JPH07334864A - Information recording medium, information recording medium substrate, and inspection method for information recording medium - Google Patents

Abstract

(57) [Abstract] [Purpose] An information recording medium substrate having high reliability, in which a foreign substance composed of a hydrolyzate does not occur in a resin substrate even after long-term use, and information provided with such a substrate. Providing a recording medium. Also, to provide a method for inspecting the long-term reliability of a substrate of an information recording medium by a simple method in a short time. [Structure] At a temperature in the range of 5 to 20 ° C. lower than the glass transition temperature of the resin (polycarbonate resin, etc.) constituting the substrate of the information recording medium, after being left under saturated water vapor pressure of water at the temperature for 2.5 hours, In addition, foreign matter having a diameter of 100 μm or more is not generated due to hydrolysis of the resin. Further, the method for inspecting the information recording medium according to the present invention is based on determining whether or not the foreign matter is generated after leaving for 2.5 hours under the above conditions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser disc, a compact disc, a CD-ROM, and a Wr for recording, reproducing or erasing information using light or light and magnetism.
The present invention relates to an information recording medium such as an ite-once type disc, a CD-R, a magneto-optical disc, a mini disc, an optical card, a substrate thereof, and an inspection method of the information recording medium.

[0002]

2. Description of the Related Art Optical discs and optical cards typified by compact discs and magneto-optical discs are made of acrylic resin,
Polycarbonate resin, amorphous olefin resin,
A metal thin film is provided on a signal-side surface (a surface on which a signal is written) of a substrate made of epoxy resin, glass or the like by using a thin film forming method such as a sputtering method or a vacuum deposition method. It is common to use a substrate injection-molded using a resin such as a polycarbonate resin.

When a substrate made of polycarbonate resin or the like is injection-molded, the molded substrate may be warped due to defective release from the mold, and defective products may occur due to defective transfer. Therefore, a releasing agent such as silicone oil, fatty acid or fatty acid ester is often added to the polycarbonate resin or the like.

On the other hand, since the above-mentioned optical disc and the like have a main function of recording information, great attention is paid to the reliability of the medium, and the fact that the substrate resin has the reliability for a long time is The fact that the recording film has high durability is an important matter. Therefore, by exposing the optical disk to a constant high temperature and high humidity for a long time, or performing a heat cycle in which high temperature and low temperature are repeated at a constant cycle, chemical changes expected to occur after a long period of time are short-term. It is common to perform a test (so-called accelerated test) to generate.

[0005]

When polycarbonate is used as the resin for the substrate of the information recording medium, silicone oil or the like is generally used as a release agent added to the resin, but silicone oil is used. When
To obtain a high effect, a large amount of silicone oil needs to be added, and the exuded oil adversely affects the adhesion between the substrate and the metal thin film. When a fatty acid, a fatty acid ester or the like is used, it causes hydrolysis of the polycarbonate resin under high temperature and high humidity, and a laser light scattering or the like occurs due to a decomposition product (precipitation as white dots) due to the hydrolysis. The signal characteristics may deteriorate.

Regarding the reliability test of the optical disk substrate by evaluating the presence or absence of the generation of hydrolyzate after a long period of time, the MIL standard, the International Standardization Committee (ISO), etc. It has been decided,
Since all of the conditions defined by these are long-term tests ranging from one week to several months, they require a great deal of time and labor even though they are accelerated tests. Therefore, if you try to feed back the evaluation results to the production line after taking out a test sample from the production line and conducting a long-term test, you may have to discard the optical disk substrate that has already been sent to the subsequent process, May cause large losses.

The present invention has been made in view of the above-mentioned problems, and has high reliability because no foreign matter composed of a hydrolyzate is generated in the resin substrate even after long-term use. An object is to provide a substrate and an information recording medium provided with such a substrate. Another object of the present invention is to provide a method for inspecting the long-term reliability of a substrate of an information recording medium by a simple method in a short period.

[0008]

The invention relating to the information recording medium according to claim 1 of the present application which solves the above-mentioned problems is a temperature in the range of 5 to 20 ° C lower than the glass transition temperature of the resin constituting the substrate. It is characterized in that no foreign matter having a diameter of 100 μm or more is generated in the substrate after standing for 2.5 hours under saturated water vapor pressure of water at a temperature. Further, the invention of the information recording medium substrate according to claim 2 of the present application is a temperature in the range of 5 to 20 ° C. lower than the glass transition temperature of the resin constituting the substrate, and 2.5 hours under the saturated vapor pressure of water at the temperature. It is characterized in that no foreign matter having a diameter of 100 μm or more is generated after being left standing. Note that the above-mentioned foreign matter is a decomposed product mainly due to hydrolysis of the resin constituting the substrate, and is deposited as white dots.

As the resin constituting the above substrate, for example, a polycarbonate resin having the following characteristics can be used. (1) contains a fatty acid ester having 10 to 30 carbon atoms,
It is characterized by containing 0.05% or less of a release agent having a pH of 7 or less. (2) contains a fatty acid ester having 10 to 30 carbon atoms,
It is characterized in that it contains 0.05% or less of a releasing agent having a monoester content of 90% by weight or more. (3) contains a fatty acid ester having 10 to 30 carbon atoms,
The fatty acid ester is characterized by containing 0.05% or less of a release agent having an alkali metal ion concentration of 8 ppm or less.

Examples of the above-mentioned fatty acid ester include stearic acid monoglyceride, behenic acid monoglyceride, palmitic acid monoglyceride and the like. The above-mentioned alkali metal ion concentration was determined by dissolving 5 g of the mold release agent in methylene chloride, adding 100 ml of ultrapure water and mixing,
It is a value measured by an ion chromatograph analyzer after isolating the aqueous layer after leaving it quietly for 24 hours. The content of the release agent is preferably in the range of 0.01 to 0.03%.

Claim 3 of the present application for solving the above-mentioned other problems
The invention relating to the method for inspecting an information recording medium of claim 1, wherein the temperature is in the range of 5 to 20 ° C. lower than the glass transition temperature of the resin constituting the substrate, and after leaving the saturated water vapor pressure of water at the temperature for 2.5 hours, It is characterized by determining whether or not a foreign matter of 100 μm or more has occurred.

As a sample used in the above inspection method, a substrate immediately after molding (before being sent to a subsequent process)
Alternatively, the substrate may be a film that has been subjected to a film forming process such as a recording film and a reflective film. The temperature for exposing the substrate is 10 to 15 ° C. lower than the glass transition temperature of the resin,
It is preferable in that the shape of pits, groups, etc. formed on the signal surface of the substrate is not changed.

[0013]

EXAMPLES The present invention will be specifically described below with reference to examples. The inspection method of the present invention using an optical disk substrate made of polycarbonate resin will be described. A substrate (diameter: 2.5) obtained by heat-melting and molding a polycarbonate resin (having a glass transition temperature of 145 ° C.).
The substrate is an inch and has a thickness of 1.2 mm before film formation. ),
The temperature was 130 ° C and the pressure was 2.5 kgf / cm ² (1
Both sides of the above substrate were sandwiched by dummy substrates so as not to come into contact with the wall surface in an autoclave kept under a saturated water vapor pressure of water at 30 ° C.). After 2.5 hours, the temperature control was turned off, and the substrate was taken out after 1 to 2 minutes. Pure water was used as water to be replenished in the autoclave.
Using a strain gauge, the number and size of defects generated in the taken-out substrate with polarization having a size of 100 μm or more were investigated. The strain gauge used here was one in which the polarization directions of two polarizing plates were made orthogonal to each other, and the observation was performed by inserting the substrate taken out from the autoclave so as to be parallel to the polarizing plates. When the foreign matter was small, it was observed using a microscope.

Next, the results of inspections made by the above-mentioned inspection method using various polycarbonate resins are shown in Tables 1 and 2.
Shown in. The polycarbonate resin shown in Table 1 contains a release agent containing a fatty acid ester having a carbon number of 10 to 30 as a release agent.
The content is not more than 05%, and the content of the monoester is variously changed. Further, the polycarbonate resin shown in Table 2 contains a release agent containing a fatty acid ester having 10 to 30 carbon atoms in an amount of 0.05% or less,
The concentration of alkali metal ions present in the fatty acid ester is variously changed. In Tables 1 and 2, a substrate made of the same resin as used in each example was placed in a constant temperature and humidity bath maintained at a temperature of 80 ° C. and a humidity of 85%, exposed for 1000 hours, and then the substrate was taken out and strained. The results of investigating the number and size of defects with polarization using a meter are also shown.

[Table 1]

[Table 2]

From Tables 1 and 2, the substrates in which the foreign substances are not generated by hydrolysis after being exposed for 2.5 hours under the conditions specified in the present invention are 1000 at 80 ° C. and 85% humidity. No such foreign matter was generated even after exposure for a period of time.
It can be seen that those that generate foreign matter due to hydrolysis after time exposure have poor durability against high temperature and high humidity.

As the resin that constitutes the substrate in the present invention, in addition to polycarbonate resin, resins that are generally used as substrates for information recording media such as acrylic resin, amorphous olefin resin, and epoxy resin can be used. Further, such a substrate is laminated with a reflection film, a recording film, a magnetic film and the like, and is used for an optical disc such as a compact disc and a magneto-optical disc, an optical card and the like.

[0017]

According to the present invention, a highly reliable information recording medium substrate is provided which does not generate a foreign substance composed of a hydrolyzate in a resin substrate even after being used for a long period of time, and a substrate having such a substrate. An information recording medium is provided. Also,
The inspection method according to the present invention is a simple method in a short time, and the temperature is 80 ° C., which is one of the environmental tests performed by the WG3 sponsored by the Japan Optical Industry Promotion Association as a reliability test of the information recording medium (optical disk). It is possible to obtain the same result in a short time as the result obtained by the method of exposing for 1000 hours in a constant environment of 85% humidity.

Claims (3)

[Claims] 1. A foreign substance having a diameter of 100 μm or more in a substrate after being left under a saturated vapor pressure of water at a temperature of 5 to 20 ° C. lower than the glass transition temperature of a resin constituting the substrate for 2.5 hours. An information recording medium, characterized in that no occurrence of 2. A diameter of 100 after being allowed to stand for 2.5 hours at a saturated steam pressure of water at a temperature of 5 to 20 ° C. lower than the glass transition temperature of the resin constituting the substrate.
An information recording medium substrate characterized in that no foreign matter of μm or more is generated. 3. A resin having a diameter of 100 after being left under a saturated vapor pressure of water at a temperature of 5 to 20 ° C. lower than the glass transition temperature of the resin constituting the substrate for 2.5 hours.
A method for inspecting an information recording medium, which comprises determining whether or not a foreign matter having a size of μm or more has occurred.