JP3177291B2 - Optical recording medium - Google Patents

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, and more particularly to a single-plate type medium in which a film containing a dye is used as a recording layer and a metal reflective layer is provided on the recording layer. The present invention also relates to an optical recording medium compatible with a commercially available compact disc player.

[0002]

2. Description of the Related Art A recordable optical recording medium in which a film containing a dye such as phthalocyanine is used as a recording layer and a metal reflective layer is provided on the recording layer in order to increase the reflectivity is disclosed in US Pat.
298975. However, the patent does not disclose any compatibility with commercially available compact disc (hereinafter abbreviated as CD) players. Further, it does not disclose conditions for providing a medium having an excellent jitter value and error rate when a pit length is recorded.

Recently, a single-plate type optical recording medium having high reflectivity and being compatible with a commercially available CD player is, for example, Optical Dat.
a Storage 1989 Technical Digest Series Vol.1 45 (1
989), EP-353393, etc., which disclose, in particular, the dyes used in the recording layer for achieving high reflectance and the characteristics of the reflective layer. Further, US-4990388 discloses a recording mechanism of a recording layer of an optical recording medium compatible with a CD player.

In such an optical recording medium, it is necessary to obtain from the medium a tracking error signal for controlling a track during recording and reproduction and a radial contrast signal for accessing a target track. You. When the recording layer is formed by a vacuum technique such as sputtering, the recording film is formed so as to closely follow the shape of the groove of the substrate, so that the tracking error signal and the radial contrast signal are optimized by, for example, Optronics. Published, monthly Optronics omnibus, easy-to-understand optical disk,
Simulations can be performed as disclosed on page 150, etc., and optimization of groove shapes and the like can be performed relatively easily.

However, in an optical recording medium in which a layer formed by applying a dye by a coating method is used as a recording film, since the surface shape of the recording film does not follow the groove shape of the substrate, it is difficult to estimate from the above-described simulation. There is no description in the above-mentioned prior patents and literatures.

The only preferable relationship between the tracking error signal and the groove shape of the substrate is described in, for example,
22224. However, the proposal of this patent alone is not sufficient for full compatibility with a commercially available CD player, and there is no problem for a commercially available CD player having a 3-beam head, but a 1-beam head For players equipped with, we have found that there is a compatibility problem, for unknown reasons. Further, the radial contrast signal has not yet been optimized, and the access speed is reduced without using the radial contrast signal when accessing. For example, an external sensor or the like is used.

According to our studies, optimization of the groove shape alone is not sufficient for compatibility with CD players and radial contrast signals. In a recordable optical recording medium in which a metallic reflective layer is provided on a recording layer containing a dye by a coating method, reflection at the interface between the recording layer and the reflective layer is dominant, and thus the recording layer The shape of the surface and the thickness of the recording layer on the grooves and lands are important. The surface shape of these recording layers and the film thickness of the recording layer on the grooves and lands may have the same coating characteristics as the substrate, even if the groove shape is the same, for example, the concentration of the coating solution, interfacial tension, viscosity, and coating solvent. Depends on the boiling point, evaporation rate, rotation method in the case of spin coating, and the like. Therefore, strict optimization has not been performed so far.

EP-0410183 discloses a difference in optical path length between a groove portion and a land portion recording layer and a modulation degree of a recording signal. However, this patent does not disclose compatibility issues with CD players or radial contrast signals.

On the other hand, when information is recorded on an optical recording medium,
Recording methods are roughly classified into two methods, that is, pit-to-pit recording and pit length recording. In the case of a CD, pit lengths are recorded by pits having nine types of lengths. In pit length recording, pits of each length and variations in length between pits of each length (hereinafter referred to as jitter values) are recorded as small as possible.
Also, it is very important to play back to reduce the error rate. At present, various types of CD players are commercially available, and the reproduction signal characteristics vary depending on the type of the player, and accordingly, the error rate also varies. Therefore,
It is required that the error rate be sufficiently small even if the data is reproduced on as many types of commercially available CD players as possible. However, the conventional write-once optical recording medium as described above, which is said to be playable on a commercial CD player, does not necessarily have a small jitter value of pits and the length between pits, and some CD players do not. We have found that even if the error rate is not sufficiently low and recording audio information or the like does not cause a significant problem, recording code data or the like has a problem.

[0010] Furthermore, such optical recording media are required to have durability, but the durability of conventional media is not always sufficient. For example, when left undisturbed under the conditions of 85 ° C. and 95% RH for a long time, the characteristics of the unrecorded portion hardly change, but the error rate of the recorded portion is greatly deteriorated. We have found that when a region where the error rate is deteriorated is observed with a microscope, a pit having a defect of several microns around the pit is observed.

[0011]

The present inventors have made various studies to improve the drawbacks of the conventional recordable optical recording medium compatible with the CD player as described above. As a result of various studies on the surface shape of the recording layer to be contained and the thickness of the recording layer in the groove and land portions, a sufficient radial contrast signal can be ensured, and compatibility with various commercially available CD players and jitter values and errors are obtained. The present inventors have found that the rate is small, and that the characteristics such as the error rate do not change even after being left for a long time under high temperature and high humidity conditions, and completed the present invention.

[0012]

That is, the present invention provides a recording layer, a reflective layer, and a protective layer containing a dye on a transparent resin substrate having a groove having a depth of 900 to 1800 mm and a width of 0.3 to 0.6 μm. A single-plate optical recording medium recordable at a wavelength of 780 nm , wherein the dye is Pd-tetra
-(T-butylcyclohexyloxy) phthalocyanine
Pd-tetra- (2,4-dimethyl-pen)
No brominated dye of tan-3-oxy) phthalocyanine
And at or Re, 800 the film thickness of the recording layer of the groove portion 1250
Å The recording layer is formed by a coating method such that the film thickness of the recording layer in the land is 500 to 1100Å and the surface of the recording layer in the land is 500 to 1200Å higher than the surface of the recording layer in the groove. optical recording medium, characterized in that it is, and the pit length recording on the groove of the medium is an optical recording medium which records information.

FIG. 1 shows a cross section of a recording layer of an optical recording medium of the present invention in which a recording layer is coated on a substrate having a groove. In the present invention, the groove portion indicates a guide groove (3 in FIG. 1). ,
Information is recorded on this groove. The land portion indicates a groove portion and a portion (4 in FIG. 1) sandwiched between the groove portions. In addition, 1 represents a substrate, 2 represents a recording layer, and 5 represents a difference (ΔT) in height between a land portion and a groove portion on the recording layer surface.

As the transparent resin substrate used in the present invention, a transparent resin substrate that transmits light for recording and reading out signals is preferable. It is desirable that the light transmittance is 85% or more and the optical anisotropy is small. For example, a substrate using a thermoplastic resin such as an acrylic resin, a polycarbonate resin, a polyamide resin, a vinyl chloride resin, or a polyolefin resin is a preferred example. Among these, acrylic resin, polycarbonate-based resin, and polyolefin-based resin substrates are preferable from the viewpoint of mechanical strength of the substrate, ease of providing a groove or a read-only signal, and economical efficiency, and particularly, a polycarbonate-based resin substrate. Is more preferred. These are formed on the substrate by injection molding or casting. The shape of these substrates may be plate-like or film-like, circular or card-like. The surfaces of these substrates have grooves for controlling the recording position. Also, a pit or the like for information or the like dedicated to part of reproduction may be provided. Such grooves, pits and the like are preferably provided when a substrate is formed by injection molding or casting, but can also be provided by applying an ultraviolet curable resin onto the substrate, superimposing the resin on a stamper, and performing ultraviolet exposure.

In the optical recording medium of the present invention, a recording layer containing a dye, a reflective layer, and a protective layer are sequentially laminated on the transparent resin substrate. The dye used is a polymethine dye, a phthalocyanine dye, a naphthalocyanine dye, a naphthoquinone dye,
Dyes having absorption in the oscillation wavelength range of a semiconductor laser, such as azulene dyes and dithiol metal complex dyes, may be mentioned. These dyes may be substituted with various substituents for controlling the solubility in a solvent within a desired range or for recording characteristics. These dyes can be used alone or in combination of two or more. Of these dyes, phthalocyanine dyes and naphthalocyanine dyes are preferable in consideration of light resistance and durability.

In the present invention, the recording layer containing the dye described above can be generally formed by a coating method such as spin coating, spraying, or immersion. When forming a film of the above dye by a coating method, a solvent that does not damage the injection molded substrate, for example, hexane, heptane, octane, decane, cyclohexane, aliphatic or alicyclic hydrocarbons such as methylcyclohexane, diethyl ether, diether Butyl ether,
A dye may be dissolved in a nonpolar solvent such as ether such as diisopropyl ether or the like, or a polar solvent such as alcohol such as methyl alcohol, ethyl alcohol, isopropyl alcohol, allyl alcohol and methyl cellosolve, and applied.

In the present invention, it is important to control the groove shape of the substrate, the thickness of the recording layer in the groove and land portions of the recording layer, and the shape of the surface of the recording layer.

That is, a radial contrast signal that satisfies the standard in both the unrecorded portion and the recorded portion is obtained, and various commercial C signals are obtained.
In order to ensure compatibility with the D player and obtain an excellent jitter value and error rate, the shape of the groove on the substrate should be 900-1800 mm in depth, 0.3-0.6 μm in width, and the groove and land Part of the recording layer
It is preferably 0 to 1250 ° and 500 to 1100 °. Further, it is more preferable that the film is formed so that the surface of the recording layer in the land portion is 500 mm or more higher than the surface of the recording layer in the groove portion.

When the thickness of the groove recording layer is less than 800 ° or when the thickness of the land recording layer is less than 500, the radial contrast signal is small and the jitter value is not so problematic, but the error rate is low. It is not preferable because it becomes large. The reason why the error rate increases despite the small jitter value is presumed to be due to the considerable difference in the length of the 11T pits and the length between the 11T pits, which should be equal.

On the other hand, if the difference between the height of the land and the groove on the surface of the recording layer is less than 500 °, the radial contrast signal becomes small, which is not preferable. If the thickness of the recording layer in the groove portion exceeds 1250 °, it is not preferable because the error rate is greatly increased when the recording layer is left under a high temperature and high humidity condition for a long time. If the thickness of the recording layer in the land portion exceeds 1100 °, the jitter value and error rate deteriorate, which is not preferable.

On the other hand, the upper limit of the difference between the height of the land and the groove on the surface of the recording layer is preferably 1200 ° or less. If it exceeds 1200 mm, the tracking error signal becomes too large,
In some cases, it is difficult to secure the reflectivity of the groove of 60% or more, and compatibility with a commercially available CD player cannot be obtained. If the groove width exceeds 0.6 μm, the pit jitter value and the pit jitter value increase,
In addition, compatibility with a commercially available CD player is difficult to obtain, and compatibility with a CD player equipped with a three-beam head is secured, but compatibility with a CD player equipped with a one-beam head is difficult to secure.

Also, when the groove depth is less than 900 mm, compatibility with a commercially available CD player is difficult to obtain, and compatibility with a CD player equipped with a three-beam head is ensured, but one-beam head is required. It is difficult to ensure compatibility with the installed CD player. C with one beam head
When the data is reproduced by the D player, it is not preferable because the data can be reproduced continuously and continuously from the beginning, but access is not possible or access takes time. When the depth of the groove exceeds 1800 °, the radial contrast signal increases, but the reflectivity of the groove becomes 60% or less, and compatibility with a CD player cannot be obtained. The depth of the groove is 900 mm or more, and the width of the groove is 0.1 mm.
Substrates less than 3 μm are practically difficult to make and impractical. Make the land on the surface of the recording layer 500 more than the groove
In order to form a film having a height of Å or more, it can be controlled depending on the groove depth of the substrate, the type of solvent used for coating, the method of coating, and the like. For example, if the groove is made deeper, ΔT becomes large, and empirically, if the evaporation rate of the solvent that dissolves the dye etc. is made slow, ΔT becomes the same.
And the opposite result can be obtained by increasing the evaporation rate.

In the present invention, the shape of the groove of the substrate and the shape of the land and groove on the surface of the recording layer can be measured by scanning tunneling microscope or microscopic observation of the cross section of the substrate or the recording layer. The thickness of the recording layer in the groove portion and the land portion of the recording layer can be measured by microscopic observation of the cross section of the recording layer. In the present invention, the width of the groove means a half width, that is, a width at a position where the depth of the groove is half. On the other hand, the radial contrast signal means that the light beam of the player is focused on the recording layer (focus control). ), A value obtained by dividing a variation value of the reflectance when the light beam crosses the track by an average value of the reflectance, that is, RC (radial contrast signal) = 2 (Imax-Imin) / (Imax +)
(Where Imax and Imin represent the maximum and minimum values of reflectivity when the beam traverses the track, respectively). According to the standard, this value is usually 0.05 or more in an unrecorded portion, Some parts require 0.2 or more.

When a recording layer containing a dye is formed, a resin such as nitrocellulose, ethyl cellulose, an acrylic resin, a polystyrene resin, a urethane resin, a leveling agent, an antifoaming agent, etc. may be used in addition to the dye of the present invention. As long as the effect of (1) is not impaired, for example, they can be used together in an amount of at least 20% or less, preferably 10% or less.

In the present invention, the reflective layer provided on the recording layer is usually preferably a metal thin film. In order to make the medium of the present invention compatible with a normal CD player, the medium preferably has a reflectance of 60% or more. Preferred metals include aluminum, gold, silver, copper, platinum, nickel and the like, and alloys containing these metals as one component. The reflective layer of these metals can be formed by a method such as vapor deposition or sputtering. The thickness of these reflective layers is usually 500 to
It is preferably about 2000 °.

Further, a protective layer is further provided on the reflective layer in order to protect these metallic reflective films. A resin is usually used as the protective film. Particularly, an ultraviolet curable resin is preferable from the viewpoint of productivity and the like. The thickness of the protective layer is 1 to 15 μm
The degree is preferred.

The optical recording medium of the present invention irradiates a laser beam through a substrate to record and read out a signal. A semiconductor laser having an oscillation wavelength of usually 640 to 850 nm is preferably used. When recording, the laser output on the recording film was adjusted to 5 to 12 while rotating the medium.
The reading should be about mW, and when reading out, the output of the laser should be about 1/10 of the recording. The optical recording medium of the present invention can be printed on the protective layer.

[0028]

EXAMPLES The present invention will be described below in more detail with reference to examples, but embodiments of the present invention are not limited thereto. The phthalocyanine dye used in Example 1 was prepared by a conventional method using 3- (t-butylcyclohexyloxy) -1,2-dicyanobenzene and PdCl ₂ (for example, EP-23
2,427), Pd-tetra- (t-butylcyclohexyloxy) phthalocyanine was synthesized. Then this Pd
By reacting 1 mol of tetra- (t-butylcyclohexyloxy) phthalocyanine with 3.3 mol of Br _{2 in a} methylene chloride solvent, Pd-tetra- (t
-Butylcyclohexyloxy) phthalocyanine dye having an average of 3.0 bromine bonds per molecule of phthalocyanine was obtained. The dyes of Example 2 and thereafter were synthesized according to this method.

Example 1 Pd-tetra is formed at the center of the grooved surface of an injection-molded polycarbonate resin substrate having a spiral groove (depth: 1400 mm, width: 0.5 μm, pitch: 1.6 μm) having a thickness of 1.2 mm and a diameter of 120 mm. -(t-butylcyclohexyloxy)
After dropping a 3.1% by weight methylcyclohexane solution of a phthalocyanine bromide (3.0 on average / molecule) dye, the resin substrate was rotated at a speed of 1000 rpm for 10 seconds. Next, this resin substrate is dried in an atmosphere of 40 ° C. for 10 minutes,
A recording layer consisting essentially of a phthalocyanine dye was formed on a resin substrate. When the film thickness and surface shape of this recording layer were measured by electron microscopic observation of the cross section, the film thicknesses of the recording layer in the groove portion and the land portion were 1100 mm and 700 mm, respectively.
ラ ン ド Also, the surface of the recording layer has a land part 1000 よ り
It was high (ΔT = 1000 °). An 80 nm thick gold thin film was formed as a reflective layer on the recording layer by sputtering, and a 5 μm ultraviolet curable resin layer was further formed on the reflective layer to prepare a medium.

This optical recording medium is put on a turntable,
While rotating at a linear velocity of 1.4 m / s, using a drive having an optical head equipped with a semiconductor laser having an oscillation wavelength of 780 nm, the laser beam was controlled to focus on the recording layer on the guide groove through the resin substrate. While the laser output of 1 mW on the recording surface, the reflectance on the groove of the unrecorded portion and the radial contrast signal were obtained. The results are shown in Table 1.

Next, the laser output was set to 7 mW, which is the optimum recording condition for this medium, and the same E as that used for CD was used.
After recording the music by the FM modulation signal, the laser output is set to 1 mW and the radial contrast signal of the recording section is set to 3T.
The pit jitter value, the jitter value between 3T pits and the error rate were determined. The results are summarized in Table 1. Furthermore, in order to check compatibility with commercial CD players, the following CD
Played on the player. The reproduction results are summarized in Table 2. NO Maker Model Head type A Sony CDP-C900 3 beam B Marantz CD-50 3 beam C Marantz CD-99SE 1 beam D Yamaha CDX-1050 3 beam E Matsushita Electric Industrial SL-PA10 1 beam F Matsushita Electric Industrial SL- P550 one beam Next, in order to examine the durability of the medium, the medium was left under the conditions of 85 ° C. and 95% RH for 1000 hours, and then the jitter value and the error rate were examined. The results are summarized in Table 2.

Examples 2 to 4 and Comparative Examples 1 to 5 Using a substrate having a groove having the shape shown below, a dye solution of the same dye as in Example 1 having the following solvent and concentration was shown below. A medium was prepared and evaluated in the same manner as in Example 1 at the number of rotations. However, the recording laser power was recorded at the optimum power of each medium. The results are summarized in Tables 1 and 2. Example Groove Shape Solvent Type Concentration Rotational Depth (A) Width (μm) (% by Weight) (rpm) 2 950 0.35 Methylcyclohexane 2.8 1000 3 1400 0.50 Dibutyl Ether 3.1 700 4 950 0.35 Octane 3.1 700 Comparative Example 1 950 0.35 Methylcyclohexane 3.5 700 2950 0.35 Methylcyclohexane 3.0 1100 3 800 0.35 Methylcyclohexane 3.1 1100 4 1900 0.58 Ethylcyclohexane 2.1 1000 5950 0.70 Methylcyclohexane 3.1 1000

Examples 5 to 6 Using a substrate having grooves of the following shapes,
A solution of a brominated dye of d-tetra- (t-butylcyclohexyloxy) phthalocyanine (average 3.5 / molecule) at the following solvent and concentration was the same as in Example 1 at the rotation speed shown below. In this way, a medium was prepared and evaluated. However, the recording laser power was recorded at the optimum power of each medium. The results are summarized in Tables 1 and 2. Example Groove shape Solvent type Concentration Rotational depth (A) Width (μm) (% by weight) (rpm) 5 1600 0.5 Dibutyl ether 4.0 700 6 1600 0.5 Ethylcyclohexane 4.0 700

Examples 7 to 8 and Comparative Examples 6 to 8 Using a substrate having grooves having the following shapes,
D-tetra- (2,4-dimethyl-pentan-3-oxy) phthalocyanine bromo (average 3.5 / molecule) bromo-modified dye solution having the following solvent and concentration and the number of rotations shown below A medium was prepared and evaluated in the same manner as in Example 1. However, the recording laser power was recorded at the optimum power of each medium. The results are summarized in Tables 1 and 2. Example Groove Shape Solvent Type Concentration Rotational Depth (A) Width (μm) (% by Weight) (rpm) 7 1250 0.45 Dimethylcyclohexane 3.1 1000 8 1250 0.45 Dimethylcyclohexane 3.5 700 Comparative Example 6 950 0.35 Dibutyl ether 3.1 700 7 950 0.35 Methylcyclohexane 4.0 700 8 1250 0.45 Octane 3.0 700

[0035]

[Table 1]

[0036]

[Table 2]

As is clear from Tables 1 and 2, all of the embodiments of the present invention have a high reflectance, and the jitter value and the erase rate are sufficiently small. The radial contrast is large in both the unrecorded area and the recorded area. Furthermore, it has excellent compatibility with commercial CD players. Further, it has an excellent characteristic that the jitter value and the error rate hardly change even when left under high temperature and high humidity conditions. Hereinafter, the following is clear when the comparative examples are summarized. First, in Comparative Examples 1 and 7, since the thickness of the groove portion of the recording layer was large, the error rate was significantly increased by the durability test. Also,
When the medium subjected to these durability tests was observed with a microscope, it was confirmed that a defect of about 2 μm was generated around the pit.

In Comparative Example 2, the error rate and radial contrast were very poor because the thickness of the groove portion of the recording layer was small. In Comparative Example 3, since the depth of the groove portion of the recording layer is small, the playability after recording is poor. In Comparative Example 4, since the depth of the groove was too deep, the reflectance was lowered, and many players could not reproduce the groove. In Comparative Example 5, since the groove width was too wide, both the jitter value and the error rate were poor, and the compatibility with commercially available CD players was poor. In Comparative Example 6, the radial contrast was poor because the difference (ΔT) between the height of the land and the groove on the surface of the recording layer was small. In Comparative Example 7, since the thickness of the recording layer in the land portion was too large, the jitter value and the error rate were very poor. In Comparative Example 8, the error rate and radial contrast were poor because the thickness of the recording layer in the land portion was too thin.

[0039]

As is apparent from the examples, in the present invention, in a single-plate optical recording medium comprising a dye-containing recording layer and a metal reflection layer, the thickness of the recording layer in the groove portion By controlling the film thickness of the recording layer in the land portion and the surface shape of the recording layer, the radial contrast signal can be optimized, and the jitter and error rate can be sufficiently reduced. In addition, it is understood that compatibility and durability with various commercially available CD players are excellent. It can be seen that the radial contrast signal is not simply determined by the shape of the groove on the substrate, but also depends on the coating method. It is considered that the shape of the clove and the application method ultimately affect the height of the recording layer surface in the groove portion and the land portion.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a state in which a recording layer is applied to a substrate having a groove.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 recording layer 3 groove 4 land 5 step between land and groove on recording layer surface (ΔT)

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Koichi Shiina 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Examiner, Mitsui Toatsu Chemicals Co., Ltd. Tatsuya Yamashita (56) References JP-A-3-54744 (JP, A) JP-A-3-22224 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 7/24 B41M 5/26

Claims (3)

(57) [Claims] 1. A depth 900 ～1800A, recording layer containing a dye on a transparent resin substrate having a groove shape having a width 0.3 to 0.6 [mu] m, the reflective layer, formed by sequentially stacking a protective layer, 780
A single plate type optical recording medium capable recordable at a wavelength of m, the color
Element is Pd-tetra- (t-butylcyclohexyloxy)
B) phthalocyanine brominated dye, Pd-tetra-
(2,4-dimethyl-pentane-3-oxy) phthalocyanine
Of is either brominated dye, the groove portion 800 a thickness of the recording layer of ～1250A, the thickness of the recording layer of the land portion 50
An optical recording medium, wherein the recording layer is formed by a coating method so that the surface of the recording layer in the land portion is higher than the surface of the recording layer in the groove portion by 500 to 1200 °. . 2. The optical recording medium according to claim 1, wherein the reflectance of the unrecorded groove portion through the substrate is 60% or more. 3. An optical recording medium according to claim 1, wherein information is recorded on said groove by pit length recording .