JP2005071601A - Method of manufacturing multilayered optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of highly precisely and easily manufacturing a multilayered optical disk. <P>SOLUTION: A light transmission resin 5 cured by UV irradiation is embedded in projecting and recessed parts on information recording recording layers 2 and 12 of first and second substrate 1 and 11 and applied on the information recording recording layer 2 and 12, the first and the second substrates 1 and 11 are superposed on and pressure-stuck to each other by making a light transmission film 4 intervene between the light transmission resin 5 on the first substrate 1 side and the light transmission resin 5 on the second substrate 11 side and then the light transmission resin 5 is cured to stick the first and the second substrates 1 and 11 to each other. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a multilayer optical disc having a plurality of information signal recording layers.

  In recent years, with the rise of so-called multimedia, it has become necessary to handle large amounts of information such as digital video, and such large amounts of information can be stored and randomly accessed and played back as necessary. There is a growing need.

  An optical disc is a recording medium that can be randomly accessed, has a large capacity, and is detachable from a recording / reproducing apparatus. It has been used in a large amount in various fields so far, but a larger capacity is required. ing.

  Under such circumstances, as a technique for expanding the capacity of an optical disc, attempts have been made to stack information storage layers in multiple layers.

  Multi-layer optical disc accumulates information in each information layer formed in multiple layers on one side of the disc, enabling reading of information of each layer by focusing reproduction light on each layer without losing random accessibility, It is intended to handle large amounts of information.

  For example, Nikkei Electronics No.2-27 in 1995 describes a multilayer optical disc having multiple information recording layers (see Nikkei Electronics, 1995, 2-27, P99). According to the multilayer optical disk shown here, the signal recording density can be doubled, and both recording information can be read from one side without turning over the optical disk.

  By the way, in a multilayer optical disc having multiple information recording layers, the signal recording layer is formed in two layers. When the signal recording layer is formed in two layers, after forming the first signal recording layer, the upper surface thereof is formed. The unevenness of the stamper was transferred to the substrate with an ultraviolet curable resin.

  On the other hand, a multilayer optical disc in which two discs are bonded is manufactured by bonding a first substrate on which an information recording layer is recorded and a second substrate with an adhesive.

  The transfer by photocuring as described above has a problem that the rate of occurrence of transfer failure is high and a long time is required for the bonding operation.

  In addition, when bonding two disks, the adhesive must be made to adhere completely to the unevenness of the substrate, so a low-viscosity UV-curable resin must be used, but a low-viscosity UV-curable resin is used. Then, it becomes difficult to form a layer having a thickness of about 40 μm, which is thick enough to optically separate the information recording layer of the first substrate and the information recording layer of the second substrate.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a multilayer optical disc, which can easily manufacture a multilayer optical disc with high accuracy.

  In order to achieve the above-mentioned object, the present invention provides the first information of the first substrate in which a concavo-convex pattern is formed on one surface by injection molding, and the first information recording layer is formed on the concavo-convex pattern. A concave / convex pattern is formed on one surface of the first information recording / recording layer by embedding a concave / convex pattern on the first recording / recording layer by applying a light-transmitting resin that is cured by irradiation of ultraviolet rays. Light transmission that is hardened by irradiating ultraviolet rays on the second information recording layer by embedding irregularities on the second information recording layer of the second substrate on which the second information recording layer is formed on the pattern Then, a light-transmitting film is applied between the light-transmitting resin on the first substrate side and the second light-transmitting resin, and then the first substrate and the second substrate are applied. Laminate the substrate and crimp it, then By irradiating an outside line and curing the light transmitting resin is obtained as manufactured by adhering the first and second substrates.

  In the present invention, the first substrate and the second substrate are pressure-bonded by pressing a roller from one substrate side, and bubbles generated between the first substrate 1 and the second substrate are generated. It is desirable to eliminate it.

  The light transmissive film desirably has a thickness in the range of 20 μm to 100 μm.

  In the method of the present invention, since the unevenness on each information recording layer of the first and second substrates is embedded and a light transmissive resin that is cured by irradiation of ultraviolet rays is applied on each information recording layer, The bonding surfaces of the first and second substrates can be flattened. Then, a light-transmitting film is interposed between the light-transmitting resin on the first substrate side to be planarized and the second light-transmitting resin on the second substrate side, and the first substrate and the second substrate Since the substrate is superposed and pressure-bonded, and then the light-transmitting resin is cured and the first and second substrates are bonded together, the thickness between the first and second information recording layers is highly accurate. In addition, the first and second substrates can be joined easily.

  Hereinafter, specific examples to which the present invention is applied will be described in detail with reference to the drawings.

  The multilayer optical disk manufactured by the method of the present invention will be described. In the multilayer optical disk, as shown in FIG. 1, the first information recording layer 2 is formed on the first substrate 1 having a thickness of 0.6 mm. The second information recording layer 12 is formed on the second substrate 11 having a thickness of 0.6 mm, and these are bonded together with the light-transmitting film 4 interposed therebetween.

  The first information recording layer 2 and the second information recording layer 12 are formed so as to have different reflectances. In particular, the first information recording layer 2 is formed of a material having a high reflectance. Yes. Therefore, information signals are obtained from both of them, and both information can be read from one side by changing the focal position of the reproduction light.

  Each of the substrates 1 and 11 is made of plastic such as polycarbonate and is formed by injection molding. The substrates 1 and 11 may be made of glass, and a protective film (not shown) may be formed on the information recording layers 2 and 12.

  The second information recording layer 12 is formed along the concavo-convex pattern of the second substrate 11 and functions as a reflective film for reading out reproduction-only information by the concavo-convex pattern.

  A light transmissive film 4 is interposed between the first substrate 1 and the second substrate 11. The light transmissive film 4 improves the efficiency of the bonding operation described later. The light transmissive film 4 has a predetermined thickness, and specifically, a thickness in the range of 20 μm to 100 μm is preferable. If the light-transmitting film 4 is too thin, the reflected light from the first information recording layer 2 and the reflected light from the second information recording layer 12 cannot be sufficiently separated. Therefore, it becomes difficult to accurately detect information recorded in each information recording layer 2 and 12. If the thickness is too thick, spherical aberration or the like occurs. In consideration of these points, it is necessary to set the thickness of the light transmissive film 4.

  As the light-transmitting film used here, it is preferable to use a transparent polymer such as polyethylene terephthalate, polycarbonate, acetylcellulose (cellulose acetate), polyacrylonitrile and the like.

  In order to manufacture the above-described multilayer optical disc, first, a first substrate 1 on which a concavo-convex pattern such as pits is formed according to an information signal read from the first information recording layer 2 in advance, and first a second information recording in advance. A second substrate 11 having a concavo-convex pattern such as pits formed in accordance with an information signal read from the layer 12 is prepared. That is, as shown in FIGS. 2 and 3, the first and second substrates 1, 11 are made of a melted resin by using a stamper having a concavo-convex pattern corresponding to the concavo-convex pattern formed on each substrate 1, 11. 9 is formed by a so-called injection molding method in which a mold 9 is injected at a high pressure and then cured.

  Next, as shown in FIG. 4, a light-transmitting resin 5 that is cured by irradiation with ultraviolet rays (UV light) is applied to the surface of the first and second substrates 1, 11 on which the concavo-convex pattern is formed. Next, as shown in FIG. 5, the surface on which the concave / convex pattern is formed and the first information recording layer 2 is formed faces the surface on which the concave / convex pattern is formed and the second information recording layer 12 is formed. Then, the first and second substrates 1 and 11 are stacked with the light transmissive film 4 interposed between the first and second information recording layers 2 and 12. Thereafter, the first substrate 1 and the second substrate 11 are pressure-bonded by the roller 6 abutted from the second substrate 11 side. Here, the thickness between the first substrate 1 and the second substrate 11 is not less than 20 μm and not more than 100 μm, and is uniformed so that bubbles do not enter.

  Thereafter, as shown in FIG. 5, the light transmissive resin 5 is cured by irradiating UV light 8 from one substrate, for example, the second substrate 11 side.

  In the present invention, the first and second light-transmitting films 4 are interposed between the first information recording layer 2 and the second information recording layer 12 that are coated with the light-transmitting resin 5 and planarized. Since the substrates 1 and 11 are bonded together, the substrates can be bonded with high accuracy and easily.

  Further, by manufacturing in this way, for example, the thickness between the first information recording layer 2 and the second information recording layer 12 that has been difficult to manufacture in the past is set to a thickness of about 40 μm, etc. Can be easily thickened.

  By the way, if the refractive index of the light-transmitting resin 5 is 0.3 or more away from the refractive indexes of the substrates 1 and 11, both signals can be read from one side of the optical disk. Further, when the refractive index of the light-transmitting resin 5 is not more than 0.3 than the refractive index of the substrate, by forming a dielectric film on the signal surface, both information signals from one surface side of the optical disk. Can be read.

  Here, when the information signal is read, the difference in the refractive index of the signal surface is used. This relationship is expressed by the following equation (1).

R = n1-n2 / n1 + n2 (Formula 1)
Here, R represents the reflectance, n1 represents the refractive index of the light-transmitting resin 5, and n2 represents the refractive index of the substrate.

  Assuming that the refractive index of the first and second substrates 1 and 11 is n2 = 1.5, the reflection is less than 10% when the refractive index of the light-transmitting resin 5 is n1 = 1.8 or less. No signal is available.

  If a dielectric film having a refractive index n1 of about 2 is formed, the reflectance increases and an information signal can be read even if the difference from the refractive index of the light-transmitting resin 5 is small.

It is sectional drawing which shows the multilayer optical disk manufactured by this invention. It is a perspective view which shows the manufacturing process of the multilayer optical disk based on this invention, and shows the process which a board | substrate shape | molds by injection molding partially expanded. It is sectional drawing of the stamper used for the manufacturing process of the multilayer optical disk based on this invention. It is a perspective view which shows the manufacturing process of the multilayer optical disk based on this invention, (a) (b) shows the process of apply | coating a transparent resin to a board | substrate. It is a perspective view which shows the manufacturing process of the multilayer optical disk based on this invention, (a) shows the process of interposing a light-transmitting film between board | substrates, (b) shows the process of bonding a board | substrate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,11 Board | substrate, 2 1st information recording layer, 4 Light transmissive film, 5 Light transmissive resin, 9 Stamper, 12 2nd information recording layer

Claims (3)

An uneven pattern is formed on one surface by injection molding, and the unevenness on the first information recording recording layer of the first substrate on which the first information recording layer is formed is embedded on the uneven pattern. A light-transmitting resin that is cured by irradiation of ultraviolet rays is applied onto the information recording / recording layer, and an uneven pattern is formed on one surface by injection molding, and a second information recording layer is formed on the uneven pattern. A light-transmitting resin that is cured by irradiation of ultraviolet rays is applied to the second information recording recording layer by embedding irregularities on the second information recording recording layer of the second substrate,
Next, the first substrate and the second substrate are overlapped with a light transmissive film interposed between the light transmissive resin on the first substrate side and the second light transmissive resin. Crimp,
Then, a method for producing a multilayer optical disc, wherein the light transmissive resin is cured by irradiating ultraviolet rays, and the first and second substrates are bonded together.   The pressure bonding between the first substrate and the second substrate is performed by pressing a roller from one substrate side to eliminate bubbles generated between the first substrate 1 and the second substrate. The method of manufacturing a multilayer optical disk according to claim 1, wherein: 2. The method of manufacturing a multilayer optical disk according to claim 1, wherein the light transmissive film has a thickness in a range of 20 [mu] m to 100 [mu] m.

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