JPS63165434A - Optical disk and production thereof - Google Patents

Abstract

PURPOSE:To obtain a highly heat-resistant optical disc of small optical strain, outstanding in adhesiveness to recording film, by use of a base plate produced by injection molding, at specified temperatures, of a resin containing specific polysulfone resin. CONSTITUTION:A resin containing pref. 15-100wt.% of a polysulfone resin of formula (X and Y are each H, 1-6C aliphatic hydrocarbon group, etc.; Z and W are each H or 1-6C aliphatic hydrocarbon group; n is 60-80) is brought to injection molding at cylinder temperatures >=370(pref., >=400) deg.C and mold temperatures >=130(pref., >=140) deg.C. The resulting base plate is sputtered with an intermediate film and recording film, etc., thus obtaining the objective optical disc.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical disc and a method for manufacturing the same, and particularly relates to a plastic optical disc with low optical distortion and good adhesion to a recording film, and a method for manufacturing the same. .

[Conventional technology]

-m, the cross-sectional structure of optical discs such as video discs and digital audio discs, for example,
There is an air sand inch method disclosed in No. 8636.

FIG. 2 shows an example of the cross-sectional structure of the optical disc.

Further, according to the configuration of the optical disc shown in FIG. 3, the spacer 24
The substrates 22 are arranged facing each other with the substrates 22 interposed therebetween, and an intermediate film (also referred to as a heat absorption film) 21, a recording film 20, and a protective film 2 are formed on both surfaces of the substrates 22 in the space formed by the substrates 22.
3 (not shown) is formed.

Depending on the type and properties of the recording film 20, optical discs may be produced by forming holes in the recording film using thermal energy such as a laser beam, by changing the structure of the recording film, or by using magneto-optical technology. There are many methods for changing the reflectance of light. In either method, there is no difference in that reproduction or recording and reproduction is performed using thermal energy such as a laser beam.

The interlayer film 21 is made of nitrocellulose, bismuth-based compounds, acrylic resins such as SiN, Sin, Stow, etc., and prevents heat from escaping to the outside, increasing the conversion efficiency of the thermal energy of the laser beam.

Further, the spacer 24 is made of metal or plastic and a plastic composite material, and performs functions such as gap adjustment and matching with the center drive shaft.

The method of rewritable optical discs is crystal state→
It is difficult to judge the superiority or inferiority of two methods: one uses a recording material that changes its phase to an amorphous state, and the other uses magneto-optical technology, but it seems likely that a commercial product will appear soon. Among these recording materials, magneto-optical recording materials, such as G
It is said that when writing and erasing are repeated using a dTbPeGe or TbFeCo alloy recording material, the surface temperature of the recording material instantaneously reaches 250 to 300°C.

In the case of a video disc, the substrate 22 is generally a PM
It is made of acrylic resin such as MA, audio discs are generally made of PC resin (polycarbonate resin) or PMMA, and write-once discs are generally made of PMMA, PC resin, or tempered glass. However, the above-mentioned substrate materials have advantages and disadvantages, and although tempered glass is excellent in long-term reliability, it has a problem of high specific gravity and high cost. Also,
Although plastic substrates have a low specific gravity and are inexpensive, they have low heat resistance and high moisture absorption, resulting in poor long-term reliability.

For example, an acrylic resin substrate has good birefringence, but has low heat resistance, high moisture absorption, and poor impact strength. In addition, in recent years, research at acrylic resin manufacturers,
Many prototypes have been made, and super heat-resistant acrylic resins have been developed, but although the heat resistance has improved compared to conventional acrylic resins, there has been little improvement in hygroscopicity, impact strength, etc.

On the other hand, with PC resin, by lowering the molecular weight and improving fluidity, although there are some problems with birefringence, moisture absorption and impact strength are good, and there are almost no problems as a playback-only or write-once disk substrate. It is said that

However, many new recording materials are being developed as the types of optical discs move from the current read-only and write-once types to rewritable types. In the case of these rewritable optical discs, the surface of the substrate becomes quite hot during recording and reproduction using a laser beam, and the recording film itself can become quite thick, so the adhesion between the recording film and the substrate is also a problem. Become. In addition, since the error rate of optical discs is targeted to be less than IQ-1, it is necessary to use discs with even lower optical distortion, that is, lower birefringence, higher heat resistance, and better adhesion to the recording film. There is a growing demand for high-quality plastic substrates. For this reason, some attempts have been made to apply heat-resistant transparent materials other than polycarbonate, which contain an aromatic ring in the main chain of their chemical structure, to plastic substrates for optical disks.

However, although these heat-resistant transparent materials have almost good heat resistance and adhesion to the recording film, when a disk substrate is made by injection molding using these materials, optical distortion, that is,
The problem of large birefringence remains.

Further, as in JP-A-61-55117, a method for manufacturing a disk substrate using a polycarbonate resin composition with improved heat resistance and birefringence has been introduced. Disk substrates molded from these polycarbonate compositions have good heat resistance and tarpaulin, but when optical disks are manufactured using these substrates, there is a problem of poor adhesion between the recording film and the disk substrate (almost no lifespan). There is.

Regarding this substrate and other substrates molded from polycarbonate resin compositions, various studies were conducted by sputtering various intermediate films between the recording film and the substrate, but similar results were obtained in all cases. Although the adhesion between the recording film and the substrate varies depending on the type of recording film, the adhesion is particularly poor when using an alloy-based recording film such as GdTbFeGe and TbFeCo, and the optical disc has almost no lifespan. Ta.

[Problem that the invention seeks to solve]

The purpose of the present invention is to have excellent heat resistance, low optical distortion,
Moreover, the objective is to obtain an optical disk with a long life.

[Means for solving problems]

As a result of extensive studies, the inventors of the present invention found that by using a specific polysulfone resin as the resin component of the substrate, optical disks with excellent heat resistance, low optical distortion, and good adhesion with the recording film have a long life. We have discovered that it is possible to produce a 100% polyurethane resin, and have solved the problems of the prior art described above.

That is, the above object is achieved by using a polysulfone material represented by the following general formula (I) as the resin component of the optical disk substrate.

General formula (1) % formula % In the above formula, X is a hydrogen atom, an aliphatic hydrocarbon group having 1 to 6 carbon atoms, an aromatic hydrocarbon group, or an alicyclic hydrocarbon group, and Y is a hydrogen atom, an aliphatic hydrocarbon group having 1 to 6 carbon atoms,
It is an aromatic hydrocarbon group or an alicyclic hydrocarbon group, and Z and W are a hydrogen atom or an aliphatic hydrocarbon group having 1 to 6 carbon atoms. However, when X, Z and W are hydrogen atoms, or when X is a methyl group and 2 and W are hydrogen atoms,
Y is an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or an alicyclic hydrocarbon group having 2 to 6 carbon atoms.

The polysulfone resin used in the present invention is
It can be manufactured according to Example 3 of No. 99.

When a disk substrate is manufactured by an injection molding method using the polysulfone resin of the general formula (1) of the present invention, although the viscosity of the molten resin is higher than that of general polysulfone resin,
Since the photoelastic constant of the resin is small, stress relaxation occurs during the cooling process, and the optical strain, ie, birefringence, of the obtained disk substrate becomes small.

However, since the birefringence of the disk substrate also changes depending on the injection molding conditions, the injection molding conditions for the polysulfone resin of the present invention are: cylinder temperature 370°C or higher, mold temperature 13°C.
The temperature is preferably 0°C or higher. More preferably cylinder temperature 40
The temperature is 0°C or higher, and the mold temperature is 140°C or higher.

The heat resistance of the polysulfone W* used in the present invention is preferably 155°C or higher in terms of glass transition temperature, and the number of repeating structural units, n, is preferably 6G-80 from the viewpoint of mechanical strength and resin fluidity. Inventive polysulfone resin (
Although the general formula [■]) and a polysulfone resin other than the general formula (1) may be appropriately mixed, considering both melt fluidity and photoelastic constant, the polysulfone resin of the present invention is
It is desirable that the content be 106% by weight.

In the above structure of the present invention, since the substrate performs recording and reproduction using a laser beam, a transmittance of 8094 or more (measured at 827 m-) is required for a substrate of, for example, 1.2-. The transmittance is preferably 90% or more. When the transmittance is less than 80%, the loss increases, so the power of the semiconductor laser used must be increased, which is disadvantageous in terms of energy.

In the optical disc according to the present invention, when the intermediate layer is formed, the above-mentioned nitrocellulose or S2 is used.

Sin, 5303. In addition to bismuth-based compounds, acrylic resins, and the like, an intermediate layer that is compatible with the type of recording film and substrate material can be used.

When actually making a disk, it is necessary to apply a hard coat etc. to the disk surface in order to improve its wear resistance.
toss SlO+ 5to1. Ti0g+ ZrO
A hard coat such as a rich or organic polymer can be applied.

[For production]

Among the properties particularly required of plastic substrates for optical discs are retardation (optical distortion) and adhesion with recording films. In addition, both polycarbonate 11m and polysulfone resin, which are generally commercially available, use bisphenol 8 shown below as a starting material for one of them.

5Is l) Improvement of retardation When materials with aromatic rings (benzene rings) in the main chain (general polycarbonate or polysulfone resins) are injection molded, the aromatic rings are arranged in layers in the flow direction, resulting in optical problems. It is thought that this makes it anisotropic, which increases the retardation.

Therefore, above the central carbon of bisphenol A.

By replacing one or both of the methyl groups (CBa) below with an aliphatic hydrocarbon group having 2 or more carbon atoms, an aromatic ring, or an alicyclic hydrocarbon, it is also possible to add aliphatic to the left and right aromatic rings of bisphenol. By substituting group hydrocarbons, the polarizability of each monomer unit changes, and the orientational birefringence due to the orientation of monomer units when stress is applied can be reduced, making it possible to lower the adhesive strength of the plastic substrate. reasoned.

2) Improving Adhesion with Recording Film In the process of sputtering a recording film onto a plastic substrate of an optical disc, first, an intermediate film such as SiN is sputtered onto the substrate, and then a recording film is sputtered onto it. For this reason,
The adhesion between the substrate and the memory depends on the adhesion between the substrate and SiN or the like.

When sputtering SiN onto a polycarbonate tree 11 substrate and then sputtering a recording film, the adhesion was poor even when the buffing conditions were varied. Therefore, in the case of bus sputtering, a part of the SiN is ionized and a substance having a polar group is generated, which is chemically bonded to the highly polar polysulfone resin substrate, so that it adheres firmly.

As is clear from the above inferences 1) and 2) and looking at the examples, if the polysulfone resin of general formula (1) is used, the retardation will be small and the plastic substrate for optical disks will have good adhesion to the recording film. was able to obtain.

〔Example〕

A polysulfone resin corresponding to the general formula (1) of the present invention was obtained using Examples 3 and 1G of Japanese Patent Publication No. 42-7799 filed by 000 Co., Ltd. and the following dihydric phenol.

The structural formulas of the obtained resins are shown in Table 1, 1lhl to 15. Similarly, Example 1 of Japanese Patent Publication No. 42-7799. 5
Polysulfone resin was obtained according to . The structural formula of the obtained resin is shown in Na16.17 in Table 1.

Example 1 The melt viscosity of polysulfone resin No. 1 in Table 1 was measured,
Table 1 shows the temperature at which the melt viscosity becomes 500 poise.

The melt viscosity was measured using a Koka type flow tester. Based on this melt viscosity value, the cylinder temperature is 430℃,
The mold temperature was set to 140°C, and Necool S manufactured by Sumitomo Heavy Industries was used.
- Using a 165/75 type injection molding machine, thickness 1.2 M,
A grooved disk substrate of φ130 was molded. In order to examine the optical distortion of the obtained disk substrate, we used a DVA manufactured by Shotō Kogaku.
Retardation was measured using a 36 LS ellipsometer and is shown in Table 1. In addition, a load was applied stepwise to the tensile test piece, the retardation was similarly measured using an ellipsometer, and the photoelastic constant was calculated and shown in Table 1.

Furthermore, the obtained disk substrate was used to create a Vacuum Riko type T? '1
The glass transition temperature (Tg) was determined as a guideline for heat resistance using a thermophysical tester model A-1500 and is shown in Table 1. Next, this disk substrate is sequentially passed through various cleaning tanks such as a surfactant aqueous solution cleaning tank with ultrasonic waves and an ultrapure water cleaning tank with ultrasonic waves, and after cleaning, the degree of vacuum (10
-2 to 10-sa (1 g) for 10 to 30 hours and thoroughly dried. Thereafter, as shown in FIG. 2 in the sputtering device, an intermediate film (SiOz) *recording film (TbPeCo),
A protective film (SiN) was sequentially formed, and then the plastic substrate with the recording film formed above was bonded to the film using an epoxy adhesive using a spacer to produce an optical disc.

According to this method of manufacturing an optical disk, it is possible to reduce the weight of the disk, and since the disk can be molded using an injection molding method, the manufacturing cost of the disk substrate is also low, and it is possible to integrate the spacer, making it economical. , which is excellent in simplification.

This optical disk was driven and the C/N ratio (a type of S/N ratio that is the ratio of signal output to noise output) was measured, and the results are shown in Table 1. In addition, as a simple method for evaluating the lifespan of an optical disk, the plastic substrate with a recording film prepared previously in an environment of 60°C/95% RH is taken out after storage, and the reflectance of the recording film is measured at room temperature. The time when it reached 70% was defined as the life span. These results are shown in FIG.

Examples 2 to 15 The same procedure as in Example 1 was carried out except that boxes 2 to 15 in Table 1 were used as the substrate material. The results are shown in Table 1.

Comparative example 1. 2 The same procedure as in Example 1 was conducted except that Na15.17 shown in Table 1 was used as the substrate material. The results are shown in Table 1.

Comparative Example 3.4 Same as Example 1 except that a high heat resistant, low birefringence polycarbonate material as described in JP-A No. 61-55117 and polycarbonate resin 80-5503 manufactured by Kijin Kasei were used as the substrate material. I did the same.

According to Table 1, the C/N ratios of the optical discs manufactured using the disc substrates molded from the substrate materials of Examples 1 to 15 were very good values of 50 to 57 dB. This is because although the fluidity of the resins used in Examples 1 to 15 is slightly lower than that of the resin of Comparative Example 1.2, the photoelastic constant is small.
It is thought that stress relaxation occurred during the flow process of the resin, and the resulting disk substrate paste turpion became smaller, resulting in an improvement in the C/N ratio. Moreover, as is clear from Fig. 1, the adhesion between these plastic substrates and the recording film is good, so the 5X10
! It has a very long lifespan (over an hour).

On the contrary, Comparative Example 1.2 has a lifespan similar to that of Examples 1 to 1.
Although they are long like No. 5, they all have a larger photoelastic constant compared to the example, so the stress relaxation of the molten resin is slow, so the disk substrate paste turbulence becomes large, and the C/N ratio of the optical disk becomes small. It is estimated that the Comparative Example 3 has a small photoelastic constant, and Comparative Example 4 has a low melt viscosity, so the tarpsion of the substrate is small.
Therefore, the ClN ratio of the optical disc was close to that of Examples 1 to 15. However, the lifespan of the polycarbonate disk substrate of Comparative 3.4 was shortened to 24 hours and 36 hours due to poor adhesion of the recording film.

Furthermore, regarding these polycarbonate resin substrates, UV
Although the substrate surface was activated by treatment, ozone treatment, etc., none of them resulted in an improvement in life.

(Margins below this page) [Effects of the Invention] As explained above, the optical disc using the polysulfone resin of the present invention has excellent heat resistance and low optical distortion, so there is little risk of errors occurring during recording and playback. Moreover, since the adhesion between the substrate and the recording film is improved, the life of the disk is extended.

[Brief explanation of the drawing]

FIG. 1 is a lifespan curve of an optical disk substrate with a recording film according to the present invention, FIG. 2 is a cross-sectional structural diagram of the optical disk, and FIG. 3 is a
FIG. 2 is a cross-sectional structural diagram of an air sand inch optical disc. 1... Data of Example 1, 2... Data of Example 2, 3... Data of Example 3, 4... Data of Example 4, 5... Data of Example 5, 6... Data of Example 6, 7... Data of Example 7, 8... Data of Example 8, 9... Data of Example 9, 10... Data of Example 10, 11...Data of Example 11, 12.
...Data of Example 12, 13...Data of Example 13, 14...Data of Example 14, 15...Data of Example 15, 16...Data of Comparative Example 1, 17.・
・Data of Comparative Example 2, 18...Data of Comparative Example 3, 1
9... Data of Comparative Example 4, 20... Recording film, 21.
...Intermediate film, 22...Plastic substrate, 23...
Protective film, 24...spacer.

Claims (1)

[Scope of Claims] 1. An optical disc having a substrate, characterized in that the substrate is made of a resin containing a polysulfone resin represented by the following general formula [I]. General formula [I] ▲There are mathematical formulas, chemical formulas, tables, etc.▼. n = 60 to 80 In the above formula, X is a hydrogen atom, an aliphatic hydrocarbon group having 1 to 6 carbon atoms, an aromatic hydrocarbon group, or an alicyclic hydrocarbon group, and Y is a hydrogen atom, ~6 aliphatic hydrocarbon groups,
is an aromatic hydrocarbon group or an alicyclic hydrocarbon group, and Z and W are hydrogen atoms or aliphatic hydrocarbon groups having 1 to 6 carbon atoms, provided that when X, Z and W are hydrogen atoms, Or when X is a methyl group and Z and W are hydrogen atoms,
Y is an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or an alicyclic hydrocarbon group having 2 to 6 carbon atoms. 2. The optical disc according to claim 1, wherein the substrate is made of a resin containing 15 to 100% by weight of a polysulfone resin represented by the general formula [I]. 3. In a method of manufacturing an optical disc having a substrate,
A resin containing a polysulfone resin represented by the following general formula [I] was heated at a cylinder temperature of 370°C or higher and a mold temperature of 130°C.
A method of manufacturing an optical disc, characterized in that a substrate is manufactured by injection molding at a temperature of ℃ or higher. General formula [I] ▲ Numerical formulas, chemical formulas, tables, etc. are available ▼ n = 60 to 80 In the above formula, X is a hydrogen atom, an aliphatic hydrocarbon group having 1 to 6 carbon atoms, an aromatic hydrocarbon group, or an alicyclic group A hydrocarbon group, Y is a hydrogen atom, an aliphatic hydrocarbon group having 1 to 6 carbon atoms,
is an aromatic hydrocarbon group or an alicyclic hydrocarbon group, and Z and W are hydrogen atoms or aliphatic hydrocarbon groups having 1 to 6 carbon atoms, provided that when X, Z and W are hydrogen atoms, Or when X is a methyl group and Z and W are hydrogen atoms,
Y is an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or an alicyclic hydrocarbon group having 2 to 6 carbon atoms.