WO2007013229A1

WO2007013229A1 - Information recording medium

Info

Publication number: WO2007013229A1
Application number: PCT/JP2006/311678
Authority: WO
Inventors: Tomonori Nakada; Toshiyuki Kaneko; Hiroshi Yokota
Original assignee: Pioneer Corporation
Priority date: 2005-07-26
Filing date: 2006-06-05
Publication date: 2007-02-01
Also published as: JPWO2007013229A1; JP4516125B2

Abstract

An information recording medium is provided with a light transmitting base body, a reflecting layer, and a data recording layer arranged between the base body and the reflecting layer. The information recording medium is also provided with a visible information recording layer arranged on an opposite side to the data recording layer through the reflection layer, and an optical distance adjusting section which specifies a distance between a reference plane, which is provided for placing the information recording medium to abut on the side of the visible information recording layer, and the visible information recording layer.

Description

Description Information Recording Medium Technical Field

The present invention relates to an information recording medium such as a ¹ ^ disc (such as a CD, DVD, B 1 u-Ray, etc.) loaded in an optical disc apparatus or an optical card. Background art

In general, in an optical disc, a CD has a configuration of one 1.2 mm thick light transmitting substrate, and a DVD has a configuration of two 0.6 mm thick light transmitting substrates bonded together. In the case of a double-sided type such as a DVD, a pair of disk bases having an information recording area on a transparent substrate are bonded to each other on the recording layer side. This DVD has a multi-layer disc having a plurality of recording layers that can be read from one side of the disc, and a dual-layer disc having two recording layers on one side is put into practical use for reproduction only or for recording.

In recent years, optical disks have been widely used as means for recording and reproducing data such as video data, audio data, and computer data. ROM-type optical discs include CDs and DVDs. CD-R, CD-RW, DVD-R, DVD-RW, DVD + R, DVD + RW, etc. There is.

After recording data on a type of optical disc that can be written to by an optical disc recorder In addition, there is a demand to take out the optical disk, set the so-called label surface on the back side of the data recording layer and print the recorded contents, etc., but since this work is complicated, the optical disk can be used without using the printer. A system has been proposed in which desired information can be printed on the label surface of the remaining data recording layer or by turning the optical disk upside down with a laser beam.

For example, as a method of recording / reproducing data by irradiating the data recording layer from one side with a laser beam and writing a visible image or recorded content on the label surface, for example,

L i ght Scri b e (registered trademark) is known. With this technology, in a specific optical disk recording device, a specific optical disk having a visible information recording layer formed on the label surface side can be set face down, and image information can be recorded using a data recording laser. This method uses a CD laser to record visible information. As shown in Fig. 1, the CD has a data recording layer 3 at a substrate thickness of 1.2 mm on which the optical disk 10 is mounted. The optical recording medium 10 is placed in contact with the turntable 12 (virtual plane including the contact surface 13 on the turntable 13), and the data recording layer 3 is focused on the substrate thickness exceeding 1.2 mm. The position of the objective lens B of the picker is set to the working distance WD. In addition, when recording visible information (when recording is performed by irradiating the visible information recording layer 4 with laser light), the optical disk is turned over so that the substrate thickness is displaced by 1.2 mm from the setting (approximately the same as the reference plane 11). It is necessary to move the objective lens OB greatly in the focus direction so that it is in focus even at the same position.

In addition to this conventional technique, a visible information recording layer is formed on the label surface side of the optical disk, and laser light modulated in accordance with image data such as characters and pictures is applied to the visible information recording layer. There are techniques for forming an image on a visible information recording layer by changing the visible light characteristics of the light (see JP 2002-203321 A, JP 2004-55076 A, and JP 2003-203348 A). Disclosure of the invention

In these conventional technologies, the CD recording layer and the visible information recording layer are positioned at a height different by 1.2 mm from the reference plane, and an image is formed on the visible information recording layer as shown in FIG. In this case, it is necessary to make the stroke St in the focus direction of the objective lens 〇B (working distance away from the optical disc from the WD) larger than that for CD data recording. For this reason, it is necessary to change the configuration of the recording apparatus itself, such as changing the setting of the objective lens drive actuator overnight. In particular, in a thin optical disk device for a notebook computer, the product height is greatly limited, so it is not easy to increase the stroke of the objective lens.

If a DVD laser is used instead of a CD laser and a specific DVD with a visible information recording layer is used, both recording layers will be 0.6 mm from the reference plane even when the optical disk is turned over. There is no need to change the position of the objective lens when recording visible information on the information recording layer. However, when recording visible information on the visible information recording layer of a CD with this DVD system, it is necessary to move the focal position of the laser by 0.6 mm (difference between the DVD bonding surface and the reference surface height) from the set value. Therefore, it is difficult to move the focal point by 0.6 mm when setting the stroke of the objective lens of the current recording device.

JP 2002-203321, JP 2004 2-55076 and JP 2003- The technology disclosed in 2 0 3 3 4 8 does not mention the configuration of the optical disc from the viewpoint of the stroke of the objective lens of the pickup. In the technology disclosed in Japanese Patent Laid-Open No. 20 0 3-2 0 3 3 4 8, an adapter having a thickness of 1.2 mm that can be mounted on the chucking portion in the center of the optical disc

Although the use of (relative position adjusting means) is shown, the thickness of the optical disk becomes too thick, and it is impossible to chuck the disk itself with the current recording apparatus.

The present invention has been made in view of such a situation, and an object thereof is to provide an information recording medium capable of recording information on a visible information recording layer without increasing the stroke of an objective lens.

An information recording medium of the present invention is an information recording medium comprising: a light transmissive substrate; a reflective layer; and a data recording layer disposed between the substrate and the reflective layer,

A visible information recording layer provided on the opposite side of the data recording layer via the reflective layer; a reference surface including a contact surface for placing the visible information recording layer in contact with the visible information recording layer; And an optical distance adjusting unit that defines a distance between the information recording layer and the information recording layer. Brief Description of Drawings

FIG. 1 is a schematic partial cross-sectional view showing an objective lens and an optical disk for explaining the prior art.

FIG. 2 is a schematic partial cross-sectional view in the thickness direction of the recording optical disk according to the embodiment of the present invention.

FIG. 3 is a schematic partial sectional view showing an object lens and an optical disc for explaining the operation of the recording optical disc according to the embodiment of the present invention. FIG. 4 is a schematic partial sectional view showing an optical disc according to an embodiment of the present invention. 5 to 10 are schematic partial cross-sectional views showing optical disks according to other embodiments of the present invention.

FIG. 11 and FIG. 12 are schematic partial cross-sectional views showing an objective lens and an optical disc for explaining the operation of the recordable optical disc according to the embodiment of the present invention. Detailed Description of the Invention

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 shows a cross section in the thickness direction of a recordable optical disc 1 such as CDR as an embodiment.

As shown in FIG. 2, in the optical disc 1, a data recording layer 3, a reflective layer 3a, and a visible information recording layer 4 are sequentially laminated on a light transmissive substrate 2, and a light transmissive cover substrate 5 is formed thereon. It is configured by pasting together. Although not shown, the optical disc 1 may have a configuration in which a transparent layer or the like is provided between the reflective layer 3 a and the visible information recording layer 4. These data recording layer 3, reflection layer 3a, visible information recording layer 4 and the like are collectively referred to as recording function layer 3 4.

The data recording layer 3 is a layer for recording data by irradiating a laser beam from the substrate 2 side. The reflective layer 3a reflects the laser light irradiated from the visible information recording layer 4 side and the data recording layer 3 side. The visible information recording layer 4 is a translucent layer whose reflectance changes, for example, when irradiated with laser light from the visible information recording layer 4 side of the optical disc 1. The cover substrate 5 is a member that reverses the optical disc 1 to define the distance between the reference surface 11 and the visible information recording layer 4 and protects the visible information recording layer 4 from the outside. As shown in FIG. 3, the optical disc 1 is provided with a substrate hole CH that penetrates the substrate 2 and the cover-substrate 5 sandwiching the recording functional layer 3 4, and the cover substrate 5 has visible information around the periphery of the sensor hole CH. A uniform thickness is provided so as to cover the recording layer 4. The optical disk 1 is loaded into the spindle table turntable 1 2 through the center hall CH. By irradiating the data recording layer 3 side of the optical disc 1 with the CD laser beam, the laser beam incident from the objective lens OB through the substrate 2 is reflected by the data recording layer 3 and the reflection layer 3a, and the Return to lens B and perform normal recording operation. By turning the optical disk 1 over and irradiating the visible information recording layer 4 side with laser light, the laser light incident from the objective lens 0 B through the cover substrate 5 is reflected by the visible information recording layer 4 and the reflective layer 3 a. Thus, the user can return to the objective lens OB, and the user can arbitrarily record image information such as characters and pictures in the visible information recording layer 4. Furthermore, the same effect can be obtained by using a DVD laser beam.

As an example of the embodiment, as shown in FIG. 4, a polycarbonate disk having a radius of 60 mm is used as the base 2 and a center hole CH having a radius of 7.5 mm is formed at the center. Further, on the visible information recording layer 4 side of the optical disc 1, the clamp area CZ is between the radius 13 mm and the radius 16.5 mm, and the image area IZ is between the radius 22 mm and the radius 59 mm, for example. Is set.

The optical disk 1 has a structure in which a substrate 2 having a thickness of 1.2 mm and a force-par substrate 5 having a thickness of 0.3 mm are bonded to each other, so that the entire thickness of the optical disk 1 is 1.5 mm, the upper limit of the CD standard.

According to this embodiment, it is possible to record the visible information on the visible information recording layer 4 of the optical disc 1 without any significant configuration change in any recording device for DVD for CD. Can be realized. As shown in FIG. 3, in this embodiment, by providing, for example, a 0.3 mm thick cover substrate 5 on the CD visible information recording layer 4, the optical disc 1 is turned over so that the visible information recording layer 4 has visible information. At the time of recording, the visible information recording layer 4 is, for example, 0.3 mm from the reference surface 11 (a plane including the contact surface 13 to the turntable 12 for placing the optical disk 1 to contact). The cover substrate 5 is positioned away from the thickness of the cover substrate 5. As a result, when a DVD laser is used to record visible information, the focal position can be moved by 0.3 mm, and there is no problem even with the stroke setting of the objective lens 0 B of the current machine. Even when a CD laser is used, the amount of movement of the focal point position decreases from 1.2 mm to 0.9 mm. That is, the cover substrate 5 serving as an optical distance adjusting unit is arranged so that the reference lens 11 from the reference surface 11 1 in the laser beam incident from the objective lens B through the reference surface 11 1 when recording on the visible information recording layer 4 is used. It has a thickness that reduces the optical distance to OB.

As a second embodiment, as shown in FIG. 5, a cylindrical projection PT projecting from the surface of the visible information recording layer 4 is provided around the center hall CH to cover the entire surface of the optical disc 1. The same effect can be obtained not by bonding the single substrate 5 but also by bonding only the data area such as the recording function layer 34. When two substrates are bonded over the entire surface, the bonded part of the substrate is exposed inside the center hole CH. Therefore, there is a risk that incomplete chucking may occur when the ball chuck enters the bonded portion of the optical disk 1 in contrast to the self-checking spindle motor used in the thin optical disk 1 device. . In the second embodiment, the bonding is not exposed on the inner surface of the center hole CH, which is advantageous for an incomplete chuck. The thicknesses of the substrate 2 and the cover substrate 5 of the optical disc 1 are not limited to the pair of thicknesses of 1.2 mm and 0.3 mm as long as they are within the CD thickness standard range. 1. It may be configured such as a pair of 1 mm-thick optical disc 1 base 2 and 0.4 mm-thick cover substrate 5 or a pair of 1.2 mm-thick optical disc 1 base 2 and 0.2 mm-thick cover substrate 5 . The thickness of the cover substrate 5 can be selected from 0.1 to 0.4 mm, and the thickness of the substrate 2 can be selected from 1.1 to L: 4 mm. The thicker the cover substrate 5 is, the greater the effect is. However, the thickness on the CD recording layer 3 side must be at least 1.1 mm. In addition, if the total thickness exceeds 1.5 mm, there is an increased possibility of malfunctions in the conventional optical disk device (optical disk 1 cannot be clamped, optical disk 1 is damaged, optical disk 1 cannot be ejected, etc.). . Therefore, the upper limit of the thickness of the cover substrate 5 is 0.4 mm. When the thickness of the bonded substrate is “1 lmm + 0.4 mm”, the visible information recording layer 4 is positioned 0.4 mm from the reference surface 11 when the optical disk 1 is turned over. In the DVD laser, the focal distance is 0.2 mm, which is more advantageous for the movement of the objective lens B.

The material of the cover substrate 5 is not limited to the poly force one point that is a CD substrate material. The cover substrate 5 as the optical distance adjusting unit may be made of a material such as acrylic, glass material, or translucent ceramic as long as it can obtain an appropriate refractive index. At this time, the lower the refractive index material, the greater the effect of reducing the stroke of the objective lens B. Bonding the two substrates of the base 2 and the cover substrate 5 easily suppresses the warp of the optical disc 1. The standard of surface blur due to warpage is ± 0.5 mm for CD (one board) and ± 0.3 mm for DVD (two boards bonded together). If you try to make the objective lens 0B follow the optical disc 1 with large surface blurring, If the required stroke becomes too large, the current pick-up will not be able to handle it, but this can be avoided with the substrate bonding structure.

In the third embodiment, as shown in FIG. 6, even if there is no actual cover substrate 5 that transmits light to the visible information recording layer 4, air having a value of 1 as the refractive index of light. Is ideal, so that it plays a role as an optical distance adjustment part that makes an air layer exist between the reference surface 11 and the visible information recording layer 4, so that the visible information recording layer 4 is surrounded around the center hole. Only the cylindrical protrusion PT is provided so as to protrude. Even in this case, the same effects as those of the above-described embodiment can be obtained. Further, in terms of refractive index, it is more advantageous than the cover substrate 5 as a substance having a value of 1 or more. That is, the optical distance adjustment unit may be a member having a thickness that reduces the optical distance from the reference surface 11 to the objective lens OB. For example, if the thickness of the air layer on the image area IZ defined by the thickness of the base 2 and the protrusion PT (clamping area CZ) is “1 lmm + 0.4 mm”, the optical disk 1 is turned over. Since the position of the visible information recording layer 4 is 0.4 mm from the reference plane 11, the focal distance of the DVD laser is 0.2 mm, which is more advantageous for the movement of the objective lens OB. Become. The thickness of the base 2 of the optical disc 1 and the height (step) of the projecting portion PT are not limited to 1.2 mm + 0.3 mm = 1.5 mm within the CD thickness standard range. 1. 1 mm thick optical disc 1 base 2 and 0.4 mm protrusion PT height pair, 1.2 mm optical disc 1 base 2 and 0.2 mm protrusion PT height A configuration such as a set may be used. The height of the protrusion PT can be selected from 0.1 to 0.4 mm, and the thickness of the base 2 can be selected from 1.1 to 1.4 mm. In this form, a layer that protects the visible information recording layer 4 (not shown) on the visible information recording layer 4 (for example, an ultraviolet curable resin is —A layer to be applied by the wrinkles) is formed. In this embodiment, since the optical disk 1 bonding step is not required, the optical disk 1 can be produced at low cost. In the third embodiment, as shown in FIG. 6, first, a method of integrally forming a shape having a step (protrusion PT) in the clamp region CZ with the same material as D-1>, and as shown in FIG. A method <D-2> is possible in which a shape without a step (protrusion PT) is formed as in a normal recording optical disc 1, and a step (protrusion PT) is added in a later process. That is, the base 2 and the projecting portion PT can be formed separately and bonded to each other.

When the projecting part PT is integrally formed as in <D 1>, the current CD production process can be used as it is simply by correcting the mold. In addition, the risk of the incomplete chuck caused by the center-hole bonded portion can be prevented. In addition, if a concave portion DP having an inner diameter that is a dog than the outer shape of the protruding portion PT is provided on the opposite side of the protruding portion PT, it becomes more stable when a plurality of optical discs 1 are stacked and placed. In FIG. 8, if the height d2 of the protrusion PT is smaller than the depth d1 of the recess DP, the optical discs 1 are loosely fitted to each other, so that they can be stacked more stably. That is, the concave portion is provided on the surface of the substrate 2 on the opposite side facing the protruding portion PT of the optical distance adjusting portion protruding from the surface of the visible information recording layer 4.

If the method of adding the projecting part PT later as shown in <D 2> is used, a step-shaped optical disk can be created without modifying the current mold. There is an advantage that it can be shared with other optical disc applications.

Further, the method of adding the projecting portion PT later as in D 2> can be easily handled technically if, for example, the D VD optical disc 1 bonding method is employed. in this case, For example, as shown in FIG. 9, if the inner diameter d3 of the projecting portion PT is larger than the inner diameter d4 of the center hole CH, problems such as a clamping mistake in the self-chucking method due to the increase in the thickness of the optical disk 1 occur. Can be prevented. That is, the projecting portion PT projecting from the surface of the visible information recording layer 4 is provided with a through-opening that is concentric with the center hole CH and has a large diameter. This can be applied even when the projecting part PT of <D 1> is integrally formed.

Furthermore, in the method of adding the projecting portion PT later as in D 2>, a recess for fitting the spacer that forms the projecting portion PT of the optical distance adjusting portion in the base 2 is provided in advance. It is also possible to bond the chip later. As shown in FIG. 10, the thickness d 5 of the spacer forming the protrusion PT and the thickness d 6 of the bottom of the recess of the base 2 do not have to be 0.3 mm + 1.2 mm. For example, if it is difficult to mold a 0.3 mm polycarbonate, it may be, for example, 0.6 mm + 0.9 mm.

Further, in the case of the slim-drawn type optical disk 1 device, the same effect can be obtained by sandwiching a projecting portion PT having a thickness of 0.3 mm between the optical disk 1 and the reference surface 11 instead of changing the shape of the optical disk 1. The slim drawer type optical disk apparatus is configured such that the chucking portion of the optical disk 1 is exposed to the reach of the user. In the case of such a self-chucking type device, when turning the optical disc 1 over, the protruding portion PT can be sandwiched between the evening table 12 and the optical disc 1.

In the above embodiment, the recording function to the visible information recording layer 4 can be realized only by the change on the recording medium side without mechanical change of the apparatus. As a result, the recording function to the visible information recording layer 4 can be easily added to existing devices on the market. Considering only the amount of movement of the objective lens OB, when using a CD laser, The part PT with a thickness of 0.77 mm is most advantageous. However, if the protrusion PT with a thickness of 0.77 mm is attached to the optical disc 1 (thickness 1.2 mm), the total thickness of the optical disc 1 greatly exceeds 1.5 mm. In this case, the optical disk 1 cannot be chucked with the current apparatus. When using a DVD laser, the protrusion PT with a thickness of 0.39 mm is ideal, but this also exceeds the thickness standard (1.5 mm), so 0.3 mm The following should be set (thickness 1.2 + 0.3 = thickness 1.5 or less).

Embodiments and effects thereof will be specifically described below.

Conventionally, the objective lens OB of a device that records and reproduces CDs and DVDs must satisfy the following conditions as a minimum in a stroke away from the optical disc 1.

In the case of a CD, the focal position of the CD disc varies from 1.2 mm to 1.1 mm due to the influence of the disc disc surface blur of 0.5 mm and the effect when the thickness of the disc substrate 2 is minimal (thickness 1 mm). The fluctuation amount is 0.065mm and the turntable / shaft adjustment variation is 0.05mm. When the inner periphery of the pick-up moves (radius from 59.5mm to 22mm), the inclination is 0.03mm, and the objective lens OB position With an adjustment amount of 0.08mm, the stroke amount of the objective lens ○ B when using a CD laser is approximately 0.675mm.

In the case of a DVD, the amount of fluctuation of the focal point from 0.6 mm to 0.57 mm due to the influence of the surface deviation of the DVD disc of 0.3 mm and the minimum thickness of the disc substrate 2 (thickness 1.14). 0.02mm and turntable / shaft adjustment fluctuation 0.05mm of inclination due to the inner circumference of the pick-up movement (radius 59.5mm to 22mm) 0.03mm, objective lens OB position 'adjustment amount 0. 08mm and D The stroke of the objective lens OB when using the VD laser is estimated to be 0.43 mm.

The current pick-up is set based on the above dimensions. In a pick-up with this setting, when focusing on the lower surface of the optical disk 1 for recording on the visible information recording layer 4, the stroke required to cope with surface blurring of the optical disk 1 is insufficient.

FIG. 11 is a cross-sectional view for explaining the stroke of the objective lens OB (working distance 0.85 mm) when the CD laser is used for various optical disks 1. As shown in Fig. 11 (a), CD recording Z playback is normally performed at the OB position of the objective lens WD with a working distance WD. In the pickup shown here as an example, the objective lens 〇 B is set to move 0.80 mm as the stroke lower limit LL from the position of the working distance WD. If the refractive index of polycarbonate (PC), which is the material of the optical disk 1 substrate 2, is about 1.55 (strictly, the refractive index varies slightly depending on the laser wavelength), the conventional technology flips it over to the visible information recording layer 4. When recording, as shown in Fig. 11 (b), the objective lens OB must be lowered by 1.2 cm 1.55 = 0.77 mm from the working distance WD position (position b). In this state, if surface blurring (CD: ± 0.5, DVD: ± 0.3) occurs when the optical disc 1 rotates, the stroke of the objective lens OB will be insufficient.

Here, as shown in FIG. 11 (c), the optical disc 1 of the first embodiment (thickness 1.2 mm optical disc 1 base 2 and thickness 0.3 mm force par substrate 5 bonded) is turned over and used. To do. Here, the visible information recording layer 4 has a height of 0.3 mm from the reference plane 11. Therefore, the objective lens B can be raised, and the cover substrate 5 can be If the disk 1 is made of the same material as the substrate 2 (for example, polycarbonate), the objective lens B can be set at a position c higher than the position b, as shown in FIG. 11 (c). At this time, a 0.22 mm margin is generated in the direction away from the optical disc 1 with respect to the stroke of the objective lens B, so that even if surface blurring of the optical disc 1 occurs, it can be handled with the current pick-up. Thus, the cover substrate 5 adjusts the optical distance to reduce the optical distance from the reference surface 11 to the objective lens OB. Here, it is desirable to set the surface blurring standard of the bonded optical disc 1 of the embodiment to about ± 0.2 mm.

FIG. 11 (d) shows the third embodiment. In this case, the 0.3 mm cover substrate 5 is replaced with air, and the air is considered to have a refractive index of 1, so the lens position in this case is a position d 0.47 mm below the working distance WD. .

FIG. 11 (e) shows a modification of the first embodiment. In this case, the thickness of the cover substrate 5 is set to 0.4 mm. As a result, the objective lens B becomes a position e that is 0.06 mm more advantageous than that in the embodiment of FIG. 11 (c).

In order to reduce the stroke of the objective lens ○ B, in addition to the method of thickening the force-par substrate 5 as the optical distance adjustment section as described above, the material of the cover substrate 5 is changed, and a material with a lower refractive index is selected. The same effect can be obtained by adopting it. For example, if the cover substrate 5 material with a thickness of 0.4 mm is replaced with a low-refractive index material (such as a fluorine-based polymer coating) from polycarbonate, the stroke of the objective lens 0B is further reduced by 0.036 mm (refractive index 1.55 to 1. 36)). FIG. 12 shows a cross-sectional view of FIG. 11 する illustrating the stroke of the object lens 〇B when the DVD laser is used for various optical disks 1. The objective lens ○ B position (working distance 1.22 mm) when using a DVD laser is lower than the position when using a CD laser. When the DVD in Fig. 12 (g) is turned upside down, the lens position is at position d 0.39mm below the working distance WD, but in Figs. 12 (h) (i) and (j), the working distance is 0. 19mm, 0.09mm, 0.13mm down to position d. Even in these cases, the moving stroke of the objective lens B can be suppressed by applying this embodiment.

Also, if the surface blurring of optical disc 1 is set to ± 0.15 mm, which is half that of the DVD standard under the conditions shown in Fig. 12, the thickness of cover substrate 5 (the material is polycarbonate) is 0 when using a CD laser. When using a 2 mm DVD laser, the same effect can be obtained even if the thickness is as thin as 0.15 mm.

Substrate bonding technology has been put to practical use on DVDs, and can be produced at low cost without significantly modifying existing production equipment. In addition, the optical disc 1 used in the prior art exposes the visible information recording layer 4 to the outside of the optical disc 1 (visible information recording layer 4 side), so there is a risk of damage to the recording layer due to external scratches. is there. However, the visible information recording layer 4 is also protected against damage from the outside by bonding the cover substrate 5 as in the present embodiment.

According to the above embodiment, the substrate bonding technique is applied not only to the CD family 1 but also to the DVD family 1 or the B 1 u-Ray family, or the optical disc 1 center. By providing protrusions around the hole, the recording function for the visible information recording layer 4 can be realized without significant changes to the current recording device. In the embodiment, an optical disc having one data recording layer 3 is used. Although described, the present invention can also be applied to a multi-layer disc such as a double-layer disc having two recording layers on one side.

Claims

The scope of the claims

1. An information recording medium comprising a light-transmitting substrate, a reflective layer, and a data recording layer disposed between the substrate and the reflective layer,

A visible information recording layer provided on the opposite side of the data recording layer via the reflective layer; a reference surface including a contact surface for placing the visible information recording layer in contact with the visible information recording layer; An information recording medium comprising: an optical distance adjusting unit that defines a distance between the information recording layer and the information recording layer.

2. The information recording medium according to claim 1, wherein a thickness of the optical distance adjusting unit is 0.1 to 0.4 mm.

3. The information recording medium according to claim 1, wherein a thickness of the light-transmitting substrate is 1.1 to 1.4 mm.

4. The optical distance adjusting unit is made of a light-transmitting material, and the visible information recording unit includes a light-transmitting substrate and a center hole penetrating the optical distance adjusting unit, and includes a periphery of the center hole. The information recording medium according to any one of claims 1 to 3, wherein the information recording medium is provided so as to cover the layer.

5. A center hole penetrating the light transmissive substrate and the optical distance adjusting portion is provided, and the optical distance adjusting portion is provided so as to protrude from the surface of the visible information recording layer around the center hole. The information recording medium according to any one of claims 1 to 3, wherein

6. The optically transparent substrate protruding from the surface of the visible information recording layer and the optical distance adjusting unit are integrally formed of the same material. The information recording medium described.

7. The information recording medium according to claim 5, wherein the light-transmitting substrate and the optical distance adjuster protruding from the surface of the visible information recording layer are separately formed and bonded to each other.

8. The information recording medium according to claim 7, further comprising a concave portion that fits into the optical distance adjusting portion that projects from the surface of the visible information recording layer.

9. The information according to claim 7, wherein the optical distance adjusting portion protruding from the surface of the visible information recording layer is provided with a through-hole having a large diameter and concentric with the center hole. recoding media.

10. The concave portion is provided on the surface of the light-transmitting substrate opposite to the optical distance adjusting portion protruding from the surface of the visible information recording layer. The information recording medium according to any one of the above.