Claims
- 1. An optical data recording medium comprising a transparent substrate, and a selected one of a recording film and a reflection film on one side of the transparent substrate for recording and/or reproducing data by radiating a light beam on said selected one of the recording film and the reflection film, wherein a given principal dielectric axis of the transparent substrate is set in regular manner within ±5 degrees of at least a selected one of the direction parallel, perpendicular and 45 degrees to a scanning direction of the light beam.
- 2. An optical data recording medium according to claim 1, wherein said given principal direction axis of the transparent substrate is set in regular manner within ±3 degrees of said at least a selected one of the directions.
- 3. An optical data recording medium according to claim 2, wherein the transparent substrate is in the form of a disk, whereby the recording medium is an optical data recording disk.
- 4. An optical data recording medium according to claim 3, wherein said principal dielectric axis of the transparent substrate is set in a regular manner within ±3 degrees of at least a selected one of the radial direction, the circumferential direction and a direction of thickness of the transparent substrate in the form of a disk.
- 5. An optical data recording medium according to claim 3, wherein aidsaid given principal dielectric axis of the transparent substrate is set in a regular manner within ±3 degrees of at least a selected one of the radial direction, the circumferential direction and a direction 45 degrees to the radial direction of the transparent substrate in the form of a disk.
- 6. An optical data recording medium according to claim 2, wherein the transparent substrate is rectangular.
- 7. An optical data recording medium according to claim 6, wherein the rectangular transparent substrate is a card, whereby the recording medium is an optical data recording card.
- 8. An optical data recording medium according to claim 7, wherein the rectangular transparent substrate has an outer peripheral longitudinal line, and wherein said principal dielectric axis of the transparent substrate is set in a regular manner within ±3 degrees of at least a selected one of a direction parallel to the outer peripheral longitudinal line, a direction perpendicular to the direction parallel to the otherouter peripheral longitudinal line and a direction 45 degrees to the direction parallel to the outer peripheral longitudinal line of the rectangular transparent substrate.
- 9. An optical data recording medium according to claim 1, wherein said selected one of a recording film and a reflection film is made of a magneto-optical recording material whereby a magneto-optical recording medium is formed.
- 10. An optical data recording system comprising:an optical data recording medium including a transparent substrate; and a selected one of a recording film and a reflection film on one side of the transparent substrate for recording and/or reproducing data by radiating a light beam on said selected one of the recording film and the reflection film, said transparent substrate having a reference principal dielectric axis that is arranged regularly in a desired direction and an optical unit for emitting a linearly polarized light beam as said light beam, wherein the principal dielectric axis of the transparent substrate of the optical data recording mediuma plane of polarization of said linearly polarized light beam is set within ±5 degrees of at least one of the directions parallel, perpendicular and 45 degrees to a scanning direction of said light beamthe principal dielectric axis of the transparent substrate of the optical data recording medium.
- 11. An optical data recording system according to claim 10, wherein said principal dielectric axis is set within ±3 degrees of said at least a selected one of the directions.
- 12. An optical recording system according to claim 11, wherein the optical unit is positioned, relative to the optical data recording medium, such that said light beam passes through the transparent substrate in irradiating said selected on of the recording film and the reflection film.
- 13. An optical data recording system according to claim 1610, wherein the transparent substrate is in the form of a disk, whereby the recording medium is an optical data recording disk.
- 14. An optical data recording system according to claim 10, wherein the transparent substrate is rectangular and in the form of a card, whereby the recording medium is an optical data recording card.
- 15. An optical data recording system according to claim 10, wherein the optical unit is positioned, relative to the optical data recording medium, such that said light beam passes through the transparent substrate in irradiating said selected one of the recording film and the reflection film.
- 16. A method of producing an optical data recording medium comprising the step of molding a transparent substrate by injecting a melt plastic material to die surfaces with a part of the cavity surface thereof formed by the signal side of a stamper, wherein said die is formed with a cold slug well and has a gate width less than 1 mm, said melt plastic material being injected at a low ratefirst rates in the beginning and end of injection and at a highsecond rate during intermediate time, the the first rates being smaller than the second rate.
- 17. An optical data recording system comprising:an optical data recording medium including a transparent substrate in the form of a disk, whereby the recording medium is an optical data recording disk, and a selected one of a recording film and a reflection film on one side of the transparent substrate for recording and/or reproducing data by radiating a linearly polarized light beam on said selected one of the recording film and the reflection film, a given principal dielectric axis of the transparent substrate being set within ±3 degrees of at least one of a radial direction, a circumferential direction and a direction of thickness of the transparent substrate; and an optical unit for emitting a linearly polarized light as said light beam, wherein a plane of polarization of said linearly polarized light beam is set within ±5 degrees of a selected one of directions parallel, perpendicular and 45 degrees to the principal dielectric axis of the transparent substrate of the optical data recording medium.
- 18. An optical data recording system according to claim 17, wherein the given principal dielectric axis of the transparent substrate is set within ±3 degrees of the direction of thickness of the transparent substrate, and the plane of polarization of the linearly polarized light beam is set within ±5 degrees of a direction parallel to said principal dielectric axis in the direction of thickness of the transparent substrate.
- 19. An optical data recording system comprising:an optical data recording medium including a transparent substrate in the form of a disk, whereby the recording medium is an optical data recording disk, and a selected one of a recording film and a reflection film on one side of the transparent substrate for recording and/or reproducing data by radiating a linearly polarized light beam on said selected one of the recording film and the reflection film, a given principal dielectric axis of the transparent substrate being set within ±3 degrees of at least one of a radial direction, a circumferential direction and a direction 45 degrees to the radial direction of the transparent substrate in the form of a disk; and an optical unit for emitting a linearly polarized light as said light beam, wherein a plane of polarization of said linearly polarized light beam is set within ±5 degrees of a selected one of directions parallel, perpendicular and 45 degrees to the principal dielectric axis of the transparent substrate of the optical data recording medium.
- 20. An optical data recording system comprising:an optical data recording medium including a transparent substrate that is rectangular and in the form of a card, whereby the recording medium is an optical data recording card, and a selected one of a recording film and a reflection film on one side of the transparent substrate for recording and/or reproducing data by radiating a linearly polarized light beam on said selected one of the recording film and the reflection film; wherein the rectangular transparent substrate has an outer peripheral longitudinal line; and wherein a given principal dielectric axis of the transparent substrate is set within ±3 degrees of at least a selected one of a direction parallel to the outer peripheral longitudinal line, a direction perpendicular to the direction parallel to the outer peripheral longitudinal line, and a direction 45 degrees to the direction parallel to the outer peripheral longitudinal line of the transparent substrate; and an optical unit for emitting a linearly polarized light as said light beam, wherein a plane of polarization of said linearly polarized light beam is set within ±5 degrees of a selected one of directions parallel, perpendicular and 45 degrees to the principal dielectric axis of the transparent substrate of the optical data recording medium.
- 21. An optical data recording system comprising:an optical data recording medium including a transparent substrate in the form of a disk, whereby the recording medium is an optical data recording disk, and a selected one of a recording film and a reflection film on one side of the transparent substrate for recording and/or reproducing data by radiating a linearly polarized light beam on said selected one of the recording film and the reflection film, a given principal dielectric axis of the transparent substrate being set within ±3 degrees of each of a radial direction and a circumferential direction of the transparent substrate in the form of a disk; and an optical unit for emitting a linearly polarized light as said light beam, wherein a plane of polarization of said linearly polarized light beam is set within ±5 degrees of a selected one of directions parallel, perpendicular and 45 degrees to the principal dielectric axis of the transparent substrate of the optical data recording medium.
- 22. A method of producing an optical data recording medium, comprising a step of molding a transparent substrate by injecting a molten plastic material into a die cavity of an injecting die, the injecting die having an injecting gate, said die cavity having a die cavity surface, with a part of the cavity surface thereof being formed of a signal side of a stamper, wherein said injecting die is provided with said injecting gate connected to said cavity at a center of said cavity, in plan view, and a sprue is connected to said cavity; wherein a temperature distribution along the cavity surface around the sprue is not more than ±5° C.; and wherein a temperature Tc of the cavity surface of said die is so adjusted that Tg−80≦Tc≦Tg, where Tg is a glass transition temperature of the plastic material.
- 23. A method of producing an optical data recording medium according to claim 22, wherein the temperature of said molten plastic material is so controlled that the viscosity of the molten plastic material injected from said injecting gate into said die cavity is less than 2000 poise.
- 24. A method of producing an optical data recording medium according to claim 22, wherein said injecting die includes a cold slug well, said injecting gate has a gate width of less than 1 mm, and an injection rate of the injecting the molten plastic material into said die cavity is so controlled such that the molten plastic material is injected at a first rate during a beginning period of an injection cycle, is injected at a second rate during an intermediate period of the injection cycle, and is injected at a third rate during an end period of the injection cycle, the first and third rates being lower than said second rate.
- 25. A method of producing an optical data recording medium according to claim 22, wherein the injecting gate of said injecting die has a gate width of less than 1 mm, and the injecting die includes a cold slug well, a capacity of the cold slug well being in the range of {fraction (1/7)} to {fraction (1/2)} of the capacity of the sprue.
- 26. A method of producing an optical data recording medium according to claim 22, wherein said injecting gate of said injecting die has a gate width of less than 1 mm, and a period of the injecting, from a start of injection of the molten plastic material into the die cavity to an end of injection of the molten plastic material into the die cavity, is within a range of 0.2-1 sec.
- 27. A method of producing an optical data recording medium according to claim 22, wherein the plastic material is a polycarbonate resin.
- 28. A method of producing an optical data recording medium, comprising a step of molding a transparent plastic substrate by injecting a molten plastic material into a die cavity of an injecting die, the infecting die having an injecting gate for injecting molten plastic material into the die cavity, the die cavity having a die cavity surface, the die cavity surface including a signal information recording pattern side of a stamper, wherein a temperature of said molten plastic material passing through said injecting gate is so controlled as to attain a viscosity of the molten plastic material of less than 2000 poise.
- 29. A method of producing an optical data recording medium, including a step of molding a transparent plastic substrate by injecting a molten plastic material into a die cavity of an injecting die, the injecting die having an injecting gate, said die cavity having a die cavity surface, with a part of the die cavity surface including a signal information recording pattern side of a stamper, the injecting gate being connected to the die cavity for injecting molten plastic material into the die cavity through the injecting gate, wherein the injecting gate has a gate width of less than 1 mm, said molten plastic material is injected into the cavity in 0.2-1 sec, and a principal dielectric axis of the transparent plastic substrate formed is aligned with a reference direction or perpendicular to said reference direction.
- 30. A method of producing an optical data recording medium according to claim 29, wherein said die includes a cold slug well and a sprue, a capacity of said cold slug well being in the range of {fraction (1/7)} to {fraction (1/2)} of the sprue.
- 31. A method of producing an optical data recording medium according to claim 29, wherein said injecting gate of said injecting die has a gate width between 0.1 mm and 0.6 mm; and wherein a temperature of the molten plastic material passing through the injecting gate is so controlled so as to provide a viscosity of the molten plastic material of 500 to 2000 poise.
- 32. A method of producing an optical data recording medium according to claim 29, wherein said molten plastic material is a polycarbonate resin.
- 33. A method of producing an optical data recording medium, comprising a step of molding a transparent substrate by injecting a molten plastic material into a die cavity of an injecting die, the injecting die having an injecting gate for injecting molten plastic material, into the die cavity, the die cavity having a die cavity surface, the die cavity surface having a part thereof formed by a signal side of a stamper, wherein said injecting die further includes a sprue connected to said injecting gate and provided at a center of the cavity surface, in plan view; wherein a temperature distribution along a circumference of the cavity surface, around the sprue, is not more than ±5° C.; and wherein a temperature Tc of the cavity surface is so adjusted to satisfy the relation Tg−80≦Tc≦Tg, where Tg is a glass transition temperature of the plastic material.
- 34. An optical data recording medium having at least one layer, said at least one layer including a recording film or reflecting film, on a surface of a transparent substrate, said recording film or reflecting film being adapted to reproduce a recorded information by irradiating a linearly polarized light, as a data reading light, at said recording film or reflecting film, from the transparent substrate side of the medium; and wherein a shift of direction of the irradiating linearly polarized light, due to the transparent substrate, is β in formula (1), Sin 4β≤2cos δ·sin θk1.8sin2δ·cos θk,(1)where δ is a retardation by a single pass of said linearly polarized light, generated by birefringence of the transparent substrate, and θk (in degrees) is a magneto-optical rotational angle (Kerr rotational angle) of a reflected light from said recording film or reflecting film, obtained by irradiating the recording film or the reflecting film with the linearly polarized light.
- 35. An optical data recording medium according to claim 34, wherein said at least one layer includes at least an enhancement layer and a magneto-optical recording layer, said magneto-optical recording layer being said recording film.
- 36. An optical data recording medium, comprising at least one layer, said at least one layer including a recording film or reflecting film, on a surface of a transparent substrate, said recording medium being adapted to have a linearly polarized light irradiated thereon, from the transparent substrate side, for reproducing information, wherein a signal-to-noise ratio of a reproduced signal from said optical data recording medium becomes a local maximum when a plane of polarization of the linearly polarized light is selected in one of a direction parallel, perpendicular or 45° to a principal dielectric axis of the transparent substrate.
- 37. An optical data recording medium according to claim 36, said principal dielectric axis is a radial direction of the substrate.
- 38. An optical data recording medium according to claim 36, wherein said at least one layer includes at least an enhancement layer and a magneto-optical recording layer, said magneto-optical recording layer being said recording film.
Priority Claims (2)
Number |
Date |
Country |
Kind |
61-269905 |
Nov 1986 |
JP |
|
61-294983 |
Dec 1986 |
JP |
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Parent Case Info
This application is a continuation of application Ser. No. 774,623, filed on Oct. 10, 1991, now abandoned which is a reissue of U.S. Pat. No. 4,876,133, issued Oct. 24, 1989 from application Ser. No. 119,471, filed Nov. 12, 1987.
US Referenced Citations (8)
Divisions (1)
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Number |
Date |
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07/119471 |
Nov 1987 |
US |
Child |
08/267550 |
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US |
Continuations (1)
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07/774623 |
Oct 1991 |
US |
Child |
07/119471 |
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US |
Reissues (1)
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Number |
Date |
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Parent |
07/119471 |
Nov 1987 |
US |
Child |
08/267550 |
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US |