JPH04226388A - Optical recording medium - Google Patents

Abstract

PURPOSE:To make both write sensitivity of a signal and a symmetrical property of a written signal excellent by a method wherein a melting point of a near- infrared absorbent contained in a recording layer of a CD-WO type optical recording medium is made within 150-300 deg.C and its decomposition start temperature is made within 200-350 deg.C. CONSTITUTION:A recording layer, a metal reflection layer, and a protective layer are laminated in this order on a transparent substrate to obtain CDWO (compact disk-write once) type optical recording medium. In that case, the recording layer contains a near-infrared absorbent consisting of a chemical compound of which a melting point is within a range of 150-300 deg.C and of which a decomposition start temperature is within a range of 200-350 deg.C or a mixture thereof.

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 used for recording and storing information.

0002

[Prior art] Conventionally, a recording layer (light absorption layer) is formed on a substrate.
, Compact Disc-Wr consisting of laminated light reflective layer and protective layer.
iteOnce) type (hereinafter abbreviated as CD-WO) optical recording media have been known (JP-A-58-183296, JP-A-53-46019, JP-A-58-37851 and JP-A-1-159842).

0003

[Problem to be solved by the invention] However, JP-A-58-
Copper phthalocyanine (manufactured by Sumitomo Chemical, Oleosol Fast Blue EL) constituting the recording layer (light absorption layer) of the optical recording medium disclosed in No. 183296 could not provide the sensitivity required as an optical recording medium.

The medium shown in Example 2 of JP-A No. 53-46019 has poor sensitivity and durability, and does not have a reflectance of 65% or more in the range from 780 to 830 nm, which is necessary for optical recording media, especially CD-WO. The condition of having one was not met.

[0005] JP-A-58-37851 describes the same structure as the present invention, but as shown in the examples,
Reflectance 30-51% and reflectance 6 required for CD-WO
It did not reach 5%, and the durability was not sufficient.

Furthermore, as shown in JP-A-1-159842, when a medium is prepared using a general cyanine dye (for example, Japan Photosensitive Color Research Institute, Photosensitive Dye Table (1969)), sensitivity may be insufficient or In some cases, the reflectance was less than 65%.

[0007] Furthermore, the cyanine dyes shown in the examples of EP 353394 and the phthalocyanine dyes shown in the examples of EP 353393 have poor sensitivity and signal characteristics, and are not suitable for CDs.
-It was unsuitable as a dye for WO type optical recording media.

An object of the present invention is to provide a CD-WO type optical recording medium having a reflectance of 65% or more, which has not been achieved in the conventional examples.

[0009]

[Means for Solving the Problems] As a result of intensive studies to achieve the above object, the present inventors have found that the melting point of the near-infrared absorber contained in the recording layer of a CD-WO type optical recording medium is 150
~300°C and the decomposition start temperature is 200 to 350°C, the optical recording medium composed of the recording layer containing the near-infrared absorber has poor signal writing sensitivity and symmetry of the written signal. It was found that the recording quality was good and the recording distortion was small.

[0010] Also, in a solution state (as a solvent, CCl4,
Maximum absorption wavelength (λm
The inventors have discovered that when a near-infrared absorber having an ax) of 670 to 720 nm is used in the recording layer, the reflectance of the medium can be maintained at 65% or more, and the present invention has been achieved. It has also been found that the introduction of a halogen atom or a specific substituent is effective, particularly with regard to the melting point and decomposition point of the near-infrared absorbent used.

In the present invention, we have found that the melting point and decomposition point of the near-infrared absorbent used have a large influence on the sensitivity during recording and the stability of reproduction stability, and based on these findings, we have completed the invention. It is something that

The optical recording medium of the present invention has a structure in which a recording layer, a metal reflective layer, and a protective layer are laminated in this order on a transparent substrate, and the recording layer has a melting point of 150 to 300° C. and a temperature at which decomposition starts. It is characterized by containing a near-infrared absorber made of a compound or a mixture thereof having a temperature within the range of 200 to 350°C.

The melting point was measured using a commercially available melting point measuring device, and the decomposition point was measured using a differential thermal thermogravimetry (DTA-TGA), and the temperature at which 5% decomposition occurred was defined as the decomposition start temperature.

The substrate used in the optical recording medium of the present invention may be any optically transparent resin. for example,
Examples include acrylic resin, polyethylene resin, vinyl chloride resin, vinylidene chloride resin, polycarbonate resin, ethylene resin, polyolefin copolymer resin, vinyl chloride copolymer resin, vinylidene chloride copolymer resin, and styrene copolymer resin. Further, the substrate may be surface-treated with a thermosetting resin or an ultraviolet curable resin.

The near-infrared absorber contained in the recording layer is a compound group represented by the following formula (I).

[0016]

[Formula (I), R1, R2, R3, R4, R5, R6,
R7, R8, R9, R10, R11, R12, R13,
R14, R15 and R16 are each independently a hydrogen atom, a halogen atom, a nitro group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxyl group, a substituted or unsubstituted aryloxy represents a substituted or unsubstituted alkylthio group, a substituted or unsubstituted arylthio group. However, R1, R4, R5
In the combinations of and R8, R9 and R12, and R13 and R16, at least one of them is a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted alkylthio group, or a substituted or unsubstituted arylthio group. Represents a group selected from among the groups, R1,
R2, R3, R4, R5, R6, R7, R8, R9, R
10, R11, R12, R13, R14, R15 and R
1 to 4 of 16 represent halogen atoms, and Me
t represents two hydrogen atoms, a divalent metal atom, or a trivalent or tetravalent metal derivative. ] Phthalocyanine compounds and their isomers, or pigments such as cyanine dyes, anthraquinone dyes, polyolefin dyes, and thiapyrylium dyes, with a melting point of 150
By selecting a dye or a dye mixture whose decomposition start temperature is 200 to 350° C., an optical recording medium with excellent recording sensitivity and recording properties can be obtained.

The CD-WO type optical recording medium of the present invention can be used in commercially available compact disc players or CD-ROMs.
It is a medium that can be read by a reproducing device, that is, a semiconductor laser of 760 to 800 nm. In order to improve sensitivity and reflectance, that is, writing or reproducing ability,
The maximum absorption wavelength (λmax) of the dye in chloroform is
Preference is given to dyes or dye mixtures which are between 670 and 720 nm, especially those with a molar extinction coefficient (εmax) at the maximum wavelength in chloroform solution of 1×10 5 l mol−
It is preferable that it is 1 cm-1 or more.

The recording layer can be prepared by coating or vapor depositing a single layer or a mixture of the above-mentioned compounds in one or two layers. Pre-compound 0.05% by weight
There is a method in which it is dissolved in a solvent to a concentration of 20% by weight, preferably 0.5% by weight to 20% by weight, and coated with a spin coater. In addition, as a vapor deposition method, 10-5 to 10-
There is a method of depositing a pre-compound on a substrate at 7 torr and 100 to 300°C.

The thickness of the layer containing the near-infrared absorber in the recording layer is preferably 50 to 300 nm.

Depending on the solvent resistance of the substrate, solvents used for spin coating include halogenated hydrocarbons (for example, dichloromethane, chloroform, carbon tetrachloride, tetrachloroethylene, dichlorodifluoroethane, etc.), ethers (for example, diethyl ether, dipropyl (ether, dibutyl ether, etc.), alcohols (for example, methanol, ethanol, propanol, etc.), cellosolves (methyl cellosolve, ethyl cellosolve, etc.), and hydrocarbons (hexane, cyclohexane, octane, benzene, toluene).

[0021]Aluminum, gold, etc. may be used as the reflective layer, and transparent photocurable or thermosetting resin is preferably used as the protective layer. In addition, its thickness is 1 to 100n
m is preferred.

[0022] Methods for producing the reflective layer include vapor deposition, sputtering, and the like.

[0023] As a method for producing the protective layer, after producing the recording layer on the substrate as described above, a UV curable resin or thermosetting resin composition is applied by spin coating, bar coater method, dipping method, etc. After that, there is a way to harden it. Further, the thickness thereof is preferably 1 μm to 500 μm.

[0024] When producing a CD-WO optical recording medium, it is preferable to use a polyacrylate substrate or a polycarbonate substrate as the substrate and to apply the coating by a spin coating method from the viewpoint of cost and user handling.

[0025]

[Examples] The present invention will be specifically explained below with reference to Examples, but the embodiments of the present invention are not limited thereto. Note that all parts in the examples indicate parts by weight.

Example 1 4,8,12,16-tetrabromo-1,5,9,13
-tetra(1,3-dimethylbutyloxy) phthalocyanine palladium (melting point 150-185°C, decomposition start temperature 280°C, λmax=703nm and εmax=1
．． 6×105 l mol-1 cm-1) was dissolved in 200 parts of dibutyl ether, and
It was applied to a D-WO optical recording medium substrate. Gold was deposited thereon, and then overcoated with a photocurable polyacrylic resin and photocured. The optical recording medium thus produced had a C/N ratio of 60 dB at a linear velocity of 1.4 m/sec and a laser power of 7 mW, and had good sensitivity. Also, fade meter 63℃/1
After 00 hours of irradiation, no deterioration of the recording layer was observed.

Example 2 10 parts of tetra(1,3-dimethylpropyloxy)phthalocyanine palladium was dissolved in 1000 parts of carbon tetrachloride, 2 parts of bromine was added dropwise at 40°C, and the mixture was reacted for 3 hours.
The precipitated crystals were filtered, washed and dried to obtain 5 parts of a dye mixture represented by the following formula.

[0028]

[Case 2]

[0029]

embedded image The melting point of this dye mixture was 170-200°C, and the decomposition onset temperature was 305°C.

Five parts of this mixture was dissolved in 500 parts of n-octane and applied to a polycarbonate substrate for CD-WO with a dry film thickness of 150 nm using a spin coater. A protective layer was formed by applying 30 nm of gold thereon by sputtering, coating it with a UV-curable resin, and curing it under UV light, thereby producing a CD-WO medium.

The CD-WO medium thus prepared had a reflectance of 65%, a linear velocity of 1.4 m/sec, and a power output of 7 mW, 7
A record with a C/N ratio of 60 dB could be written using a 90 nm laser beam. Further, this recording medium did not change even in a light resistance test under a carbon arc lamp at 63° C. for 200 hours.

Example 3 1,5,9,13-tetra(2,4,4-trimethyl-
3-Hexyloxy) Phthalocyanine Palladium 10
1 part was dissolved in 1000 parts of acetic acid, 10 parts of iodine was added, and 5 parts of
The reaction was carried out at 0°C for 3 hours, and the precipitated crystals were filtered and purified.
A mixture represented by the following structural formula was obtained.

[0033]

[Chemical formula 4] (Melting point 200-245℃, decomposition start temperature 285
°C, λmax=708nm and εmax=1.5×1
05 l mol-1 cm-1) Five parts of this dye mixture was dissolved in n-octane and applied to a polycarbonate substrate for CD-WO using a spin coater. The film thickness was 120 nm. 50 nm of gold was deposited thereon, and then a protective layer was formed using a UV curable resin.

When the thus produced CD-WO medium was recorded with a 780 nm laser at a linear velocity of 1.3 m/sec and 7 mW, recording with a C/N ratio of 55 dB was obtained.

Further, when this medium was subjected to a light resistance test using a xenon lamp at 50° C., it was confirmed that there was no change even after 200 hours.

Example 4

[0037]

[Chemical formula 5] Phthalocyanine represented by the above formula (melting point 165-200
℃, decomposition start temperature 295℃) was dissolved in 300 parts of a 3:1 mixture of dibutyl ether and diisopropyl ether, and coated on a PMMA CD-WO substrate to a thickness of 120 nm using a spin coater, and then gold was sputtered to a thickness of 20 nm. Finally, a protective layer was formed using a UV curable resin to produce a recording medium.

The obtained medium had a linear velocity of 1.4 m/sec,
When recorded with a 8mW, 780nm laser, C/
A record with an N ratio of 60 dB was obtained.

Example 5 Mixture of two types of compounds below [(A)/(B)=1/1]

[
0040

[C6]

[0041]

[Chemical 7] (The physical properties of this mixture are λmax=710nm, εmax
= 1.7 x 105 l mol-1 cm-1, melting point 230-240°C, decomposition start temperature 270°C), a CD-WO type optical recording medium was prototyped in the same manner as in Example 1.

The obtained medium had a linear velocity of 1.4 m/sec,
When recorded with a 6.5mW, 780nm laser,
A recording with a C/N ratio of 55 dB was obtained.

Example 6

[0044]

[Chemical 8] Phthalocyanine represented by the above formula (melting point 195-225
°C, decomposition start temperature 253 °C, λmax = 707 nm,
εmax=2.0×105 l mol−1 c
Dissolve 5 parts of m-1) in 300 parts of dibutyl ether, apply it to a thickness of 150 nm on a polycarbonate CD-WO substrate using a spin coater, then sputter gold to a thickness of 30 nm, and finally form a protective layer with UV curable resin. was formed to produce a recording medium.

The obtained medium had a linear velocity of 1.3 m/sec,
When recorded with a 8mW, 780nm laser, C/
A record with an N ratio of 60 dB was obtained.

Example 7

[0047]

embedded image Phthalocyanine represented by the above formula (λmax=694n
m, εmax=1.7×105l mol-1 c
m-1, melting point 250℃ or higher, decomposition start temperature 309℃)5
The sample was dissolved in 300 parts of chloroform, the surface of which was treated with an acrylic photopolymer, and coated onto a groove-formed substrate.An optical recording medium was produced in the same manner as in Example 6.

The obtained medium had a linear velocity of 1.4 m/sec,
When recorded with a 7mW, 780nm laser, C/
A record with an N ratio of 55 dB was obtained.

Example 8

[0050]

embedded image Phthalocyanine represented by the above formula (λmax=708n
m, εmax=1.8×105 l mol−1
cm-1, melting point 262-286℃, decomposition start temperature 31
A CD-WO type optical recording medium was produced in the same manner as in Example 6, using a temperature of 0°C.

The obtained medium had a linear velocity of 1.4 m/sec,
When recorded with a 7mW, 780nm laser, C/
A record with an N ratio of 57 dB was obtained.

Example 9

[0053]

embedded image Phthalocyanine represented by the above formula (λmax=706n
m, εmax=1.8×105 l mol−1
cm-1, melting point 225-245℃, decomposition start temperature 28
A CD-WO type optical recording medium was produced in the same manner as in Example 6 using a temperature of 9°C.

The obtained medium had a linear velocity of 1.3 m/sec,
When recorded with a 7mW, 780nm laser, C/
A record with an N ratio of 62 dB was obtained.

Example 10

[0056]

embedded image Phthalocyanine represented by the above formula (λmax=707n
m, εmax=1.9×105 l mol−1
cm-1, melting point 280-292℃, decomposition start temperature 29
A CD-WO type optical recording medium was produced in the same manner as in Example 6.

The obtained medium had a linear velocity of 1.4 m/sec,
When recorded with a 7mW, 780nm laser, C/
A record with an N ratio of 61 dB was obtained.

Comparative Test The performance of the CD-WO type optical recording medium of the present invention obtained above was compared with that of an optical recording medium prepared according to known requirements. The media produced in Examples 2, 4, and 5 were used as the media of the present invention, and the media produced according to the following seven known examples were used as comparative examples.

Comparative Example 1: Example in which the recording layer contains silver nitrate (see JP-A-58-37851) Comparative Example 2: Example using the following dye (see JP-A-1-1598)
42)

[0060]

Comparative Example 3: Example of recording layer made of inorganic compound
019) Comparative Example 4: An example using a copper-phthalocyanine dye (see JP-A-58-183296) Comparative Example 5: An example using a dye of the following formula, and a medium was produced in the same manner as in Example 1.

[0061]

[Chemical formula 14] However, the mp of the dye is 80 to 90°C, and the decomposition starting point is 310°C.
Comparative Example 6: A medium was produced in the same manner as in Example 1 using the following dyes.

[0062]

[Chemical 15] (The physical properties of the dye are that the melting point is >250°C and the decomposition starting temperature is 3.
The temperature was 05°C. ) Comparative Example 7: Example using the following compound (EP035339
3 was referred to. )

[0063]

[Formula 16] (The physical properties of this compound are as follows: melting point: 145-148°C, decomposition onset temperature: 210°C) The physical properties of all of the above comparative examples were measured by the following procedure, and the results are compared with the examples in Table 1. It was shown to.

The reflectance is for light of 780 nm, and the sensitivity is measured at a linear velocity of 1.4 m/sec at 780 nm. 1) Symmetry is a fluctuation rate of 5% or less at a recording power of 5 to 90 mW (○), a fluctuation rate of 5% or less. 5% or more (×)
, 2) Pulse width correction is a 4T signal (231×4=924
nsec), the necessary correction width is 0 to -100
nsec is (○), -100 to -200 nsec is (△), and -200 nsec or more is (x). 3) Recording distortion is measured by measuring the distortion of the recording waveform with an oscilloscope, and recording with a microscope. As a result of observing the distortion of the gold layer by observing the pits, those with no distortion are marked (○), those with distortion are marked (x), and 4) Durability is 10 at 0.5 mW and linear speed of 1.4 m/sec.
The change in the record when read five times (reproduction light stability) and the change in the record by accelerated sunlight fastness test using a xenon lamp at 40°C for 100 hours are each 10% or less (〇),
10 to 20% was rated as (△), and 20% or more was rated as (×).

[0065]

[Table 1]

[0066]

[Table 2] *Measured by TG-DTA ** No data because the medium is an inorganic compound.

[0067]

Effects of the Invention The present invention has a structure in which a recording layer, a metal reflective layer, and a protective layer are laminated in this order on a transparent substrate, and the recording layer has a melting point of 150 to 300°C and a decomposition start temperature of 200 to 350°C.
By using a dye having λmax of 670 to 720 nm, a CD-WO type optical recording medium with high sensitivity, low recording distortion, and high durability can be obtained. This CD-WO
The quality of molded optical recording media is more stable than in the past.

Claims (5)

[Claims] 1. A structure in which a recording layer, a metal reflective layer, and a protective layer are laminated in this order on a transparent substrate, and the recording layer has a melting point of 150 to 300°C and a decomposition start temperature of 200 to 300°C.
A compact disc-write-once (CD-WO) type optical recording medium characterized by containing a near-infrared absorber consisting of a compound or a mixture thereof within the range of 350°C. 2. The optical recording medium according to claim 1, wherein the recording layer is composed of a near-infrared absorber having a maximum absorption wavelength of 670 to 720 nm in a chloroform solution. 3. The near-infrared absorber has a molar extinction coefficient of 1×10 5 at the maximum absorption wavelength in a chloroform solution.
3. The optical recording medium according to claim 2, which is a compound having a molecular weight of 1 mol-1 cm-1 or more. 4. The optical recording medium according to claim 3, wherein the recording layer is composed of a near-infrared absorber containing 1 to 4 halogen atoms in one molecule. 5. The optical recording medium according to claim 4, wherein the near-infrared absorber constituting the recording layer is phthalocyanine.