U.S. patent application number 11/838922 was filed with the patent office on 2009-01-08 for method of producing stamper for optical recording medium, method of producing substrate, and method of producing optical recording medium.
This patent application is currently assigned to FUJIFILM Corporation. Invention is credited to Yanlong Che, Michihiro Shibata.
Application Number | 20090008257 11/838922 |
Document ID | / |
Family ID | 39180811 |
Filed Date | 2009-01-08 |
United States Patent
Application |
20090008257 |
Kind Code |
A1 |
Che; Yanlong ; et
al. |
January 8, 2009 |
METHOD OF PRODUCING STAMPER FOR OPTICAL RECORDING MEDIUM, METHOD OF
PRODUCING SUBSTRATE, AND METHOD OF PRODUCING OPTICAL RECORDING
MEDIUM
Abstract
A method of producing a stamper for roughening a substrate of an
optical recording medium contains the steps of placing a conductive
ring having a hole at the center thereof on a major surface of an
original metal plate, electroforming a metal layer over a portion
of the metal plate exposed in the hole of the conductive ring, an
inner end-face of the conductive ring, and a portion of a major
surface of the conductive ring, and entirely or partly roughening a
major surface of the metal layer by a blasting treatment to obtain
an original stamper.
Inventors: |
Che; Yanlong; (Odawara-shi,
JP) ; Shibata; Michihiro; (Odawara-shi, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W., SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
FUJIFILM Corporation
Tokyo
JP
|
Family ID: |
39180811 |
Appl. No.: |
11/838922 |
Filed: |
August 15, 2007 |
Current U.S.
Class: |
205/68 |
Current CPC
Class: |
G11B 7/261 20130101 |
Class at
Publication: |
205/68 |
International
Class: |
C25D 1/10 20060101
C25D001/10 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 18, 2006 |
JP |
2006-222999 |
Claims
1. A method of producing a stamper for roughening a substrate of an
optical recording medium, the method comprising the steps of:
placing a conductive ring having a hole at a center thereof on a
major surface of an original metal plate; electroforming a metal
layer over a portion of said metal plate exposed in said hole of
said conductive ring, an inner end-face of said conductive ring,
and a portion of a major surface of said conductive ring; and
entirely or partly roughening a major surface of said metal layer
by a blasting treatment to obtain an original stamper.
2. A method of producing a stamper according to claim 1, wherein
said inner end-face of said conductive ring contains a stepped
surface.
3. A method of producing a stamper according to claim 1, wherein
said inner end-face of said conductive ring contains a tapered
surface.
4. A method of producing a stamper according to claim 1, wherein a
pressing jig having a hole at a center thereof is used for pressing
said conductive ring against said metal plate in said
electroforming step, and an inner diameter of said conductive ring
is smaller than that of said pressing jig.
5. A method of producing a stamper according to claim 1, wherein in
said blasting treatment step, said major surface of said metal
layer exposed in said hole of said conductive ring is entirely or
partly roughened by said blasting treatment after removing said
metal plate.
6. A method of producing a stamper according to claim 1, further
comprising the step of electroforming another metal layer on said
roughened metal layer of said original stamper to obtain a
second-generation stamper comprising said other metal layer.
7. A method of producing a stamper according to claim 1, wherein a
pit forming site for forming a pre-pit on said optical recording
medium is formed on a portion of said major surface of said metal
plate.
8. A method of producing a stamper according to claim 7, wherein a
transfer pattern of said pit forming site is formed on said major
surface of said metal layer and the transferred pattern is
protected before said blasting treatment for roughening said major
surface of said metal layer.
9. A method of producing a substrate for an optical recording
medium having an image recording layer on which a visible image is
recorded, the method comprising the steps of producing a stamper
having an entirely or partly roughened major surface, and producing
said substrate having an entirely or partly roughened major surface
by using said stamper, wherein said stamper producing step
comprises the steps of: placing a conductive ring having a hole at
a center thereof on a major surface of an original metal plate;
electroforming a metal layer over a portion of said metal plate
exposed in said hole of said conductive ring, an inner end-face of
said conductive ring, and a portion of a major surface of said
conductive ring; and entirely or partly roughening a major surface
of said metal layer by a blasting treatment to obtain an original
stamper.
10. A method of producing an optical recording medium having a
substrate and an image recording layer on said substrate, a visible
image being recorded on said image recording layer, the method
comprising the steps of producing a stamper having an entirely or
partly roughened major surface, and producing said substrate having
an entirely or partly roughened major surface by using said
stamper, and forming said image recording layer on said substrate,
wherein said stamper producing step comprises the steps of: placing
a conductive ring having a hole at a center thereof on a major
surface of an original metal plate; electroforming a metal layer
over a portion of said metal plate exposed in said hole of said
conductive ring an inner end-face of said conductive ring, and a
portion of a major surface of said conductive ring; and entirely or
partly roughening a major surface of said metal layer by a blasting
treatment to obtain an original stamper.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method of producing a
stamper for an optical recording medium, a method of producing a
substrate, and a method of producing an optical recording medium,
particularly a method of producing a stamper for an optical
recording medium containing a substrate having an entirely or
partly roughened major surface, a method of producing such a
substrate, and a method of producing such an optical recording
medium.
[0003] 2. Description of the Related Art
[0004] In several known optical recording media such as CD-Rs and
DVD-Rs, electronic information is recorded on a recording surface,
and a label is attached to the reverse surface. Visible information
of the contents of the electronic information, such as a song title
of music data or a title of recorded data, is printed on the label,
and the reverse surface is called a label surface.
[0005] Such optical recording media are produced by printing a
title or the like on a circular label sheet using a printer, and by
attaching the label sheet to the label surface.
[0006] Thus, the printer is needed in addition to a disc drive for
producing the optical recording media. Data is recorded by the disc
drive on the recording surface of the optical recording medium, the
medium is removed from the disc drive, and then the label sheet
printed by the printer is attached thereto. Therefore, complicated
operations are required for producing the optical recording
media.
[0007] Optical recording media with label surfaces, on which
information can be displayed by changing the contrast using laser
markers, have been proposed in Japanese Laid-Open Patent
Publication No. 11-66617, etc. In the optical recording media, by
using only an optical recording medium drive, information can be
recorded on the recording surface and a visible image can be
recorded on the label surface. Thus, additional printers are not
needed, and also the complicated operations of attaching the label
sheet are not required.
[0008] In optical recording media such as DVD-Rs, a substrate for a
recording layer may have regular grooves, and also another
substrate for a visible image recording layer may have such regular
grooves. In this case, the grooves on the other substrate act as a
diffraction grating for external lights to cause strong
interference, thereby resulting in poor visibility of a recorded
visible image.
[0009] Accordingly, there has been a demand for further improving
the visibility of an image recorded on the label surface.
SUMMARY OF THE INVENTION
[0010] In view of the above problem, an object of the present
invention is to provide a method for producing a stamper useful for
producing an optical recording medium excellent in visibility of an
image on a label surface, and a method for producing a
substrate.
[0011] Another object of the present invention is to provide a
method for producing an optical recording medium excellent in
visibility of an image on a label surface.
[0012] According to a first aspect of the present invention, there
is provided a method of producing a stamper for roughening a
substrate of an optical recording medium, the method comprising the
steps of: placing a conductive ring having a hole at a center
thereof on a major surface of an original metal plate;
electroforming a metal layer over a portion of the metal plate
exposed in the hole of the conductive ring, an inner end-face of
the conductive ring, and a portion of a major surface of the
conductive ring; and entirely or partly roughening a major surface
of the metal layer by a blasting treatment to obtain an original
stamper.
[0013] In the first aspect, the obtained original stamper can be
used for producing a stamper for an optical recording medium.
Further, by using the stamper, an optical recording medium
excellent in the visibility of an image on a label surface can be
produced.
[0014] In the first aspect, the inner end-face of the conductive
ring may contain a stepped surface or a tapered surface. The inner
end-face may contain a tapered, stepped surface, and may have no
steps, or no taper.
[0015] Further, in the first aspect, it is preferred that a
pressing jig having a hole at the center thereof is used for
pressing the conductive ring against the metal plate in the
electroforming step, an inner diameter of the conductive ring being
smaller than that of the pressing jig.
[0016] The major surface of the metal layer exposed in the hole of
the conductive ring may be entirely or partly roughened by the
blasting treatment after removing the metal plate.
[0017] In the first aspect, the method may further comprise the
step of electroforming another metal layer on the roughened metal
layer of the original stamper to obtain a second-generation stamper
comprising the other metal layer.
[0018] The obtained second-generation stamper can be used for
producing the product stamper. Further, a third-generation,
fourth-generation, or fifth-generation . . . stamper may be
produced by using the second-generation stamper, and may be used
for producing the product stamper.
[0019] In the first aspect, a pit forming site for forming a
pre-pit on the optical recording medium may be formed on the major
surface of the metal plate. It is preferred that a transfer pattern
of the pit forming site is formed on the major surface of the metal
layer and the transferred pattern is protected before the blasting
treatment for roughening the major surface of the metal layer.
[0020] According to a second aspect of the present invention, there
is provided a method of producing a substrate for an optical
recording medium having an image recording layer on which a visible
image is recorded, the method comprising the steps of producing a
stamper having an entirely or partly roughened major surface, and
producing the substrate having an entirely or partly roughened
major surface by using the stamper. The stamper producing step
comprises the steps of: placing a conductive ring having a hole at
a center thereof on a major surface of an original metal plate;
electroforming a metal layer over a portion of the metal plate
exposed in the hole of the conductive ring, an inner end-face of
the conductive ring, and a portion of a major surface of the
conductive ring; and entirely or partly roughening a major surface
of the metal layer by a blasting treatment to obtain an original
stamper.
[0021] By using the substrate produced by the method of the second
aspect, an optical recording medium excellent in the visibility of
an image on a label surface can be produced.
[0022] According to a third aspect of the present invention, there
is provided a method of producing an optical recording medium
having a substrate and an image recording layer on the substrate, a
visible image being recorded on the image recording layer, the
method comprising the steps of producing a stamper having an
entirely or partly roughened major surface, and producing the
substrate having an entirely or partly roughened major surface by
using the stamper, and forming the image recording layer on the
substrate. The stamper producing step comprises the steps of:
placing a conductive ring having a hole at a center thereof on a
major surface of an original metal plate; electroforming a metal
layer over a portion of the metal plate exposed in the hole of the
conductive ring, an inner end-face of the conductive ring, and a
portion of a major surface of the conductive ring; and entirely or
partly roughening a major surface of the metal layer by a blasting
treatment to obtain an original stamper.
[0023] An optical recording medium excellent in the visibility of
an image on a label surface can be produced by the method of the
third aspect.
[0024] As described above, by using the stamper producing method,
or the substrate producing method of the present invention, the
optical recording medium excellent in the visibility of an image on
a label surface can be obtained.
[0025] Further, by using the optical recording medium producing
method of the present invention, the visibility of an image on a
label surface can be improved.
[0026] The above and other objects features and advantages of the
present invention will become more apparent from the following
description when taken in conjunction with the accompanying
drawings in which a preferred embodiment of the present invention
is shown by way of illustrative example.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is a cross-sectional view partly showing an optical
recording medium according to an embodiment of the present
invention;
[0028] FIG. 2 is a plan showing an optical recording medium of a
modification example according to the embodiment;
[0029] FIG. 3 is an enlarged cross-sectional view showing a pre-pit
region of the optical recording medium of FIG. 1;
[0030] FIG. 4 is a cross-sectional view partly showing a master
stamper according to the embodiment;
[0031] FIG. 5 is a production process chart of a method according
to the embodiment;
[0032] FIG. 6A is a cross-sectional view showing a metal plate used
in the method according to the embodiment;
[0033] FIG. 6B is an enlarged cross-sectional view showing a
portion of the metal plate;
[0034] FIG. 7A is a cross-sectional view showing a conductive ring
placed on a metal plate;
[0035] FIG. 7B is an enlarged cross-sectional view showing a
portion of the conductive ring;
[0036] FIG. 8 is a perspective view showing the conductive
ring;
[0037] FIG. 9 is a cross-sectional view showing a conductive ring
of a first modification example placed on the metal plate;
[0038] FIG. 10 is a cross-sectional view showing a conductive ring
of a second modification example placed on the metal plate;
[0039] FIG. 11 is a cross-sectional view showing a conductive ring
of a third modification example placed on the metal plate;
[0040] FIG. 12 is a cross-sectional view showing a conductive ring
of a fourth modification example placed on the metal plate;
[0041] FIG. 13 is a cross-sectional view showing the conductive
ring pressed against the metal plate by a pressing jig;
[0042] FIG. 14 is a cross-sectional view showing a first metal
layer formed by Ni electroforming on a portion of the major surface
of the conductive ring, the inner surface of the conductive ring,
and a portion of the major surface of the metal plate;
[0043] FIG. 15 is a cross-sectional view showing an original
stamper subjected to a blasting treatment after removing the metal
plate;
[0044] FIG. 16 is an enlarged cross-sectional view showing a
portion of the original stamper of FIG. 15;
[0045] FIG. 17A is a cross-sectional view showing a conductive ring
pressed against a metal plate by a pressing jig in a first
process;
[0046] FIG. 17B is a cross-sectional view showing a metal layer
formed by Ni electroforming on a portion of the inner end-face of
the conductive ring and a portion of a major surface of the metal
plate;
[0047] FIG. 18A is a cross-sectional view showing an original
stamper subjected to a blasting treatment after removing the metal
plate;
[0048] FIG. 18B is a cross-sectional view showing the metal layer
(a metal sheet) of the original stamper, isolated from the
conductive ring after a blasting treatment;
[0049] FIG. 18C is a cross-sectional view showing the metal sheet
greatly deformed after a blasting treatment;
[0050] FIG. 19A is a cross-sectional view showing a metal layer
formed by Ni electroforming on a portion of a metal plate while
using a pressing jig for pressing the metal plate in a second
process;
[0051] FIG. 19B is a cross-sectional view showing the metal layer
(a metal sheet) of an original stamper, isolated from the metal
plate and subjected to a blasting treatment;
[0052] FIG. 19C is a cross-sectional view showing the metal sheet
greatly deformed by the blasting treatment;
[0053] FIG. 20 is a cross-sectional view showing a second metal
layer formed by Ni electroforming on a portion of a major surface
of the first metal layer and a portion of the other major surface
of the conductive ring in the method according to the
embodiment;
[0054] FIG. 21A is a cross-sectional view showing a
second-generation stamper of the second metal layer isolated from
the major surface of the original stamper;
[0055] FIG. 21B is an enlarged cross-sectional view showing a
portion of the second-generation stamper of FIG. 21A;
[0056] FIG. 22 is a cross-sectional view showing a third-generation
stamper produced from the second-generation stamper by Ni
electroforming;
[0057] FIG. 23 is a cross-sectional view showing a
fourth-generation stamper produced from the third-generation
stamper by Ni electroforming; and
[0058] FIG. 24 is a table showing the results of evaluating shape
and warping state after blasting, probability of producing a
second-generation stamper, and probability of producing a master
stamper, in Example 1 and Comparative Examples 1 and 2.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0059] An embodiment of the stamper producing method, the substrate
producing method, and the optical recording medium producing method
according to the present invention will be described below with
reference to FIGS. 1 to 24.
[0060] An optical recording medium 10 according to this embodiment
is such that information can be recorded thereon by irradiating one
surface with a laser light, and a desired visible image can be
recorded thereon by irradiating the other surface with the laser
light. Thus, in this optical recording medium, at least an
information recording layer and an image recording layer are formed
in this order on a first substrate, and a second substrate is
placed on the image recording layer. A third substrate may be
disposed between the information recording layer and the image
recording layer.
[0061] In the optical recording medium, a surface of the second
substrate facing the image recording layer is partly roughened. The
roughened portion of the surface of the second substrate may be
referred to as "the roughened substrate surface" in the following
description. The roughened substrate surface is formed by
transferring a roughened pattern on a stamper for an optical
recording medium onto the second substrate as hereinafter
described.
[0062] The optical recording medium may have a structure of a DVD
such as a DVD-R, an HD-DVD, etc. The structure is such a bonded
structure that the first substrate having the information recording
layer is attached to the second substrate having the image
recording layer by an adhesion layer.
[0063] Further, the optical recording medium of the embodiment may
have a structure of Blu-ray Disc (BD).
[0064] A specific structure example of the optical recording medium
10 according to this embodiment will be described below with
reference to FIGS. 1 to 3.
[0065] The optical recording medium 10 shown in FIG. 1 has a first
stack 12 and a second stack 14. The first stack 12 contains a
transparent first substrate 16, an information recording layer 18
formed on the first substrate 16, and a first reflective layer 20
formed on the information recording layer 18. The second stack 14
contains a transparent second substrate 22, an image recording
layer 24 formed on the second substrate 22, and a second reflective
layer 26 formed on the image recording layer 24. The first stack 12
is attached to the second stack 14 by an adhesion layer 28, and the
first reflective layer 20 faces the second reflective layer 26.
[0066] For example, data (pit information) can be recorded on
and/or reproduced from the information recording layer 18 by
irradiating the layer with a laser light through the first
substrate 16.
[0067] For example, a visible image can be recorded on the image
recording layer 24 by irradiating the layer with a laser light
through the second substrate 22.
[0068] In the optical recording medium 10, a roughened substrate
surface 30 is formed on a portion of the surface of the second
substrate 22 facing the image recording layer 24. The surface
roughness of the roughened substrate surface 30 of the second
substrate 22 is preferably such that the arithmetic average
roughness Ra is 0.05 to 0.3 .mu.m and the ten-point average
roughness Rz is 0.1 to 5 .mu.m. The image visibility of the optical
recording medium 10 is largely improved when the roughened
substrate surface 30 has such a surface roughness. The values of Ra
and Rz of the roughened substrate surface 30 on the second
substrate 22 can be measured by an atomic force microscope (AFM),
an optical interference-type roughness meter, a stylus-type
roughness meter, or the like. The stylus-type roughness meter is
particularly preferred because it has a long scanning length and a
large dynamic range in the depth direction. Thus, the values of Ra
and Rz are obtained by the stylus-type roughness meter in the
present invention.
[0069] The roughened substrate surface 30 may be formed over the
entire surface of the second substrate 22. The roughened substrate
surface 30 is formed preferably in a region of 20 to 60 mm, more
preferably in a region of 24 to 58 mm, from the center of the
medium. When the roughened substrate surface 30 is formed in a
region of less than 20 mm from the center, the visibility is seldom
improved by the roughened substrate surface 30 because an optical
pickup is hardly placed in the region. On the other hand, when the
roughened substrate surface 30 is formed in a region of more than
58 mm from the center, it becomes difficult to wash the edge of the
image recording layer 24.
[0070] In the optical recording medium 10, there is a pre-pit
region 32 on a portion of the surface of the second substrate 22
(the surface on which the image recording layer 24 is formed). One
or more pre-pits 34, preferably a plurality of pre-pits 34, are
formed in the pre-pit region 32.
[0071] The combination of the pre-pits 34 may provide various
information of the optical recording medium 10 such as information
for distinguishing the presence of the image recording layer 24,
information of output or a spot diameter of a laser light for
forming a visible image on the image recording layer 24, or
information of tone of a visible image.
[0072] Thus, by detecting the pre-pits 34, the presence of the
image recording layer 24 in the optical recording medium 10 can be
easily detected, and a visible image can be recorded on the image
recording layer 24 under an optimum laser output with excellent
imaging properties. Further, the combination of the pre-pits 34 may
provide manufacturer information, etc.
[0073] The position of the pre-pit region 32 on the second
substrate 22 is not particularly limited. For example, as shown in
FIG. 2, the pre-pit region 32 may be formed inside a region having
the image recording layer 24 (an imaging region 36) in an optical
recording medium 10a of a modification example. In this case, the
pre-pits 34 are not filled with a dye compound, so that a light
returned from the pre-pits 34 is easily detected advantageously. It
should be noted that, to prevent the image recording layer 24 from
being formed in the pre-pit region 32, it is necessary to form a
certain margin between the outer circumference of the pre-pit
region 32 and the inner circumference of the imaging region 36.
[0074] As shown in FIG. 1, the pre-pit region 32 may be partly
overlapped with the imaging region 36 to make the imaging region 36
as large as possible. Thus, a portion of the image recording layer
24 may be formed on a part of the pre-pit 34.
[0075] In the case of forming the pre-pit region 32 on an inner
portion of the second substrate 22 as shown in FIGS. 1 and 2, the
pre-pit region 32 is preferably in a region of 21 to 24 mm in the
radius direction from the center of the second substrate 22.
[0076] The average of the depths hp of the pre-pits 34, shown in
FIG. 3, is 150 to 400 nm, preferably 200 to 300 nm. When the
average depth is 150 to 400 nm, a light returned from the pre-pits
34 can be converted to an electronic signal (a returned light
signal) having a large signal amplitude, whereby the accuracy of
reading the returned light signal can be improved. Further, when
the average depth is 200 to 300 nm, the returned light signal can
be detected more accurately.
[0077] The average of the widths W (the half widths, which are
widths at half the depths hp) of the pre-pits 34 in the radius
direction is preferably 200 to 500 nm, more preferably 250 to 450
nm. When the average width is 200 to 500 nm, the inter-track
crosstalk superposed with the returned light signal is reduced,
whereby a signal amplitude sufficient for detection can be
obtained. The lengths (the half widths) of the pre-pits 34 in the
circumferential direction are appropriately controlled depending on
information to be recorded.
[0078] The ratio h1/h2, in which h1 represents an average thickness
of the image recording layer 24 on the convex portions 34A of the
pre-pits 34, and h2 represents an average thickness of the image
recording layer 24 on the concave portions 34B, is preferably 0.1
to 0.9. The depth hp+h1-h2 of depression of the image recording
layer 24 on the concave portions 34B is preferably 70 to 250
nm.
[0079] When the ratio h1/h2 and the depth hp+h1-h2 are within the
above ranges, a surface of the image recording layer 24, on which
the second reflective layer 26 is formed, has appropriate convexes
and concaves suitable for reading a laser light, so that an
excellent reproduced signal can be obtained. The ratio h1/h2 is
more preferably 0.2 to 0.8, and the depth hp+h1-h2 is more
preferably 100 to 200 nm, further preferably 120 to 180 nm.
[0080] The second reflective layer 26 is preferably formed along
the image recording layer 24 as shown in FIG. 3. The ratio t1/t2,
in which t1 represents an average thickness of the second
reflective layer 26 on the convex portions 34A, and t2 represents
an average thickness of the second reflective layer 26 on the
concave portions 34B, is preferably 0.8 to 1.2, more preferably 0.9
to 1.1.
[0081] The above values of hp, h1, h2, etc. can be obtained by an
AFM, a transmission spectrum, or an ellipsometer. Further, the
values can be obtained by observing a cross-section of the produced
optical recording medium 10 using an SEM, etc.
Stamper and Method of Producing the Same:
[0082] The above second substrate 22, which has the pre-pits 34 and
the roughened substrate surface 30 on a portion of the surface, can
be produced by using a master stamper 40 according to the present
embodiment.
[0083] As shown in FIG. 4, in the master stamper 40, a pit forming
site 42 for forming the pre-pits 34 on the inner surface of the
second substrate 22 is formed in a portion of a major surface, and
a roughened stamper surface 44 for forming the roughened substrate
surface 30 on the second substrate 22 is formed in a portion of the
major surface other than the pit forming site 42. The pit forming
site 42 contains concave portions and convex portions, and the
average height of the convex portions is preferably 150 to 400 nm.
The optical recording medium 10 can be efficiently produced by
using the master stamper 40.
[0084] The method of the present invention for producing the master
stamper 40 will be described below with reference to FIGS. 5 to
23.
[0085] First, an original metal plate 46 is prepared as shown in
step S1 of FIG. 5, and FIGS. 6A and 6B. First pit forming sites 48
for forming the pit forming site 42 on the master stamper 40 are
formed on a flat major surface 46a of the metal plate 46. The metal
plate 46 is a Ni disc produced by Ni (nickel) electroforming. The
enlarged view of FIG. 6B illustrates only an area near the center
line m, as with the other enlarged views to be hereinafter
described.
[0086] The thickness ta of the metal plate 46 may be approximately
300 .mu.m, which is a usual thickness for producing the master
stamper 40. The thickness ta may be 140 to 160 .mu.m, and in this
case, the time required for the Ni electroforming for producing the
metal plate 46 can be reduced, resulting in a high productivity. In
addition to the above Ni, Cu (copper), Al (aluminum), Ni alloys, Cu
alloys, Al alloys, etc. may be used for the metal plate 46.
[0087] Then, as shown in step S2 of FIG. 5, and FIGS. 7A, 7B, and
8, a conductive ring 52 having a hole 50 at the center is placed on
the major surface 46a of the metal plate 46. The conductive ring 52
is, for example, composed of a stainless steel, and one or more
steps 54 are formed on the inner end-face 56 of the hole 50. In
other words, as shown in FIG. 7B, the inner end-face 56 of the
conductive ring 52 contains two or more stepped surfaces 58a, 58b
with different diameters. Step 54 is a surface parallel to a major
surface 52a of the conductive ring 52, and the stepped surfaces
58a, 58b are surfaces perpendicular to the major surface 52a,
facing the central axis (shown by a dashed-dotted line m) of the
conductive ring 52. In the example of FIGS. 7A, 7B, and 8, one step
54 is formed in the inner end-face 56 of the conductive ring 52,
and two stepped surfaces (a first stepped surface 58a and a second
stepped surface 58b) are formed in the inner end-face 56. The inner
diameter D1 of the first stepped surface 58a is larger than the
inner diameter D2 of the second stepped surface 58b. The inner
end-face 56 may contain three or more stepped surfaces.
[0088] A plurality of modification examples of the conductive ring
52 with various shapes will be described below.
[0089] As shown in FIG. 9, in a conductive ring 52A of a first
modification example, the inner end-face 56 is a tapered surface
60. More specifically, the tapered surface 60 of the conductive
ring 52 is such that the inner diameter D1 of the major surface 52a
is larger than the inner diameter D2 of the other major surface 52b
(the surface in contact with the metal plate 46), and the inner
diameter is continuously reduced from the major surface 52a to the
other major surface 52b.
[0090] As shown in FIG. 10, in a conductive ring 52B of a second
modification example, the inner end-face 56 has a shape of a
combination of the conductive ring 52 shown in FIG. 7A and the
conductive ring 52A shown in FIG. 9. Thus, the first stepped
surface 58a of the inner end-face 56 corresponds to the tapered
surface 60.
[0091] As shown in FIG. 11, in a conductive ring 52C of a third
modification example, the inner end-face 56 has a shape of a
combination of the conductive ring 52 shown in FIG. 7A and the
conductive ring 52A shown in FIG. 9. Thus, the second stepped
surface 58b of the inner end-face 56 corresponds to the tapered
surface 60.
[0092] As shown in FIG. 12, in a conductive ring 52D of a fourth
modification example, the inner end-face 56 has a shape of a
combination of the conductive ring 52 shown in FIG. 7A and the
conductive ring 52A shown in FIG. 9. Thus, the first and second
stepped surfaces 58a and 58b of the inner end-face 56 correspond to
the tapered surface 60.
[0093] The above modification examples of the conductive ring 52
are considered in all respects to be illustrative and not
restrictive, and various changes may be made in the number of the
steps, the number of the tapered surfaces, etc.
[0094] Then, the electroforming step S3 of FIG. 5 is carried out.
As shown in FIG. 13, a pressing jig 64 for pressing the conductive
ring 52 against the metal plate 46, which has a hole 62 at the
center, is used in the electroforming. The inner diameter D3 of the
pressing jig 64 is larger than the inner diameter D1 of the largest
stepped surface of the conductive ring 52 (the first stepped
surface 58a in this case), and smaller than the outer diameter D4
of the metal plate 46. Thus, the conductive ring 52 can be brought
into tight contact with and pressed against the metal plate 46 by
the pressing jig 64 while preventing the center portion of the
conductive ring 52 from rising. Further, because the inner diameter
D3 of the pressing jig 64 is larger than the inner diameter D1 of
the first stepped surface 58a of the conductive ring 52, a portion
of the major surface 52a around the hole 50 is exposed in the hole
62 of the pressing jig 64.
[0095] A Ni electroforming process is carried out while using the
pressing jig 64 for pressing the conductive ring 52 against the
metal plate 46. A portion of the major surface 46a exposed in the
hole 50, the inner end-face 56 of the conductive ring 52, and a
portion of the major surface 52a of the conductive ring 52 are
covered with a first metal layer 66 (an Ni layer) by the Ni
electroforming. The first metal layer 66 formed by the Ni
electroforming has a thickness of approximately 300 .mu.m, moreover
the thickness can be increased more than 300 .mu.m.
[0096] Then, step S4 of the blasting treatment in FIG. 5 is carried
out. As shown in FIG. 15, the metal plate 46 is removed, and the
major surface 66a of the first metal layer 66, exposed in the hole
50 of the conductive ring 52, is partly roughened by the blasting
treatment. Thus, first roughened surfaces 68 are formed on a
portion of the major surface 66a of the first metal layer 66 by the
blasting treatment. In the blasting treatment, metal particles or
non-metal particles such as silica sand, emery, glass beads, resin
beads, or SiC particles are sprayed onto a blasting subject surface
at a high speed, to roughen the surface.
[0097] When the metal plate 46 is removed, the first pit forming
site 48 of the metal plate 46 (shown in FIGS. 6A and 6B) is
transferred onto the first metal layer 66 to form a second pit
forming site 70. Thus, the second pit forming site 70 is protected
before the blasting treatment to prevent the second pit forming
site 70 from being broken by the blasting treatment. The second pit
forming site 70 may be protected by placing a metal sheet mask 72,
or by forming a mask 74 of an adhesive tape, an oxide film or the
like.
[0098] Thus, after the second pit forming site 70 is protected, a
portion of the major surface 66a of the first metal layer 66 is
roughened by the blasting treatment to form the first roughened
surfaces 68. In this step, an original stamper 76 composed of the
first metal layer 66 and the conductive ring 52 is produced. In a
case where the pre-pits 34 are not formed in the optical recording
medium 10, the first pit forming site 48 on the metal plate 46 and
the second pit forming site 70 on the first metal layer 66 are not
needed, and the major surface 66a of the first metal layer 66 may
be entirely roughened by the blasting treatment.
[0099] The following two processes (a first process and a second
process) for producing the master stamper 40 have been examined in
view of accomplishing the present invention.
[0100] In the first process, as shown in FIG. 17A, a conductive
ring 80, which has a hole 78 at the center and has no stepped
surfaces, is placed on a major surface 46a of a metal plate 46.
Then, a Ni electroforming step is carried out while pressing the
conductive ring 80 against the metal plate 46 by using a pressing
jig 82. The inner diameter D3 of the pressing jig 82 is equal to
the inner diameter D5 of the conductive ring 80 in the first
process, whereby a metal layer 84 is formed by the Ni
electroforming on a portion of the major surface 46a of the metal
plate 46 exposed in the hole 78 of the conductive ring 80 and a
portion of the inner end-face of the conductive ring 80 as shown in
FIG. 17B. Thus, when the metal plate 46 is removed, the metal layer
84 is held only by the inner end-face 86 of the conductive ring 80
as shown in FIG. 18A.
[0101] When the metal layer 84 is then subjected to a blasting
treatment, the metal layer 84 is isolated from the conductive ring
80 by the pressure of non-metal particles or metal particles
colliding with the metal layer 84 as shown in FIG. 18B. The metal
layer 84 isolated from the conductive ring 80 is represented as a
metal sheet 88. During the blasting treatment, the non-metal
particles or metal particles are colliding with the metal sheet 88,
which is disadvantageously warped and greatly deformed such that a
major surface 88a becomes a convex surface as shown in FIG. 18C. As
a result of the examination, the height ha between the edge and the
top of the warped metal sheet 88 was several tens of mm.
[0102] In the second process, as shown in FIG. 19A, a pressing jig
82 is placed directly on a metal plate 46 without a conductive ring
80, and then a Ni electroforming step is carried out. A metal layer
84 is formed only on the metal plate 46 by the Ni electroforming in
the second process. When the metal plate 46 is removed, the metal
layer 84 is in the state of a metal sheet 88 as shown in FIG. 19B,
as with the first process. Thus, when the non-metal particles or
metal particles are colliding with the metal sheet 88 during a
blasting treatment, the metal sheet 88 is disadvantageously warped
and greatly deformed such that a major surface 88a becomes a convex
surface as shown in FIG. 19C. As a result of the examination, the
height ha between the edge and the top of the warped metal sheet 88
was several tens of mm.
[0103] In the above first and second processes, the metal sheet 88
is greatly deformed, so that a master stamper 40 with a partly
roughened surface cannot be produced.
[0104] In contrast, in this embodiment of the present invention,
the first metal layer 66 is formed over the inner end-face 56 and a
portion of the major surface 52a in the conductive ring 52 as shown
in FIG. 15, and further the two or more stepped surfaces with
different diameters (the first stepped surface 58a and the second
stepped surface 58b) are formed on the inner end-face 56, whereby
the contact area between the first metal layer 66 and the
conductive ring 52 is remarkably large and the first metal layer 66
is not isolated from the conductive ring 52 in the following
blasting treatment. Thus, the master stamper 40 having a partly
roughened surface can be produced with high accuracy by the method
of the present embodiment.
[0105] In this embodiment, in step S5 of FIG. 5, a further Ni
electroforming is carried out using the original stamper 76 having
the first metal layer 66 with a major surface 66a partly roughened.
As shown in FIG. 20, a second metal layer 90 is formed by the Ni
electroforming on a major surface 76a of the original stamper 76.
Specifically, the second metal layer 90 (an Ni layer) is formed
over a portion of the major surface 66a of the first metal layer 66
exposed in the hole 50 and a portion of the other major surface 52b
of the conductive ring 52. The second metal layer 90 formed by the
Ni electroforming has a thickness of approximately 300 .mu.m.
[0106] In step S6 of FIG. 5, as shown in FIGS. 21A and 21B, the
second metal layer 90 is isolated from the major surface of the
original stamper to obtain a second-generation stamper 92 made of
the metal. A third pit forming site 94 is formed on a major surface
92a of the second-generation stamper 92, and it has a transfer
pattern of the second pit forming site 70 on the major surface 66a
of the first metal layer 66 in the original stamper 76 shown in
FIG. 16. In addition, a second roughened surface 96 is formed in
the major surface 92a, and it has a transfer pattern of the first
roughened surface 68 formed in the major surface 66a of the first
metal layer 66.
[0107] A plurality of the second-generation stampers 92 can be
produced using the original stamper 76 by repeating steps S5 and S6
of FIG. 5.
[0108] The second-generation stamper 92 may be used as the master
stamper 40 for producing the above second substrate 22, or a
third-generation stamper 98 shown in FIG. 22 may be produced from
the second-generation stamper 92 by Ni electroforming and may be
used as the master stamper 40 for producing the second substrate
22. In this case, a fourth pit forming site 100 is formed on a
major surface 98a of the third-generation stamper 98, and it has a
transfer pattern of the third pit forming site 94 on the major
surface 92a of the second-generation stamper 92 shown in FIG. 21B.
In addition, a third roughened surface 102 is formed in the major
surface 98a, and it has a transfer pattern of the second roughened
surface 96 formed in the major surface 92a of the second-generation
stamper 92. An example of the third-generation stamper 98 used as
the master stamper 40 is shown in FIG. 4. Thus, the fourth pit
forming site 100 of FIG. 22 corresponds to the pit forming site 42
of FIG. 4, and the third roughened surface 102 of FIG. 22
corresponds to the roughened stamper surface 44 of FIG. 4.
[0109] Further, a fourth-generation stamper 104 shown in FIG. 23
may be produced using the third-generation stamper 98 by Ni
electroforming and may be used as the master stamper 40. In this
case, a fifth pit forming site 106 is formed on a major surface
104a of the fourth-generation stamper 104, and it has a transfer
pattern of the fourth pit forming site 100 on the major surface 98a
of the third-generation stamper 98 shown in FIG. 22. In addition, a
fourth roughened surface 108 is formed in the major surface 104a,
and it has a transfer pattern of the third roughened surface 102
formed in the major surface 98a of the third-generation stamper
98.
[0110] The third-generation stamper 98 and the fourth-generation
stamper 104 can be repeatedly produced by the Ni electroforming
using the second-generation stamper 92 and the third-generation
stamper 98 respectively. Thus, a large number of the master
stampers 40 can be more easily produced with lower production costs
and higher productivity in the case of using the third-generation
or fourth-generation stampers, as compared with the case of using
the second-generation stamper 92 as the master stamper 40.
[0111] As described above, in this embodiment, a portion of the
major surface 66a of the first metal layer 66 in the original
stamper 76 is roughened by the blasting treatment to form the first
roughened surface 68, and any one of the second-generation stamper
92, the third-generation stamper 98, and the fourth-generation
stamper 104, having the transfer pattern of the first roughened
surface 68, can be used as the master stamper 40. Therefore, an
incident light is easily scattered on the roughened substrate
surface 30 of the second substrate 22 produced by using the master
stamper 40, whereby an image formed thereon is visible from any
direction. Thus, the resultant optical recording medium 10 has an
excellent visibility of the image on the label surface.
[0112] The surface roughness of the roughened stamper surface 44 of
the master stamper 40 is preferably such that the arithmetic
average roughness Ra is 0.05 to 0.3 .mu.m and the ten-point average
roughness Rz is 0.1 to 5 .mu.m. The values of Ra and Rz of the
roughened stamper surface 44 of the master stamper 40 are measured
by a stylus-type roughness meter.
[0113] The structure of the optical recording medium 10 is not
particularly limited as long as it contains the pre-pit region 32
with one or more pre-pits 34 and the image recording layer 24 on
which a visible image can be formed by irradiation of a laser
light. Thus, the optical recording medium 10 may be a read-only-,
WORM (Write Once, Read Many)-, or rewritable-type medium, and is
preferably a WORM-type medium. The recording manner of the optical
recording medium 10 may be selected from phase change-, magnetic
optical-, and dye-type recording manners without particular
restrictions, and is preferably dye-type.
[0114] The optical recording medium 10 shown in FIG. 1 is such that
the information recording layer 18 on the first substrate 16 is
attached to the image recording layer 24 on the second substrate
22. Thus, the optical recording medium 10 is preferably used for
DVDs such as DVD-Rs, DVD-RWs, and HD DVDs.
[0115] Examples of the layer structure of the optical recording
medium 10 include the following first to sixth unillustrated layer
structures in addition to the above structure shown in FIG. 1.
[0116] (1) The first layer structure is such that the information
recording layer 18, the first reflective layer 20, and the adhesion
layer 28 are formed in this order on the first substrate 16, and
the second substrate 22 having the image recording layer 24 is
attached to the adhesion layer 28.
[0117] (2) The second layer structure is such that the information
recording layer 18, the first reflective layer 20, a protective
layer, and the adhesion layer 28 are formed in this order on the
first substrate 16, and the second substrate 22 having the image
recording layer 24 is attached to the adhesion layer 28.
[0118] (3) The third layer structure is such that the information
recording layer 18, the first reflective layer 20, a first
protective layer, the adhesion layer 28, and a second protective
layer are formed in this order on the first substrate 16, and the
second substrate 22 having the image recording layer 24 is attached
to the second protective layer.
[0119] (4) The fourth layer structure is such that the information
recording layer 18, the first reflective layer 20, a first
protective layer, the adhesion layer 28, a second protective layer,
and a third protective layer are formed in this order on the first
substrate 16, and the second substrate 22 having the image
recording layer 24 is attached to the third protective layer.
[0120] (5) The fifth layer structure is substantially equal to the
structure of FIG. 1, and is such that the information recording
layer 18, the first reflective layer 20, the adhesion layer 28, and
the second reflective layer 26 are formed in this order on the
first substrate 16, and the second substrate 22 having the image
recording layer 24 is attached to the second reflective layer
26.
[0121] (6) The sixth layer structure is such that the information
recording layer 18, the first reflective layer 20, and a first
protective layer are formed in this order on the first substrate
16, the image recording layer 24, the second reflective layer 26,
and a second protective layer are formed in this order on the
second substrate 22, and the first protective layer is attached to
the second protective layer by the adhesion layer 28.
[0122] The layer structure of FIG. 1 and the first to sixth layer
structures are considered in all respects to be illustrative and
not restrictive, and the above layers may be formed in another
order and the layers other than the image recording layer 24 may be
removed. Further, each of the layers may have a single- or
multi-layer structure.
[0123] When an optical information is recorded or reproduced on the
optical recording medium 10, the first substrate 16 side of the
optical recording medium 10 is irradiated with a laser light having
a predetermined wavelength, which may be 650 to 670 nm for DVD-Rs
and 400 to 410 nm or less for HD-DVDs.
[0124] When a visible image is recorded on the image recording
layer 24, the second substrate 22 side of the optical recording
medium 10 is irradiated with a laser light (such as a laser light
having a linear speed of 3.5 m/s, a wavelength of 660 nm, an NA
value of 0.6, and a medium surface power of 10 mW), and the
irradiated portions are degenerated to change the contrast, which
results in the visibility of the image.
[0125] In the present invention, the desired image can be
efficiently recorded on the label surface (the image recording
surface) of the optical recording medium 10 by the laser light
using an optical recording medium drive without a printer or the
like. Further, the surface of the second substrate 22, facing the
image recording layer 24, is roughened, whereby the visibility of
the image can be improved.
[0126] In this embodiment, the first substrate 16 is disposed on
one side of the information recording layer 18, etc., and the
second substrate 22 is disposed on the other side. The second
substrate 22 may have a cover layer, a transparent sheet, or the
like. Thus, the optical recording medium 10 of this embodiment may
have a structure of CDs such as CD-Rs, in which an information
recording layer, an image recording layer, and a cover layer are
formed in this order on a substrate.
[0127] In the CD-type structure, the information recording layer
18, the first reflective layer 20, a protective layer, the second
reflective layer 26, and the image recording layer 24 are formed in
this order on the first substrate 16, and a roughened cover layer
is formed on the image recording layer 24. In this structure, the
surface of the cover layer, facing the image recording layer 24, is
roughened, whereby the image visibility can be improved.
[0128] In this case, when optical information is recorded or
reproduced on the CD-type optical recording medium 10, the first
substrate 16 side of the optical recording medium 10 is irradiated
with a laser light having a predetermined wavelength of 660 nm,
etc.
[0129] When a visible image is recorded on the image recording
layer 24, the cover layer side (the second substrate 22 side) of
the CD-type optical recording medium 10 is irradiated with a laser
light, and the irradiated portions are degenerated to change the
contrast as a visible image.
[0130] Thus, even when the optical recording medium has the CD-type
structure, an image can be formed thereon by a laser light. The
desired image can be efficiently recorded on the label surface (the
image recording surface) of the optical recording medium 10 by
using an optical recording medium drive without a printer or the
like. Further, the surface of the second substrate 22, facing the
image recording layer 24, is roughened, whereby the visibility of
the image can be improved.
[0131] The optical recording medium 10 having the DVD-type
structure shown in FIG. 1 may be produced in the following manner.
Thus, for example, the master stamper 40 having the roughened
stamper surface 44 on one major surface is prepared, the second
substrate 22 having the roughened substrate surface 30 on one major
surface is prepared using the master stamper 40, the image
recording layer 24 is formed on the second substrate 22, the
information recording layer 18 is formed on the first substrate 16,
and the first substrate 16 and the second substrate 22 are bonded
such that the information recording layer 18 and the image
recording layer 24 face each other, whereby the optical recording
medium 10 can be produced.
[0132] A reflective layer or a protective layer may be formed in
the step of forming the information recording layer and the step of
image recording layer if necessary.
[0133] The optical recording medium having the CD-type structure
can be produced by forming at least the information recording layer
18, the image recording layer 24, and a cover layer (the second
substrate 22) having a roughened surface on the first substrate
16.
[0134] The layer structure of FIG. 1 and the first to sixth layer
structures are considered in all respects to be illustrative and
not restrictive, and the above layers may be formed in another
order and the layers other than the image recording layer 24 may be
removed. Further, each of the layers may have a single- or
multi-layer structure.
[0135] The layers and forming methods thereof will be described
below with reference to the layer structure of the optical
recording medium 10 shown in FIG. 1.
(Information Recording Layer 18)
[0136] The information recording layer 18 is a layer on which
information, particularly code information such as digital
information, is recorded and reproduced by a laser light.
[0137] The information recording layer 18 may be a dye recording
layer or a phase change recording layer, and is preferably a dye
recording layer.
[0138] Examples of dyes used in the information recording layer 18
include cyanine dyes, oxonol dyes, azo dyes, phthalocyanine dyes,
triazole compounds such as benzotriazole compounds, triazine
compounds, merocyanine compounds, aminobutadiene compounds,
cinnamic acid compounds, benzoxazole compounds, pyrromethene
compounds, and squarylium compounds. The dyes may have a metal atom
as a coordination center.
[0139] Dyes described in Japanese Laid-Open Patent Publication Nos.
4-74690, 8-127174, 11-53758, 11-334204, 11-334205, 11-334206,
11-334207, 2000-43423, 2000-108513, and 2000-158818 may be used in
the present invention.
[0140] When the optical recording medium is a CD-R, preferred ones
among the above are the cyanine dyes, azo dyes, and phthalocyanine
dyes. When the optical recording medium is a DVD-R, preferred ones
are the cyanine dyes, oxonol dyes, azo dyes (including Ni complexes
and Co complexes), and pyrromethene compounds. When the optical
recording medium is a Blu-ray disc or an HD-DVD, preferred ones are
the cyanine dyes, oxonol dyes, azo dyes, phthalocyanine dyes,
benzotriazole compounds, and triazine compounds.
[0141] Further, the cyanine dyes, azo dyes, and phthalocyanine dyes
are more preferred in the case of the CD-R, the cyanine dyes,
oxonol dyes, and azo dyes (including Ni complexes and Co complexes)
are more preferred in the case of the DVD-R, and the cyanine dyes,
oxonol dyes, azo dyes, and phthalocyanine dyes are more preferred
in the case of the Blu-ray disc or HD-DVD.
[0142] The information recording layer 18 may be formed by the
steps of dissolving a binder, etc. and a recording substance such
as the dye in an appropriate solvent to prepare a coating liquid,
applying the coating liquid to the first substrate 16, and drying
the applied liquid. The concentration of the recording substance in
the coating liquid is generally 0.01% to 15% by mass, preferably
0.1% to 10% by mass, more preferably 0.5% to 5% by mass, most
preferably 0.5% to 3% by mass.
[0143] The information recording layer 18 may be formed by vapor
deposition, sputtering, CVD, or liquid coating, and is preferably
formed by liquid coating. In the case of the liquid coating, a
quencher, a binder, or the like is dissolved in the solvent
together with the dye, etc. if necessary, and the obtained coating
liquid is applied to the substrate and dried.
[0144] Examples of the solvents for the coating liquid include
esters such as butyl acetate, ethyl lactate, and cellosolve
acetate; ketones such as methyl ethyl ketone, cyclohexanone, and
methyl isobutyl ketone; chlorinated hydrocarbons such as
dichloromethane, 1,2-dichloroethane, and chloroform; amides such as
dimethylformamide; hydrocarbons such as methylcyclohexane; ethers
such as dibutyl ether, diethyl ether, tetrahydrofuran, and dioxane;
alcohols such as ethanol, n-propanol, isopropanol, n-butanol, and
diacetone alcohol; fluorine-containing solvents such as
2,2,3,3-tetrafluoropropanol; and glycol ethers such as ethylene
glycol monomethyl ether, ethylene glycol monoethyl ether, and
propylene glycol monomethyl ether.
[0145] These solvents may be used singly or in combination
depending on the solubility of the dye. Various additives such as
antioxidants, UV absorbers, plasticizers, and lubricants may be
added to the coating liquid if necessary.
[0146] Examples of the binders include natural organic
high-molecular substances such as gelatins, cellulose derivatives,
dextrans, rosins, and rubbers, and synthetic organic high-molecular
substances. The synthetic organic high-molecular substances include
hydrocarbon resins such as polyethylenes, polypropylenes,
polystyrenes, and polyisobutylene; vinyl resins such as polyvinyl
chlorides, polyvinylidene chlorides, and vinyl chloride-vinyl
acetate copolymers; acrylic resins such as polymethyl acrylates and
polymethyl methacrylates; and initial condensation products of
thermosetting resins such as polyvinyl alcohols, chlorinated
polyethylenes, epoxy resins, butyral resins, rubber derivatives,
and phenol-formaldehyde resins.
[0147] In the case of using the binder in the information recording
layer 18, the mass of the binder is generally 0.01 to 50 times the
dye, preferably 0.1 to 5 times the dye.
[0148] The coating liquid may be applied by a spraying method, a
spin coating method, a dipping method, a roll coating method, a
blade coating method, a doctor roll method, a screen printing
method, etc. The information recording layer may have a single- or
multi-layer structure. The thickness of the information recording
layer is generally 10 to 500 nm, preferably 15 to 300 nm, more
preferably 20 to 150 nm.
[0149] An anti-fading agent may be added to the information
recording layer 18 to increase the light fastness. In general, the
anti-fading agent is a singlet oxygen quencher.
[0150] The singlet oxygen quencher may be selected from those
described in known publications such as patent publications.
[0151] Specific examples of the singlet oxygen quenchers include
those described in Japanese Laid-Open Patent Publication Nos.
58-175693, 59-31194, 60-18387, 60-19586, 60-19587, 60-35054,
60-36190, 60-36191, 60-44554, 60-44555, 60-44389, 60-44390,
60-54892, 60-47069, 63-209995, and 4-25492, Japanese Patent
Publication Nos. 1-38680 and 6-26028, Germany Patent No. 350399,
Nippon Kagakukaishi, 1992, October issue, Page 1141, etc.
[0152] The ratio of the anti-fading agent such as the singlet
oxygen quencher to the dye is generally 0.1% to 50% by mass,
preferably 0.5% to 45% by mass, further preferably 3% to 40% by
mass, particularly preferably 5% to 25% by mass.
[0153] In a case where the information recording layer 18 is a
phase change-type recording layer, it is preferred that the layer
comprises a phase change-type optical recording material containing
Ag, Al, In, Te, or Sb, which can be converted to at least two
stages of the crystalline state and the amorphous state. Specific
examples of such optical recording materials include Sb--Te alloys,
Ge--Sb--Te alloys, Pd--Ge--Sb--Te alloys, Nb--Ge--Sb--Te alloys,
Pd--Nb--Ge--Sb--Te alloys, Pt--Ge--Sb--Te alloys, Co--Ge--Sb--Te
alloys, In--Sb--Te alloys, Ag--In--Sb--Te alloys, Ag--V--In--Sb--Te
alloys, and Ag--Ge--In--Sb--Te alloys. Among them, Ge--Sb--Te
alloys and Ag--In--Sb--Te alloys are capable of rewriting many
times, and thus are preferably used. The thickness of the phase
change-type information recording layer 18 is preferably 10 to 50
nm, more preferably 15 to 30 nm.
[0154] The phase change-type information recording layer 18 may be
formed by a gas-phase film deposition method such as a sputtering
method or a vacuum vapor deposition method. A known dielectric
layer may be formed on the information recording layer 18 if
necessary.
(Image Recording Layer 24)
[0155] As described above, the optical recording medium 10 contains
the image recording layer 24, which is closer to the second
substrate 22 (or the cover layer) than the information recording
layer 18. A desired visible image (visible information) such as
character, figure, or picture is recorded on the image recording
layer 24. The visible image is an image that can be visually
detected, and may contain any visible information such as a
character (text), picture, or figure.
[0156] The visible image recorded on the image recording layer 24
may contain a desired image such as a character, figure, or
picture. Specifically, the visible image may contain a disc title,
content information, a thumbnail of contents, a related picture, a
design picture, a copyright notice, a recording date, a recording
method, a recording format, a bar code, etc.
[0157] Further, the visible image may contain character information
such as accessible personal information, accessible period
information, accessible number information, rental information,
resolution information, layer information, user designation
information, copyright holder information, copyright number
information, manufacturer information, manufacturing date
information, sale date information, vendor or seller information,
set number information, regional designation information, language
designation information, use designation information, user
information, or use number information.
[0158] The image recording layer 24 is not particularly limited as
long as a visible image such as a character, image, or picture can
be recorded thereon by irradiation of a laser light. It is
preferred that the image recording layer 24 contains a dye compound
from the viewpoint of forming a clear visible image by the
irradiation of a laser light. The dye compound for the image
recording layer 24 is preferably selected from the above described
examples of the dyes for the information recording layer 18. It is
preferred from the viewpoint of costs that the image recording
layer 24 is formed by applying a coating liquid containing the dye
compound by spin coating.
[0159] In the optical recording medium 10, the component (the dye
or the phase change recording material) of the information
recording layer 18 may be the same as or different from the
component of the image recording layer 24. Because the desired
functions are different between the information recording layer 18
and the image recording layer 24, the components thereof are
preferably different. Specifically, it is preferred that the
information recording layer 18 comprises a component excellent in
recording/reproducing properties, and the image recording layer 24
comprises a component capable of forming a high-contrast image. In
the case of using the dye, it is particularly preferred that the
image recording layer 24 comprises a cyanine dye, a phthalocyanine
dye, an azo dye, an azo metal complex, or an oxonol dye from the
viewpoint of increasing the contrast of the recorded image.
[0160] The image recording layer 24 may comprise a leuco dye.
Specifically, preferred examples of the leuco dyes include crystal
violet lactones; phthalide compounds such as
3,3-bis(1-ethyl-2-methylindol-3-yl)phthalide and
3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azapht-
halide; and fluoran compounds such as
3-cyclohexylmethylamino-6-methyl-7-anilinofluoran,
2-(2-chloroanilino)-6-dibutylaminofluoran,
3-diethylamino-6-methyl-7-anilinofluoran,
3-diethylamino-6-methyl-7-xylidinofluoran,
2-(2-chloroanilino)-6-diethylaminofluoran,
2-anilino-3-methyl-6(N-ethylisopentylamino)fluoran,
3-diethylamino-6-chloro-7-anilinofluoran,
3-benzylethylamino-6-methyl-7-anilinofluoran, and
3-methylpropylamino-6-methyl-7-anilinofluoran.
[0161] The image recording layer 24 may be formed by dissolving the
dye in a solvent to prepare a coating liquid, and by applying the
coating liquid. The solvent may be the same as that of the coating
liquid for the information recording layer 18. Additives and
application methods for the image recording layer 24 are the same
as those for the information recording layer.
[0162] The thickness of the image recording layer 24 is preferably
0.01 to 50 .mu.m, more preferably 0.02 to 20 .mu.m, further
preferably 0.03 to 5 .mu.m.
[0163] It is preferred that the visible information is recorded on
the image recording layer 24 by repeatedly moving a laser light
having a predetermined power in approximately the same trajectory.
Further, it is preferred that the laser light having a
predetermined power is oscillated in the radius direction of the
optical recording medium and moved in approximately the same
trajectory.
(First Substrate 16)
[0164] The first substrate 16 may comprise a material selected from
materials used in conventional optical recording medium
substrates.
[0165] Examples of the materials for the first substrate 16 include
glasses, polycarbonates, acrylic resins such as polymethyl
methacrylates, vinyl chloride resins such as polyvinyl chlorides
and vinyl chloride copolymers, epoxy resins, amorphous polyolefins,
and polyesters. These materials may be used in combination. The
materials may be used in the state of a film or a rigid substrate
as the first substrate 16. Among the materials, polycarbonates are
preferred from the viewpoints of humidity resistance, dimensional
stability, and cost.
[0166] The thickness of the first substrate 16 is preferably 0.05
to 1.2 mm, more preferably 0.1 to 1.1 mm.
[0167] Guide grooves for tracking or concavities (pregrooves) with
information of address signal, etc. are formed in the first
substrate 16.
[0168] In a case where the optical recording medium is a DVD-R or
DVD-RW, the track pitch of the pregrooves is preferably 300 to 900
nm, more preferably 350 to 850 nm, further preferably 400 to 800
nm.
[0169] The depth (the groove depth) of each pregroove is preferably
100 to 160 nm, more preferably 120 to 150 nm, further preferably
130 to 140 nm. The groove width (the half width) of each pregroove
is preferably 200 to 400 nm, more preferably 230 to 380 nm, further
preferably 250 to 350 nm.
[0170] The first substrate 16 may have grooves with a track pitch
smaller than those of conventional DVD-Rs, to achieve a higher
recording density. In this case, the track pitch of the grooves is
preferably 280 to 450 nm, more preferably 300 to 420 nm, further
preferably 320 to 400 nm. The depth (the groove depth) of each
groove is preferably 15 to 150 nm, more preferably 25 to 100 nm.
The groove width of each groove is preferably 50 to 250 nm, more
preferably 100 to 200 nm.
[0171] In a case where the optical recording medium is a CD-R, the
track pitch of the grooves is preferably 1.2 to 2.0 .mu.m, more
preferably 1.4 to 1.8 .mu.m, further preferably 1.55 to 1.65 .mu.m.
The depth (the groove depth) of each groove is preferably 100 to
250 nm, more preferably 150 to 230 nm, further preferably 170 to
210 nm. The groove width of each pregroove is preferably 400 to 650
nm, more preferably 480 to 600 nm, further preferably 500 to 580
nm.
[0172] An undercoat layer may be formed on the grooved surface of
the first substrate 16, on which the information recording layer 18
is formed, to improve flatness and adhesion and to prevent
deterioration of the recording layer.
[0173] Examples of materials of the undercoat layer include
polymers such as polymethyl methacrylates, acrylic acid-methacrylic
acid copolymers, styrene-maleic anhydride copolymers, polyvinyl
alcohols, N-methylolacrylamide, styrene-vinyltoluene copolymers,
chlorosulfonated polyethylenes, nitrocelluloses, polyvinyl
chlorides, chlorinated polyolefins, polyesters, polyimides, vinyl
acetate-vinyl chloride copolymers, ethylene-vinyl acetate
copolymers, polyethylenes, polypropylenes, and polycarbonates, and
surface modifying agents such as silane coupling agents. The
undercoat layer may be formed by dissolving or dispersing the
material in an appropriate solvent, and by applying thus-obtained
coating liquid to the substrate by a coating method such as spin
coating, dip coating, or extrusion coating. The thickness of the
undercoat layer is generally 0.005 to 20 .mu.m, preferably 0.01 to
10 .mu.M.
(First Reflective Layer 20 and Second Reflective Layer 26)
[0174] The first reflective layer 20 and the second reflective
layer 26 are preferably formed on the information recording layer
18 and the image recording layer 24 to increase the reflectance to
the laser light for information reproduction.
[0175] The first reflective layer 20 and the second reflective
layer 26 preferably comprise a light reflective substance having a
high reflectance to the laser light. Examples of the light
reflective substances include metals of Mg, Se, Y. Ti, Zr, Hf, V,
Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Co, Ni, Ru, Rh, Pd, Ir, Pt, Cu, Ag,
Au, Zn, Cd, Al, Ga, In, Si, Ge, Te, Pb, Po, Sn, Bi, etc.,
metalloids, stainless steels, and semiconductor materials. These
substances may be used singly or in combination, or as an
alloy.
[0176] Among them, the light reflective substance is preferably Cr,
Ni, Pt, Cu, Ag, Au, Al, or a stainless steel, particularly
preferably Au, Ag, Al, or an alloy thereof, most preferably an Ag
alloy such as an Ag--Nd--Cu alloy or an Ag--Pd--Cu alloy.
[0177] For example, the first reflective layer 20 and the second
reflective layer 26 can be formed on the information recording
layer 18 and the second substrate 22 by vapor-depositing,
sputtering, or ion-plating the light reflective substance. The
thickness of each of the first reflective layer 20 and the second
reflective layer 26 is generally 10 to 300 nm, preferably 50 to 200
nm.
(Adhesion Layer 28)
[0178] The adhesion layer 28 is formed to bond the first stack 12
containing the first substrate 16 to the second stack 14 containing
the second substrate 22 in production of a bond type optical
recording medium such as a DVD. The adhesion layer 28 is preferably
composed of a light curing resin. It is preferred that the light
curing resin has a small cure shrinkage ratio from the viewpoint of
preventing warping of the resultant disc. Examples of such light
curing resins include SD-640 and SD-661 available from Dainippon
Ink and Chemicals, Inc., and SK6100, SK6300, and SK6400 available
from Sony Chemical Corporation. The thickness of the adhesion layer
28 is preferably 1 to 100 .mu.m, more preferably 5 to 60 .mu.m,
particularly preferably 20 to 55 .mu.m, in view of flexibility.
(Protective Layer, not Shown)
[0179] The protective layer is optionally formed to prevent
penetration of water and scratching. The protective layer
preferably comprises a UV curing resin, a visible light curing
resin, a thermosetting resin, or silicon dioxide, particularly
preferably comprises a UV curing resin. For example, SD-640
available from Dainippon Ink and Chemicals, Inc. can be used as the
UV curing resin. Further, SD-347 and SD-694 available from
Dainippon Ink and Chemicals, Inc., and SKCD1051 available from SKC
can be used in the protective layer. The thickness of protective
layer is preferably 1 to 200 .mu.m, more preferably 50 to 150
.mu.m.
(Second Substrate 22)
[0180] The step of roughening the second substrate 22 is described
in detail above, and thus duplicate explanations therefor are
omitted.
[0181] The second substrate 22 having the roughened substrate
surface 30 faces the first substrate 16 in the bond type optical
recording medium 10. The second substrate 22 may comprise the same
material as the first substrate 16. It is not necessary to form a
groove on the surface of the second substrate 22, on which the
image recording layer 24 is formed, as with the first substrate 16.
The thickness of the second substrate 22 is preferably 0.05 to 1.2
mm, more preferably 0.1 to 1.1 mm, further preferably 0.5 to 0.7
mm.
[0182] In a case where the second substrate 22 is the cover layer,
generally the cover layer is formed to physically and chemically
protect the information recording layer 18, the image recording
layer 24, etc. In this embodiment, the cover layer on the image
recording layer 24 is roughened to increase the image visibility.
The cover layer preferably has a thickness of 10 nm to 5 .mu.m.
[0183] A transparent sheet of a polycarbonate or cellulose
triacetate may be used as the cover layer. In this case, the
transparent sheet preferably has a thickness of 0.01 to 0.2 mm. It
is preferred that a surface of the transparent sheet, facing the
image recording layer, is roughened by the stamper.
[0184] As described above, at least the image recording layer 24
and the information recording layer 18 are formed in this order on
one surface of the roughened second substrate 22 in the optical
recording medium 10.
[0185] The second substrate 22 can be used in an optical member
having an image recording layer 24 on which an image is formed by a
light, other than the optical recording medium 10. Thus, in the
optical member, at least the image recording layer is formed on the
roughened surface of the substrate. Examples of such optical
members include stickers.
[0186] In the optical recording medium 10 of this embodiment, an
intermediate layer adjacent to the second substrate 22 may have a
roughened surface facing the image recording layer 24. When the
intermediate layer has the roughened surface facing the image
recording layer 24, it is not necessary to form the roughened
substrate surface 30 on the second substrate 22. The intermediate
layer may be the protective layer, which may comprise a UV curing
resin.
Recording Method:
[0187] Specifically, an image is recorded on the image recording
layer 24 in the optical recording medium 10 of the embodiment by
using at least a recording apparatus capable of recording image
information.
[0188] In this embodiment, by using only one optical recording
medium drive (a recording apparatus), image information can be
recorded on the image recording layer 24 and optical information
can be recorded on the information recording layer 18. In the case
of using only one optical recording medium drive, for example,
information is recorded on one of the image recording layer 24 and
the information recording layer 18, the optical recording medium 10
is reversed, and then another information is recorded on the other
layer. Examples of such optical recording medium drives having a
function of recording a visible image on an image recording layer
are described in Japanese Laid-Open Patent Publication Nos.
2002-203321, 2003-203348, and 2003-242750, etc.
[0189] In this embodiment, by detecting the pre-pits 34, the
presence of the image recording layer 24 in the optical recording
medium 10 can be easily detected. Further, based on the information
of the pre-pits 34, a visible image can be recorded on the image
recording layer 24 under an optimum laser output with excellent
imaging properties. The combination of the pre-pits 34 may provide
manufacturer information.
EXAMPLES
[0190] An original stamper 76 and metal sheets 88 of Example 1 and
Comparative Examples 1 and 2 were produced in the following manner.
Each of them was evaluated with respect to shape and warping state
after blasting, probability of producing a second-generation
stamper, and probability of producing a master stamper. The results
are shown in FIG. 24.
Example 1
[0191] The original stamper 76 was produced by steps S1 to S6 shown
in FIG. 5 of the method of the above embodiment. The conductive
ring 52A of the first modification example shown in FIG. 9 was used
in this example, and the inner diameter D1 of the major surface was
193 mm and the inner diameter D2 of the other major surface was 180
mm.
[0192] As shown in FIG. 24, the original stamper 76 was flat
without warping after the blasting treatment. Thus, a
second-generation stamper 92 could be produced by using the
original stamper 76, and further a master stamper 40 could be
produced by using the second-generation stamper 92.
Comparative Example 1
[0193] The metal sheet 88 (the original stamper) was produced by
the first process of FIGS. 17A to 18C using the conductive ring 80.
The conductive ring 80 had an inner diameter of 193 mm.
[0194] As shown in FIGS. 18C and 24, the metal sheet 88 was curved
by the blasting treatment. The warping of the metal sheet 88 was
such that the height ha between the edge and the top of the metal
sheet 88 was within a range of several mm to several tens mm. Thus,
a second-generation stamper 92 could not be produced by using the
metal sheet 88, and a master stamper 40 could not be produced
naturally.
Comparative Example 2
[0195] The metal sheet 88 (the original stamper) was produced by
the second process of FIGS. 19A to 19C using no conductive
rings.
[0196] As shown in FIGS. 19C and 24, the metal sheet 88 was curved
by the blasting treatment. The warping of the metal sheet 88 was
such that the height ha between the edge and the top of the metal
sheet 88 was within a range of several mm to several tens mm. Thus,
a second-generation stamper 92 could not be produced by using the
metal sheet 88, and a master stamper 40 could not be produced
naturally.
[0197] It should be noted that the stamper producing method, the
substrate producing method, and the optical recording medium
producing method according to the present invention are not limited
to the above embodiment, and various changes and modifications may
be made therein without departing from the scope of the present
invention.
* * * * *