WO2003017266A1

WO2003017266A1 - Optical recording medium

Info

Publication number: WO2003017266A1
Application number: PCT/JP2002/007763
Authority: WO
Inventors: Mamoru Usami; Tsuyoshi Komaki; Hideki Hirata; Tomoki Ushida; Toshifumi Tanaka
Original assignee: Tdk Corporation
Priority date: 2001-08-10
Filing date: 2002-07-30
Publication date: 2003-02-27
Also published as: TWI241579B

Abstract

An optical recording medium having a support base and a relatively thick light transmission layer and not undergoing any warp caused by expansion contraction of the light-transmission layer caused by a sharp change in temperature. An optical recording medium (10) has a polycarbonate support base (12). A reflecting film (16), a recording layer (20), and acrylic resin light-transmission layer (24) of about 100 μm thickness are formed on one side of the polycarbonate supporting base (12). And a warp suppressive layer (28) is formed on the opposite side of the supporting base body (12) Expansion-contraction of the light transmission layer (24) caused by steep change in temperature is canceled by that of the warp suppressive layer (28).

Description

Specification

Optical recording medium

Technical field

The present invention relates to an optical recording medium.

Background technology,

Conventional CD (Compact Disc) and DVD (Digital Versatile)

Optical recording media (discs) such as Discs are manufactured so that various characteristics (electrical and mechanical characteristics) are within specified standards in the manufactured state (initial state), and furthermore, long-term reliability. In order to guarantee the properties, the degree of deterioration of various characteristics before and after accelerated tests such as high-temperature and high-humidity storage tests is also specified. As one of the indicators of this long-term reliability, it is required that the amount of change in the warpage of the entire disk before and after the accelerated test be within a certain value. Such conventional CDs and DVDs are mainly composed of a light-transmitting substrate (light-transmitting layer) made of polycarbonate, and the main cause of warpage is at least when the polycarbonate substrate and the recording substrate are configured to be recordable. If the recording layer, reflective layer and protective layer, and if configured for playback only, the long-term reliability is confirmed because it is at least due to the balance of stress due to expansion and contraction of the reflective layer and protective layer. Accelerated tests (high-temperature and high-humidity, or accelerated tests using only high-temperature and high-humidity) were carried out as tests, and sufficient management was performed.

On the other hand, as disclosed in, for example, Japanese Patent Application Laid-Open No. 1996-235 638, a recording / reproducing layer is provided on a support base in a recordable and / or reproducible state. An optical disc (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 resin film is provided as the light transmitting layer via an adhesive layer. In addition, there has been proposed a case in which an energy-curable or heat-curable resin layer is provided by a spin coating method. In these cases, we thought that the main causes of warpage and loss of stress balance were due to stress relaxation of each layer and expansion due to moisture absorption of 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. Found to occur.

This large change in the amount of warpage immediately after the accelerated test means that after a high-temperature storage (for example, 80 ° C for 12 hours) or a low-temperature storage (for example, 0 ° C for 12 hours), the warpage occurs at room temperature. When the amount is measured, it changes suddenly in a short time, and the occurrence of such a sudden warp in a short time is caused, for example, in a hot summer 3 in a room that is suddenly cooled from the outside. This is more likely to occur when an optical recording medium is brought in or suddenly brought into a warm room in a cold winter, in which case the optical recording medium can be inserted into the drive for a while, The problem is that they cannot be used. Disclosure of the invention

The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical recording medium that suppresses warpage caused by a rapid temperature change in a short time.

The present inventor has conducted intensive studies and found that, when the light transmitting layer has a certain thickness or more, and when the coefficient of linear expansion is different from that of the support, the stress balance of each layer in a high-temperature and high-humidity acceleration test is used. Prior to the occurrence of warpage or warpage caused by expansion of a resin such as polycarbonate acryl due to moisture absorption, it was discovered that a rapid and rapid warpage occurred due to a change in temperature. By suppressing the generation of steep warpage, even when the temperature changes steeply, It has been found that a recording medium can be used.

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

(1) Information formed on the supporting substrate, which is an optical recording medium that covers at least the information recording surface and is provided with at least a light transmitting layer, and the amount of change in the amount of warpage of the optical recording medium due to a rapid temperature change An optical recording medium characterized by being within 0, 4 degrees.

Here, the information recording surface is also referred to as an information recording area, and indicates at least a sputtering area portion at the time when the sputtering on the support substrate is completed.

Further, the rapid temperature change, although a detailed explanation of an example and changes in various environments after, here was rapid temperature change the temperature change of more than l ° C / rain _c

(2) The optical recording medium according to (1), wherein the maximum change in the amount of warpage of the optical recording medium with respect to the rapid temperature change is 0.2 degrees / minute or less.

(3) The optical recording medium according to (1) or (2), wherein the thickness of the light transmitting layer is 20 to 150 m.

(4) The optical recording medium according to (1), (2) or (3), wherein the light transmission layer and the support have different coefficients of linear expansion.

(5) The optical recording medium according to any one of (1) to (4), wherein the light transmitting layer is made of a material whose coefficient of linear expansion is larger than that of the support base. (6) The optical recording medium according to any one of (1) to (5), wherein the light transmitting layer is made of an energy ray-curable resin or a heat ray-curable resin.

(7) The optical recording medium ( _c ) according to any one of (1) to (6), wherein the support base is made of polycarbonate or polyolefin. The optical recording medium according to (7), wherein the amount of change in the amount of warpage within 60 minutes after being taken out of the atmosphere having a temperature difference of at least 30 ° C. (9) The optical recording medium according to (8), wherein a warp suppressing means is provided on at least a surface of the support base opposite to the light transmitting layer.

(10) In the above (10), the warp suppressing means comprises a warp suppressing layer provided on a surface of the support base opposite to the light transmitting layer, and the warp suppressing layer has a linear expansion. The optical recording according to (9), characterized in that the optical recording is made of a material in which the product of the modulus and the thickness is 0.3 to 1.7 times the product of the linear expansion coefficient and the thickness of the light transmitting layer. Medium.

(11) The optical recording medium according to (9) or (10), wherein the material of the light transmitting layer and the material of the warp suppressing layer are the same.

(12) The optical recording medium of (9), (10) or (11), wherein a moisture-proof layer is formed between the warp suppressing layer and the support base.

Further, the present inventor has found that the adoption of the design concept of suppressing the generation of the steep warpage in a short time makes it possible to use the optical recording medium even when the temperature change is steep.

That is, the following design method was adopted.

(13) At least an optical recording medium having a light transmissive layer having a thickness of 20 to 150 im over an information recording surface formed on the support base is placed in an atmosphere of 60 ° C or more. After storing for 60 minutes or more, the optical recording medium is designed so that when the optical recording medium is taken out to a room temperature environment and the amount of warpage of the optical recording medium is measured, the amount of change becomes a target value. How to design an optical recording medium.

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

(15) The method for designing an optical recording medium according to (13) or (14), wherein the target value of the variation is set to be within 0.4 degrees.

(16) The maximum change amount of the warpage amount with respect to the sudden temperature change is 0.

The method for designing an optical recording medium according to (13), (14) or (15), wherein the temperature is not more than 2 degrees / minute. ' (17) The measurement of the amount of change in the amount of warpage is taken out in a room temperature environment, and from the start of measurement of the change in the amount of warpage to 10 minutes, the interval is 1 minute. (13) to (13) 16 6) The method of designing an optical recording medium.

(18) A warp suppressing layer is disposed on at least a surface of the support base opposite to the information recording surface, and the warp of the optical recording medium is set to be within a predetermined value. The method for designing an optical recording medium according to any one of (13) to (17).

(19) The light according to (18), wherein the warp suppressing layer is at least one of a resin layer and a printing layer, and the printing layer is a resin layer containing one of a pigment and a dye. How to design a recording medium. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic cross-sectional view schematically showing a layer configuration of an optical recording medium according to an example of 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 according to the example of the embodiment.

FIG. 3 is a schematic sectional view similar to FIG. 1, showing a recording medium according to a second example of the embodiment. '

FIG. 4 is a schematic view showing a pattern of a warp suppressing layer according to a second example of the embodiment.

FIG. 5 is a diagram showing the amount of change in the amount of warpage during heat radiation in the optical recording media of the example of the present invention and 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, an optical recording medium 10 according to an example of this embodiment is provided on a support base 12 made of polycarbonate (the lower side in FIG. 1). At least a reflective film 16, a second dielectric layer 18, a recording layer 20, a first dielectric layer 22, and a light transmitting layer 24 are formed in this order. At least a moisture-proof film 27 and a warp suppressing layer 28 are formed in this order on the opposite side of the support base 12 from the light transmitting layer 24 and the like.

Here, the support base 12 is formed by injection molding of a polycarbonate resin, and has a thickness of about 1.1 mm. On this, the reflective film 16, the second dielectric layer 18, the recording layer 20, and the first dielectric layer 22 are formed in this order by a sputtering method, and the light transmitting layer 24 is It is made by spin-coating an acrylic resin, and its thickness is about 100 m.

In addition, the light transmitting layer 24 may be made of epoxy resin other than the ataryl resin, and the forming method is not limited to the spin coating method. Various coating methods may be employed, or the light transmitting layer 24 may be formed in a sheet shape in advance and bonded. You may.

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 thickness of the protective layer on the reflective film (about 5βτη) is compared. Thus, the light transmitting layer 24 is formed quite thick. The reflective film 16 is not limited as long as it satisfies the required reflectance, and various metal materials and the like can be applied. Here, Ag is used as a main component. First and second dielectric layers 2 2, 1 8 also forces the various materials are applicable S, a common Z n S- S i 0 ₂ was used herein. The recording layer 20 was of the GeSbTe type, which is a phase-change type recording layer composition.

The warp suppressing layer 28 is formed of the same material (acrylic resin) as the light transmitting layer 24 and has a thickness substantially equal to that of the light transmitting layer 24, or controls the thickness by using another material having a different coefficient of linear expansion. Thus, it is appropriately used depending on the design method of the present invention. For example, there is a method of forming a material having a higher linear expansion coefficient than the material of the light transmitting layer to be thinner than the light transmitting layer, or forming a material having a small linear expansion coefficient to be thicker. The moisture-proof film 27 provided here was sputtered. It consists of an A1 layer and has a thickness of 50 nm.

Since the light transmitting layer 24 is formed of an acrylic resin integrally with the support substrate 12 made of a polycarbonate resin as described above, the atmosphere has a rapid temperature change and the change is large. In such a case, warpage occurs due to a difference in a coefficient of linear expansion in each unit time.

In this optical recording medium 10, a surface of the support base 12 opposite to the light transmitting layers 2 and 4 (the upper surface in FIG. 1) ′ is made of the same acrylic resin as the light transmitting layer 24. Since the warp suppressing layer 28 is formed with substantially the same thickness, the amount of change in the amount of warp of the entire optical recording medium 10 due to expansion and contraction due to the temperature change of the light transmitting layer 24 is determined by the stress balance of each layer. By taking it, it can be suppressed.

The specific amount of change in the amount of warpage shall 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. In this test, after the optical recording medium 10 has been placed in an atmosphere of 60 ° C or more for 60 minutes or more, the atmosphere in a room temperature environment (temperature 21 to 25 ° C, relative humidity 40 to 60%) Then, the amount of warpage is measured as described later, and the amount of change in the amount of warpage due to heat radiation during the first 0 to 20 minutes from the start of the measurement is measured. Manage to within 4 degrees. For example, the design is performed by adjusting the thickness of the warp suppressing layer 28 so that the change amount is within 0.4 degrees.

More preferably, in order to suppress steep warpage, the amount of change in the warpage amount is set to 0.2 degrees / minute.

The moisture-proof film 27 is for preventing the support base 12 from elongating and suppressing elongation, and is taken out of the high-temperature storage environment and the poly-force after the temperature is lowered to some extent. Suppress.

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 reflected light at this time is received by a semiconductor position detector (hereinafter referred to as PSD), and the amount of warpage of the optical recording medium 10 is detected based on the incident position of the reflected laser beam on the PSD 32.

More specifically, as shown by the broken line in FIG. 2, when the optical recording medium 10 is in a straight plane state without warpage, the reflected laser beam is set so as to be incident on the center of the PSD 32, and When the recording medium 10 is warped, the reflection angle of the reflected laser beam increases by 2 XyS, and this is detected as a deviation of the incident position of the reflected laser beam on the PSD 32. The amount of deviation from the previously set reference is defined as the amount of change in the amount of warpage.

In the example of this embodiment, as described above, the warp suppressing layer 28 of the same material and the same thickness is formed on the support base 12 on the side opposite to the light transmitting layer 24. Therefore, the expansion and contraction of these layers due to the temperature change are offset on both sides of the support substrate 12, and the stress balance is maintained, so that the warpage can be optimally managed.

Note that, in the example of the above embodiment, the warp suppressing layer 28 is a force provided with the same material and the same thickness as the light transmitting layer 24, and the present invention is not limited to this. It is sufficient that the amount of change in the amount of warp with respect to the temperature change within the range is within 0.4 degrees. Therefore, the material, thickness, and thickness of the warp suppressing layer 28 are limited to those in the above-described embodiment. Not something. For example, the material of the warp suppressing layer 28 may be selected from an epoxy resin, a urethane resin, and the like. Further, the adjustment range of the thickness of the warp suppressing layer 28 is, for example, the same material as that of the light transmitting layer 24 and the thickness thereof is about 30 to 50% of the light transmitting layer 24. However, since 30 to 50% of the warpage of the light transmitting layer 24 is offset, the change in the amount of remaining warpage may be within the above range. Conversely, the thickness of the warp suppressing layer 28 may be about 1.7 to 1.5 times the thickness of the light transmitting layer 24.

Further, in the example of the above-described embodiment, the light transmitting layer 24 is formed of an acryl-based resin. It is generally applied when a material with high elasticity is used. It can be selected from a variety of materials such as soil energy curing resin cured by energy rays such as ultraviolet rays, and heat ray curing resin cured by heat. Acrylic resin, epoxy resin, urethane resin, etc. are applicable.

Further, the warp suppressing layer 28 is made of the same material as the light transmitting layer 24. However, since the warp suppressing layer 28 is not required to have a light transmitting property, another material such as opaque or translucent is used. It may be. Here, the thickness of the light transmitting layer 24 is set to 100 m, but the present invention relates to an optical recording medium provided with a light transmitting layer having a thickness of 20 to 150 im. Applicable.

The minimum value of 20 / m is because when the thickness is less than this, expansion and contraction due to temperature change is small, and it is not necessary to provide a warp suppressing means. The maximum value of 150 jum is the distance between the objective lens of the optical head and the recording layer 20 and the distance between the objective lens and the optical recording medium 10 at the time of information recording and reproduction. Is determined from the relationship with the minimum allowable gap distance.

In addition, when the support base 12 has a small amount of moisture absorption or a small amount of change in the amount of warpage due to the moisture absorption, like the optical recording medium 40 of the second example of the embodiment of the present invention shown in FIG. The moisture absorbing film 27 need not be provided.

Further, in the example of the above embodiment, the warp suppressing layer 28 is formed with a uniform thickness on the surface of the support base 12 opposite to the light transmitting layer 2.4. The present invention is not limited to this, and other warpage control means may be used. Therefore, for example, as shown in FIG. 4, the warp suppressing pattern 34 may be formed of the same material as the warp suppressing layer 28 at a radially long and circumferentially equiangular interval. .

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

In addition, the method for forming the warp suppressing layer is not particularly limited, either. Various methods such as a roll coating method and a screen printing method can be applied, and a print layer formed by using the screen printing method also has an effect of suppressing warpage.

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 / or reproducible. Any material having a light transmitting layer may be used.

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)

FIG. 5 shows the same optical recording medium as in the embodiment shown in FIGS. 1 and 3 together with other comparative examples, after aging at 80 ° C. for 12 hours to 20 to 2 hours. In an environment at 2 ° C and a humidity of 50 to 60%, the amount of change in the amount of warpage was measured by the same measurement method as shown in FIG. 2, and the amount of change was plotted on the vertical axis, from the start of measurement. Is shown 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.

5 is a comparative example in which the warp suppressing layer and the moisture-proof film are removed from the optical recording medium in FIG. 1, and B is a comparative example in which the warp suppressing layer is removed from the optical recording medium in the embodiment of FIG. C is an embodiment similar to the optical recording medium of the embodiment of FIG. 1, D is an example similar to the optical recording medium of FIG. 3, E is a moisture-proof layer removed from the optical recording medium of FIG. Here, as a warp suppressing layer, a general pigment-based ink is used to cover about 90% of the doughnut-shaped area of 44 to 118 mm in the optical recording medium having a diameter of 120 iii m. It is a measured value of the example of printing. As can be seen from FIG. 5, within 10 minutes from the start of the measurement, the heat transmission causes the light transmitting layer to contract, which causes a sharp and large warpage. In addition, in the case of C, D, and E provided with the warp suppressing layer, it can be seen that the amount of change in the amount of warp due to the temperature change is smaller than that of A and B. Furthermore, when the heat radiation spreads as a whole, the distortion due to heat dissipation is rapidly eliminated between 30 minutes and 100 minutes in FIG. 5, as seen in A, B, D, and E. Next, in the cases of A, D, and E between 100 minutes and 100 minutes, the amount of change in the amount of warpage increases due to moisture absorption of the polycarbonate constituting the support base.

At this time, in the case of B and C provided with the moisture-proof layer, it can be seen that the change in the amount of warpage due to the moisture absorption of the polycarbonate hardly occurs. Industrial applicability

Since the present invention is configured as described above, even if a steep temperature change occurs in an optical recording medium provided with a relatively thick light transmission layer together with the supporting base, the light transmission layer expands and contracts due to the temperature change. It has the excellent effect that the amount of change in the amount of warpage caused by the collapse of the stress balance based on the above can be suppressed within a certain value.

Claims

The scope of the claims

1. An optical recording medium provided with at least a light transmitting layer over an information recording surface formed on a supporting substrate, wherein a change in the amount of warpage of the optical recording medium due to a rapid temperature change is 0. An optical recording medium characterized by being within 4 degrees.

2. The optical recording medium according to claim 1, wherein the maximum change in the amount of warpage of the optical recording medium with respect to the rapid temperature change is 0.2 degrees Z or less.

3. The optical recording medium according to claim 1, wherein the thickness of the light transmitting layer is 20 to 150 m.

4. The optical recording medium according to claim 1, 2 or 3, wherein the light transmission layer and the support base are made of materials having different linear expansion coefficients.

5. The optical recording medium according to claim 1, 2 or 4, wherein the light transmitting layer is made of a material having a coefficient of linear expansion larger than that of the support base.

6. The optical recording medium according to any one of claims 1 to 6, wherein the light transmission layer is made of an energy-curable resin or a heat-curable resin.

7. The optical recording medium according to claim 1, wherein the support base is made of polycarbonate or polyolefin.

8. The warp according to any one of claims 1 to 7, wherein the change in the amount of warp with respect to the temperature change of the optical recording medium is within 60 minutes after being taken out of the atmosphere having a temperature difference of at least 30 ° C or more. An optical recording medium characterized by a change in the amount.

9. In any one of claims 1 to 8, wherein at least a surface of the support base opposite to the light transmitting layer is provided with a warp suppressing means. Optical recording medium. '

10. In claim 9, the warp suppressing means comprises a warp suppressing layer provided on a surface of the support base opposite to the light transmitting layer, and the warp suppressing layer has a linear expansion coefficient and An optical recording medium comprising a material whose thickness is 0.3 to 1.7 times the product of the linear expansion coefficient and the thickness of the light transmitting layer.

11. The optical recording medium according to claim 9, wherein the material of the light transmitting layer and the material of the warp suppressing layer are the same.

12. The optical recording medium according to claim 9, 10 or 11, wherein a moisture-proof layer is formed between the warp suppressing layer and the support base.