Protecting film for optical recording medium and optical recording medium
First Claim
1. An optical recording medium protecting film characterized by being a single transparent film made of a thermoplastic resin, having a glass transition temperature of 120°
- C. or higher and a water absorption of no greater than 1 wt %, and having a retardation at a wavelength of 550 nm that satisfies both of the following inequalities (1) and (2);
|R(550)|≦
15 nm
(1)
|K(550)|<
40 nm (2) where R(550) is the in-plane retardation of the transparent film at a wavelength of 550 nm and K(550) is the value calculated by K=[nz−
(nx+ny)/2]×
d (where nx, ny and nz are the three-dimensional refractive indexes of the transparent film in the x-axis, y-axis and z-axis directions, respectively, and d is the thickness of the transparent film) for the transparent film at a wavelength of 550 nm, wherein the retardations at wavelengths of 450 nm and 550 nm satisfy (a) both the following inequalities (3) and (4), (b) the following inequality (3), or (c) the following inequality (4);
R(450)/ R(550)<
1
(3)
K(450)/ K(550)<
1
(4) where R(450) and R(550) are the in-plane retardation of the transparent film at wavelengths of 450 nm and 550 nm, respectively, and K(450) and K(550) are the values calculated by K=[nz−
(nx+ny)/2]×
d (where nx, ny and nz are the three-dimensional refractive indexes of the transparent film in the x-axis, y-axis and z-axis directions, respectively, and d is the thickness of the transparent film) for the transparent film at a wavelength of 450 nm and 550 nm respectively;
and the thickness irregularity of the transparent film is no greater than 1.5 μ
m.
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Abstract
An optical recording medium protecting film which is a protecting film comprising a single transparent film made of a thermoplastic resin, having a retardation of no greater than 15 nm at a wavelength of 550 nm and a K value of no greater than 40 nm at 550 nm, having a glass transition temperature of 120° C. or higher and a water absorption of no greater than 1 wt %.
|R(550)|≦15 nm (1)
|K(550)|≦40 nm (2)
(the K value being calculated by K=[nz−(nx+ny)/2]×d {where nx, ny and nz are the three-dimensional refractive indexes of the transparent film in the x-axis, y-axis and z-axis directions, respectively, and d is the thickness of the transparent film}). Also, an optical recording medium having a data recording layer and the above-mentioned protecting film on a substrate, wherein light is incident from the protecting film side.
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Citations
10 Claims
-
1. An optical recording medium protecting film characterized by being a single transparent film made of a thermoplastic resin, having a glass transition temperature of 120°
- C. or higher and a water absorption of no greater than 1 wt %, and having a retardation at a wavelength of 550 nm that satisfies both of the following inequalities (1) and (2);
|R(550)|≦
15 nm
(1)
|K(550)|<
40 nm (2)where R(550) is the in-plane retardation of the transparent film at a wavelength of 550 nm and K(550) is the value calculated by K=[nz−
(nx+ny)/2]×
d (where nx, ny and nz are the three-dimensional refractive indexes of the transparent film in the x-axis, y-axis and z-axis directions, respectively, and d is the thickness of the transparent film) for the transparent film at a wavelength of 550 nm,wherein the retardations at wavelengths of 450 nm and 550 nm satisfy (a) both the following inequalities (3) and (4), (b) the following inequality (3), or (c) the following inequality (4);
R(450)/ R(550)<
1
(3)
K(450)/ K(550)<
1
(4)where R(450) and R(550) are the in-plane retardation of the transparent film at wavelengths of 450 nm and 550 nm, respectively, and K(450) and K(550) are the values calculated by K=[nz−
(nx+ny)/2]×
d (where nx, ny and nz are the three-dimensional refractive indexes of the transparent film in the x-axis, y-axis and z-axis directions, respectively, and d is the thickness of the transparent film) for the transparent film at a wavelength of 450 nm and 550 nm respectively;
and the thickness irregularity of the transparent film is no greater than 1.5 μ
m.- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
(2) wherein the R(450)/R(550) of the polymer based on the first monomer unit is smaller than the R(450)/R(550) of the polymer based on the second monomer unit; and
(3) which has a positive refractive index anisotropy.
- C. or higher and a water absorption of no greater than 1 wt %, and having a retardation at a wavelength of 550 nm that satisfies both of the following inequalities (1) and (2);
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4. An optical recording medium protecting film according to claim 1, which comprises a transparent film
(1) which is a film made of a polymer comprising a monomer unit that forms a polymer with positive refractive index anisotropy (hereunder referred to as “ - first monomer unit”
) and a monomer unit that forms a polymer with negative refractive index anisotropy (hereunder referred to as “
second monomer unit”
);
(2) wherein the R(450)/R(550) of the polymer based on the first monomer unit is larger than the R(450)/R(550) of the polymer based on the second monomer unit; and
(3) which has a negative refractive index anisotropy.
- first monomer unit”
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5. An optical recording medium protecting film according to claim 1, wherein said transparent film comprises a polycarbonate with a fluorene skeleton.
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6. An optical recording medium protecting film according to claim 1, characterized in that the transparent film is a transparent film made of a polycarbonate copolymer and/or blend comprising 10-90 mole percent of a repeating unit represented by the following formula (I)
where R1-R8 each independently represent at least one selected from the group consisting of hydrogen, halogens and hydrocarbons of 1-6 carbon atoms, and X is and 90-10 mole percent of a repeating unit represented by the following formula (II) where R9-R16 each independently represent at least one selected from the group consisting of hydrogen, halogens and hydrocarbons of 1-22 carbon atoms, and Y is one of the following formulas where R17-R19, R21 and R22 each independently represent at least one selected from among hydrogen, halogens and hydrocarbons of 1-22 carbon atoms, R20 and R23 each independently represent at least one selected from among hydrocarbons of 1-20 carbon atoms, and Ar1, Ar2 and Ar3 each independently represent at least one selected from among aryl groups of 6-10 carbon atoms. -
7. An optical recording medium protecting film according to claim 6, characterized in that the transparent film is a transparent film made of a polycarbonate copolymer and/or blend comprising 30-85 mole percent of a repeating unit represented by the following formula (III)
where R2. and R25 each independently represent at least one selected from among hydrogen and methyl, and 70-15 mole percent of a repeating unit represented by the following formula (IV) where R26 and R27 are each independently selected from among hydrogen and methyl, and Z is selected from among the following groups. -
8. An optical recording medium protecting film according to claim 4, wherein said polymer with positive refractive index anisotropy is poly(2,6-dimethyl-1,4-phenylene oxide), said polymer with negative refractive index anisotropy is polystyrene, and the polystyrene content is 67-75 wt % based on the total of said polymers with positive and negative refractive index anisotropy.
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9. An optical recording medium protecting film according to claim 1, characterized in that the transparent film is fabricated by solution cast film formation.
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10. An optical recording medium protecting film according to claim 1, characterized in that the film thickness of the transparent film is 5-200 μ
- m.
Specification