g. a polycarbonate resin or an amorphous polyolefin resin) with 10-500 pts.wt. org. silane compd.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a resin composition for a phase change type optical disk substrate on which recorded information can be optically written and rewritten, and more particularly, to a magneto-optical disk that applies magnetic change. The present invention relates to a resin composition that provides a substrate material for optical disks such as optical disks and phase-change optical disks, which has sufficient transparency to laser beams and has good adhesion to inorganic films.

0002

[Prior Art] Currently, magnetic recording methods are mainly used for recording information. In particular, magnetic floppy disks and magnetic hard disks have poor reliability in information recording, access speed, record storage performance, storage capacity, etc. Because it is also excellent, it is mainly incorporated into external storage devices such as computers.

On the other hand, optical recording systems are being put into practical use as data storage media because they enable higher density information storage. The basic disk structure used in this recording method has a structure in which an inorganic metal thin film for recording is layered on a transparent medium, making it possible to record large volumes that could not be achieved with magnetic recording methods. .

These substrate materials for optical disks are required to have a high degree of transparency so that laser beams can pass through the disk body, so inorganic glass or transparent resin is mainly used as the substrate material.

The currently widely used transparent resins are:
It is polycarbonate resin. However, polycarbonate resins may exhibit birefringence depending on the conditions during molding, so in order to improve this problem, it is also being considered to form composite polymers with polystyrene or the like. On the other hand, as transparent resins that can improve the above-mentioned drawbacks of polycarbonate resins, for example, "Plastics" Vol.
Amorphous polyolefin resins such as those disclosed in Publication No. 133413 and the like have been developed, and studies for practical use are underway.

[0006]

[Problems to be Solved by the Invention] Polycarbonate resins currently in general use have relatively excellent processability and mechanical properties among general transparent resins, but they are more prone to birefringence than glass. , and there are problems with heat resistance, water absorption, reliability of data storage, etc. The biggest problems among these are birefringence and water absorption resistance, and when birefringence occurs, recorded information may become unclear depending on the location of the recorded bits, leading to reading errors. In addition, regarding water absorption resistance, polycarbonate resin itself has a relatively low water absorption rate (about 0.2 to 0.3%), so there is almost no fear that physical properties or optical properties will deteriorate due to water absorption. Rare metals such as terbium and gadolinium, which are components of the recording thin film, are susceptible to corrosion and deterioration due to the influence of a small amount of moisture in the resin, resulting in insufficient recording of information or loss of recorded information during storage. Furthermore, the adhesion with the inorganic thin film formed as a recording film component is insufficient, resulting in frequent bit error rates.
In extreme cases, problems such as peeling or cracking of the inorganic thin film may occur over time or when used in high temperature or high humidity environments. Therefore, it is desirable to further lower the water absorption.

On the other hand, amorphous polyolefin resins have lower water absorption and birefringence than polycarbonate resins, but they still have the same problems as polycarbonate resins in terms of adhesion to inorganic alloy thin films. Further, although glass substrates have excellent reliability, they have poor workability and are expensive to manufacture. Several improved techniques have been developed to address these problems, but at present no one that is fully satisfactory has been developed.

[0008] Furthermore, as disclosed in JP-A-1-187471, a method for improving the adhesion between a resin substrate and an inorganic thin film improves the adhesion, but at the same time, stress is applied to the substrate due to the adhesion improvement treatment. Therefore, this distortion must be removed after processing, making post-processing very troublesome.

The present invention was made in view of the above circumstances, and its purpose is to provide a film that has good transparency and water absorption resistance, excellent adhesion to inorganic thin films, and has good moldability. The present invention aims to provide an excellent resin composition for optical disc substrates.

0010

[Means for Solving the Problems] The composition of the resin composition for optical disc substrates according to the present invention that has solved the above problems is a resin composition for optical disc substrates on which recorded information can be optically written and rewritten. In the resin composition, 10 parts by weight of an organic silane compound represented by the following general formula [I] or a part thereof produced by hydrolysis and dehydration condensation is added to 100 parts by weight of the matrix resin.
The gist is that the content is 500 parts by weight. (However, in the formula, X represents an alkoxyl group having 1 to 6 carbon atoms, a halogen, a hydroxyl group, an alkoxyalkyl group, an isopropenyl group, or an oxygen radical, Y is a hydrocarbon group having 1 to 4 carbon atoms, and Z represents a carbon number 1 ~20 represents an organic group containing a reactive group such as an epoxy group, an amino group, an imino group, a sulfonyl group, a thiol group, a (meth)acryloyl group, a carbonate group, a phenyl group, or a vinyl group, and a and b
are each independently an integer of 0 to 2, and the sum of a and b represents an integer of 3 or less).

[0011]

[Operation] First, the matrix resin used in the present invention will be described. Any matrix resin can be used as long as it has excellent optical and physicochemical properties, but among them, polycarbonate resin is one that exhibits well-balanced properties. The preferred viscosity average molecular weight of the polycarbonate resin is 1,000.
~100,000, more preferably 10,000
- 30,000, and if the molecular weight is small, the molded product tends to become brittle, while if the molecular weight is too large, fluidity decreases and moldability deteriorates, making it unsuitable for optical disk substrates. Further, a composite resin obtained by blending polycarbonate resin with polystyrene, ABS resin, etc. can also be used as long as it has compatibility and affinity with the organic silane compound described below. Moreover, an amorphous polyolefin resin can also be used as a preferable resin other than polycarbonate resin.

Next, the organic silane compound used in the present invention is represented by the general formula [I], and specific examples thereof include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, and trimethoxysilane. (methyl)silane, triethoxy(methyl)silane,
Trimethoxy(vinyl)silane, triethoxy(vinyl)silane, trimethoxy(chloro)silane, chloropropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriisopropenylsilane, γ-glycidoxy Propyl(methyl)dimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-methacryloylpropyltrimethoxysilane, γ-methacryloylpropyl(methyl)dimethoxysilane, 4-phenylpropyltrimethoxysilane, γ-mercapto Propyltrimethoxysilane, γ-mercaptopropyl(methyl)dimethoxysilane, γ-aminopropyltrimethoxysilane, γ-diethylaminopropyltrimethoxysilane,
N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-phenyl-γ-
Organic silane compounds such as aminopropyltrimethoxysilane, prepolymers or polydimethylsiloxanes obtained by hydrolysis and partial dehydration condensation of these compounds,
Examples include polydiphenylsiloxane and block copolymers of bisphenol and siloxane.

The method of blending the organic silane compound and the matrix resin is not particularly limited, and conventional methods can be used as they are or with appropriate improvement; however, as a typical method, (1) ) A method in which the matrix resin is heated to a molten state, an organic silane compound is added thereto, blended uniformly, and then injection molded (this method is useful when the matrix resin and the organic silane compound have good compatibility), (2) A method in which the matrix resin is dispersed or dissolved in an organic solvent, and an organic silane compound is added thereto and mixed.

Next, the composition ratio of the matrix resin and the organic silane compound depends on the type and blending state of the matrix resin and the organic silane compound to be blended,
Furthermore, the preferred composition varies depending on the required properties (mechanical properties, durability, etc.) of the substrate, so it cannot be determined uniformly, but in order to ensure the properties for optical disk substrates, matrix resin 100 The organic silane compound must be contained in an amount of 10 to 500 parts by weight, preferably 50 to 200 parts by weight. However, if the amount of organic silane compound is insufficient,
Adhesion to the inorganic thin film provided on the disk substrate cannot be sufficiently improved, and conversely, if the amount is too high, the elasticity of the resin composition deteriorates, making it unsuitable as a substrate.

[0015] The essential components in the present invention are as described above, but in addition to these, if necessary, silicon oxide fine particles or metal oxide fine particles other than silicon may be added as a component to reinforce the blending effect of the organic silane compound. It can also be blended in an appropriate amount. The silicon oxide fine particles used here preferably have a particle size of 2 to 100 nm, and specific examples include colloidal silica and aerosols obtained by air oxidation. Furthermore, it is also possible to add coupling agents such as titanium, aluminum, zirconium, and tin as other components, or to add antioxidants and various stabilizers.

The resin composition used in the present invention must have sufficient transparency when molded as a substrate, and can be used for disk substrates of any thickness (currently 1.2 mm is the mainstream). It is desirable that the total light transmittance of (a) is 80% or more, and the haze value, which indicates the degree of scattered light that becomes noise with respect to the transmitted light, is 10% or less, more preferably 5% or less, and these required characteristics It is desirable to adjust the type, amount, dispersion state, etc. of the organosilane compound so as to satisfy the following conditions.

[0017] The haze value here is a value also called haze. For example, as stipulated in the special optical properties section of JIS K7105, the amount of light transmitted through the sample and the amount of scattered light are measured, and these are calculated. The total light transmittance (Tt
) and diffuse transmittance (Td), haze value (H) is:
It is calculated using the formula H=(Td/Tt)×100(%).

When the haze value exceeds 10%, the amount of scattered light increases, making recording and reading difficult. Note that this value varies depending on the type of functional group contained in the organic silane compound and its amount, so it is desirable to appropriately select the type and amount of the organic silane compound in each case.

[0019]Also, it is desirable that the total light transmittance is 80% or more as mentioned above.
When an optical grade polycarbonate resin or amorphous polyolefin resin is used as the matrix resin, this condition is satisfied in most cases as long as the haze value is 10% or less. However, when using a polycarbonate resin, amorphous polyolefin resin, or the like that has undergone various modifications, care must be taken because the total light transmittance may fall below 80%.

The resin composition thus obtained is molded into pellets using an extruder or the like in a conventional manner, and
A disk substrate may be formed by injection molding or the like using a stamper or the like.

The method for forming a recording thin film on the substrate obtained in this manner may be carried out according to a conventional method. For example, a dielectric film such as silicon nitride or silicon oxide and Tb, Fe, Co, Gd, N
It is possible to adopt a method in which an alloy target such as d is formed by a method such as sputtering, and a reflective film of aluminum, aluminum nitride, or the like is formed on the upper layer to form a recording thin film.

Furthermore, although it is common practice to perform annealing before forming the above-mentioned thin film, when the resin composition of the present invention is used, the annealing process is relatively gentle compared to the case where a substrate consisting only of matrix resin is used. The advantage is that the degree of vacuum can be reached even under such annealing conditions.

As described above, in the present invention, the specific organic silica compound is dispersed in the matrix resin, and in some cases, a part of it reacts with the matrix resin, so that the coefficient of linear expansion of the composite material decreases, and the surface layer Not only can the stress generated between the resin and the inorganic thin film that is provided as a thin film be minimized, but the organic silane compound dispersed in the resin can also be used to deposit silicon components on the surface through surface activation such as sputtering performed during thin film formation. It also exhibits the effect of increasing the adhesion and chemical stability with the inorganic thin film that is exposed and laminated on the surface.

[0024]

[Examples] The present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples. Note that "parts" in the examples mean "parts by weight" unless otherwise specified.

Example 1 100 parts of polycarbonate resin pellets having a viscosity average molecular weight of about 20,000 were suspended and dissolved in 100 parts of methylene chloride. 100 parts of tetraethoxysilane was added to this and thoroughly kneaded to disperse it. Next, methylene chloride was distilled off under reduced pressure to obtain a raw resin composition. This composition was pelletized using an extruder, and then a magneto-optical disk substrate having a diameter of 130 mm and a thickness of 1.2 mm was molded using an injection molding machine.

Next, this substrate is set in a sputtering device,
After annealing under vacuum at 90° C. for 30 minutes, a high frequency electric field was applied while argon gas and oxygen gas were introduced at a ratio of 1:1, and plasma treatment was performed for 10 minutes. This plasma-treated surface is coated with a thickness of 0 by sputtering.
．． A 1 μm silicon nitride film is formed, and then Tb/F is added on top of it.
After forming e.Co alloy to a thickness of 0.1 μm and silicon nitride to a thickness of 0.1 μm, an aluminum layer with a thickness of 0.1 μm was formed as a reflective layer to obtain a magneto-optical disk.

Table 2 shows the characteristics of the obtained disk. The characteristics evaluation method was performed based on the following criteria. [Evaluation Criteria] Haze: Direct reading haze meter (No. 20 manufactured by Toyo Kiki Co., Ltd.)
6 type) was used for direct reading. Adhesion test: The disk on which the thin film was formed was heated to 80°C.
, after being left in an atmosphere with relative humidity of 90% for 500 hours,
A cross-cut tape test was conducted. That is, 100 squares of 1 mm2 were formed on the surface of the test product, an adhesive tape was pressed, and then the tape was peeled off in the vertical direction to examine the state of the thin film on the product surface and expressed as the number of squares remaining. Heat resistance: After leaving the disk on which the thin film was formed for 500 hours in an atmosphere with a temperature of 80°C and a relative humidity of 90%, the presence or absence of pinholes was checked using an optical microscope and a polarizing microscope to confirm that no burst changes had occurred. Those without were considered good. Reliability: The disk on which the thin film was formed was left in an atmosphere with a temperature of 80°C and a relative humidity of 90% for 500 hours, and the bit error rate (BER) was measured before and after the test.
Those whose initial value and post-test value were 5×10 −5 or less were considered good. Birefringence: Measured using an ellipsometer. The wavelength used was 630 nm. Coefficient of linear expansion: Using a test piece with a thickness of 1.2 mm,
The average value of linear expansion coefficient in the range from room temperature to 100°C was measured. Water absorption: A test piece with a thickness of 1.2 mm was immersed in pure water, and the water absorption rate was calculated from the weight change after leaving it at room temperature for 48 hours.

Examples 2 to 6 The same procedure as in Example 1 was carried out except that the type and amount of the organic silane compound used in Example 1 were changed to those shown in Table 1.
A magneto-optical disk was obtained. Table 2 shows the characteristics evaluation results of the obtained discs.

Example 7 A magneto-optical disk was obtained in the same manner as in Example 1, except that an amorphous polyolefin resin was used in place of the polycarbonate resin in Example 1, and cyclohexane was used as the solvent. Table 2 shows the characteristics evaluation results of the obtained discs.

Examples 8 to 12 In place of the organic silane compounds in Examples 2 to 6, their hydrolysates were used. That is, the organic silane compounds shown in Table 1 were dissolved in 100 parts of methanol, then 0.1 N hydrochloric acid was slowly added to hydrolyze the organic silane compounds, and the organic silane compounds were left at room temperature for 24 hours to partially dissolve the organic silane compounds. An optical disc was produced in the same manner as in Example 1, except that a silane solution obtained by dehydration and condensation was used to produce a raw material resin pellet, a disc substrate, and a thin film. The obtained optical disk was a reliable magneto-optical disk product with excellent characteristics similar to those of Example 1.

Example 13 The same procedure as in Example 8 was carried out, except that an amorphous polyolefin resin was used instead of the polycarbonate resin in Example 8, and cyclohexane was used as the solvent.
A magneto-optical disk was obtained. The characteristics evaluation results of the obtained disk are shown in Table 2, and it was a reliable magneto-optical disk product with excellent characteristics.

Example 14 As an organic silane compound, 100 parts of methacryloyloxypropyltrimethoxysilane was mixed with 100 parts of cyclohexane.
and then add 30% of 0.1 N acetic acid aqueous solution to this.
The reaction product obtained was used as a silane component, and as a matrix resin, 100 parts of an amorphous polyolefin resin was mixed with cyclohexane as a solvent. An optical disc was obtained in the same manner as in Example 8 except that the suspension was used. The characteristics and reliability of the obtained disk were as excellent as those obtained in Example 8.

Comparative Example 1 A magneto-optical disk was obtained in the same manner as in Example 1, except that the addition of an organic silane compound to the resin composition in Example 1 was omitted and the plasma treatment was not performed during forming the recording thin film. Ta. The resulting disc showed partial peeling of the thin film during a high-humidity durability test, and local defects occurred when measuring the bit error rate.

Comparative Example 2 An experiment was conducted in exactly the same manner as in Example 1, except that the amount of organic silane compound used was 5 parts. As in Comparative Example 1, durability was insufficient.

Comparative Example 3 An experiment was conducted in exactly the same manner as in Example 1 except that the amount of organic silane compound used was 800 parts. The resultant substrate was brittle and had numerous cracks after the thin film was formed. It was not possible to write entry records.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Effects of the Invention] The present invention is constructed as described above, and by combining the matrix resin and the organic silane compound in a specific ratio, the substrate formed using the same can have its own water absorption resistance enhanced. At the same time, the adhesion between the dielectric film and the magnetic recording film is dramatically improved, and a highly reliable optical disc can be obtained.

Furthermore, the above matrix resin undergoes a partial condensation reaction with an organic silane compound to form a composite structure, thereby improving heat resistance and water absorption resistance, increasing the processing temperature during thin film formation, and reducing linear expansion. Since the coefficient is also reduced, stress that occurs when an inorganic dielectric film is formed on the surface layer is also suppressed, and a disk substrate with excellent heat resistance, water absorption resistance, and dimensional accuracy can be obtained.

Furthermore, since the organic silane compound is dispersed in the resin composition of the present invention to disturb the orientation of the matrix resin, it has good physical and optical properties such as suppressing birefringence when used as a substrate. It exhibits various characteristics in.

Claims (3)

[Claims] 1. A resin composition for a substrate of an optical disk on which recorded information can be optically written and rewritten, the resin composition comprising an organic silane compound represented by the following general formula, based on 100 parts by weight of a matrix resin. Alternatively, an organic silane compound produced by hydrolysis and dehydration condensation of a part of it is
A resin composition for an optical disc substrate, characterized in that the resin composition contains 0 to 500 parts by weight. (However, in the formula, X represents an alkoxyl group having 1 to 6 carbon atoms, a halogen, a hydroxyl group, an alkoxyalkyl group, an isopropenyl group, or an oxygen radical, Y is a hydrocarbon group having 1 to 4 carbon atoms, and Z represents a carbon number 1 ~20 represents an organic group containing a reactive group such as an epoxy group, an amino group, an imino group, a sulfonyl group, a thiol group, a (meth)acryloyl group, a carbonate group, a phenyl group, or a vinyl group, and a and b
are each independently an integer from 0 to 2, and the sum of a and b represents an integer of 3 or less) 2. The resin composition for an optical disc substrate according to claim 1, wherein the matrix resin is a polycarbonate resin. 3. The resin composition for an optical disc substrate according to claim 1, wherein the matrix resin is an amorphous polyolefin resin.