WO2003025926A1

WO2003025926A1 - Optical recording medium inspecting method

Info

Publication number: WO2003025926A1
Application number: PCT/JP2002/009072
Authority: WO
Inventors: Mamoru Usami; Tsuyoshi Komaki; Hideki Hirata; Tomoki Ushida; Toshihumi Tanaka
Original assignee: Tdk Corporation
Priority date: 2001-09-18
Filing date: 2002-09-05
Publication date: 2003-03-27
Also published as: TWI283865B

Abstract

Generation of warp attributable to expansion and contraction of a light transmissive layer caused by a steep temperature change in an optical recording medium having a relatively thick light transmissive layer is inspected in a short time. The optical recording medium (10) has a reflecting film (16), a recording layer (20) and the light transmissive layer (24) formed of a resin of about 100 μm thick on the polycarbonate supporting base body (12). This optical recording medium (10) is maintained in the atmosphere of 60-80°C for at least 60 minutes, and taken out to a room-temperature environment to measure the change in warp within 60 minutes.

Description

Specification

Inspection method for optical recording media

The present invention relates to an optical recording medium warpage amount change inspection method. Background art

Conventional optical recording media (discs) such as CDs (Compact Discs) and DVDs (Digital Versatile Discs) are standards in which various characteristics (electrical and mechanical characteristics) are determined in the manufactured state (initial state). In order to guarantee long-term reliability, various characteristics are defined so as to satisfy the specified values even after accelerated tests such as high-temperature and high-humidity storage tests. As one of the indicators of this long-term reliability, it is required that the amount of warpage of the entire disk before and after the accelerated test is within a certain value. Such conventional CDs, DVDs, and the like are mainly composed of a light-transmitting substrate (light-transmitting layer) made of polycarbonate, and the main cause of warpage is such that the polycarbonate substrate and the recording substrate are recordable. This is due to the balance of stress caused by expansion and contraction including at least the recording layer, the reflective layer and the protective layer, and the reflective layer and the protective layer if it is configured for reproduction only, and the print layer if it has a print layer. Therefore, as a test to confirm the long-term reliability, an accelerated test (high-temperature and high-humidity, or an accelerated test using only high-temperature and high-humidity only) was performed, and sufficient management was performed.

On the other hand, for example, as disclosed in Japanese Patent Application Laid-Open No. 19996-235638, a recording / reproducing layer is provided on a support base in a recordable and / or reproducible state. An optical disk (optical recording medium) has been proposed in which a light transmitting layer is formed and a laser beam for recording / reproducing is irradiated from the light transmitting layer side.

Here, a case in which a resin film is provided via an adhesive layer as the light-transmitting layer has been proposed. 'Other than this, an energy-ray-curable or heat-ray-hardened resin by spin coating is proposed. Proposals have also been made for layers. In these cases, we thought that the main causes of warpage and the loss of stress balance were due to stress relaxation of each layer and expansion due to moisture absorption of the supporting base and the resin layer. However, the present inventors have found that when the material of the light transmitting layer is different from the material of the support and the thickness of the light transmitting layer is 20 m or more, a large change in the amount of warpage immediately after the acceleration test is obtained. Found to occur.

Immediately after this accelerated test, the optical recording medium undergoes a change in the amount of warpage. The change in the amount of warpage can be determined by removing the optical recording medium after storage at high temperature (for example, 80 ° C for 12 hours) or after storage at low temperature (for example, at —20 ° C for 12 hours). Is measured, the large change in the amount of warpage is measured as a steep change in a short time. Such a steep warpage in a short time is caused, for example, when an optical recording medium is suddenly brought into a cooled room from the outside on a hot summer day, or when the optical recording medium is suddenly brought into a warm room in a cold winter. This is highly likely to occur when brought in, and in this case, there is a problem that the optical recording medium cannot be mounted on the drive or used for a while.

However, according to the conventional accelerated test method described above, since the optical recording medium is taken out of the accelerated test environment and left in the measurement environment for at least 48 hours, the steepness generated on the optical recording medium is reduced. No change in warpage was found. Disclosure of the invention

The present invention has been made in view of the above-described problems, and has been made in consideration of the above-described problem. It is an object of the present invention to provide a method for inspecting a change in the amount of warpage of a recording medium. The inventor of the present invention has found that, as a result of intensive studies, when the light transmitting layer has a certain thickness or more, when the linear expansion coefficient is different from that of the support, the stress balun of each layer in a high temperature and high humidity acceleration test Prior to the occurrence of warpage due to heat or expansion due to moisture absorption of resins such as polycarbonate and ataryl, it was discovered that there was rapid and rapid warpage due to temperature changes. It has been found that steep warpage can be efficiently and reliably detected by a short test.

That is, the above object is achieved by the following inventions.

(1) After storing the optical recording medium provided with at least the light transmitting layer over the information recording surface formed on the supporting base for at least 60 minutes in an atmosphere of 60 ° C or more, the medium is placed in a room temperature environment. Taking out and measuring the change in the amount of warpage of the optical recording medium Inspection method for optical recording media.

Here, the information recording surface is also referred to as an information recording area, and indicates at least a recording layer area and a reflection layer area at the time when the formation of the recording layer and / or the reflection layer on the support base is completed. '

Further, the rapid temperature change will be described in detail later with examples of various environmental changes and the like. Here, a temperature change of 1 ° C / rain or more is defined as a rapid temperature change.

(2) The method for inspecting an optical recording medium according to (1), wherein the temperature of the atmosphere of the optical recording medium is 70 ° C. or more, and the storage time is 60 minutes or more.

(3) The method for inspecting an optical recording medium according to (1) or (2), wherein the temperature of the atmosphere is not more than 80 ° C. '

(4) The method for inspecting an optical recording medium according to (1), (2) or (3), wherein the room temperature environment is a temperature of 23 ± 2 ° C. and a relative humidity of 50 ± 10% RH.

(5) The method for inspecting an optical recording medium according to any one of (1) to (4), wherein the thickness of the light transmitting layer is 20 to 150 m.

(6) The method for inspecting an optical recording medium according to any one of (1) to (5), wherein the light transmitting layer and the support base are made of materials having different coefficients of linear expansion.

(7) The inspection of the optical recording medium according to any one of (1) to (4) and (6), wherein the light transmitting layer is made of a material whose linear expansion coefficient is larger than that of the support base. Method.

(8) The method for inspecting an optical recording medium according to any one of (1) to (7), wherein the light transmission layer is made of an energy ray-curable resin or a heat ray-curable resin.

(9) The method for inspecting an optical recording medium according to any one of (1) to (8), wherein the support base is made of polycarbonate or polyolefin.

(10) The change in the amount of warpage with respect to the change in temperature of the optical recording medium is a change in the amount of warpage within 60 minutes after being taken out to a room temperature environment. Any one of the optical recording medium inspection methods.

(11) The optical recording medium is taken out into the room temperature environment, and measurement is performed at one-minute intervals for 10 minutes from the start of the measurement of the change in the amount of warpage, (1) to (10). Inspection method for optical recording media '. Further, as a result of earnest studies, the present inventor has found that when the light transmitting layer has a certain thickness or more and has a linear expansion coefficient different from that of the supporting substrate, the light transmitting layer collapses due to moisture absorption in a high temperature and high humidity acceleration test. Prior to the occurrence of warpage due to balance, it was discovered that there was a short-time steep warpage due to a temperature change, and by adopting a design concept to suppress this short-time steep warpage, the temperature variation was reduced. It has been found that the optical recording medium can be used even when the dagger is steep.

That is, the following design method was used. ,

(12) After storing at least an optical recording medium having a light transmission layer having a thickness of 20 to 150 m in an atmosphere of 60 ° C or more for 60 minutes or more, covering the information recording surface formed on the support base. A method for designing an optical recording medium, wherein the optical recording medium is designed so that when the optical recording medium is taken out in a room temperature environment and the amount of warpage of the optical recording medium is measured, the amount of change becomes a target value.

(13) The method for designing an optical recording medium according to (12), wherein the indoor environment has a temperature of 23 ± 2 ° C. and a relative temperature of 50 ± 10% RH.

(14) The method for designing an optical recording medium according to (1) or (2), wherein a target value of the change amount is set within 0.4 degrees.

(15) The optical recording medium according to (12), (13) or (14), wherein a maximum change amount of the warpage amount with respect to the sudden temperature change is 0.2 degrees / minute or less. Method. '

(16) The measurement of the amount of change in the amount of warpage is taken out in a room temperature environment, and is performed at intervals of one minute from the start of the measurement of the amount of change in the amount of warpage to 10 minutes. 15) Design method of optical recording medium.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a sectional view schematically showing a layer configuration of an optical recording medium to be inspected by a method according to an embodiment of the present invention.

FIG. 2 is a schematic side view showing an apparatus for measuring the amount of change in the amount of warpage of the optical recording medium by the inspection method according to the example of the embodiment. FIG. 3 is a diagram showing the results of measuring the amount of change in the amount of warpage during heat radiation in an optical recording medium according to the method of Example 1 of the present invention.

FIG. 4 is a diagram showing the results of measuring the amount of change in the amount of warpage during heat radiation in an optical recording medium according to the method of Embodiment 2 of the present invention.

FIG. 5 is a diagram showing the results of measuring the amount of change in the amount of warpage during heat radiation in an optical recording medium according to the method of Embodiment 3 of the present invention.

FIG. 6 is a diagram showing the results of measuring the amount of change in the amount of warpage during heat radiation in an optical recording medium by the method of the comparative example. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1, the optical recording medium 10 on which the change in the amount of warpage is inspected by the inspection method according to the example of this embodiment is placed on a support base 12 made of polycarbonate (the lower side in FIG. 1). Further, by forming various recording layers and reflection layers, recording and Z or reproduction are enabled, and the light transmission layer 24 is formed.

Here, the support base 12 is formed by injection molding of a resin such as polycarbonate or polyolefin, and has a thickness of about 1.1. Here, as an example, a reflective film 16, a second dielectric layer 18, a recording layer 20, and a first dielectric layer 22 are formed thereon in this order by sputtering.

The light transmitting layer 24 is formed by spin-coating an acryl-based resin containing an ultraviolet-curing agent and irradiating with an ultraviolet ray to cure the acryl-based resin, or formed by a heat-ray-curable resin. May be formed by bonding a resin sheet formed in advance. The thickness of the light transmitting layer 24 is about 1 OOjUm.

The method of forming the light transmitting layer 24 is not limited to the spin coating method, and various coating methods may be adopted, or the light transmitting layer 24 may be formed in a sheet shape in advance and bonded.

Therefore, in a conventional CD, DVD, or the like, the thickness of the resin layer corresponding to the position of the light transmitting layer 24 of the optical recording medium 10, that is, the protective layer on the reflective film (about 5 to: LO im) In comparison, the light transmitting layer 24 is formed to be considerably thick. The reflective film 16 is not limited as long as it satisfies the required reflectance, and various metal materials can be used. Here, Ag is the main component. Although various materials can be applied to the first and second dielectric layers 22 and 18, here, ZnS—SiO ₂ was used. The recording layer 20 was of a GeSbTe type having a phase-change recording layer composition.

Since the light transmitting layer 24 is formed of an acrylic resin or the like integrally with the support base 12 made of the polycarbonate resin as described above, when the atmosphere has a rapid temperature change and the change is large, Warpage occurs due to the difference in the coefficient of linear expansion per unit time.

In the optical recording medium 10, the amount of warpage of the entire optical recording medium 10 based on the expansion and contraction of the light transmitting layer 24 caused by the temperature change of the light transmitting layer 24 of the support base 12 is determined by the stress balance of each layer. It can be suppressed by taking.

The specific amount of change in the amount of warpage should be within a range of 0.4 degrees from the initial state. More specifically, the amount of change in the amount of warpage is measured by a high-temperature storage test.

According to the inspection method of the present invention, the optical recording medium to be inspected is kept in an apparatus (not shown) similar to that used in the high-temperature storage test in an atmosphere at 60 ° C. to 80 ° C. for 60 minutes or more. After the recording, remove the optical recording medium 10 into the room temperature environment, measure the amount of warpage as described below, and measure the amount of change in the amount of warpage due to heat radiation during the first 0 to 20 minutes from the start of measurement. Based on the result, the amount of change is designed to be within 0.4 degrees, for example, by adjusting the stress balance of each layer as described above.

More preferably, in order to suppress steep warpage, the amount of change in the warpage amount is set to 0.2 degrees / minute. Here, the room temperature environment refers to an atmosphere having a temperature of 23 ± 2 ° C. and a relative humidity of 50 ± 10% RH.

Here, the measurement of the amount of change in the amount of warpage is performed, for example, by irradiating a recording medium 10 with a laser beam from a laser light source 30 as shown in FIG. The amount of warpage of the optical recording medium 10 is detected by detecting the position of the reflected laser beam, which is received by a detector (hereinafter referred to as a PSD) and incident on the PSD 32.

More specifically, as shown by the broken line in FIG. In the case of no straight plane, the reflected laser beam is set to enter the center of the PSD 32, and when the optical recording medium 10 is warped i8, the reflected laser beam has an angle of reflection of 2X.) It is detected as a shift in the incident position of the reflected laser beam on PSD 32. The amount of deviation from the previously set reference is referred to as the amount of warpage, and the amount of change from the time immediately after being taken out in a high-temperature atmosphere for a certain period of time and taken out is referred to as the amount of change in the amount of warpage.

If the storage time in the above-mentioned 60 ° C to 80 ° C atmosphere is less than 60 minutes, the disk does not reach the amount of warpage originally possessed, but if it is more than 1 hour, the warpage and deviation will not occur. Even in this case, the amount of change in the amount of warpage is almost constant, and reaches the amount of warpage originally possessed by the disk. Therefore, the change amount can be reliably and stably inspected for 60 minutes or more.

As with the above, the storage temperature was insufficient at 50 ° C, and the change could be inspected at 60 ° C or higher.

If the storage temperature exceeds 80 ° C, energy is wasted.Also, depending on the material used as the optical recording medium, if the storage temperature exceeds 80 ° C, these materials will be adversely affected, and the temperature will be 80 ° C. The temperature is preferably 60 ° C. to 80 ° C. It is preferable to store at 70 ° C.

According to the study of the present inventor, the time during which the steep change in the warp occurs after the optical recording medium is taken out at room temperature under the above storage conditions is within 10 minutes, but within 60 minutes. If so, a steep warpage will surely occur in that time zone. Considering the inspection efficiency, if the optical recording medium was taken out from the storage temperature to the room temperature average, and the amount of warpage was measured for 20 minutes, the sharp warpage could be almost certainly detected.

In the example of the above embodiment, the light transmitting layer 24 is formed of an acrylic resin. However, the present invention relates to an optical recording medium using a material which is greatly expanded and contracted by a rapid temperature change in a short time. It is generally applied to inspections, and the light transmitting layer can be made of an energy ray-curable resin that is cured by energy rays such as ultraviolet rays or a heat-ray-curable resin that is cured by heat. Various selections are possible, and acrylic resin, epoxy resin, urethane resin, etc. can be applied.

Furthermore, although the thickness of the light transmitting layer 24 is set to 100 μm, the present invention This is applied to an optical recording medium provided with a light transmission layer of 20 to 150 // m.

The minimum value of 20 μm is less when the thickness is less than this, there is little expansion and contraction due to temperature change, and the maximum value of 150 μm is the pair of optical heads when recording / reproducing information. It is determined from the relationship between the distance between the object lens and the recording layer 20 and the minimum allowable gap distance between the objective lens and the optical recording medium 10.

If the amount of change in the amount of warpage of the support base 12 due to moisture absorption is large, a moisture-proof film may be provided.

In addition, as the material of the support base 12, besides polycarbonate as in the example of the embodiment, polyolefin or the like may be used.

Furthermore, the recording layer is not limited to the example of the embodiment, and may be a single layer or a plurality of layers configured to be recordable and Z or reproducible. As an optical recording medium, light is recorded on the recording layer. What is necessary is just to have a transmission layer.

Therefore, the presence or absence of the reflective film and the dielectric layer or the order of laminating these layers with the recording layer, the light transmitting layer, and the support base are not limited to the example of the embodiment.

[Example 1]

An optical recording medium similar to that shown in FIG. 1 was subjected to aging (storage) at 70 ° C. for 30 minutes, an IB interval, 2 hours and 24 hours, and then room temperature environment (21 to 25 ° C.). C, and relative humidity of 40 to 60%), and measure the amount of change in the amount of warpage by the same measurement method as shown in FIG. 2 above. Figure 3 shows time on the horizontal axis. Here, the amount of warpage immediately after removal from the high-temperature environment was set to 0, and the difference from that was compared.

As can be seen from Fig. 3, within 10 minutes from the start of the measurement, the heat radiation disturbs the shrinkage of the light-transmitting layer and the shrinkage balance of the supporting substrate. It can be seen that the warpage is sharp and large.

Furthermore, it can be seen that when the entire heat dissipation is performed, the distortion due to the heat dissipation is rapidly eliminated between 10 minutes and 60 minutes in FIG.

[Example 2, Example 3]

The storage temperature was set to 60 ° C (Example 2), 80 ° C (Example 3), and other The measurement results are shown in FIGS. 4 and 5 under the same conditions as in Example 1.

From FIGS. 4 and 5, it can be seen that the same tendency as in Example 1 is observed.

[Comparative Example].

For the above example, after aging at a storage temperature of 50 ° C and a storage time of 30 minutes, 1 hour, 2 hours, 3 hours, and 8 hours, after taking out to a room temperature environment, Figure 6 shows the results of measuring the amount of change in the amount of warpage in the same manner.

As can be seen from FIG. 6, the warpage occurred within 10 minutes from the start of the measurement. This was due to the change in the maximum warpage despite the same optical recording medium as in Example 1. The amount of warping is small, and it seems that the original warpage of the disk has not been reached. Industrial applicability

Since the present invention is configured as described above, the present invention has an excellent effect that the amount of change of the steep warpage due to the temperature change of the optical recording medium can be effectively and reliably detected in a short time.

Claims

The scope of the claims

1. After storing the optical recording medium with at least the light transmission layer over the information recording surface formed on the supporting base for at least 60 minutes in an atmosphere of 60 ° C or more, place it at room temperature. A method for inspecting an optical recording medium, comprising taking out the optical recording medium and measuring a change in the amount of warpage of the optical recording medium. ,

2. The method for inspecting an optical recording medium according to claim 1, wherein the room temperature environment is a temperature of 23 ± 2 ° C. and a relative humidity of 50 soil 10% RH.

3. The method for inspecting an optical recording medium according to claim 1 or 2, wherein the thickness of the light transmitting layer is 20 to 150 m.

4. The light according to any one of claims 1 to 3, wherein the change in the amount of warpage of the optical recording medium is a change in the amount of warpage within 60 minutes after being taken out to a room temperature environment. Inspection method for recording media.

5. The optical recording medium according to any one of claims 1 to 4, wherein the optical recording medium is taken out in the room temperature environment, and measurement is performed at one-minute intervals from the start of the measurement of the change in the amount of warpage to 10 minutes. Inspection method for optical recording media.