JP2908532B2 - Optical recording element - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an optical recording element in which a transparent resin layer mixed with a conductive filler is provided on one main surface of a plastic substrate.

[Prior Art] Substrate materials for optical recording elements include glass and plastic. Although glass substrates are expensive, various required characteristics can be obtained. On the other hand, a plastic substrate is rich in mass productivity and low in cost.

Examples of the plastic substrate material include a polycarbonate resin, an epoxy resin, an acrylic resin, and a polyester resin. These resins are insulative and are easily charged, so that dust easily adheres. In addition, these resins have low hardness and are easily damaged. These factors increase the bit error rate (hereinafter referred to as BER) and cause the read performance of the element to decrease.

In order to solve the above-mentioned problem, SiO ₂
It has been proposed to form an inorganic film such as
63-155,450, and JP-A-63-292,441).

However, when an optical recording element having this configuration was additionally tested and an environmental test was performed to evaluate durability performance, it was found that swelling occurred between the substrate and the inorganic film, and the BER was reduced. For this reason, antistatic treatment different from the formation of a simple inorganic film is required.

[Problems of the Invention] The present invention provides a method for manufacturing a semiconductor device, comprising:
By providing a transparent resin layer in which a conductive filler smaller than 1.8 is mixed, antistatic treatment of the substrate is performed. (1) Light scattering in the transparent resin layer is prevented,
It is an object to reduce the influence of the film pressure of the resin layer by reducing the power loss at the time of reading, (2) preventing adhesion of dust, and (3) reducing the power loss in the resin layer.

[Configuration and Function of the Invention] The optical recording element of the present invention is obtained by mixing a conductive filler having a refractive index of light of less than 1.8 on the other main surface of a plastic substrate having an optical recording layer formed on one main surface. Characterized in that a transparent resin layer is provided.

Generally, the refractive index of the transparent resin is about 1.5 to 1.6. If a conductive filler having a different refractive index n is mixed here, laser light for recording / reproduction is scattered due to microscopic non-uniformity of the refractive index. If the pressure of the resin layer varies from place to place, the degree of light scattering also varies from place to place. As a result,
It is also necessary to strictly control the thickness of the resin layer to make the degree of light scattering uniform. This is caused by light scattering,
This is the second problem.

On the other hand, in the present invention, light scattering is prevented by using a conductive filler having a refractive index close to that of the transparent resin. The refractive index n of the filler is smaller than 1.8, preferably 1.7 or less. The inventors have found that, with a conductive filler obtained by adding Sb to SnO ₂ (refractive index n is 2.0), the recording sensitivity of the element is deteriorated due to light scattering, but a mixture of WO ₃ and WO ₂ having a refractive index n of 1.7 ( It has been confirmed that sensitivity does not decrease in WO ₃ (hereinafter referred to as WO ₂ ) and the like.

Note that the refractive index is measured in the range of 400 nm to 850 nm, which is a wavelength normally used in an optical recording element. The filler preferably uses a ceramic filler that is stable to temperature and humidity and various environments. For example, WO ₃ (WO ₂ ) having a refractive index of about 1.7 or Al ₂ O ₃ and ZrO ₂ having a refractive index of about 1.6 is used. A mixture such as CaWO ₄ having a refractive index of about 1.7 is used. These fillers are transparent and have conductivity. These fillers may be used alone, but high refractive index SnO ₂ , SnO 2
₂ (Sb), In ₂ O ₃ (Sn), ZnO, TiOx, ZrO _{2 and the} like may be mixed in a small amount. In this case, it is sufficient if the average refractive index of the entire filler is smaller than 1.8 (more preferably, 1.7 or less). Elements in parentheses indicate valence controlling impurities for increasing conductivity. The particle size of the filler depends on the wavelength used for recording and reproduction, but is preferably several hundreds to several thousand. The transparent resin layer is provided on the substrate reading surface, but is not limited thereto, and may be provided on the surface on the optical recording layer side.

Embodiment FIG. 1 shows an optical recording element of an embodiment. In the figure,
Reference numeral 2 denotes a disc-shaped transparent plastic substrate made of polycarbonate resin (130 mm in diameter), which can be changed to any transparent plastic substrate such as epoxy resin, polyester resin, amorphous polyolefin resin, or acrylic resin.

Reference numeral 4 denotes a lower dielectric layer provided on one main surface of the substrate 2, in this case, amorphous yttrium sialon (YSiAlON)
And The lower dielectric layer 4 may further include, for example, silicon nitride, aluminum nitride, titanium nitride, silicon carbide, cadmium sulfide, zinc sulfide, magnesium fluoride,
Aluminum oxide, cerium oxide, zirconium oxide,
Silicon oxide, cadmium oxide, bismuth oxide, or the like is used.

Reference numeral 6 denotes an optical recording layer, which uses an amorphous thin film having a magnetization direction perpendicular to the plastic substrate 2. GdDyFe, GdTbFe, TbFeCo, DyFeCo, GdTbDyFe, GdTbF
eCo, TbDyFeCo, GdDyFeCo, NdGdDyFe, NdDyFeCo, NdGdDyFeCo
And so on.

Reference numeral 8 denotes an upper dielectric layer, similarly to the lower dielectric layer 4, using yttrium sialon. Reference numeral 10 denotes Al, Ti, Cr, Cu, Ag, A.
u, SUS or other metal reflective layer. Reference numeral 12 denotes a resin protective layer, which is made of an ultraviolet curable resin such as acrylic triester, epoxy, polyester, acrylic, and acrylic urethane. The resin protective layer 12 may not be provided, or a conductive filler may be mixed into the resin protective layer 12 to perform antistatic treatment on the optical recording layer 6 side.

Reference numeral 14 denotes a transparent resin layer provided on the readout surface of the substrate 2, which is obtained by mixing a transparent resin with a conductive filler having a refractive index n smaller than 1.8, preferably 1.7 or less. As a material of the transparent resin, an ultraviolet-curing resin such as an acrylate, an epoxy, a polyester, an acrylic, or an acrylic urethane is used, and the refractive index thereof is generally 1.5 to 1.6.

A conductive and transparent filler is used, and the particle size is about several hundreds to several thousand degrees. The refractive index n is measured at a wavelength of 400 to 850 nm. Preferred materials for the filler include, for example, WO ₃ (WO ₂ ) having a refractive index n of about 1.7, Al ₂ O ₃ (a mixture of ZrO ₂ and Al ₂ O ₃ ) made conductive with ZrO ₂ having a refractive index of about 1.6, Refractive index is 1.
It is about 7 CaWO ₄ . Of course, these materials have higher refractive indices of In ₂ O ₃ (Sn) (n ≒ 2.0), SnO ₂ (n ≒ 2.0), and SnO ₂ (S
b) (n ≒ 2.0), ZnO (n ≒ 2.1), TiOx (n ≒ 2.2), ZrO ₂
(N ≒ 2.05) may be mixed in a small amount. The thickness of the transparent resin layer 14 is, for example, 5 μm, preferably 1 to 15 μm, and more preferably 3 to 10 μm.

On one main surface of the polycarbonate substrate 2, a transparent resin layer 14 to which a conductive filler is added by a spin coating method is applied to a thickness of 5
It was formed to a thickness of μm. As the transparent resin, an acrylic ultraviolet curable resin 12 ("SD17", "SD17" manufactured by Dainippon Ink and Chemicals, Inc., trade names) was used. As the filler, WO ₃ (WO ₂ ) of the example was used.
In addition to the mixture of Al ₂ O ₃ and ZrO ₂ , CaWO ₄ , as a comparative example,
nO ₂ (Sb) having a maximum particle diameter of 1 μm and an average particle diameter of several hundred to several thousand Å was used. Filler content in resin is 3
Experiments were performed in the range of ~ 70% by weight. The preferable content of the filler is 3 to 70% by weight, more preferably 3 to 60% by weight based on the total amount of the resin. In the case of a filler having high conductivity, a sufficient effect can be obtained even with 3% by weight, and a material having a refractive index close to that of a resin does not cause any problem even if added up to 70% by weight. The ultraviolet-curable resin was dissolved in a butanol / IPA mixed solvent, spin-coated, and then cured with ultraviolet light. First, the transparent resin layer 14
Is formed in order to prevent dust and the like from entering the readout surface in the process of forming the optical recording layer 6 and the like. Of course, the transparent resin layer 14 may be formed after the formation of the optical recording layer 6 and the like. Butanol / IPA solvent evaporates during spin coating,
No change in hardness of the transparent resin layer 14 could be confirmed even when heated.

An amorphous yttrium sialon film 4 is formed on the other main surface of the substrate 2 by a magnetron sputtering apparatus.
GdDyF sputtered to 920mm thickness, then containing Ti atoms
The optical recording layer 6 consisting of the perpendicular magnetization film of e was formed at 200 °.
Further, the same yttrium sialon as described above is formed in a thickness of 300 mm to form an upper dielectric layer 8, on which an Al metal reflective film 10 is formed.
Was laminated to a thickness of 800 mm. An acrylic UV curable resin (same SD17 as above) was spin-coated on the metal reflective film 10 to form a resin protective layer 12 having a thickness of 5 μm.

For the manufactured optical recording element, the specific resistance of the transparent resin layer 14 and the amount of change in the optimum recording sensitivity were measured. The results are shown in the table.
Sample A in the table has a WO ₃ (WO ₂ ) content of 40% by weight, sample B has a content of 60% by weight, and sample C has a SnO ₂ content of 7% by weight.

As is clear from the table, the refractive index n is smaller than 1.8.
In the example using O ₃ (WO ₂ ), the change in the optimum recording sensitivity is small. This means that light scattering does not occur in the transparent resin layer 14 and the power loss is small. Further in addition to WO ₃ (WO _2), a mixture or ZrO ₂ and Al ₂ O _3, even CaWO _4, 3 to 60 wt%
, The change in the optimum recording sensitivity was slight as in WO ₃ (WO ₂ ).

[Effects of the Invention] In the present invention, a transparent resin layer containing a conductive filler having a refractive index of less than 1.8 is provided on the other main surface of a plastic substrate having an optical recording layer formed on one main surface.

In this case, since the difference in the refractive index between the transparent resin and the filler is small, light scattering in the transparent resin layer can be suppressed, and the light energy required for recording and reproduction can be reduced.

Since light scattering by the filler is small, the filler content can be increased, and as a result, a highly conductive transparent resin layer can be formed.

Then, the transparent resin layer is made conductive by the filler, and the adhesion of dust is small.

Further, since light scattering is small, unevenness in the thickness of the transparent resin layer can be tolerated, and the recording characteristics do not change even if there is a difference in the thickness of the transparent resin layer between the inner circumference and the outer circumference of the substrate.

Further, when ceramic is used for the filler, a transparent resin layer which is stable to temperature and humidity and has excellent durability in various environments can be obtained.

[Brief description of the drawings]

 FIG. 1 is a sectional view of an optical recording element according to an embodiment. In the figure, 2 ... plastic substrate, 4 ... lower dielectric layer, 6 ... optical recording layer, 8 ... upper dielectric layer, 10 ... metal reflective layer, 12 ... resin protective layer, 14 ... transparent Resin layer.

Claims (2)

(57) [Claims] 1. A plastic substrate having an optical recording layer formed on one main surface, and a transparent resin layer mixed with a conductive filler having a light refractive index of less than 1.8 is provided on the other main surface of the plastic substrate. An optical recording element. 2. The light according to claim 1, wherein said conductive filler is at least one of a mixture of ZrO ₂ and Al ₂ O _3, a mixture of WO ₃ and WO ₂ or CaWO _4. Recording element.