JP2002092963A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording medium by which address information or rotation control information of a disk are correctly obtained and a signal is recorded with high density to make its reproduction signal quality excellent. SOLUTION: At least, a recording layer is arranged on a light transmission baseboard provided with a groove and a land where a pre-pit is formed in the optical recording medium. The medium is characterized in such a way that the pre-pit is formed by providing a pre-pit length being >=3T (T: (1/cannel bit rate) × reference linear velocity) in a nearly center part in a land width direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium having a recording layer provided on a substrate having grooves and lands on which prepits are formed. More specifically, the present invention relates to an optical recording medium that can accurately read address information from prepits without affecting recording / reproduction on a recording layer. The invention is particularly applicable to DVD-R and DVD-R
It is suitably applied to a recordable optical recording medium such as W.

[0002]

2. Description of the Related Art A DVD (Digital Versatile Disc), which is an optical recording medium capable of digital recording, generally has a structure in which a recording layer, a reflective layer, and a protective layer are sequentially laminated on a light transmitting substrate.

In a recordable optical recording medium such as a DVD-R or a DVD-RW, the substrate has a land / groove structure, and a land and a land are required to record a data signal by a laser beam. A guide groove called a groove is formed. These shapes are optimized in consideration of overall signal quality such as recording / reproducing characteristics and servo signal characteristics. Groove is 0.6-0.8
It is formed at a pitch of about μm, and is usually provided with a constant period of waviness (meander) called a wobble. By detecting this period, the disk can be rotated at an accurate linear velocity. .

On the other hand, the lands are provided with pits called pre-pits on which address information on the disk is recorded at predetermined intervals, thereby obtaining a positional relationship on the blank disk (unrecorded disk). You can do it. The pre-pits are formed so as to maintain a fixed positional relationship with the wobble, and recording / reproducing of a data signal to / from the groove is performed on a land adjacent to the groove (for example, on the outer periphery of the groove). It is performed while detecting the pre-pit signal.

[0005] In order to accurately obtain address information even when the track pitch is narrow, or to improve the recording and reproduction of data signals in adjacent grooves, such pre-pits have a shape and a forming method. varied,
Research and development are ongoing. For example, JP-A-9-326
JP-A-138, JP-A-2000-149330, and the like disclose an optical recording medium in which a prepit is formed by cutting out one side of a land portion and connecting to an adjacent groove. Japanese Patent Application Laid-Open No. 2000-11460 discloses an optical recording medium in which prepits are formed so as to be deviated toward one groove (inner circumferential groove) adjacent to a land.

[0006]

However, when the pre-pit is formed so as to be continuous with the adjacent groove by cutting out the land, or when the pre-pit is formed by displacing the pre-pit toward one of the grooves adjacent to the land, the pre-pit is formed. The signal has too much influence on the groove signal,
There are problems such as causing a read error during reproduction of the groove signal.

In addition to the above forming method, there is a method in which a prepit smaller than the land width is formed at the center of the land in the width direction and the height of the prepit wall is substantially equal to the land height. In such a case, there is a problem that the quality of the reproduction signal obtained from the prepits is reduced because the formed prepits are small.

The present invention has been made in view of the above circumstances, and can accurately obtain address information and disc rotation control information even at a narrow track pitch, and can record signals at high density. It is an object of the present invention to provide an optical recording medium having good reproduction signal quality.

[0009]

The following inventions are provided to solve the above-mentioned problems.

(1) An optical recording medium comprising at least a recording layer provided on a light-transmitting substrate having grooves and lands on which prepits are formed, wherein the prepits are
An optical recording medium characterized by being formed with a pre-pit length of 3T [T: (1 / channel bit rate) × reference linear velocity] or more substantially at the center of the land in the width direction.

(2) The prepit is formed with a boundary wall between adjacent grooves, and the height of the boundary wall (h ₂ ) is larger than the height of the land (h ₁ ) by h _2. / H ₁ > 0.
80, wherein said optical recording medium is 80.

(3) The optical recording medium as described above, wherein the recording layer contains one or more organic dyes selected from organic dyes having a maximum absorption wavelength (λ _max ) of 400 to 700 nm in a thin film.

(4) The organic dye is represented by the following general formula (I)
Wherein the optical recording medium is at least one member selected from the group consisting of a trimethine cyanine dye represented by formula (I) and a chelate compound of a dye represented by the following general formula (II) and a metal (metal-containing azo dye).

[0014]

[0015]

In the general formulas (I) and (II), each symbol has the following meaning. R ₁ , R ₂ : each independently a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted alkenyl group having 1 to 6 carbon atoms; Z ₁ , Z ₂ : each independently, An atomic group forming a 5- or 6-membered heterocyclic ring or a condensed ring containing a 5- or 6-membered heterocyclic ring; Y ₁ : a hydrogen atom, a halogen atom, or a carbon atom number of 1
Or two alkyl groups; X: a monovalent anion; A, B: each independently containing two carbon atoms to which each is bonded, and an aromatic ring which may have the same or different substituent, or condensed Atomic group forming a ring; Q: group having active hydrogen; m: number of 1 or 2;

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the accompanying drawings.

The optical recording medium according to the present invention is not particularly limited as long as it is an optical recording medium for recording information by light, such as a tape, a card and a disk. It is particularly desirable to apply the present invention to a DVD-R, a DVD-RW, or the like, which is in the form of a disk and can record information at high density.

The optical recording medium of the present invention uses a substrate having a land / groove structure. The specific structure of the land / groove is appropriately determined according to the performance required for the optical recording medium. Therefore, in the present invention, any of optical recording media having wobbled (meandering) grooves, optical recording media having non-wobbled grooves, such as optical recording media in which the grooves draw a smooth curve along the circumferential direction, etc. Can be applied to the optical recording medium.

FIG. 1 is a view for explaining an outline of a main part of a light-transmitting substrate used for the optical recording medium of the present invention. In FIG. 1, grooves 3 and lands 2 defined by the grooves 3 are alternately formed in a circumferential direction on a light transmitting substrate 1 used for the optical recording medium of the present invention. A recording layer and a reflective layer are formed on the light-transmitting substrate 1 having the land / groove structure, and a protective layer (neither is shown) is further formed thereon as desired.

The land 2 forms a substantially rectangular cross section - trapezoidal having a top surface 4 and the side wall 5 has a height (land height) h _1.

At a substantially central portion in the width direction of the land 2, a pre-pip
(Land pre-pits) 6 are formed.
Then, the pre-pit 6 is 3T [T: (1 / channel video).
Pre-pit length (round)
Direction length, running method length; L ₁) Is formed with
It is characterized by that.

Preferably, the pre-pits 6 are formed with a boundary wall 5a between the adjacent grooves 3. Although the height of the boundary wall 5a is not particularly limited, in the present invention, the height (h ₂ ) of the boundary wall 5a is larger than the height (h ₁ ) of the land 2 by h ₂ / h ₁ >. Preferably, it is formed to be 0.80. The upper limit of h ₂ / h ₁ is 1.0, that is, the height and the height of the land 2 of the boundary wall 5a is preferable if the same.

In the above description, "T" which is the basis of the prepit length (L ₁ ) means the reciprocal of the channel bit rate. In the DVD family, the channel bit rate is usually 26.16 Mbps, and the reciprocal of this channel bit rate is 38.226 ns. This is “1T”.

The length of "T" depends on the linear velocity (reference linear velocity) at the time of recording / reproducing. For example, in the case of a DVD-R, at present, the same disc area has two lengths of 3.95 GB and 4.7 GB.
There are two capacities, different in each case.

In the case of a 3.95 GB disc, the reference linear velocity is 3.84 m / s. In this case, the length of 1T is 3.84 ×
38.226 (nm), about 0.1468 μm
m. Therefore, the length of “3T” is about 0.44 μm
Becomes

For a 4.7 GB disc, the reference linear velocity is 3.
At 49 m / s, the length of 1T is 3.49 × 3
Calculated from 8.226 (nm), about 0.13334 μm
m. Therefore, the length of “3T” is about 0.40 μm
Becomes

That is, in the present invention, specifically, 3.9
The land pre-pit length (L ₁ ) is formed with a length of about 0.44 μm or more for a 5 GB disc, and is formed with a length of about 0.40 μm or more for a 4.7 GB disc.

Conventionally, the pre-pit length is formed to record the shortest pit "2T" signal. Therefore, the conventional pre-pit length is almost the same as "2T" or slightly less. It was formed longer.

In the case where land prepits are formed at substantially the center of the land in the width direction without exceeding the land width, and both side portions of the land are left, and this is used as a boundary wall between adjacent grooves. The height (h ₂ ) of this boundary wall is the same as the land height (h ₁ ). Making the height of the boundary wall the same as the land height is ideal for recording and reproduction of groove signals, but on the other hand, the height of the boundary wall prevents high-quality reproduction of pre-pit signals, There is a problem that the quality of the obtained reproduced signal is reduced. Also, since the land pre-pit width must be formed narrow, this also causes a reduction in the quality of the land pre-pit reproduced signal.

In the present invention, the length of the land pre-pit is set to "3".
Since the length of the pre-pit is set to about 2T, the quality of the reproduced signal from the pre-pit is deteriorated due to the height of the boundary wall and the narrow pre-pit width. Resolved, even if the boundary wall of the land pre-pit is as high as the land height,
Even if the pre-pit width is narrow, a high-quality pre-pit reproduced signal can be obtained.

In the present invention, the upper limit is not particularly limited as long as the land pre-pit length (L ₁ ) is “3T” or more. The longer the pre-pit length, the easier it is to detect the pre-pit reproduced signal. However, if the pre-pit length is too long, misreading (crosstalk) with the groove recording signal is likely to occur, and a phase shift with the wobble is also expected. The upper limit is not particularly limited as long as it does not occur.

In the present invention, even if the height of the boundary wall is not the same as the height of the land and h ₂ / h ₁ exceeds 0.8, the signal of the pre-pit is stabilized. Thus, the recording and reproduction of the groove signal can be performed satisfactorily. That is, even if the land pre-pits are formed by omitting the upper portions of the lands in the manufacturing process, the effects of the present invention are not adversely affected.

In the present invention, the height of land 2 (h
₁ ) shows a height difference between the bottom surface of the groove 3 and the upper surface 4 of the land 2.

The boundary wall 5a for forming the pre-pit 6
Height (h ₂ ) of the bottom surface of the groove 3 and the boundary wall 5a
Indicates the height difference from the upper end. Normally, the bottom surface of the pre-pit 6 is formed so as to be substantially flush with the bottom surface of the groove 3. Therefore, the height (h ₂ ) of the boundary wall 5a is determined by the bottom surface of the pre-pit 6 and the upper end of the boundary wall 5a. It shows almost the same value as the height difference from

In the case of a disk having wobbles,
When the groove meanders due to the wobble, the width of the land existing therebetween changes slightly. As a result, the position of the pre-pit may vary slightly from the substantially central portion in the width direction of the land. However, even in such a case, the pre-pit length is within the above range, and both boundary walls 5a, It is preferable that both heights of 5a are within the above range.

If there is no boundary wall for forming the prepit, the groove and the prepit are connected to each other, and the signal of the prepit has an excessive effect on the quality of the signal recorded in the groove. ,
It will result in poor reproduction. The reproduction failure refers to a state in which, when the recorded signal is a video signal, a part of the video is thinned out (mosaic) or the reproduction operation itself is not smooth and stops.

Even if there is a boundary wall forming a pre-pit,
If the height of the boundary wall is too low relative to the height of the land, the effect on the recording / reproducing signal is undesirably large, as in the case described above. According to the present invention, it is possible to stably detect the address signal even when the height of the boundary wall is almost the same as the height of the land.

In an optical recording medium having a land pre-pit structure, in recording a data signal, the pre-pits of the land and the groove on one of the sides adjacent to the land operate in conjunction. For example, when recording a data signal,
The laser beam is made to follow the groove, and data is recorded in the groove while detecting address information and the like from the prepits on the adjacent one of the lands.

Therefore, when the prepit is formed so as to be deviated toward the inner or outer periphery of the land, a signal to be recorded in a groove adjacent to the deviated side is formed in the groove under the influence of the prepit. The pits become imperfect and have an excessive effect on the groove reproduction signal.

For example, the following is an example of an optical recording medium that records a groove signal while detecting a prepit signal on a land on the inner circumferential side of the groove.

That is, when a groove signal is recorded, a laser beam is spot-irradiated. When pre-pits are formed so as to be deviated from the center in the land width direction to the inner circumference side, the inner circumferential side of the groove required for recording the groove signal is formed. The pre-pit position of the land moves away from the groove by the deviation,
The pre-pit area for detection occupying the laser spot irradiation surface is reduced by that much, and pre-pit signal detection cannot be performed sufficiently.
Reading of address information during recording becomes unstable, which adversely affects the recording operation. Furthermore, since the prepits of the land adjacent to the other side (outer peripheral side) which are not necessary for signal detection are deviated at a position close to the recording groove, the non-detection area on the laser spot irradiation surface is The proportion occupied by the pre-pit area increases, the pits formed by the groove signals to be recorded are not formed properly, and the signal reproduction from the pits is not performed accurately.

On the other hand, when the prepits are formed so as to be deviated from the center in the land width direction toward the outer periphery, the prepit positions detected during signal recording of the groove (grooves on the inner circumference of the land) correspond to the deviation. And the pre-pit signal output is sufficient, but the proportion of the non-detection pre-pit area on the laser spot irradiation surface increases, and pits due to groove signals to be recorded are not formed properly, and signal reproduction from the pits Is not done correctly. However, the other side that is not necessary for signal detection (inner side)
The non-detection pre-pits do not adversely affect the recording because the pre-pits of the land adjacent to the non-detection pre-pits are formed at a position deviated from the recording groove.

In the present invention, the land prepit is formed substantially at the center of the land in the width direction, preferably with a boundary wall having substantially the same height as the land height, and the land prepit length (L ₁ ) is determined. Since it was made longer than "3T",
Groove signals can be recorded and reproduced with high quality, and reproduction signals from pre-pits can be obtained with high quality.

The production of the light-transmitting substrate on which such prepits are formed can be carried out by known means, but is preferably carried out, for example, by the following method.

For example, a photoresist layer (thickness of less than 0.1 μm) is provided on a glass disk having a thickness of about 6 mm, and a laser beam is selectively irradiated on the photoresist layer. Specifically, for example, an argon laser is dispersed in two directions while shifting the focal position through a half mirror, and one is used for forming a groove while inputting a wobble signal as a main beam through an optical modulator. On the other hand, a groove and land pre-pit pattern are simultaneously formed on the photoresist layer while inputting a pre-pit formation input signal to the land as a sub-beam.

Subsequently, after this was developed, Ag plating was performed.
A template (disk master) on which patterns of grooves and land prepits are formed is obtained.

Next, after a metal plating layer such as Ni plating is provided on the disk master, the metal plating layer is peeled off to obtain a metal mask, and a stamper (die) serving as a master is formed from the metal mask. Make it.

Next, the stamper is used to obtain a light-transmitting substrate having grooves and land prepits formed thereon by injection press molding or 2P method using a light-transmitting member such as a transparent resin. As the transparent resin, a thermoplastic resin (for example,
Polycarbonate, polyolefin, etc.) can be used, but in this case, if the resin temperature is too low, the mold temperature is too low, or the mold opening / closing pressure is too small, the moldability will deteriorate and Resin does not spread to
It should be noted that the height of the prepit boundary wall varies and it becomes difficult to obtain a desired height.

As described above, since the shape of the land prepits and the like greatly contribute to the production of a matrix called a stamper, in the production of a stamper, the beam diameter of a laser beam used when exposing and cutting a photoresist layer. It is necessary to manufacture a stamper in which a desired pre-pit pattern is formed by adjusting the light quantity and the amount of light. Further, by adjusting the optical axis, a prepit pattern can be accurately formed at a substantially central portion in the width direction of the land formed between the grooves.

In the present invention, a recording layer is formed on a light-transmitting substrate having the above-mentioned land / groove structure. However, the recording layer is not particularly limited, and may be an organic dye recording layer, a phase change layer, or the like. Any type of recording layer can be used.

When the organic dye recording layer is formed, general organic dye components conventionally used for organic dye recording layers, such as cyanine dyes, phthalocyanine dyes, and azo dyes, can be used. In this case, those containing one or more organic dyes selected from organic dyes having a maximum absorption wavelength (λ _max ) of 400 to 700 nm in a thin film are preferably used. These are dye components mainly used for recording and reproducing data on the recording layer in DVD-Rs and the like.

Since the maximum absorption functions as an optical medium, the absorption spectrum in a thin film is important.
In the present invention, the “maximum absorption wavelength (λ _max ) in a thin film” means the maximum absorption wavelength when an organic dye film is formed as a recording layer. The behavior of the maximum absorption spectrum of a thin film differs from that of a solution in which a dye is dissolved in a solvent.

The maximum absorption spectrum of a thin film can be measured, for example, as follows, but is not limited thereto. That is, a target dye is dissolved in an organic solvent at a concentration of 1 to 20% by weight, and a film is formed by spin coating on a PC flat plate having no grooves or pits so as not to have a specific orientation so as to have a specific orientation. Thick and 50
Dry at ~ 70 ° C to form a film. The organic solvent can dissolve the dye, and has a boiling point in the air of 50 to 1
It is preferred to choose one that is 50 ° C. If the dye is remarkably crystallized or associates when the solvent is volatilized during spin coating, another solvent is selected. After film formation, it is common to measure a transmission absorption spectrum of a PC flat plate with a dye thin film prepared by a spectrophotometer.

In the present invention, as such an organic dye component, in particular, a trimethinecyanine dye represented by the following general formula (I) and a chelate compound of the dye represented by the following general formula (II) and a metal (metal-containing compound) Or two or more selected from azo dyes).

[0056]

[0057]

In the general formulas (I) and (II), each symbol has the following meaning.

R ₁ and R ₂ each independently represent a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, preferably 1 to 5 carbon atoms, and a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, preferably 1 to 6 carbon atoms. 5 to 5 alkenyl groups. As the substituted alkyl group, an alkoxyalkyl group is preferable. In the present invention,
R ₁ and R _{2 each have} 1 to 5 carbon atoms of a straight or branched chain;
Of these, an alkyl group and an alkoxyalkyl group are particularly preferred.

Z ₁ and Z ₂ are each independently an atomic group forming a 5- or 6-membered heterocyclic ring or a condensed ring containing a 5- or 6-membered heterocyclic ring. As Z ₁ and Z ₂ , specifically, an indolenine ring represented by the following formula (V), an α-naphthoindolenine ring represented by the following formula (VI), and a compound represented by the following formula (VI)
Β-naphthoindolenine ring shown in I), the following formula (VIII)
A benzothiazole ring represented by the following formula (IX), a β-naphthothiazole ring represented by the following formula (X), a benzoselenazole ring represented by the following formula (XI), and the like. These include a halogen atom, an alkyl group having 1 to 4 carbon atoms (—R) or an alkoxyalkyl group (—OR), a nitro group (NO ₂ ), a sulfonyl group (SO ₃
H), a phenyl group (C ₆ H ₅ ) and the like may be substituted. Further, a benzene ring substituted with a dialkylamino group (wherein R independently represents an alkyl group having 1 to 3 carbon atoms) represented by the following formula (XII) is also preferably exemplified.

[0061]

[0062]

[0063]

[0064]

[0065]

[0066]

[0067]

[0068]

Y ₁ represents a hydrogen atom, a halogen atom, or an alkyl group having 1 or 2 carbon atoms. In the present invention, a hydrogen atom is preferred.

X represents a monovalent anion. Specifically, P
F ₆ ⁻ , ClO ₄ ⁻ , BF ₄ ⁻ , I ^{− and the} like.

A and B each independently represent an atomic group containing two carbon atoms bonded to each other to form an aromatic ring or a condensed ring which may have the same or different substituents.

As at least one of A and B, a nitro or dinitrobenzene ring represented by the following formulas (XIII-1) to (XIII-4) is preferable.

[0073]

As the other group of A and B, a dialkylaminobenzene ring represented by the following formula (XIV)
Each independently represents an alkyl group having 1 to 4 carbon atoms), a diphenylamine ring represented by the following formula (XV), a morpholinobenzene ring represented by the following formula (XVI), a formula (XVII)
And the like are preferred.

[0075]

[0076]

[0077]

[0078]

Q is a group having active hydrogen, specifically O
H, COOH, NH _{2 and the} like are preferred.

M represents a number of 1 or 2. In the present invention, 2
Is preferred.

As a specific example of the trimethine cyanine dye represented by the general formula (I), a compound represented by the following formula (XVIII) is exemplified as a preferable example.

[0082]

In the chelate compound of the dye represented by the general formula (II) and a metal (metal-containing azo dye), the metal is preferably a monovalent or divalent metal. Specifically, Co, Ni, V , Cu, Zn and the like. This chelate compound (metal-containing azo dye) may have a negative charge as a whole depending on the metal used. In such a case, an alkali metal such as Na ⁺ ,
It is preferable to form a salt with a positively charged dye such as a rhodamine dye, a triphenylmethane dye, and a trimethine cyanine dye from the viewpoint of the electrical characteristics and light resistance of the disk. Specific examples of the chelate compound of the dye represented by the general formula (II) and a metal (metal-containing azo dye) include, for example, a compound represented by the following formula (XIX) as a preferable example.

[0084]

The organic dye component is dissolved in a solvent, applied to a light-transmitting substrate by spin coating or the like, and dried to form an organic dye layer having a desired thickness. The method of forming the dye layer is not limited to the spin coating method, and a spray coating method, a screen printing method, a dipping method, and a vapor deposition method can also be applied.
Selected.

When the spin coating method is applied, the dye component is dissolved in a solvent and used as an organic dye solution. The solvent is one that can sufficiently dissolve the dye and does not adversely affect the permeable substrate. Select and use. The concentration is preferably about 0.01 to 10% by weight.

Examples of the solvent include alcohols such as methanol, ethanol, isopropyl alcohol, octafluoropentanol, allyl alcohol, methyl cellosolve, ethyl cellosolve, and tetrafluoropropanol; hexane, heptane, octane, decane, cyclohexane, methylcyclohexane, and the like. Aliphatic or alicyclic hydrocarbon solvents such as ethylcyclohexane and dimethylcyclohexane; aromatic hydrocarbon solvents such as toluene, xylene and benzene; halogenated hydrocarbon solvents such as carbon tetrachloride, chloroform, tetrachloroethane and dibromoethane Solvents; ether solvents such as diethyl ether, dibutyl ether, diisopropyl ether and dioxane; 3
Ketone solvents such as -hydroxy-3-methyl-2-butanone; ester solvents such as ethyl acetate and methyl lactate; water; and among them, those that do not attack the substrate material can be used. These may be used alone or as a mixture of two or more.

The thickness of the organic dye layer is not particularly limited, but is preferably about 10 to 300 nm, and particularly preferably 60 to 300 nm.
About 250 nm.

A reflective layer is provided on the organic dye layer. As a material of the reflection layer, a material having a sufficiently high reflectance at the wavelength of the reproduction light, for example, Au, Ag, Cu, Al, Ni, Pd, C
Elements such as r and Pt are used alone or as an alloy. In addition to the above, the following may be included. For example, M
g, Se, Hf, V, Nb, Ru, W, Mn, Re, F
e, Co, Rh, Ir, Zn, Cd, Ga, In, S
Metals such as i, Ge, Te, Pb, Po, Sn, and Bi and metalloids can be exemplified.

The formation of the reflective layer includes, for example, a sputtering method, an ion plating method, a chemical vapor deposition method, and a vacuum vapor deposition method, but is not limited to these examples. Further, a known inorganic or organic intermediate layer or adhesive layer may be provided on the substrate or below the reflective layer to improve the reflectance and the recording characteristics. The thickness of the reflective layer is not particularly limited, but is preferably about 10 to 300 nm, and particularly preferably 8 to 300 nm.
It is about 0 to 200 nm.

A protective layer is usually provided on the reflective layer. Alternatively, two media may be attached. The material of the protective layer is not particularly limited as long as it protects the reflective layer from external force, such as an organic substance and an inorganic substance. Examples of the organic substance include a thermoplastic resin, a thermosetting resin, and a UV curable resin. Examples of the inorganic substance include SiO ₂ , SiN ₄ , MgF ₂ , and SnO ₂ . A thermoplastic resin, a thermosetting resin, or the like can be formed by dissolving in a suitable solvent, applying a coating solution, and drying. The UV-curable resin can be formed by preparing a coating solution as it is or by dissolving it in an appropriate solvent, applying the coating solution, and irradiating with UV light to cure the resin. As the UV-curable resin, for example, acrylate resins such as urethane acrylate, epoxy acrylate, and polyester acrylate can be used. These materials may be used alone or as a mixture, or may be used as a multilayer film as well as a single layer.

As a method for forming the protective layer, a coating method such as a spin coating method and a casting method, a method such as a sputtering method and a chemical vapor deposition method are used as in the recording layer.

This protective layer is sometimes applied to the light incident surface side of the light transmitting substrate for the purpose of enhancing the scratch resistance and the moisture resistance.

When a phase-change recording layer is formed as a recording layer, this may be a known phase-change recording material, for example, Ag.
-In-Sb-Te-based or Ge-Te-Sb-based recording materials may be used. A dielectric layer is formed on a light-transmitting substrate, and a barrier layer, a recording layer (phase change recording layer), It has a multilayer structure such as a body layer and a reflective layer. An organic protective layer made of an ultraviolet curable acrylic resin is formed thereon.

Next, if necessary, the two disks or one disk thus obtained and another disk having a layer structure different from that of the disk are bonded together with the light incident surface outside. As the adhesive used for bonding, a hot melt adhesive, an ultraviolet curable adhesive, a heat curable adhesive, an adhesive adhesive, and the like are used, and a method suitable for each, for example, a roll coater method or a screen printing method is used. , Spin coating, etc.
In the case of R, a screen printing method or a spin coating method is used by using an ultraviolet-curing adhesive, which is comprehensively determined from workability, productivity, disk characteristics, and the like.

The recording on the optical information recording medium thus obtained is performed, for example, as follows.

First, recording light such as a semiconductor laser beam is irradiated from the substrate side while rotating the optical recording medium at a constant linear velocity or a constant angular velocity. By this light irradiation,
The light reflection of the recording layer changes.

As the recording light, a semiconductor laser beam having a wavelength in the range of 400 to 660 nm is used. Reproduction of the information recorded as described above can be performed by irradiating the semiconductor laser beam from the substrate side while rotating the optical information recording medium in the same manner as described above, and detecting the difference in the amount of reflected light.

In the present invention, the prepits having the boundary walls are formed at a length of 3T or more at the approximate center of the land in the width direction, so that the prepit signals can be detected stably and the high-density recording can be performed. Even in the case of (1), a reproduction error does not occur in the reproduction of the data signal, and a good reproduction signal can be obtained.

[0100]

Next, the present invention will be described in more detail with reference to examples, but the scope of the present invention is not limited by these examples.

The light-transmitting substrates used in each of the following Examples and Comparative Examples were manufactured by a known method. That is, the pre-pits were cut on the lands by the sub-beams using an argon laser in conjunction with the groove cutting of the main beam. The amount of exposure was changed by changing the power of the sub-beam, and prepits were formed with the boundary wall height on both sides of the land left. Also, the length of the pre-pit was changed by adjusting the length of the exposure time.

[LPP signal characteristics] DVD Specifications f
or Recordable Disc (DVD-R) Part 1 PHYSICAL SPECIFI
According to CATIONS, DVR-S101 (Pioneer Corporation)
Ltd.) was measured was used to evaluate the LPP _b error.
LPP _b can be detected accurately decode the LLP signal smaller the value of the error, it is possible to perform normal recording operation which gave the correct control information of the absolute address or the like. On the other hand, LPP _b error values larger the L
Since the Lp signal cannot be detected properly, it is difficult to perform a normal recording operation. (Evaluation) Good: LPP _b error less than 3% poor: LPP _b error not less than 3% 5%: LPP _b error of 5% or more

[PI Error] As a method of evaluating how much the signal of the recorded disk is affected by the pre-pits, evaluation of the PI error was performed.

Regarding the PI error, the EFM + signal (8-16 signal) was optimized for each obtained optical recording medium at a linear velocity of 3.5 m / sec using DDU-1000 (manufactured by Pulstec Industrial Co., Ltd.). Recording laser power (Po)
Was recorded and evaluated. The evaluation was based on the average of five measurements. The PI error decoder is M-5298E.
(Manufactured by Kenwood Corporation) was used.

(Example 1) A tracking groove (groove) meandering periodically, and a pre-pit is provided on a land defined by the formation of the groove, having a diameter of 120 mm and a thickness of 0.1 mm.
6 mm polycarbonate was used as the light transmissive substrate. The land pre-pit is formed to have a length of 3T,
It was manufactured so that the boundary wall height (h ₂ ) on both sides was the same as the land height (h ₁ ).

The recording layer was prepared by mixing the trimethine cyanine dye represented by the above formula (XVIII) and the metal-containing azo dye represented by the above formula (XIX) in a ratio of 4: 6, and dissolving the mixture in tetrafluoropropanol. A 4% coating solution was applied on the light transmitting substrate by spin coating so that the film thickness after drying was 70 nm.

Next, an Ag layer (average thickness: 190 nm) was formed as a light reflecting layer on the organic dye recording layer by a DC magnetron sputtering method using a sputtering apparatus. The sputtering apparatus is a CD-Coat 1200
(Manufactured by Shibaura Co., Ltd.).

Subsequently, an ultraviolet curing agent SD-318 (manufactured by Dainippon Ink and Chemicals, Inc.) is applied on the light reflecting layer to a thickness of 6 μm by a spin coating method, and irradiated with ultraviolet rays by an ultraviolet irradiation device. And cured to form a protective layer.

Two discs each comprising the above-mentioned light-transmitting substrate, organic dye recording layer, light reflecting layer and protective layer were prepared, and a UV-curable resin SK7000 (manufactured by Sony Chemical Corporation) was screened on each protective layer. By applying by a printing method and irradiating ultraviolet rays, the discs having a thickness of 0.6 mm were bonded so that the protective layers of the discs face each other to produce an optical recording medium.

(Embodiment 2) The length of the land pre-pit is 4
An optical recording medium was produced in the same manner as in Example 1 except that T was used.

(Embodiment 3) The length of the land prepit is 6
An optical recording medium was produced in the same manner as in Example 1 except that T was used.

(Comparative Example 1) The length of the land prepit was 2
An optical recording medium was produced in the same manner as in Example 1 except that T was used.

(Comparative Example 2) The length of the land prepit was 1
An optical recording medium was produced in the same manner as in Example 1 except that T was used.

For each of the optical recording media obtained in Examples 1 to 3 and Comparative Examples 1 and 2, LPP signal characteristics and PI error were evaluated by the above evaluation methods. Table 1 shows the results.

[0115]

[Table 1]

[0116]

As described above in detail, according to the present invention, address information and disk rotation control information can be accurately obtained even at a narrow track pitch, and signals can be recorded at a high density. An optical recording medium with good reproduction signal quality could be provided.

[Brief description of the drawings]

FIG. 1 is a view for explaining an outline of a main part of a light transmitting substrate used for an optical recording medium of the present invention.

[Explanation of symbols]

Reference Signs List 1 light-transmitting substrate 2 land 3 groove 4 land upper surface 5 land side wall 5a boundary wall (pre-pit boundary wall) 6 pre-pit L ₁ pre-pit length h ₁ land height h ₂ boundary wall height

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C09B 23/00 C09B 45/14 A 45/14 45/20 45/20 B41M 5/26 Y

Claims (4)

[Claims] 1. An optical recording medium comprising a recording layer provided on a light-transmitting substrate having grooves and lands on which pre-pits are formed, wherein the pre-pits are located substantially at the center of the lands in the width direction. 3T
[T: (1 / channel bit rate) x reference linear velocity]
An optical recording medium formed with the above prepit length. 2. The pre-pit is formed to have a boundary wall between adjacent grooves, and the height of the boundary wall (h ₂ ) is h ₂ / h with respect to the land height (h ₁ ). h ₁ > 0.8
The optical recording medium according to claim 1, wherein 0. 3. The light according to claim 1, wherein the recording layer contains one or more organic dyes selected from organic dyes having a maximum absorption wavelength (λ _max ) of 400 to 700 nm in a thin film. recoding media. 4. The method according to claim 1, wherein the organic dye is a trimethinecyanine dye represented by the following general formula (I):
4. The optical recording medium according to claim 3, wherein the optical recording medium is at least one selected from chelate compounds (metal-containing azo dyes) of a dye and a metal represented by I). In the general formulas (I) and (II), each symbol has the following meaning. R ₁ and R ₂ : each independently a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted alkenyl group having 1 to 6 carbon atoms; Z ₁ , Z ₂ : each independently An atomic group forming a 5- or 6-membered heterocyclic ring, or a condensed ring containing a 5- or 6-membered heterocyclic ring; Y ₁ : a hydrogen atom, a halogen atom, or a carbon atom number of 1
Or two alkyl groups; X: a monovalent anion; A, B: each independently containing two carbon atoms to which each is bonded, and an aromatic ring which may have the same or different substituent, or condensed Atomic group forming a ring; Q: group having active hydrogen; m: number of 1 or 2;