JPS63184943A - Production of optical recording medium - Google Patents

Abstract

PURPOSE:To decrease the influence of double refractions that diagonal incident laser light receives from a substrate by subjecting one or both of the light transmittable substrates constituting a medium to one or plural times of heat treatments at the temp. near the glass transition point of the substrate material or above said temp. CONSTITUTION:One or both of the light transmittable substrates constituting the medium of the optical recording medium are annealed at the temp. near (+ or -10 deg.C) the glass transition point of the substrate material or above. The difference in the refractive index in the perpendicular direction of the substrates is thereby decreased and the influence (substrate noise) of the double refractions that the diagonal incident laser light on the substrates receives from the substrates is minimized; in addition, the CNR value exhibits the stable value without having a change in the CNR value in this annealing even after a long- term weatherability test.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical recording medium that can be read and aged using laser light, and relates to a CD-ROM, DRAW, E-
Can be used for DRAW.

[Conventional technology]

Conventionally, the light-transmissive substrate of an optical recording medium for recording and reproducing information using an optical method is produced by injection molding at a temperature of 41°C and 80°C in a mold.
It was molded by soft melting at ~120°C.

[Problem that the invention seeks to solve]

In a light-transmitting substrate molded by conventional injection molding, it was possible to significantly reduce the value of the tentative in-plane refractive index difference (optical anisotropy). However, the value of the refractive index difference in the vertical l'f direction of the substrate was large. In an optical pickup for reading information, the objective lens passes the light through the light-transmitting substrate and focuses it on the information recording film, so the light travels through the substrate at various angles. As a result of the above, if the value of the refractive index difference in the vertical direction is large, it causes fluctuations in the light intensity toward the point where the light is obliquely incident on the substrate. In a medium using magneto-optical characteristics, the absolute value of the amount of light entering the signal detector is small, which tends to push up the CNR noise by several decibels. The present invention reduces the refractive index difference in the vertical direction of the substrate, minimizes the influence of birefringence that the laser beam obliquely incident on the substrate receives as it moves up the substrate, and
The purpose is to improve CNR by reducing NR noise.

[Means for solving problems]

The method for manufacturing an optical recording medium of the present invention is to produce an optical recording medium in which information is recorded and reproduced using an optical method, in which one or both of the light-transmitting substrates forming the medium (?4) are glass substrate material r1. It is characterized by being heat-treated once or multiple times at a temperature near the turning point (±10°C) or higher.

[Example 1] FIG. 1(a) shows a cross-sectional view of the structure of an optical recording medium manufactured by subjecting the substrate to annealing according to the present invention. Reference numeral 6 denotes a 1.2-n thick polybonate substrate having an information recording layer 0 portion on the bonding surface side. 5 is a radical reaction type ultraviolet curing adhesive. FIG. 1(b) shows the detailed structure of the medium. 1 is a grooved polycarbonate substrate with a track pitch of 1.6 μm.
1 groove z? j, 650 people, 0.6 μm in the groove. 2 is a composite film of silicon nitride and aluminum nitride with a thickness of 80 mm.
There are 0 people. 3 is magneto-optical recording medium NdDyFeCoT
i is 400 people thick. 4 is a composite film of silicon nitride and animinium nitride and has a thickness of 1,500 mm. The polycarbonate substrate 1 was annealed under the conditions shown in Table 1 before forming the information recording area. The polycarbonate used in this test was made by Teijin! Panlight A I) -55 made by Boru
It is 03. The glass transition point Tg of HachiD-5503 is 13
It is 5°C. Rotation speed 90ORPM, recording frequency IM
IIz.

Table 1 shows C N R measured by reflection using the Kerr effect at 30 K II z in the band. The results showed that the CNR value was better for the substrate annealed at a temperature higher than the glass transition point. The CNR was 53 to 54 dll under a temperature condition higher than the glass transition point of polycarbonate. On the other hand, when annealing at 120°C below the glass transition temperature, the CNR is 51.
．． It was 5d13. After annealing at 160°C for 10 minutes, 180°C for 5 minutes, and 180°CIO, the substrate track grooves disappeared. Then temperature 60" C1 temperature 90% 1000
A time durability test was conducted, but no change was observed in CNR.

Table 1 shows a cross-sectional view of the structure of an optical recording medium manufactured by applying the substrate annealing of the present invention to (temporary annealing conditions and CNI section of optical recording medium [Example 2] 2nd CEICa). 1G has an information recording layer portion on the bonding surface side 1.2. , thick polycarbonate substrate. 15 is a radical reaction type ultraviolet curing adhesive. 17 is a smooth surface polycarbonate substrate with a diameter of 1.2@■. The detailed medium structure is not shown in FIG. 2(b). 11 is a polycarbonate substrate with grooves, track pitch 1.6 μm 1 groove JW 650 people, groove inside 0.8 μm
It is m. 12 is silicon oxide (Sin) with a thickness of 100
There are 0 people. 13 is the magneto-optical recording medium NdDyFeCo
It is made of Ti and has a thickness of 400λ. 4 is silicon oxide (S i
O) and has a thickness of 1000 people.

Polycarbonate board 11.17 is a passion vI! Those used were annealed under the conditions shown in Table 2 before forming the recording layer section. The polycarbonate used in this test was Panrai) AD-5503 manufactured by Kijin Kasei Co., Ltd. as in Examples 1 and II1. Rotation speed 900 RPM 1 record frequency IMII z s bunt medium 3
Table 2 shows the CNR measured by laser transmitted light using the Faraday effect at 0KIIz. The results showed that the CNR was better for the substrate annealed at a temperature higher than the glass transition point.

Table 2: Substrate annealing conditions and CNR of the medium at complete distribution t'' [Example 3] Figure 3(a) shows the optical recording medium 'A' produced by subjecting the substrate annealing of the present invention (1 is the structured cross section. The figure is shown. 28 is a temporary polycarbonate substrate of 1.2□ thickness with an information recording layer portion on the bonding surface side. 25 is a j' agent after UV curing of a radial reaction system. 29 is 1 It is a smooth polycarbonate substrate with a thickness of .2 cm. Figure 2 (b) shows the detailed media structure. 21 is a polycarbonate substrate with a groove of 1.6 μm, a groove depth of 600 mm, and a groove depth of 600 mm. 0.6
It is μm.

22 is a composite film of silicon nitride and aluminum nitride, and its size is 1,000 people. 23 is the N d of the magnetic recording medium
It is D y F c Co F e and has a thickness of 400 people.

24 is a composite film of silicon nitride and nitride (1?aluminum) with a thickness of 1000 mm. 026 is a composite film of silicon nitride and aluminum nitride with a thickness of 1000 mm. Polycarbonate substrate 2i 27 is exposed before forming the information recording area. The polycarbonate used in this test was Panrai) AD-5503 manufactured by Kijin Kasei Co., Ltd., as in Example 1. Rotation speed 00 ORP M
, 30 K II in the band at recording frequency I M II z
Table 3 shows the CNR measured by the amount of laser transmission using the Faraday effect at z. The results showed that the CNR of 1f1 was better for the substrate annealed at a temperature higher than the glass transition point.

Table 3: Substrate annealing conditions and CNR of optical recording medium The present invention can be applied not only to the closely laminated structure shown in the embodiment, but also to an air sandwich (one-piece optical recording medium). As the recording medium, a magneto-optical recording medium NdDyFeCoTi was shown in the example, but T b F
c CO% G d T b F c ,, ? F) Can be applied to all magneto-optical recording media. It is also applicable to phase difference type recording media.

〔Effect of the invention〕

By annealing one or both of the optically transparent substrates constituting the optical recording medium at a temperature close to or higher than the glass transition point of the substrate material, the difference in refractive index in the direction perpendicular to the substrates can be reduced and The effect of birefringence (substrate noise) on the angled laser beam from the substrate can be minimized as much as possible. As for the annealing effect, it was possible to improve the CNR by 2 to 3 dL3CNR compared to the product annealed at 120°C and 4 to 5d13 compared to the product without annealing. Furthermore, in the annealing according to the present invention, even after a long-term weathering test, CN
There was no change in the R value, indicating stable C N R l1il.

[Brief explanation of the drawing]

FIG. 1(a) is a cross-sectional view of the structure of the optical recording medium of the present invention. FIG. 1(b) is a detailed view of the tank 12 in FIG. 1(a).
a) is a structural sectional view of the fully distributed Ti medium of the present invention. FIG. 2(b) is a detailed groove structure diagram of FIG.
a) is a cross-sectional view of the structure of the complete LA medium of the present invention; FIG. 3(b) is a detailed structural view of FIG. 1 Horror 1 Figure (b) /l! J3 koto)

Claims (1)

[Claims] In a method of manufacturing an optical recording medium for recording and reproducing information using an optical method, one or both of the light-transmitting substrates constituting the medium are near the glass transition point of the substrate material (±10 ° C.),
A method for producing an optical recording medium, characterized in that the medium is heat-treated once or multiple times at a temperature higher than or equal to that temperature.