JPS63201930A - Optical recording medium - Google Patents

Abstract

PURPOSE:To improve adhesiveness after record writing and solvent resistance and signal and address signal, etc., by providing an underlying layer of a plasma-polymerized film formed by polymn. of a silane silicon compd. between a recording layer and substrate. CONSTITUTION:This recording medium has the recording layer 12 consisting of a dye or dye compsn. on the substrate 11 and has the underlying layer 13 of the plasma-polymerized film formed by polymn. of the silane silicon compd. between the recording layer 12 and the substrate 11. The plasma-polymerized film is formed preferably to 1.3-1.7 refractive index (n) at 6,328Angstrom . The adhesiveness and more particularly the adhesiveness after the record writing are thereby improved. The solvent resistance is improved and the good reproduction signal is obtd. at a high reflection level; further, embedment of grooves and pits for tracking control and pits for the address signal is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Background of the Invention Technical Field The present invention relates to an optical recording medium, particularly a heat mode optical recording medium.

Prior art and its problems Optical recording media have the characteristic that the recording medium does not deteriorate due to wear and tear because there is no contact between the medium and the writing or reading head.For this reason, research and development of various optical recording media are being carried out. .

Among such optical recording media, heat mode optical recording media are being actively developed because they do not require development in a dark room.

This heat mode optical recording medium is an optical recording medium that uses recording light as heat. For example, a part of the medium is melted or removed using recording light such as a laser, and a part of the medium is melted or removed to form a pit. There is a pit-forming type in which writing is performed by forming small holes, information is recorded using the bits, and the bits are detected with readout light and read out.

Most of these bit-forming type media, particularly those using a semiconductor laser as a light source that can miniaturize the device, have a recording layer made of a material mainly composed of To.

In addition, in recent years, organic materials mainly containing dyes have been used instead of Te-based materials due to the toxicity of Te-based materials and the need for higher sensitivity and lower manufacturing costs. There are an increasing number of proposals and reports on media using recording layers of the above-mentioned type (Japanese Patent Laid-Open No. 60-203488, etc.)
.

In pit-forming optical recording media having a recording layer made of such a dye, a so-called air sensor is used to prevent a decrease in sensitivity and S/N ratio.

It is preferable to have a switch structure.

Further, when a recording layer containing these dyes is formed on a substrate and recording/reproduction is performed, the recording/reproduction is normally performed by irradiating writing light and reading light from the back side of the substrate.

However, when using a substrate made of transparent resin such as polycarbonate or acrylic resin, the surface of the resin substrate is damaged by the coating solvent used when coating the recording layer, reducing the reflectance of the recording layer and reducing the readout S. There is a drawback that the /N ratio cannot be kept high enough.

Furthermore, during long-term storage, there is a risk that dyes and other additives may dissolve and diffuse into the substrate resin, resulting in a decrease in reflectance.

Furthermore, writing causes damage such as denting of the substrate due to heat, which also reduces the S/N ratio. Moreover, the noise after erasing increases.

In contrast, the present inventors have proposed the use of a coating film of a colloidal particle dispersion of a silicon-based condensate as the underlayer (Japanese Patent Laid-Open No. 60-203489).

However, the base layer made of such a coating film does not have sufficient adhesion to the substrate, and there is a problem in that the adhesion is particularly poor after recording and writing.

In addition, due to the existence of such an underlayer, groups or bits for tracking control formed on the substrate in advance and bits for address signals formed on the substrate in the track are buried, causing playback signals and address Another problem was that it was difficult to detect the signal.

■ Purpose of the Invention The purpose of the present invention is to provide an optical recording medium that has good adhesive properties, especially adhesive properties after recording and writing, has excellent solvent resistance, and can also reproduce reproduction signals, address signals, etc. well. be.

■Disclosure of the invention Such objects are achieved by the invention described below.

That is, the present invention provides an optical recording medium having a recording layer of a dye or a dye composition on a substrate, in which a plasma-polymerized film base layer is formed between the recording layer and the substrate by polymerizing a silane-based silicon compound. An optical recording medium characterized by having:

■Specific configuration of the invention The specific configuration of the present invention will be described in detail below.

Optical recording medium of the present invention! As shown in FIG.
A recording layer 12 is shown on top of the substrate 1, and an underlayer 13 is provided between the recording layer 12 and the substrate 11.

The substrate 11 is preferably substantially transparent (preferably with a transmittance of 80% or more) to the writing light and the reading light, and if it is substantially transparent, writing and reading can be performed from the back side of the substrate. can be done,
This is advantageous in terms of sensitivity, S/N ratio, etc., and is also advantageous in terms of implementation, such as countermeasures against lumps.

The shape of the substrate may be a disk, tape, drum, belt, etc. depending on the intended use.

As shown in FIG. 1, it is preferable that a pre-group 115 for tracking is formed on the surface of the substrate 11 on which the recording layer 12 and the underlayer 13 are formed.

The depth of the groove of the pre-group 115 is about λ/8n,
In particular, the range is λ/7n to λ/12n (where n is the refractive index of the substrate). Also, Puri Group 115
The width of the groove is approximately the width of the track.

It is preferable to use the recording layer 12 located in the concave or convex portions of the pre-group 115 as a recording track section, and to irradiate the write light and the read light from the back side of the substrate.

With this configuration, the writing sensitivity and the reading S/N ratio are improved, and the tracking control signal is also increased.

Instead of forming such groups, bits may be formed.

Further, a bit for an address signal can be provided in the track portion.

The formation of such groups and bits on the substrate 11 is as follows:
22 method or injection molding method may be used.

The substrate 11 is usually made of resin, such as acrylic resin, polycarbonate resin, epoxy resin, or olefin resin such as polymethylpentene, but may also be made of glass or the like.

The substrate preferably has at least a resin surface, and examples of the resin used include those mentioned above.

On such a substrate 11, a base layer 13 and a recording layer 1 are provided.
2 is formed.

The base layer 13 in the present invention is formed from a plasma polymerized film, and this plasma polymerized film is obtained by polymerizing a silane-based silicon compound.

As the organic silane silicon compound, the following are preferred.

Vinyltrichlorosilane, dimethyldichlorosilane, methylthiotrimethylsilane, dimethylpropylchlorosilane, diallyldichlorosilane, butyldimethylsilane, tetraethylsilane, hexamethyldisilane, tetramethylsilane, diethylsilane, ethynyltrimethylsilane, allyldimethylchlorosilane, trimethylvinylsilane, diethyl Methylsilane, dimethylaminotrimethylsilane, triethylsilane, allyltrimethylsilane, methyltrivinylsilane, tetravinylsilane, phenyltrimethylsilane, hexamethyldisilazane, 1
゜1.3.3-tetramethyldisilazane, 1゜1.3,
3,5.5-hexamethylcyclotrisilazane, 1,1
,3,3,5,5,7.7-ocdomethylcyclotetrasilazane.

These may be used alone or in combination of two or more.

In addition, the various organosilicon compounds mentioned above, silane (SiH4
) and a hydrocarbon compound may be used.

Hydrocarbon compounds that are usually gaseous at room temperature include methane, ethane, propane, butane, pentane, ethylene, propylene, butene, butadiene, and
One or more types of acetylene, methylacetylene, and other saturated or unsaturated hydrocarbons are used, and the hydrocarbon compound can usually be used in a molar ratio of about 50 times or less to the silicon compound such as silane.

The plasma polymerized film of the present invention preferably has a refractive index n of 1.3 to 1.7 based on 6328 people.

The reason for setting such a refractive index is that if n is less than 1.3, the denseness of the film will be insufficient, and sufficient solvent resistance will not be obtained.
This is because the adhesiveness is not sufficient, and if it exceeds 1.7, the water repellency and hardness of the polymeric film increase, and the adhesion with the recording layer 12 (coated film) formed in contact with the polymeric film becomes difficult. becomes defective,
It also makes layering difficult.

When n is set like this, plasma polymerization conditions such as a low film formation rate and low pressure may be selected as described later.

In the present invention, the thickness of the plasma polymerized film base layer 13 is as follows:
The number is preferably 10 to 1000 people, preferably 50 to 600 people.

The reason why this thickness is set is that the effectiveness of the present invention cannot be obtained if the thickness is less than 10λ, and there is no difference in the effectiveness of the present invention even if the number of people exceeds 1000, and there is no need to increase the thickness above this value. .

Note that the film thickness may be measured using an ellipsometer or the like.

Such film thickness can be controlled by controlling the reaction time, raw material gas flow rate, etc. during plasma polymerized film formation.

The plasma polymerized film base layer 13 is a polymerized film formed by bringing discharge plasma of the above-mentioned raw material gas into contact with the substrate.

To give an overview of the principle of plasma polymerization, when a gas is kept at a low pressure and an electric field is applied, the free electrons present in small amounts in the gas are accelerated by the electric field due to the very large intermolecular distance compared to normal pressure, and are accelerated at 5 to 10 eV. Obtain the kinetic energy (electron temperature) of

When these accelerated electrons collide with atoms and molecules, they disrupt atomic and molecular orbits and dissociate them into chemical species that are unstable under normal conditions, such as electrons, ions, and neutral radicals.

The dissociated electrons are accelerated by the electric field again, causing them to dissociate from other atoms or molecules, and this chain reaction quickly turns the gas into a highly ionized state. And this is called plasma gas.

Gas molecules have fewer chances of collision with electrons, so they do not absorb much energy and are kept at a temperature close to room temperature.

A system in which the kinetic energy of electrons (electron temperature) and the thermal motion of molecules (gas temperature) are separated is called a low-temperature plasma. The present invention aims to utilize this situation to form a plasma polymerized film on a substrate. Since low-temperature plasma is used, there is no thermal effect on the substrate.

An example of an apparatus for forming a plasma polymerized film on a substrate surface is shown in FIG. FIG. 2 shows a plasma polymerization apparatus using a frequency variable power source.

In FIG. 2, raw material gas is supplied to the reaction vessel R from a raw material gas source 511 or 512 via mass flow controllers 521 and 522, respectively. Gas source 5
When separate gases are supplied from 11 or 512, they are mixed and supplied at mixing 1I53.

The raw material gas is 1 to 250 mjl each! ,/min flow range.

Inside the reaction vessel R, a substrate to be processed 111 is supported by one rotary electrode 552 .

Rotary electrodes 552 are placed across the substrate 111 to be processed.
An electrode 551 facing the is provided.

One electrode 551 is connected to, for example, a variable frequency power source 54, and the other rotary electrode 552 is grounded at 8.

Furthermore, a vacuum system for evacuating the inside of the reaction vessel R is provided, and this includes an oil rotary pump 56, a liquid nitrogen trap 57, an oil diffusion pump 58, and a vacuum controller 59. These vacuum systems operate within the reaction vessel at 0. Less than ITorr, preferably 0.005-0.0
Maintain a vacuum level of 8 Torr.

In the operation, the inside of the reaction vessel R is first set at 1O-5 Torr.
The inside of the container is evacuated until the amount is below, and then the processing gas is supplied into the container in a mixed state at a predetermined flow rate.

The film forming rate is preferably 50 to 200 λ/win in the case of forming a polymer film of n as described above.

At this time, the vacuum inside the reaction vessel is 0. It is controlled to be less than I Torr, preferably in the range of 0.005 to 0.08 Torr.

When the flow rate of the source gas becomes stable, the power is turned on.
In this way, a polymeric film is formed on the plasma on the substrate.

Note that Ar and N2 are used as carrier gas.

He, H2, etc. may also be used.

Further, the applied current, processing time, etc. may be set to normal conditions.

As the plasma generation source, in addition to high frequency discharge, microwave discharge, direct current discharge, alternating current discharge, etc. can be used.

In the present invention, especially when the operating pressure is low, it is preferable to use a magnetron system that also uses a magnetic field.

In addition, in the case of using a liquid droplet as a raw material in the present invention, a container containing the liquid droplet may be placed in a constant temperature bath at the galley sources 511 and 512 in FIG.

The Si content in the plasma polymerized film of the charged recording medium of the present invention formed in this way is usually 2 to 95 at%, particularly 2
~80 at%.

Further, the C content in the plasma polymerized film is 5 to 50 at%
It is preferable that H is contained in an amount of about 5 to 90 at%.

By the way, the zero content in the plasma polymerized film is usually 40 at%
It is considered to be below that level.

The content of Si, C, t (and other elements) in the plasma polymerized film may be analyzed by SIMS (secondary ion mass spectrometry) or the like.

When using SIMS, Si
, C, H, and other elements may be counted.

Alternatively, while performing ion etching with Ar etc.,
It may be calculated by measuring profiles of t, C, H, and other elements.

Regarding SIMS measurement, please refer to Surface Science Basic Course No. 39 (
1984) Fundamentals and applications of surface analysis (p70) S I
MSs3 and LAMMA'' may be followed.

It is preferable that such a plasma polymerized film base layer 13 be formed on the plasma-treated substrate 11 .

By plasma-treating the surface of the substrate 11, the substrate 1
1, the adhesive force between the substrate and the plasma polymerized film base layer 13 is improved.

The principle, method, formation conditions, etc. of the plasma treatment method for the surface of the substrate 11 are basically almost the same as those of the plasma polymerization method described above.

However, in plasma processing, in principle, an inorganic gas is used as a processing gas (an inorganic gas may be mixed in depending on the case) as a raw material gas.

There are no particular limitations on the plasma processing gas of the present invention.

That is, H2* A r + He + 02+ N
* *Air, NHs, Os, H20: No, N
20°02, etc., and may be used alone or in combination.

Furthermore, the frequency of the plasma processing power source is not particularly limited, and may be either direct current, alternating current microwave, or the like.

The recording layer 12 may be made of various materials, however, in the present invention, it is preferably made of a dye alone or a dye composition.

The dye to be used may be appropriately determined from among those that effectively absorb the wavelengths of the writing light and reading light. In this case, these light sources are
Since it is preferable to use a semiconductor laser because the device can be made smaller, the dyes may be cyanine-based, phthalocyanine-based, anthraquinone-based, azo-based, triphenylmethane-based,
Byrylium or thiapyrillicum salts are preferred.

Further, when the dye composition is used as a recording layer, it can contain a self-oxidizing resin such as nitrocellulose, or a thermoplastic resin such as polystyrene or nylon. In addition, a quencher may be included in order to prevent the dye from becoming acidic or deteriorating. Furthermore, other additives may also be included.

In such a case, a mixture of an indolenine cyanine dye and a quencher such as bisphenyldithiol is particularly preferred.

It is also preferable to use these as an ionic bond between a dye cation and a quencher anion.

For details on preferred dyes and quenchers, see JP-A Nos. 59-55794, 59-55795, and 59-59.
-81194, 59-83695, 60-18
No. 387, No. 60-19586, No. 60-19587
No. 60-35054, No. 60-36190, No. 60-36191, No. 60-44554, No. 60-
No. 44555, No. 60-44389, No. 60-443
No. 90, No. 60-47069, No. 60-20991, No. 60-71294, No. 60-54892, No. 6
No. 0-71295, No. 60-71296, No. 60-7
No. 3891, No. 60-73892, No. 60-7389
No. 3, No. 60-83892, No. 60-85449,
No. 60-92893, No. 60-159087, No. 6
〇-162691, 60-203488, 60
-201988, 60-234886, 60-
No. 234892, No. 61-16894, No. 61-1'
No. 1292, No. 61-11294, No. 61-1689
No. 1, No. 61-8384, No. 61-14988, No. 61-163243, No. 61-210539, Japanese Patent Application No. 60-54013, etc.

The recording layer 12 may be formed by spinner coating using a ketone, ester, ether, aromatic, halogenated alkyl, or alcohol solvent. In the present invention, by providing the underlayer 13, solvent resistance is improved, and an optimal solvent can be selected from a wide range of solvent groups and used.

The i-recording layer 12 may have a thickness of 0.01 to 10-.

Note that when groups or bits for tracking control are provided, the thickness of the recording layer is preferably 0.2 mm or less, more preferably 0.05 to 0.154 mm.

At this time, the writing sensitivity improves. Further, due to multiple reflections in the recording layer, the reflectance becomes extremely high, and the read S/N ratio becomes extremely high. Then, the difference in reflectance based on the difference in thickness between the recording track portion and other areas increases, making tracking control easier.

An upper layer of the recording layer can also be provided in such a recording portion.

Further, the optical recording medium of the present invention may be provided with a protection plate.

It is preferable that the substrate 11 having the base layer 13 and the recording layer 12 and the protective plate are integrated with a gap between them. Sonic fusion may be used.

When performing ultrasonic fusion, if the protrusion is made into a rod shape, for example, the protrusion will be effectively heated, resulting in good fusion efficiency and workability, as well as high bonding strength and precise control of gap spacing. can do.

When the deformation is large and the protrusion arrangement density is high, an airtight outer peripheral wall may be formed over the entire surface.

Also, vents can be formed between the partition walls.

The vent is formed in the gap between the protrusions.

Fixing can also be achieved by injecting adhesive.

Alternatively, a combination of so-called adhesion and fusion may be used, in which a hot-melt resin is applied as an adhesive to the peripheral edge of the substrate 1, and then the inner substrates are combined and subjected to ultrasonic fusion.

In order to form such a plurality of rod-shaped protrusions, it is sufficient to process a master or a stamper and integrally mold them when molding the substrate.

Above, we have explained the integration using rod-shaped protrusions, but
In addition, various known integrated structures are possible.

Although the case of single-sided recording has been described above, the present invention may also be a double-sided recording medium in which recording layers are provided on both substrates. In this case, it is necessary that both substrates be made of substantially transparent resin, and that both substrates be provided with an underlayer.

(2) Specific Effects of the Invention The optical recording medium of the present invention is a regular disk, and writing light is irradiated from the back side of the substrate while rotating. As a result, bits are preferably formed in a track shape in the recording track portion located in the groove recess.

The bits formed in this manner are detected by emitting readout light from the back side of the substrate while rotating and detecting the reflected light.

In order to control tracking, the reflected light is usually split while writing and reading.
Introduce it to a pair of sensors divided into two. At this time, when the beam spot begins to deviate from the recording track section, the primary light due to the interference effect due to the phase difference due to the step of the groove is biased toward one sensor, so the signals from both sensors are detected.
A track error signal is detected.

Note that the bits once formed on the recording layer can be erased by light or heat and then written again.

In addition, the light source used for writing and reading is
Although various lasers can be used, it is particularly preferable to use a semiconductor laser.

■Specific Effects of the Invention The optical recording medium of the present invention has a recording layer of a dye or a dye composition on a substrate, and is formed by polymerizing a silane-based silicon compound between the recording layer and the substrate. Since it has a plasma-polymerized film base layer, it has good adhesion, especially adhesion after recording and writing, and has excellent solvent resistance, a high reflection level, and a good reproduction signal. Furthermore, it is possible to prevent groups or bits for tracking control and bits for address signals from being buried, no error signals are generated due to burying of groups or bits for tracking control, and there is no burying of address signal bits. Address signals can also be reproduced well.

(2) Specific Examples of the Invention The present invention will be explained in more detail below by giving specific examples of the invention.

Example A substrate 11 made of bisphenol A polycarbonate resin (molecular weight 15,000) with a diameter of 13 cm and a thickness of 1.2 mm was molded into a spiral shape with a width of 0.6-1 mm by injection molding.
A group for tracking control with a depth of O, t4 was provided, and a bit for response signal -@- was provided at 7 with a width of 0.6 um-PJ, O, lum. Such a substrate 11 is placed in a vacuum chamber, and after the vacuum is once drawn to 10-'Torr, Ar is used as a processing gas, and the flow rate is 50 m1.
! /min gas pressure 0. 13.5 while keeping it at ITorr
Plasma was generated by applying a high frequency voltage of 6 MHz, and the surface of the substrate 11 was plasma-treated.

Thereafter, a plasma polymerized film base layer 13 was further formed on the substrate 11 under the conditions shown in Table 1.

Note that the refractive index values shown in Table 1 were measured by 6238 people.

Further, the elemental analysis of these plasma polymerized films was measured by SIMS, and the film thickness was measured by an ellipsometer.

The recording layer 12 is made of indolenine cyanine dye (1,3,3
, 1', 3', 3'-hexatrimethylindotricarbocyanine cation) and a bisphenyldithiol-based quencher (bis(trichlorophenyldithiol)Ni anion) using a 2.2% cyclohexanone solution. Then, the underlayer 13 was coated on the substrate 11 on which the underlayer 13 had been formed to a thickness of o, os, and a as described above.

Samples 1 to 8 were thus obtained.

In addition, a sample without a base layer was also produced, and this was designated as sample 10.

For comparison, a sample using a colloid of a silicon-based condensate disclosed in JP-A No. 60-203489 was also prepared, and this was designated as Sample 11.

In this case, the base layer consists of 1 part ethyl acetate and ethyl alcohol.
Mix at a ratio of 0:11 and gradually add 5i(O
After adding C214,)4 at a ratio of 2/25 to ethyl acetate, the solution was left to stand for 3 to 4 days, and the solution was further diluted 10 times with n-propatool, and then coated on a substrate and heated at 60°C.
It was formed by processing for 30 minutes.

The particle size of the silicon oxide colloid was 50 to 80 particles, and the thickness of the base layer was 400 particles.

The following measurements were performed using the above samples.

(1) Adhesive strength between the substrate and the underlayer: At the initial stage of each sample, at 60°C, at 90% R1
The adhesive strength after being left in the atmosphere for 10 days was evaluated by cross-cutting each sample 11 times vertically and horizontally at 1 mm intervals and performing a peel test using cellophane tape.

Note that recording was performed at a recording power of 3.8 mW and a linear velocity of 1.3 m.
I went with /S.

(2) Reflection level was measured at a reflection level of 830 nm from the back side of the substrate while tracking control of the groove portion was performed using an optical disk drive device. Note that the values in the table are in arbitrary units.

(3) Tracking Error Signal Using a fluorescent disk drive device, light was focused on the recording film surface (unrecorded area), and the amount of push-pul 1 ) racking error signal was measured without tracking control. Note that this is an arbitrary unit in the table.

(4) Reproducing Address Signal Light was focused on the recording film surface (address signal area) using an optical disk drive device, and the amount of address signal light was measured while tracking control was performed. Note that the values in the table are in arbitrary units.

These results are shown in Table 2.

From the results in Table 2, the effects of the present invention are clear.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the optical recording medium of the present invention. FIG. 2 is a schematic diagram of a plasma polymerization apparatus. Explanation of symbols 1... Optical recording medium, 11-- Substrate, 115-- Group, 12-- Recording layer, 13-- Plasma polymerized film base layer, 53-- Mixer, 54-- Direct current. , AC and variable frequency power supply, 56-・
- Oil rotary pump, 57 - Liquid nitrogen trap, 58 - Oil diffusion pump, 59 - Vacuum controller, 111 - Processed substrate, 511.512 - Raw material gas source, 521.522 - Mass flow controller, 551
．． 552--Electrode patent applicant TDC Co., Ltd. FIG, 2

Claims (4)

[Claims] (1) In an optical recording medium having a recording layer of a dye or a dye composition on a substrate, a plasma polymerized film base layer formed by polymerizing a silane-based silicon compound is provided between the recording layer and the substrate. An optical recording medium characterized by: (2) The refractive index at 6328 Å of the plasma polymerized film is 1
．． 3 to 1.7. The optical recording medium according to claim 1. (3) The thickness of the plasma polymerized film base layer is 10 to 1000 Å
An optical recording medium according to claim 1 or 2. (4) The optical recording medium according to any one of claims 1 to 3, wherein the substrate has at least a resin surface.