JP2755100B2 - optical disk - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc,
In particular, the present invention relates to an optical disk on which level printing is performed and which is suitable for high density use.

[0002]

2. Description of the Related Art A conventional technique will be described below with reference to the accompanying drawings. FIG. 3 is an enlarged sectional view showing a conventional optical disc. FIG. 4 shows a conventional optical disk.
FIG. 3 is a top view of the optical disc viewed from the bell printing unit side. FIG.
4 and FIG. 4, reference numeral 20 denotes an optical disk, and 1 denotes a polycarbonate.
Reference numeral 1a denotes a signal pit, 2 denotes a reflection film, 3 denotes a protective film, 4 denotes a level portion, and 6 denotes a center hole.

First, a schematic configuration of a conventional optical disk will be described. Signal pits 1a are formed on a polycarbonate resin substrate 1 formed by injection molding using a stamper. The optical disk 20 on the signal pit 1a side
Is formed with a reflective film 2 for enabling signal reading by laser light, and a protective film 3 is further formed thereon. The optical disc 20 is provided with a center hole 6 to be mounted on a signal reproducing device. Also, a record for clearly indicating the contents of the optical disc 20
The bell part 4 is printed on the protective film 3.

Next, the level unit 4 will be described.
In the case of an optical disc, for example, a CD, the label section 4 displays not only the contents, but also the name of the manufacturer, the name of the singer, the name of the performer, the playing time, and the like. The level section 4 is obtained by printing an opaque monochromatic or multicolor ultraviolet curable ink (UV ink) containing a pigment or the like. That is, these UV inks are printed by a pad printing method or a screen printing method, and are irradiated with ultraviolet rays to cure and dry the UV inks.

[0005]

By the way, when the above-mentioned level portion is formed on the protective film of the optical disk, the U.S. Pat.
The V ink causes shrinkage when cured and dried by irradiation with ultraviolet light, and thus warps the optical disc. Therefore,
The warp angle in the optical disc will be described. FIG.
FIG. 3 is a conceptual diagram for explaining a warp angle in an optical disc. In FIG. 5, the same reference numerals as those in the above-described conventional example denote the same components, and a description thereof will be omitted. O
-O 'is the center axis of rotation of the center hole, m is the surface in contact with the optical disk perpendicular to OO', Iin is the incident optical path of laser light, Iout is the reflected optical path of laser light, indicates the angle between the incident light path and the reflected light path of the laser light.

[0006] A laser device, not shown here,
It is arranged below the optical disc 20. The incident optical path Iin of the laser light emitted from this laser device is parallel to the rotation center axis OO 'of the center hole 6 of the optical disk 20. The laser light passes through the polycarbonate resin substrate 1 and reaches the reflection film 2 formed on the signal pit 1a, where it is reflected. Then, the light passes through the polycarbonate resin substrate 1 again and exits the optical disk 20. A detector (not shown) is disposed there, and detects the position of the laser light. As a result,
The reflected light path Iout of the laser light is determined, and the angle θ (warp angle) between the incident light path of the laser light and the reflected light path is measured. This is the warp angle θ in the optical disk.

Incidentally, the measurement of the warp angle is actually performed by using I
The measurement is performed using a dedicated measuring device capable of measuring the level of the warpage angle defined in SO / IEC 10089.

On the other hand, a laser formed on the optical disc 20
The ratio that the bell portion 4 occupies on the disk surface varies.
When the level portion 4 is uniformly formed on a small area on the disk surface, the amount of UV ink is small, and accordingly,
The compressive force associated with the curing of the UV ink is small, and the absolute value of the warpage angle and the fluctuation in one rotation are small. When the level portion 4 is formed uniformly over substantially the entire surface of the disk, the absolute value of the warp angle is large, but the fluctuation in one rotation of the warp angle is small. However, when the level portion 4 is formed on the half circumference of the disk surface, the absolute value of the warp angle increases, and the fluctuation in one rotation of the warp angle increases.

If the fluctuation in the rotation of the warp angle in one rotation of the disk surface becomes large, the pickup for signal reproduction cannot keep a predetermined distance from the disk surface and follow the disk surface. Will not be performed correctly. In particular, in the case of a high-density optical disk, the effect is remarkable. On the other hand, there is a method of improving the followability of a pickup for signal reproduction in order to cope with an optical disk for high density while the fluctuation in one round rotation of the warp angle in the disk surface is large, but if this method is adopted, Pickups are very expensive.

[0010] The UV ink constituting the level portion is cured and dried by irradiation with ultraviolet rays. When the UV ink is an opaque UV ink colored with a pigment or the like, the reach of the ultraviolet rays is limited. The inside of the UV ink is not completely cured and dried because it is limited to the surface of the UV ink and its vicinity. However, if the optical disk has a history of being exposed to a high-temperature atmosphere, the high temperature causes the curing and drying of the inside of the UV ink to proceed, so that the absolute value of the warpage angle in the disk surface and the fluctuation in one rotation are increased.

Therefore, the present invention relates to an optical disc,
It is possible to reduce the variation in one round rotation of the warp angle in the disk surface, which is caused by forming the label portion using an opaque UV ink colored with a pigment or the like. It is an object of the present invention to provide an optical disk suitable for high density use.

[0012]

The optical disk of the present invention comprises:
In an optical disk having a disk surface having a level portion formed of UV ink having a Young's modulus E, ± 10% of the Young's modulus E is applied to a portion of the disk surface other than the level portion at a predetermined ratio or more. The above object is achieved by forming a transparent UV resin film having a Young's modulus within 20%.

[0013]

An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an enlarged sectional view showing one embodiment of the optical disk of the present invention. FIG. 2 is a top view of the optical disk according to an embodiment of the present invention, as viewed from the label printing unit side. 1 and 2, reference numeral 10 denotes an optical disk, and reference numeral 5 denotes a transparent UV resin. In addition, the same reference numerals are given to the same components as those in the above-described conventional example, and the description is omitted.

First, the configuration of an embodiment of the optical disk of the present invention will be described. Signal pits 1a are formed on a transparent polycarbonate resin substrate 1 formed by injection molding using a stamper. On the surface of the optical disk 10 on the signal pit 1a side, a reflective film 2 made of aluminum having a film thickness of about 1000 angstroms is formed by a sputtering method or the like in order to enable signal reading by laser light. ing. Further, a protective film 3 made of an acrylic UV resin having a film thickness of 5 to 10 μm is formed on the reflective film 2 by a spin coating method or the like in order to prevent oxidation of aluminum and damage of the signal pit 1a. Is formed. The optical disk 10 is provided with a center hole 6 to be mounted on a signal reproducing device.

In order to form the level section 4 for clearly indicating the contents of the optical disk 10, the Young's modulus is 100
An opaque UV ink of kg / mm ² containing a pigment or the like is printed on the protective film 3 by a screen printing method. Further, the level portion 4 on the protective film 3
A transparent UV resin 5 film having a predetermined Young's modulus is formed in a predetermined ratio of the unprinted area with the same thickness as the level portion 4 by a screen printing method.

Next, the results of a study on a transparent UV resin film will be described. First, for the level portion to be formed on the protective film of the optical disk, conditions were set so that the level portion had the greatest effect on the warpage angle. As described above, when the level portion is formed uniformly on a small area on the disk surface, the amount of UV ink is also small,
The compressive force associated with the curing of the V ink is small, and the absolute value of the warpage angle and the fluctuation in one rotation are small. Further, when the level portion is formed uniformly on almost the entire surface of the disk surface, the absolute value of the warp angle is large, but the fluctuation in one rotation of the warp angle is small. However, when a level portion is formed on the half circumference of the disk surface, the absolute value of the warp angle increases, and the fluctuation in one rotation of the warp angle increases. Therefore, the time when the level portion was formed on the half circumference of the disk surface was set as a reference.

The Young's modulus of the semi-peripheral portion where the level portion is not formed is changed by changing the covering ratio with respect to the semi-peripheral portion.
A transparent UV resin film having a thickness of 00 kg / mm ² was formed by a screen printing method so as to have the same thickness as that of the label portion. The coverage was 25, 50, 75 and 100%. Coverage 5
In the case of 0%, the coverage of 75% and the coverage of 100%, an example of the present invention is shown. As a comparative example, the case of the coverage of 25% and the conventional example are shown as the coverage of 0%. For each of them, the warp angle over one round at a radius of 55 mm was measured, and the fluctuation width was obtained. Table 1 shows the results.

[0018]

[Table 1]

In Table 1, the variation width of the warp angle during one round before the environmental test is measured after the transparent UV resin is printed at a predetermined coverage, irradiated with ultraviolet rays, and cured and dried. The warpage angle fluctuation width in the middle is, after printing the transparent UV resin at a predetermined coverage, irradiating ultraviolet rays, curing and drying, and further,
It was measured after conducting an environmental test in which it was left at a temperature of 55 ° C. and a humidity of 95% RH for 96 hours. The Young's modulus of the opaque-colored UV ink containing a pigment constituting the level portion is 100 kg / mm ² .

The allowable absolute value of the warp angle and the fluctuation range of one rotation are 0.5 ° or less and 0.1 ° or less, respectively. Since the absolute values of the warp angles are all within the allowable range, they are not intentionally described in Table 1. The variation width of one round rotation of the warp angle, the value before the environmental test shows 0.1 ° or less regardless of the coverage of the transparent UV resin, but the value after the environmental test is
When the coverage of the transparent UV resin is 50% or more, a good value of 0.1 ° or less is shown.

Next, the results when the transparent UV resin having various Young's moduli is coated will be described. When the label portion is formed on the half-periphery of the disk surface (50% of the disk surface area) by opaque colored UV ink containing a pigment or the like having a Young's modulus of 100 kg / mm ² . A transparent UV resin film having various Young's moduli is formed on a semi-peripheral portion where no label portion is formed by changing the coverage of the semi-peripheral portion, and the same film as the label portion is formed by a screen printing method. It was formed thick. 50% and 75% coverage
And Young's modulus is 70, 80, 90, 110, 120
And a transparent UV resin film of 130 kg / mm ² was formed. A case where the Young's modulus is 80 to 120 kg / mm ² shows one example of the present invention, and the rest is shown as a comparative example. For each of them, the warp angle over one round at a radius of 55 mm was measured, and the fluctuation width was obtained. Table 2 shows the results.

[0022]

[Table 2]

In Table 2, the variation width of the warp angle during one round before the environmental test is measured after printing the transparent UV resin at a predetermined coverage, irradiating with ultraviolet rays, and curing and drying. The warpage angle fluctuation width in the middle is, after printing the transparent UV resin at a predetermined coverage, irradiating ultraviolet rays, curing and drying, and further,
It was measured after conducting an environmental test in which it was left at a temperature of 55 ° C. and a humidity of 95% RH for 96 hours.

The allowable absolute value of the warp angle and the fluctuation range of one rotation are 0.5 ° or less and 0.1 ° or less, respectively. Since the absolute values of the warp angles are all within the allowable range, they are not described in Table 2 on purpose. The fluctuation range of one rotation of the warp angle is as follows. For the level portion formed of an opaque UV resin containing a pigment or the like having a Young's modulus of 100 kg / mm ² , the value before the environmental test is as follows. 50 and 75 rates
% Shows a good value of the warpage angle of 0.1 ° or less regardless of the Young's modulus of the transparent UV resin.
The values after the environmental test show that the Young's modulus of the transparent UV resin is 80 to 120 kg /
mm ² indicates a good warp angle value of 0.1 ° or less.

[0025]

As described above, according to the optical disk of the present invention, in an optical disk having a disk surface having a level portion formed of UV ink having a Young's modulus E, other than the level portion, By forming a transparent UV resin film having a Young's modulus within ± 20% of the Young's modulus E on a portion of a predetermined ratio or more of the disk surface, an opaque UV ink colored with a pigment is formed. In this case, it is possible to reduce the fluctuation in one round rotation of the warp angle in the disk surface, which is caused by forming a label portion by using the optical disk, thereby providing an optical disk suitable for high-density use with little change over time. .

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view showing one embodiment of an optical disk of the present invention.

FIG. 2 is a top view of the optical disk, showing one embodiment of the optical disk of the present invention, as viewed from a label printing unit side.

FIG. 3 is an enlarged sectional view showing a conventional optical disc.

FIG. 4 is a top view of the conventional optical disc, viewed from the label printing unit side.

FIG. 5 is a conceptual diagram for explaining a warp angle in an optical disc.

[Explanation of symbols]

 4 Label part 5 Transparent UV resin 10 Optical disk

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G11B 7/24 571 G11B 23/40

Claims (1)

(57) [Claims] An optical disk having a disk surface having a label portion formed of UV ink having a Young's modulus E, wherein a portion of the disk surface other than the label portion has a predetermined ratio or more. An optical disc characterized by forming a transparent UV resin film having a Young's modulus within ± 20% of the Young's modulus E.