JP2010009702A - Optical information recording medium and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To materialize a multilayer optical information recording medium at a low cost. <P>SOLUTION: The optical information recording medium 1 has interfaces among resin layers 11-13 as reflection surfaces, wherein the resin layers 11, 13 with a first refractive index and the resin layer 12 with a second refractive index are alternately laminated. In this constitution, all differences in refractive index between the adjacent resin layers are the same, and reflectance of the media of respective layers are uniform. Reproduction from the respective layers of the optical information recording medium 1 is facilitated. Furthermore, the optical information recording medium 1 is flexibly adapted to have multiple layers at a low cost by arbitrarily increasing the number of resin layers without being restricted by the possible range of refractive indexes of the materials of the resin layers 11-13. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical information recording medium having a reflection surface at the interface between resin layers.

  In recent years, further increase in capacity of optical information recording media has been demanded. In order to realize this large capacity, a technique for providing a plurality of information recording layers on an optical information recording medium has been proposed, and has already been implemented in DVD (Digital Versatile Disc) and BD (Blu-ray Disc). Yes.

  For example, Patent Document 1 discloses a multilayer optical information recording medium having three or more resin layers on which a recording surface having concavo-convex recording pits and a reflective layer is formed. Non-Patent Document 1 and Non-Patent Document 2 disclose a multilayer optical information recording medium having eight intermediate layers on which a reflective film of a SiN alloy or an Ag alloy is formed.

  In the multilayer optical information recording media described in Patent Document 1 and Non-Patent Documents 1 and 2, a reflective film (reflective layer) is a plurality of intermediate layers (resin layers) on which recording surfaces are formed as reflection means for reproducing light. It is provided between. In addition, a metallic material such as an Ag alloy is used as the reflective film, and in order to control the reflectance, the reflective film is formed with a very thin film thickness (several nm to several tens nm) with high accuracy. ing.

On the other hand, Patent Document 2 discloses an optical information recording medium in which an interface between resin layers is a reflective surface without using a reflective film. In the configuration described in Patent Document 2, another resin layer (intermediate layer) having a refractive index different from that of the resin layer (substrate) is laminated on the resin layer (substrate) on which the recording surface is formed. Since the refractive indexes of the substrate and the intermediate layer are different from each other, the interface between these resin layers functions as a reflecting surface that reflects the reproduction light.
JP 2007-12224 A (published January 18, 2007) "APPLIED OPTICS", (USA), March 10, 2006, Vol. 45, No. 8, p.1794-1803 ISO 2004 participation report, page 3, lines 6-12, [online], July 26, 2005, International Conference Bulletin H16-No. 11. Internet <URL: http://www.oitda.or.jp/main/cofrep/H16/H16No11.pdf> Japanese Patent Laid-Open No. 2-331348 (published on February 1, 1990)

  The manufacturing method of the multilayer optical information recording medium in Patent Document 1 and Non-Patent Documents 1 and 2 includes a step of forming a reflective film on each of a plurality of intermediate layers. However, the process of forming a reflective film requires a complicated procedure using a vacuum apparatus, and a multilayer optical information recording medium must repeat a number of reflective film processes due to the multilayering. For this reason, the manufacturing cost of the multilayer optical information recording medium increases remarkably as the number of layers increases.

Further, when reproducing a multilayer optical information recording medium, it is assumed that a reflective film having a common material, film thickness, and reflectance is applied to the information recording surface of each layer. In that case, when the reproduction light is focused on the information recording surface (reflection film) on the back side with respect to the reproduction light, the incident light is transmitted through the reflection film on the near side and then the target information is obtained. The reflected light that reaches the recording surface is transmitted through the reflective film on the near side and then received externally. For this reason, when calculating the reflectance from the ratio between the reproduction light and the reflected light detected externally, the reflectance of the reproduction light focused on the back side is the reflection of the reproduction light focused on the near side. Smaller than the rate. Therefore, in order to obtain the same level of signal intensity from the information recording surface on the front side and the back side, reproduction is performed on the information recording surface on the back side, rather than when reproducing light is irradiated on the information recording surface on the front side. When irradiating light, higher reproduction power is required.

  In the present specification, hereinafter, the theoretical reflectance defined by the energy ratio between the intensity of incident light incident on an information recording surface and the intensity of reflected light reflected on the information recording surface is expressed as Expressed as the single theoretical reflectance of the information recording surface. That is, the single theoretical reflectance of an information recording surface is a reflectance defined without considering the influence of other information recording surfaces other than the information recording surface. On the other hand, the energy reflectance calculated from the intensity of the incident light incident on the multilayer optical information recording medium in a state of being focused on a certain information recording surface and the intensity of the reflected light emitted from the multilayer optical information recording medium at that time, Expressed as the medium reflectivity of the information recording surface. That is, the medium reflectance of a certain information recording surface is a reflectance including the influence of not only the information recording surface but also all other information recording surfaces positioned on the near side. For example, when the information recording surface of each layer is configured by a common reflecting film, the single theoretical reflectance of each information recording surface is common, whereas the medium reflectance of each information recording surface is high on the near side and on the far side It becomes low at.

  The medium reflectivity and the single theoretical reflectivity are definitions for convenience for comparative explanation of the reflectivity of each layer of the multilayer medium, and do not ask for strict numerical values. In a medium having only one information recording surface, in reality, interface reflection of transparent resin, reflection and scattering at each optical element, etc. occur. Therefore, the medium reflectance does not completely match the single theoretical reflectance. In the present specification, it is assumed that the medium reflectance is substantially equal to the single theoretical reflectance. In the following description, unless otherwise specified, when the term “reflectance” is simply used, it refers to the reflectivity of the medium actually measured.

  In a configuration in which a common reflective film is applied to the information recording surface of each layer, the single theoretical reflectance is also common. However, since the voltage value of the focus error signal depends on the medium reflectivity, the voltage value of the focus error signal on each information recording surface also differs if the medium reflectivity of the reproduction light differs for each layer. For this reason, the gain for setting the voltage value of the focus error signal detected from the information recording surface to an appropriate value is different for each information recording surface. Therefore, in the focus search process, the gain must be changed on each information recording surface, and the focus search process takes time. Furthermore, there arises a problem that a circuit for adjusting the gain must be provided on each information recording surface.

  In order to solve the above problem, it is necessary to make the medium reflectivity uniform on each information recording surface in order to obtain the same signal intensity with the same reproduction power. That is, it is necessary to design the single theoretical reflectance and the medium reflectance of the reproduction light on each information recording surface by controlling the reflective film to an optimum film thickness on each information recording surface. In the multilayer optical information recording medium described in Patent Document 1 and Non-Patent Documents 1 and 2, such a design is contemplated depending on the film thickness and material. However, it is difficult to control and reduce the thickness of the reflective film, and there is a limit in the case of multilayering.

  Moreover, it is difficult to apply the configuration disclosed in Patent Document 2 to a multilayer optical information recording medium for the following reason.

In Patent Document 2, an intermediate layer having a refractive index larger than that of the substrate is formed on the substrate. For example, this intermediate layer is used as a first intermediate layer, and an information recording surface and a second intermediate layer having a refractive index higher than that of the first intermediate layer are formed on the first intermediate layer, and the third, fourth, Suppose that it is formed in the same manner as described above and applied to an n-layer multilayer optical information recording medium. At this time, in order to use the interface between adjacent intermediate layers as a reflection surface, the difference in refractive index between adjacent intermediate layers must have a sufficient magnitude. However, there is a limit to the numerical range of the refractive index of the material constituting the intermediate layer. Therefore, when the number of intermediate layers is increased, it becomes impossible to form the (n + 1) th intermediate layer having a refractive index higher than that of the nth intermediate layer. In addition, it is necessary to set an appropriate refractive index for each intermediate layer, and for n layers, it is necessary to prepare intermediate layer materials having n types of refractive indexes, and an increase in cost is inevitable.

  The present invention has been made in view of the above problems, and its purpose is that the medium reflectivity is easy to reproduce, and can flexibly cope with multi-layering at low cost. It is to realize an optical information recording medium that can be used.

  An optical information recording medium according to the present invention is an optical information recording medium having a reflection surface at an interface between resin layers, and alternately includes a resin layer having a first refractive index and a resin layer having a second refractive index. It is characterized by comprising three or more resin layers formed by laminating.

  In the optical information recording medium according to the present invention, the interface between adjacent resin layers functions as a reflecting surface. The reflection surface has a function of reflecting the reproduction light when reproducing the optical information recording medium.

  The resin layers each have a first refractive index or a second refractive index, and the resin layers having the first refractive index and the resin layers having the second refractive index are alternately stacked. ing. According to the above configuration, the difference in refractive index at the interface between adjacent resin layers is the difference between the first refractive index and the second refractive index. For this reason, if the first refractive index and the second refractive index are set to numerical values having a certain difference, the difference in refractive index between all adjacent resin layers causes the interface between the adjacent resin layers to be a reflective surface. A sufficient size can be secured.

  In the optical information recording medium according to the present invention, since the refractive index used for the resin layer is two refractive indexes, ie, a first refractive index and a second refractive index, the number of resin layers is a general resin. The range of refractive index that the material can take is not limited. Therefore, the optical information recording medium according to the present invention can arbitrarily increase the number of resin layers, and can flexibly cope with multilayering at low cost.

  Moreover, according to the said structure, the difference of the refractive index of adjacent resin layers becomes all the same. Since the single theoretical reflectance at each reflecting surface depends on the difference in refractive index between the two resin layers sandwiching the reflecting surface, the single theoretical reflectance at each reflecting surface is equal. Further, in the above configuration, since the reflection layer that is always provided in the conventional multilayer optical information recording medium is not used, the transmittance at each reflection surface becomes sufficiently high, and absorption and scattering can be virtually ignored. . As a result, the medium reflectivity of the reproduction light at each reflecting surface is substantially equal.

  For this reason, when reproducing the optical information recording medium according to the present invention, reproduction conditions such as a focus error signal can be reproduced in the same manner on the information recording surface formed on each resin layer. Therefore, reproduction of the optical information recording medium according to the present invention is facilitated.

In addition, in the case of a conventional multilayer optical information recording medium that uses a blue laser (wavelength of about 405 nm), which is a blue visible light region suitable for a larger capacity, which is now widely used as reproduction light, Ag formed thinly on the ROM surface A metal reflective film such as Al, Au, or Au has an absorption coefficient in the blue visible light region. For this reason, compared with the red laser (wavelength of about 660 nm) which is the conventional red visible light region, the film is greatly deteriorated by the reproduction light irradiation, and sufficient reproduction durability cannot be obtained. On the contrary,
In the optical information recording medium according to the present invention, the absence of the reflective layer reduces the light absorption rate and can improve the reproduction durability of the optical information recording medium.

  Furthermore, with regard to the blue laser wavelength, even if the Ag metal reflection film, which has the highest transmittance among the conventional ROM layer materials, is formed so thin that it can be uniformly formed, the Ag The transmittance of the metal reflective film is about 80%, and the reflectance is about 10%.

  On the other hand, in the optical information recording medium according to the present invention, since there is no reflective layer, each information recording surface can maintain high transmittance and suppress the single theoretical reflectance low. Use efficiency is increased. Therefore, the optical information recording medium according to the present invention is suitable for a multilayer optical information recording medium. Furthermore, in the optical information recording medium according to the present invention, the reflectance of each information recording surface can be controlled by adjusting the refractive index of each resin layer to the first refractive index and the second refractive index. The absence of the layer eliminates the need for adjustment and design of the reflective layer film thickness conventionally required for each information recording surface. This facilitates the production of the optical information recording medium according to the present invention.

  In the optical information recording medium according to the present invention, the difference between the first refractive index and the second refractive index is preferably 0.2 or more.

  According to the above configuration, when the reproduction light is irradiated onto the multilayer optical information recording medium, the reflection of the reproduction light on the reflection surface is within the refractive index range of a general transparent resin (for example, 1.3 to 1.7). The rate is 0.3% or more. If the reflectance is 0.3% or more, a sufficient signal intensity can be obtained without excessively increasing power consumption when reproducing an optical information recording medium.

  In the optical information recording medium according to the present invention, the base material of the resin layer is preferably a common functional group material.

  According to the said structure, the resin layer which mutually adjoins can make the other characteristic the same, making the refractive index different. Other characteristics include linear expansion coefficient and moisture permeability (humidity permeability). For example, if the difference in linear expansion coefficient between adjacent resin layers is reduced, the stress and warpage of the resin layer caused by temperature changes can be prevented. Further, if the moisture permeability of adjacent resin layers is made common, the humidity distribution in the resin becomes uniform, and stress and warpage due to humidity change can be prevented. Furthermore, since the resin layers having similar characteristics are in contact with each other, the adhesion between the resins is enhanced. Therefore, the optical information recording medium according to the present invention can improve strength and durability, and as a result, reliability.

  In the optical information recording medium according to the present invention, the resin layer preferably contains transparent fine particles made of a metal oxide or a metal nitride.

  According to the above configuration, the refractive index of the resin layer can be adjusted from the original refractive index to the range of the refractive index of the metal oxide or metal nitride to be contained depending on the content of the transparent fine particles with respect to the resin layer. . That is, the control range of the refractive index can be expanded. As a result, when the optical information recording medium according to the present invention is manufactured, the refractive index of the resin layer can be adjusted precisely and easily in a wide range, so that the reflectance can be easily controlled by the reflecting surface.

  An optical information recording medium manufacturing method according to the present invention is an optical information recording medium manufacturing method in which an interface between resin layers is a reflection surface, and a resin layer having a first refractive index and a second refractive index are set. It is characterized by including a step of forming three or more resin layers by alternately laminating resin layers.

  According to the above method, the optical information recording medium according to the present invention can be efficiently produced.

  According to the optical information recording medium of the present invention, in the optical information recording medium in which the interface between the resin layers is a reflection surface, the resin layer having the first refractive index and the resin layer having the second refractive index are alternately arranged. An optical information recording medium that can be easily reproduced and can flexibly cope with multi-layering at low cost by having three or more resin layers formed by laminating Can be realized.

[Embodiment 1]
An embodiment of an optical information recording medium according to the present invention will be described below with reference to FIGS. In the following description, various technically preferable limitations for carrying out the present invention are given, but the scope of the present invention is not limited to the following embodiments and drawings.

(Optical information recording medium 1)
First, the configuration of the optical information recording medium 1 will be described below with reference to FIG. FIG. 1 is a sectional view partially showing the optical information recording medium 1. As shown in FIG. 1, the optical information recording medium 1 includes a substrate 2 and three resin layers 11 to 13 stacked on the substrate 2. The resin layer 11 is made of, for example, a transparent ultraviolet curable resin having a thickness of 75 μm, and the resin layers 12 and 13 are made of, for example, a transparent ultraviolet curable resin having a thickness of 25 μm.

  The board | substrate 2 should just have sufficient intensity | strength in order to reinforce the resin layers 11-13, for example, consists of transparent resin with a thickness of 1.1 mm. As the transparent resin, for example, polycarbonate or polyolefin resin can be used. Further, since the reproduction light 4 enters from the resin layer 11 side, the substrate 2 made of metal may be used. Moreover, a multilayer structure may be sufficient.

  On the board | substrate 2, the resin layer 13, the resin layer 12, and the resin layer 11 are laminated | stacked in order from the board | substrate 2 side. The resin layer 12 is formed on the surface of the resin layer 13 that is in contact with the resin layer 12 after the formation of concave and convex prepits (information pits) corresponding to the information to be recorded. Similarly, the resin layer 11 is formed on the surface of the resin layer 12 in contact with the resin layer 11 after information pits are formed. As a result, the interface between the resin layer 13 and the resin layer 12 forms an information recording surface 22, and the interface between the resin layer 12 and the resin layer 11 forms an information recording surface 21. The information recording surfaces 21 and 22 are ROM surfaces, and information recorded on the information recording surfaces 21 and 22 can be read by the reproduction light 4 incident from the resin layer 11 side.

  In the optical information recording medium 1, each of the resin layers 11 to 13 only needs to have one of two different refractive indexes so that adjacent resin layers have different refractive indexes. That is, it is only necessary that the resin layers 11 and 13 have the first refractive index, and the resin layer 12 disposed between the resin layers 11 and 13 has the second refractive index. Specifically, when the two different refractive indexes are 1.45 and 1.70, the refractive index of the resin layer 11 is 1.45, the refractive index of the resin layer 12 is 1.70, and the resin layer The refractive index of 13 is 1.45. At this time, the difference in refractive index between adjacent resin layers is 0.25. In general, the refractive index of the transparent resin layer in the optical information recording medium is often used within the range of 1.45 to 1.70, and this configuration is a sufficiently realizable configuration.

The interface between the adjacent resin layers 11 to 13 functions as a reflection interface (reflection surface). As shown in FIG. 1, the interface between the resin layer 11 and the resin layer 12 is the information recording surface 21, and the interface between the resin layer 12 and the resin layer 13 is the information recording surface 22. By focusing the reproduction light on each information recording surface 21, 22 (that is, each reflection interface), reflection and diffraction of the reproduction light occur on each information recording surface 21, 22. The single theoretical reflectance of the reproduction light on the information recording surfaces 21 and 22 (flat portions thereof) is theoretically (calculated) 0.6%.

  For example, when the two types of refractive indexes are set to 1.3 and 1.5, the single theoretical reflectance on each of the information recording surfaces 21 and 22 is 0.5%, and the two types of refractive indexes are set to 1. In the case of 5 and 1.7, the single theoretical reflectance at the information recording surfaces 21 and 22 is 0.4%.

  In addition, the refractive index of the resin layers 11-13 in this invention is not restricted to the said numerical value, What is necessary is just to be selected from two types of refractive indexes which have a difference required in order to form a reflective interface. Further, the difference in refractive index between adjacent resin layers is preferably 0.2 or more. If it is within the range of the refractive index of a general transparent resin (for example, 1.3 to 1.7), by setting the difference in refractive index to 0.2 or more, the single theory of the reproduction light on the information recording surfaces 21 and 22 The reflectance can be 0.3% or more. In the optical information recording medium 1, the transmittance at each reflecting surface is sufficiently high, and absorption and scattering can be virtually ignored. Therefore, the single theoretical reflectance and medium reflectance of the reproduction light at each reflecting surface are the facts. Almost equal. Therefore, if the single theoretical reflectance is 0.3% or more, the medium reflectance is 0.3% or more. When the medium reflectance is 0.3% or more, it is possible to obtain signal intensity necessary for focusing and reproduction when reproducing an optical information recording medium.

  Further, the thickness of the resin layer 12 should be such that there is a sufficient distance between the information pits on the information recording surface 21 and the information pits on the information recording surface 22 to prevent interlayer crosstalk. That's fine. Interlayer crosstalk refers to reproduction noise caused by stray light from an information recording surface other than the target, which occurs during reproduction of the optical information recording medium 1.

  Further, the thickness of the resin layer 11 disposed on the side farthest from the substrate 2 can be changed as appropriate according to the reproducing apparatus used for the optical information recording medium 1. Further, the resin layer 11 may be provided with a hard coat for surface protection on the surface opposite to the substrate 2.

(Material of resin layers 11-13)
Next, materials used for the resin layers 11 to 13 will be described.

  As the material for the resin layers 11 to 13, it is preferable to use a transparent ultraviolet curable resin. The refractive index of the ultraviolet curable resin is generally adjusted in the range of 1.30 to 1.70. Regarding the material of the resin layers 11 to 13, the present invention is not limited to the ultraviolet curable resin, but may be any resin that has a high transmittance with respect to the wavelength of the reproduction light and can adjust the refractive index. For example, a photocurable resin other than an ultraviolet curable resin may be used, or a thermosetting resin may be used. Furthermore, the material of the resin layers 11 to 13 is not limited to a liquid resin before formation, and may be a sheet-like material, a solid material, or a substrate-like material.

  In the present specification, “refractive index” means a refractive index with respect to the wavelength of reproduction light used in the optical information recording medium 1, and “transparent” and “high transmittance” This means that the transmittance of the reproduction light to the information recording medium 1 is 80% or more.

  Further, the resin layer 11 arranged farthest from the substrate 2 may be formed of a polycarbonate film and a transparent adhesive material in addition to the ultraviolet curable resin, and is a 0.6 mm polycarbonate substrate. Also good.

Examples of the ultraviolet curable resin include epoxy, vinyl, acrylic, and methacrylic resins, each having an epoxy group, a vinyl group, an acrylic group, or a methacryl group as a functional group. For example, the acrylic resin is composed of a mixture obtained by adding a compound such as a photocuring initiator to an acrylate monomer or an acrylate oligomonomer.

  Adjustment of the refractive index of the ultraviolet curable resin is generally performed by blending another material having a different refractive index with respect to the resin material. As a material to be blended, a material containing a fluorine atom having a low atomic refraction or a sulfur atom having a high atomic refraction (in addition, an aromatic ring, a halogen other than fluorine, etc.) is used.

  Normally, when selecting an ultraviolet curable resin to be used from among various ultraviolet curable resins, there are cases where an ultraviolet curable resin having various functional groups is selected in combination in consideration of only light loss and curability.

  On the other hand, in this invention, it is preferable to use the ultraviolet curable resin which has a respectively common functional group for the material of the resin layers 11-13.

  According to the said structure, the linear expansion coefficient in the resin layers 11-13 and a water vapor transmission rate (humidity permeability) can be made into a near value. If the difference in linear expansion coefficient between adjacent resin layers is reduced, stress and warpage of the resin layer caused by temperature change can be prevented. Further, if the moisture permeability of adjacent resin layers is made common, the humidity distribution in the resin becomes uniform, and stress and warpage due to humidity change can be prevented. Furthermore, since resin layers having similar characteristics are in contact with each other, the adhesion between the resins is increased, and the strength of the optical information recording medium 1 is improved.

Moreover, you may use the thing which mixed the transparent fine particle with the transparent ultraviolet curable resin as the material of the resin layers 11-13. A metal oxide or a metal nitride can be used for the transparent fine particles. Specifically, indium oxide (In ₂ O ₃ ), indium tin oxide (ITO: In ₂ SO ₃ —Sn), tin oxide (SnO ₂ ), antimony-containing tin oxide (ATO: SnO ₂ —Sb), zinc oxide (ZnO), titanium oxide (TiO ₂ ), quartz (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), barium titanate (BaTiO ₃ ), and silicon nitride (SiN).

  Here, the transparent fine particles preferably have a refractive index different from that of the transparent ultraviolet curable resin. For example, when transparent fine particles (tin oxide) having a refractive index of 2.0 are used, the refractive index of the resin layers 11 to 13 exceeds the refractive index range (1.30 to 1.70) of the ultraviolet curable resin. The refractive index can be adjusted. Moreover, the refractive index of the resin layers 11-13 can be accurately adjusted by adjusting the quantity of the transparent fine particles mixed with transparent ultraviolet curable resin.

  The particle diameter of the transparent fine particles is preferably small enough to enter the uneven shape of the information recording surface 21 or 22. Furthermore, when reproducing the optical information recording medium 1, it is preferable that the reproduction information wavelength is small enough not to generate reproduction noise with respect to the wavelength of the reproduction light.

(Method for manufacturing optical information recording medium 1)
A method for manufacturing the optical information recording medium 1 will be described below with reference to FIG. In the following manufacturing method, an ultraviolet curable resin is used as the material of the resin layers 11 to 13, but the manufacturing method of the optical information recording medium 1 is not limited to this.

  The manufacturing method of the optical information recording medium 1 includes the following steps.

  (S1) An ultraviolet curable resin (material of the resin layer 13) is applied on the substrate 2.

  (S2) By pressing the stamper on which the information pits are formed, the pit shape is transferred to the ultraviolet curable resin applied in step S1.

  (S3) The resin layer 13 is formed by curing the ultraviolet curable resin by irradiating ultraviolet rays while transferring the pit shape.

  (S4) After removing the stamper, an ultraviolet curable resin (material of the resin layer 12) is applied on the resin layer 13.

  (S5) By pressing the stamper on which the information pits are formed, the pit shape is transferred to the ultraviolet curable resin applied in step S4.

  (S6) The resin layer 12 is formed by curing the ultraviolet curable resin by irradiating ultraviolet rays while transferring the pit shape.

  (S7) After removing the stamper, an ultraviolet curable resin (material of the resin layer 11) is applied on the resin layer 12.

  (S8) The resin layer 11 is formed by irradiating ultraviolet rays to cure the ultraviolet curable resin.

  The optical information recording medium 1 can be manufactured through the above steps.

In addition, this invention is not limited to the said manufacturing method, It can change suitably. For example, the step of applying a liquid UV curable resin in the above manufacturing method may be replaced with a step of bonding a sheet of UV curable resin, and each finally formed resin layer satisfies predetermined requirements. It only has to be.
(Multi-layered optical information recording medium 1)
According to the present invention, it is easy to further multilayer the optical information recording medium 1 by laminating other resin layers. Hereinafter, the multilayered optical information recording medium 40 will be described with reference to FIG. FIG. 2 is a cross-sectional view partially showing the optical information recording medium 40, and the same reference numerals are used for the same components as those of the optical information recording medium 1.

  As shown in FIG. 2, the optical information recording medium 40 has a configuration in which resin layers 14 and 15 are further laminated as compared with the configuration of the optical information recording medium 1. That is, in the optical information recording medium 40, five resin layers 11 to 15 are laminated on the substrate 2. The resin layer 11 is made of, for example, a transparent ultraviolet curable resin having a thickness of 70 μm, and the resin layers 12 to 15 are made of, for example, a transparent ultraviolet curable resin having a thickness of 10 μm.

  Further, in the optical information recording medium 40, in addition to the information recording surfaces 21 and 22, information recording surfaces 23 and 24 are formed. Specifically, the interface between the resin layer 15 and the resin layer 14 becomes the information recording surface 24, and the interface between the resin layer 14 and the resin layer 13 becomes the information recording surface 23.

  Also in the optical information recording medium 40, each of the resin layers 11 to 15 only needs to have one of two different refractive indexes so that the refractive indexes of adjacent resin layers are different. When the refractive index of each of the resin layers 11 to 15 is, for example, either 1.45 or 1.70, the refractive index of the resin layers 11 to 15 is 1.45, 1. 70, 1.45, 1.70, 1.45. At this time, the difference in refractive index between adjacent resin layers is 0.25.

  According to the above configuration, the optical information recording medium 40 realizes a configuration in which the optical information recording medium 1 is multilayered while ensuring a sufficient difference in refractive index between adjacent resin layers.

  Note that the multilayered optical information recording medium 1 is not limited to the optical information recording medium 40. According to the present invention, since the number of laminated resin layers is not limited to the numerical range of the refractive index that can be taken by the material of the resin layer, it is possible to realize an optical information recording medium in which the number of resin layers is further increased. it can.

  Also in the multilayered optical information recording medium 40, the difference in refractive index between adjacent resin layers is always constant. For this reason, the single theoretical reflectances for the reproduction light on each of the information recording surfaces 21 to 24 are all uniform values, and the medium reflectances are all substantially uniform values. Therefore, when reproducing the multilayered optical information recording medium 40, it is possible to reproduce the reproduction conditions for the information recording surfaces 21 to 24 such as a focus error signal in the same manner. This facilitates the reproduction of the optical information recording medium 40.

(Combination with other information recording layers)
In the optical information recording medium 1, another information recording layer may be provided between the resin layer group including the resin layers 11 to 13 and the substrate 2. FIG. 3 shows an optical information recording medium 41 provided with an RE (repetitively writable) layer as another information recording layer. FIG. 3 is a sectional view partially showing the optical information recording medium 41. Since the resin layers 11 to 13 are configured in the same manner as the optical information recording medium 1 shown in FIG. 1, the description thereof is omitted here.

As shown in FIG. 3, the RE layer 5 is composed of seven thin films. Regarding each layer of the RE layer 5, the first protective film 51 has a thickness of 35 nm of zinc sulfide-silicon oxide (ZnS—SiO ₂ ), the second protective film 52 has a thickness of 5 nm of ZrO ₂ , and the recording layer 53 has a thickness of 10 nm. GeTe—Sb ₂ Te ₃ , ZrO _{2 having} a thickness of 5 nm as the third protective film 54, ZnS—SiO _{2 having} a thickness of 35 nm as the fourth protective film 55, ZrO _{2 having} a thickness of 5 nm as the fifth protective film 56, and As the reflective film 57, silver palladium copper (APC: AgPdCu) having a thickness of 20 nm can be used.

  However, the material of each layer in the RE layer 5 is not limited to these, and any material that functions as an RE layer may be used. Further, as a substrate on which the RE layer 5 is formed, grooves or irregularities may be formed on the surface of the substrate 2.

  According to the optical information recording medium 41, the transmittance from the resin layers 11 to 13 is high and the light utilization efficiency is high. Can play.

  Moreover, the manufacturing method of the optical information recording medium 41 includes the following steps instead of the step S1 in the manufacturing method of the optical information recording medium 1 described above.

  (S1) The reflection film 57, the fifth protective film 56, the fourth protective film 55, the third protective film 54, the recording layer 53, the second protective film 52, Then, the RE layer 5 is formed by sequentially forming the first protective film 51 by sputtering or the like.

  (S2) An ultraviolet curable resin (material of the resin layer 13) is applied on the RE layer 5.

  (S3) By pressing the stamper on which the information pits are formed, the pit shape is transferred to the ultraviolet curable resin applied in step S2.

  (S4) The resin layer 13 is formed by curing the ultraviolet curable resin by irradiating ultraviolet rays while transferring the pit shape.

  (S5) After removing the stamper, an ultraviolet curable resin (material of the resin layer 12) is applied on the resin layer 13.

  (S6) By pressing the stamper on which the information pits are formed, the pit shape is transferred to the ultraviolet curable resin applied in step S4.

  (S7) The resin layer 12 is formed by curing the ultraviolet curable resin by irradiating ultraviolet rays while transferring the pit shape.

  (S8) After removing the stamper, an ultraviolet curable resin (material of the resin layer 11) is applied on the resin layer 12.

  (S9) The resin layer 11 is formed by irradiating ultraviolet rays to cure the ultraviolet curable resin.

  The optical information recording medium 41 can be manufactured by the above process.

(Comparison with conventional technology)
A comparison between the optical information recording medium 1 according to the present invention and a conventional optical information recording medium will be described below.

  First, the optical information recording medium 1 according to the present invention eliminates the need for a reflective film that has always been provided on each information recording surface, and eliminates the need for a film forming process that requires a vacuum apparatus on each information recording surface. Manufacture is easy and manufacturing cost can be reduced.

  Next, in the optical information recording medium 1 according to the present invention, since the resin layers are desired to be bonded to each other, compared to the case where different materials are bonded such as the reflective film and the resin layer in the conventional optical information recording medium, It becomes easy to ensure adhesion. Furthermore, in the optical information recording medium 1 according to the present invention, the base material of the resin layer is made of a material having the same functional group, so that the adhesiveness is higher than the adhesiveness between resin layers mainly composed of different functional group materials. It has improved. Thus, the optical information recording medium 1 can realize the strength, durability, and reliability of the medium.

  Next, the conventional optical information recording medium has a problem that the step coverage is deteriorated by the formation of the reflective film. That is, as the film thickness of the reflective film increases, the original uneven shape becomes distorted and the signal quality decreases. On the other hand, in the optical information recording medium 1 according to the present invention, information is reproduced on each of the information recording surfaces 21 and 22 by reflected light from the reflective interface, so that information can be reproduced on the originally formed uneven surface. Thus, the signal quality is improved as compared with the conventional case.

  In addition, in the case of an optical information recording medium using a blue laser (wavelength of about 405 nm) having a blue visible light region suitable for a larger capacity, which is becoming popular, as reproduction light, Ag, Al, Alternatively, a metal reflective film such as Au has an absorption coefficient in the blue visible light region, and therefore, the deterioration of the reflective film due to reproduction light irradiation is severe compared to a red laser (wavelength of about 660 nm) that is a conventional red visible light region. , Sufficient reproduction durability cannot be obtained. On the other hand, according to the optical information recording medium 1 according to the present invention, since there is no reflective film, the light absorptance is reduced and the reproduction durability can be improved.

  Furthermore, in the case of an optical information recording medium having a three-layer structure or more, even if the film thickness is made thin enough to the extent that the film thickness can be uniformly formed in Ag that can obtain the most transmittance among conventional ROM layer materials, The transmittance is about 80%, and the reflectance at that time is about 10%.

  On the other hand, according to the optical information recording medium 1 of the present invention, since there is no reflective layer, the transmittance of each information recording surface can be kept high, and the single theoretical reflectance and the medium reflectance can be kept low. . Therefore, the optical information recording medium 1 according to the present invention has high light utilization efficiency and is suitable as a multilayer optical information recording medium. Furthermore, in the optical information recording medium 1, the reflectance of each information recording surface 21 and 22 can be controlled by adjusting the refractive index of each resin layer to the first refractive index and the second refractive index. The absence of the layer eliminates the need for adjustment and design of the reflective layer film thickness conventionally required for each information recording surface. For this reason, manufacture of the optical information recording medium 1 becomes easy.

[Embodiment 2]
A second embodiment of the present invention will be described below with reference to FIG. FIG. 4 is a sectional view partially showing the optical information recording medium 42 according to this embodiment. In addition, the same code | symbol is used for the element similar to the element in Embodiment 1. FIG. For the description of similar elements, refer to the description in the first embodiment.

  The resin layer 11 is made of, for example, a transparent ultraviolet curable resin having a thickness of 75 μm, and the resin layer 12 is made of, for example, a transparent ultraviolet curable resin having a thickness of 25 μm. The substrate 2a is made of a transparent resin having a thickness of 1.1 mm, for example.

  As shown in FIG. 4, in the optical information recording medium 42, resin layers 11 and 12 are laminated on the substrate 2a. In the substrate 2 a, information pits are formed on the surface in contact with the resin layer 12, and this surface is referred to as an information recording surface 25. In the resin layer 12, information pits are formed on a surface (information recording surface 21) in contact with the resin layer 11. The information recording surfaces 21 and 25 are ROM surfaces, and information recorded on the information recording surfaces 21 and 25 can be read by the reproduction light 4 incident from the resin layer 11 side.

  In the present embodiment, the interface between the substrate 2a and the resin layer 12 also functions as a reflective interface. For this reason, it is necessary to adjust the refractive index of the substrate 2a. That is, it is only necessary to have one of two different refractive indexes so that the refractive indexes of adjacent resin layers are different. The substrate 2a and the resin layer 11 have a first refractive index, and the resin layer 12 has a second refractive index. For example, when the two different refractive indexes are 1.45 and 1.70, the refractive index of the substrate 2a is 1.45, the refractive index of the resin layer 11 is 1.45, The refractive index is 1.70.

  According to the said structure, the difference of the refractive index of the adjacent resin layers 11 and 12 and the difference of the refractive index of the board | substrate 2a and the resin layer 12 are similarly set to 0.25. As a result, the optical information recording medium 42 including the substrate 2a can achieve the same effects as the optical information recording medium 1 in the first embodiment.

  As the material of the substrate 2a in this embodiment, an ultraviolet curable resin or the like may be used similarly to the resin layers 11 and 12, or other resin materials may be used as long as the refractive index condition is satisfied.

(Method for Manufacturing Optical Information Recording Medium 42)
A method for manufacturing the optical information recording medium 42 will be described below with reference to FIG. In the following manufacturing method, an ultraviolet curable resin is used as the material of the substrate 2a and the resin layers 11 and 12, but the manufacturing method of the optical information recording medium 1 is not limited to this.

  The manufacturing method of the optical information recording medium 42 includes the following steps.

  (S1) An ultraviolet curable resin (material of the resin layer 12) is applied on the substrate 2a on which the information pits are formed.

  (S2) By pressing the stamper on which the information pits are formed, the pit shape is transferred to the ultraviolet curable resin applied in step S1.

  (S3) The resin layer 12 is formed by curing the ultraviolet curable resin by irradiating ultraviolet rays while transferring the pit shape.

  (S4) After removing the stamper, an ultraviolet curable resin (material of the resin layer 11) is applied on the resin layer 12.

  (S5) The resin layer 11 is formed by irradiating ultraviolet rays to cure the ultraviolet curable resin.

  The optical information recording medium 42 can be manufactured through the above steps.

  In addition, this invention is not limited to the said manufacturing method, It can change suitably. For example, the step of applying a liquid UV curable resin in the above manufacturing method may be replaced with a step of bonding a sheet of UV curable resin, and each finally formed resin layer satisfies predetermined requirements. It only has to be.

  The present invention will be described more specifically based on examples and comparative examples, but the present invention is not limited to this. Those skilled in the art can make various changes, modifications, and alterations without departing from the scope of the present invention.

  First, Example 1 and Comparative Example 2 will be described.

[Example 1]
In Example 1, an optical information recording medium having the configuration shown in FIG. The specific configuration is as follows.

  As the substrate 2, a disk-shaped substrate having a diameter of 120 mm and a thickness of 1.1 mm was used. Note that a transparent polycarbonate having a refractive index of 1.58 was used as the material of the disk-shaped substrate.

  Transparent ultraviolet effect resin was used for the material of the resin layers 11-13, the thickness of the resin layer 11 was 75 micrometers, and the thickness of the other resin layers 12 and 13 was 25 micrometers. Moreover, each refractive index of the resin layers 11-13 was set to 1.45, 1.70, 1.45 in order from the reproduction light irradiation side. Note that the refractive index and the layer thickness are within a range satisfying the BD standard described later.

  In addition, the information recording surfaces 21 and 22 are composed of pits and spaces having the shortest mark length (0.149 μm) in the Blu-ray Disc (BD) standard for reproduction-only optical information recording media (BD-ROM). A continuous pattern was formed using a 2P method (photo polymerization method).

[Comparative Example 1]
In Comparative Example 1, an optical information recording medium 101 having a conventional reflective film was used.

  The optical information recording medium 101 was manufactured by the following method. This manufacturing method will be described below with reference to FIG. FIG. 5 is a sectional view partially showing the optical information recording medium 101.

  First, an information recording surface was formed on the resin layer 113 formed on the substrate 102, and then a reflective film 121 was formed to a thickness of 5 nm using a conventional metal translucent film APC. Thereafter, a resin layer 112 was formed on the reflective film 121, an information recording surface was formed on the resin layer 112, and then a reflective film 122 was formed with a thickness of 5 nm using a metal translucent film APC. Thereafter, a resin layer 111 was formed on the reflective film 122.

  The layer thickness and materials of the substrate 102 and the resin layers 111 to 113 were the same as in Example 1. In addition, the refractive indexes of the resin layers 111 to 113 were set to 1.6 for all the three layers, and they were all set to a common refractive index as in the past.

  Next, with respect to Example 1 and Comparative Example 2, evaluation of signal intensity, reflectance, and light utilization efficiency was performed as follows.

[Evaluation of signal strength and reflectance]
Regarding the signal intensity, the optical information recording medium of Example 1 was reproduced with a BD optical system (NA 0.85, reproduction wavelength 400 nm to 410 nm), and the signal intensity (CNR: carrier to noise ratio, carrier to noise ratio) was It was measured. The signal intensity was measured after adjusting the BD optical system according to the medium reflectance.

  Regarding the reflectance, the optical information recording medium of Example 1 was reproduced by a BD optical system (NA 0.85, reproduction wavelength 400 nm to 410 nm), and the reflectance by each information recording surface based on the amount of reflected light detected by the light receiving unit. Was calculated. Note that the reflectance was measured in an area where no irregularities exist in the optical information recording medium (planar portion, mirror portion) in a state where the focus servo was applied.

  Here, the reflectance (medium reflectance) in this example was calculated as follows. First, the amount of reproduction light irradiated onto the medium while focusing on a mirror portion (planar portion) of a certain information recording surface and the amount of reflected light reflected on the information recording surface and detected outside the multilayer optical information recording medium The ratio was calculated. It was further corrected by the result of calculating the same ratio as described above with a reference disk having a known absolute reflectance. For this reason, the reflectance (medium reflectance) in the present embodiment is an absolute reflectance.

  Further, Comparative Example 1 was evaluated in the same manner as Example 1.

  As a result, in the measurement of signal intensity, focusing and tracking can be performed satisfactorily in both Example 1 and Comparative Example 1, and each signal intensity is 40 dB or more, which is a signal intensity that can be put to practical use. Respectively.

  However, in Example 1, in order to obtain the same level of signal on the two information recording surfaces, the same level of reproduction power was required, whereas in Comparative Example 1, the reflective film 122 was more than the reflective film 121. Needed higher playback power.

  In the measurement of reflectance, the reflectance of Example 1 was about 0.6% on the information recording surfaces 21 and 22. On the other hand, the reflectance of Comparative Example 1 was about 10% in the reflective film 121 and about 6% in the reflective film 122.

  In Comparative Example 1, it is considered that the amount of transmitted light is reduced by the metal translucent film APC of the reflective film 121, and a higher reproduction power is required when reproducing the reflective film 122. Further, even after the reproduction light is reflected by the reflection film 122, it is necessary to transmit the reflection film 121 again, so that the reflectance of each of the reflection films 121 and 122 is considered to be different.

[Evaluation of light utilization efficiency]
The light utilization efficiency was evaluated by the following method.

  In Example 1 and Comparative Example 1, it is assumed that a virtual layer X (recording layer or reproducing layer) exists further on the back side when viewed from the reproducing light incident side. The larger the amount of light reaching the virtual layer X, the higher the light utilization efficiency, the less the signal quality degradation in the virtual layer X, and the more advantageous the multilayering including the virtual layer X.

  In the case of Example 1, the amount of reproduction light transmitted through the resin layer 11, the information recording surface 21, the resin layer 12, the information recording surface 22, and the resin layer 13 corresponds to the amount of light reaching the virtual layer X. In the case of Comparative Example 1, the reproduction light transmitted through the resin layer 111, the reflective film 121, the resin layer 112, the reflective film 122, and the resin layer 113 similarly corresponds to the amount of light reaching the virtual layer X. When the number of layers is actually increased, when the amount of light reaching the virtual layer X is evaluated, the reproduction light is focused only on the virtual layer X, so that the inclined light that is being collected is transmitted through the previous layers. Evaluation with parallel light is sufficient for relative comparison. Therefore, the amount of light reaching the virtual layer X can be evaluated by comparing the amount of transmitted parallel light transmitted through the mirror portion where the irregularities (information pits) of the optical information recording medium are not present.

  Therefore, light is transmitted from the resin layer 11 to the substrate 2 in Example 1 and from the resin layer 111 to the substrate 102 in Comparative Example 1 to the mirror portion of the optical information recording mediums of Example 1 and Comparative Example 1, and the spectrophotometer The transmittance was measured with a meter and compared. In this measurement, light that has also passed through the substrate 2 or the substrate 102 is actually measured, but both the substrate 2 of Example 1 and the substrate 102 of Comparative Example 1 are both transparent with a refractive index of 1.58. Therefore, it is possible to compare the relative amount of transmitted light.

  As a result, the transmittance of Example 1 was about 85%, and the transmittance of Comparative Example 1 was about 55%. Therefore, it was found that Example 1 far exceeded Comparative Example 1 in the amount of light reaching the virtual layer X, that is, the light utilization efficiency. That is, it can be said that Example 1 is more advantageous for further multilayering.

  In a multilayered optical information recording medium, the greater the amount of reproduction light that reaches the information recording surface (the virtual layer X in this evaluation) arranged at the farthest when viewed from the reproduction light incident side, the more efficient the light utilization. It can be said that it is big. If the light use efficiency is high, the signal quality is less deteriorated on the information recording surface arranged at the back, so the first embodiment is advantageous for multilayering optical information recording media.

  The present invention relates to optically readable discs such as CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RW, BD, and BD-ROM, magneto-optical disc, and phase change disc. The present invention can be applied to various optical information recording media.

It is sectional drawing which shows a part of optical information recording medium based on one Embodiment of this invention. It is sectional drawing which shows a part of optical information recording medium which concerns on other embodiment of this invention. It is sectional drawing which shows a part of optical information recording medium which concerns on other embodiment of this invention. It is sectional drawing which shows a part of optical information recording medium which concerns on other embodiment of this invention. 6 is a cross-sectional view showing a part of an optical information recording medium according to Comparative Example 1. FIG.

Explanation of symbols

1, 40-42, 101 Optical information recording medium 2, 2a, 102 Substrate 4 Reproducing light 11-15, 111-113 Resin layers 21-25 Information recording surface

Claims (5)

An optical information recording medium having a reflection surface at an interface between resin layers,
An optical information recording medium comprising three or more resin layers formed by alternately laminating a resin layer having a first refractive index and a resin layer having a second refractive index .   2. The optical information recording medium according to claim 1, wherein a difference between the first refractive index and the second refractive index is 0.2 or more.   The optical information recording medium according to claim 1, wherein the base material of the resin layer is a common functional group material.   The optical information recording medium according to any one of claims 1 to 3, wherein the resin layer includes transparent fine particles made of a metal oxide or a metal nitride. A method for producing an optical information recording medium having a reflection surface at an interface between resin layers,
An optical information comprising a step of forming three or more resin layers by alternately laminating a resin layer having a first refractive index and a resin layer having a second refractive index. A method for manufacturing a recording medium.

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