DESCRIPTION
MULTILAYER OPTICAL RECORDING MEDIUM
Technical Field
5 [OOOl] The p r e s e n t invention r e l a t e s t o a multilayer
o p t i c a l recording medium including an N (N I 5) number
of i n t e r f a c e s capable of r e f l e c t i n g i n c i d e n t l i g h t .
Background A r t
[0002] For example, o p t i c a l recording media such as
10 a CD (Compact Disc), a DVD ( D i g i t a l V e r s a t i l e Disc),
and a BD (Blu-ray Disc: r e g i s t e r e d trademark) are
widely used.
[0003] In a recordable o p t i c a l recording medium
including a recording film among such o p t i c a l recording
15 media, many recording films are provided i n order t o
increase a recording capacity. In p a r t i c u l a r , i n recent
years, a multilayer o p t i c a l recording medium including
t h r e e or more recording films has been developed.
[0004] However, i n the case of the multilayer
20 o p t i c a l recording medium, so-called i n t e r l a y e r s t r a y
l i g h t is generated and the occurrence of multiple
i n t e r f e r e n c e becomes a problem. Here, the multiple
i n t e r f e r e n c e means t h a t , i n the multilayer o p t i c a l
recording medium, two d i f f e r e n t l i g h t waves t h a t are
25 r e f l e c t e d on an i n t e r f a c e capable of r e f l e c t i n g
incident l i g h t one or more times i n t e r f e r e with each

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Claims
[1] A multilayer optical recording medium, which
includes an N (N ^ 5) number of interfaces capable of
reflecting incident light, the multilayer optical
5 recording medium satisfying, provided that each of an M
(M ^ N) number of interfaces selected from the N number
of interfaces is defined as Li (i = 0, 1, ..., M,
where, it is assumed that as a value of i becomes
smaller, the layer in which the interface is formed
10 becomes lower as viewed from an uppermost surface as a
light incident surface) and j < k : ^ l < m ^ M i s set,
when light having a wavelength X is collected to an
objective lens having a numerical aperture NA with an
interface Lj being a target, regarding an interface Lk,
15 an interface Lm, and an interface LI, which cause stray
light due to three-times reflections via Lk (or LI) -.
Lm -• LI (or Lk) , and the interface Lj, condition that a
difference I Sj to k - Si to ml between a total sum Sj to k of
a thickness of a spacer formed between the interface Lj
20 and the interface Lk and a total sum Si to m of a
thickness of a spacer formed between the interface LI
and the interface Lm is larger than nX/NA^ (n is a
refractive index of the spacer).
[2] The multilayer optical recording medium according
25 to claim 1, satisfying
provided that a thickness of a spacer formed